External Factors Influencing Cognitive Performance

Dr Oliver Finlay

KEY POINTS

· Good sleep is crucial for cognitive performance as it plays a crucial role in memory consolidation, attention and cognitive processing, restoration of the prefrontal cortex, regulation of emotions, and physiological changes in the brain. Sleep deprivation can impair attention, working memory, decision-making, and reaction time, and disrupt memory consolidation and retention.

· Chronic stress can lead to sustained elevated levels of stress hormones, impairing attention, memory, decision-making, and emotional regulation. This can further exacerbate cognitive impairment, making it harder to concentrate and process information effectively.

· Good nutrition, hydration, and a healthy gut biome positively impact cognitive performance by providing essential nutrients, promoting blood flow to the brain, improving neurotransmitter function, and reducing inflammation and oxidative stress, whilst poor nutrition and dehydration negatively affect cognitive performance by impairing attention, memory, and decision-making, reducing blood flow to the brain, and disrupting electrolyte balance.

· Regular aerobic exercise and resistance exercise can positively impact cognitive performance in several ways, including increasing the production of hormones such as endorphins and dopamine, improving blood flow to the brain, promoting the production of brain-derived neurotrophic factor (BDNF) and myokines, reducing inflammation, and improving the function of neurotransmitters.

· Exposure to natural environments such as forests, green spaces, and parks positively impacts cognitive performance by reducing stress levels, providing opportunities for physical activity, clean air, and restorative experiences, while also mitigating the negative impact of noise pollution on cognitive performance.

Cognition is the mental process of acquiring knowledge and understanding through thought, experience, and the senses. It involves a range of mental abilities, such as perception, attention, memory, language, problem-solving, and decision-making.

The prefrontal cortex is the structure in the brain primarily responsible for cognitive processes. Located in the front of the brain, it is heavily involved in high-level cognitive functions and plays a critical role in working memory, attention, and decision-making. Additionally, the parietal cortex, located in the upper back part of the brain, is involved in perception and attention. The temporal lobe, located on the sides of the brain, is associated with memory and language processing. The occipital lobe, located at the back of the brain, is responsible for vision processing.

External factors, including sleep deprivation, stress, nutrition, hydration, exercise, and environmental characteristics can significantly impact cognitive performance.

Cognitive Performance and Sleep

Research has shown that good sleep positively impacts cognitive performance in several ways.

Firstly, sleep plays a crucial role in memory consolidation. During sleep, the brain consolidates memories and transfers them from short-term to long-term storage. This process is essential for learning and retaining new information. Good sleep also promotes the formation of new neural connections, which can enhance cognitive performance.

Secondly, sleep is essential for attention and cognitive processing. Adequate sleep improves reaction time, attention, and decision-making. One study found that individuals who received more sleep had improved cognitive flexibility, allowing them to shift their attention more effectively between tasks.

Moreover, good sleep is crucial for the restoration of the prefrontal cortex, which is responsible for executive function and working memory. The prefrontal cortex is highly active during the day and requires adequate rest to function optimally. Good sleep also restores the brain's ability to regulate emotions, leading to improved mood and emotional regulation.

In terms of physiology, during sleep, the brain undergoes various physiological changes, including an increase in cerebrospinal fluid production, which helps to remove waste products from the brain. Additionally, during deep sleep, the brain releases growth hormones, which are essential for tissue repair and growth, including the brain.

In contrast, research has shown that sleep deprivation can impair attention, working memory, decision-making, and reaction time. One study found that sleep-deprived individuals had reduced activity in the prefrontal cortex, which is responsible for executive function and working memory. This decreased activity in the prefrontal cortex can lead to poor decision-making and impaired cognitive flexibility.

In relation to learning and memory, the brain consolidates memories and transfers them from short-term to long-term storage during sleep. However, sleep deprivation can disrupt this process, leading to poor memory consolidation and retention.

Cognitive Performance and Stress

Our body releases stress hormones such as cortisol and adrenaline in response to stressful experiences. These hormones activate the body's "fight or flight" response, preparing us to respond to a perceived threat. While this response is beneficial in the short term, chronic stress can lead to sustained elevated levels of stress hormones, which can negatively impact cognitive performance.

Studies have shown that chronic stress can lead to impaired attention, memory, and decision-making. Specifically, stress can impair working memory, which is essential for maintaining information in the short term, and impair long-term memory, which can affect our ability to recall information learned previously.

In addition to memory, stress can also impair attention and decision-making. One study found that individuals exposed to chronic stress had difficulty shifting their attention from one task to another, leading to reduced cognitive flexibility. Chronic stress can also lead to impaired decision-making, as it can cause individuals to focus on short-term outcomes rather than long-term goals.

Furthermore, chronic stress can negatively impact emotional regulation, leading to increased anxiety and depression. These emotional states can further exacerbate cognitive impairment, making it harder to concentrate and process information effectively.

Cognitive Performance and Nutrition

Good nutrition plays a critical role in maintaining mental health, and studies have shown that it positively impacts cognitive performance in several ways.

Firstly, a healthy diet can enhance brain function by providing essential nutrients that support cognitive processes. For example, omega-3 fatty acids found in fish, nuts, and seeds, are essential for brain health and have been shown to improve cognitive function, including memory and attention. Secondly, nutrients such as flavonoids, found in fruits and vegetables, can improve blood flow to the brain, leading to enhanced cognitive performance. Moreover, nutrients such as antioxidants found in fruits and vegetables can help to reduce inflammation and oxidative stress, leading to improved cognitive performance.

In terms of physiology, a healthy diet in conjunction with exercise can also promote the growth of new brain cells and neural connections. For example, exercise and a healthy diet have been shown to increase the production of brain-derived neurotrophic factor (BDNF), which is essential for the growth and survival of new brain cells.

Furthermore, a healthy diet can also improve gut health, which has been linked to cognitive function. The gut-brain axis is a communication network between the gut and the brain, and a healthy gut microbiome has been linked to improved cognitive function and mood.

In contrast, poor nutrition can negatively impact cognitive performance in several ways. The brain requires adequate glucose to function optimally. Glucose is the primary energy source for the brain, and insufficient glucose can lead to cognitive impairment. Low blood sugar levels can impair attention, memory, and decision-making. Additionally, a diet high in saturated and trans fats can lead to inflammation, which can negatively impact cognitive performance.

Cognitive Performance and Gut Microbiome

The gut microbiome refers to the community of microorganisms that live in our gastrointestinal tract. These microorganisms play a critical role in maintaining our health, and studies have shown that the gut biome is linked to cognitive performance in several ways. Whilst the gut biome is technically an internal factor that affects cognitive performance, the relationship between nutrition and the gut biome justifies discussing it here.

Firstly, the gut biome plays a role in the production and regulation of neurotransmitters such as serotonin and dopamine, which are essential for mood regulation and cognitive function. These neurotransmitters are produced by the gut bacteria and are transported to the brain via the gut-brain axis, a communication network between the gut and the brain.

Secondly, the gut biome also plays a role in the production of short-chain fatty acids (SCFAs), which are produced by the gut bacteria during the fermentation of dietary fibre. These SCFAs have been shown to improve cognitive function and memory by reducing inflammation in the brain and improving blood flow.

Moreover, the gut biome also plays a role in the regulation of the immune system, which can impact cognitive function. A healthy gut biome can reduce inflammation in the body, including the brain, which can improve cognitive function and reduce the risk of cognitive decline.

In terms of physiology, the gut-brain axis is a two-way communication network that involves the vagus nerve, a nerve that connects the gut and the brain. The gut bacteria produce neurotransmitters and other signalling molecules that are transported to the brain via the vagus nerve, which can impact cognitive function.

Furthermore, the gut biome can also impact the production of brain-derived neurotrophic factor (BDNF), a protein that is essential for the growth and survival of new brain cells. Studies have shown that a healthy gut biome can increase the production of BDNF, leading to improved cognitive function and memory.

Cognitive Performance and Hydration

Good hydration positively impacts cognitive performance in several ways. The brain is made up of around 75% water, and dehydration can lead to shrinkage of brain cells, which can impair cognitive function. By staying hydrated, we can maintain the proper function and structure of brain cells, leading to improved cognitive performance.

Firstly, good hydration improves blood flow to the brain, which is essential for cognitive function. When we are dehydrated, our blood volume decreases, and blood flow to the brain is reduced, leading to impaired cognitive function. By staying hydrated, we can maintain blood volume and improve blood flow to the brain, leading to improved cognitive performance.

Secondly, good hydration also improves cognitive performance by impacting the brain's executive functions, such as attention, memory, and decision-making. Studies have shown that even mild dehydration can impair cognitive performance, including attention, memory, and reaction time.

Moreover, good hydration also promotes the removal of toxins from the body, including the brain, which can improve cognitive function. Adequate hydration helps to flush out toxins and waste products from the body, reducing inflammation and oxidative stress in the brain.

Furthermore, good hydration also impacts the function of neurotransmitters, which are essential for cognitive function. Adequate hydration helps to maintain the balance of neurotransmitters in the brain, leading to improved cognitive performance.

In contrast, dehydration can lead to cognitive impairment. The brain is approximately 75% water, and dehydration can lead to reduced blood flow to the brain. Studies have shown that even mild dehydration can impair attention, memory, and decision-making.

Dehydration can lead to a reduction in the availability and transport of electrolytes such as sodium and potassium, which are essential for proper brain function. Electrolytes play a crucial role in nerve conduction, which is necessary for cognitive processes such as perception, attention, and memory.

Cognitive Performance and Exercise

Aerobic exercise, also known as cardio exercise, is any type of physical activity that raises your heart rate and breathing rate. Studies have shown that regular aerobic exercise positively impacts cognitive performance in several ways.

From a physiological perspective, aerobic exercise increases the production of hormones such as endorphins and dopamine, which are essential for mood regulation and cognitive function. These hormones are released during exercise and can improve cognitive performance and reduce stress and anxiety.

Furthermore, aerobic exercise also impacts the function of neurotransmitters, which are essential for cognitive function. Regular aerobic exercise can improve the function of neurotransmitters, leading to improved cognitive performance. Aerobic exercise improves blood flow to the brain. During exercise, the heart pumps more blood to the brain, which delivers more oxygen and nutrients to the brain cells, leading to improved cognitive performance.

Aerobic exercise also promotes the production of brain-derived neurotrophic factor (BDNF), a protein that is essential for the growth and survival of new brain cells. Studies have shown that regular aerobic exercise can increase the production of BDNF, leading to improved cognitive function and memory.

Moreover, aerobic exercise also reduces inflammation in the body, including the brain, which can improve cognitive function. Inflammation is a natural response of the immune system, but chronic inflammation can damage brain cells and impair cognitive function. Regular aerobic exercise can reduce chronic inflammation and improve cognitive performance.

Resistance exercise, also known as strength training, involves using weights or resistance to build muscle strength and endurance. Research shows that, as with aerobic exercise, regular resistance exercise positively impacts cognitive performance through mechanisms both similar to and distinct from aerobic exercise forms.

Firstly, just as with aerobic forms of exercise, resistance exercise improves blood flow to the brain, which is essential for cognitive function. During resistance exercise, the muscles contract, and the heart pumps more blood to the brain, delivering more oxygen and nutrients to the brain cells, leading to improved cognitive performance.

Secondly, resistance exercise promotes the production of hormones such as testosterone and growth hormone, which are essential for muscle growth and repair. These hormones also have a positive impact on cognitive function, leading to improved memory and executive function.

Moreover, resistance exercise also increases the production of brain-derived neurotrophic factor (BDNF), a protein that is essential for the growth and survival of new brain cells. Studies have shown that regular resistance exercise can increase the production of BDNF, leading to improved cognitive function and memory.

Resistance exercise also stimulates the production and release of myokines, which are cytokines produced by muscle cells. Myokines have anti-inflammatory properties and have been shown to play a role in improving cognitive function. Studies have found that regular resistance exercise can increase the production and release of myokines, leading to improved cognitive function and memory.

Furthermore, resistance exercise also impacts the function of neurotransmitters, which are essential for cognitive function. Regular resistance exercise can improve the function of neurotransmitters, leading to improved cognitive performance.

Cognitive Performance and the Environment

Numerous studies have shown that exposure to natural environments, such as forests, green spaces, and parks, can positively impact cognitive performance. The benefits of natural environments on cognitive performance are attributed to several mechanisms.

Natural environments are known to have a calming effect on the brain, leading to improved cognitive function. Exposure to natural environments has been shown to reduce stress levels, which can impair cognitive function. Stress reduction in natural environments has been linked to decreased levels of cortisol, a hormone that is associated with stress.

Additionally, natural environments provide opportunities for physical activity, which can have a positive impact on cognitive performance, as previously discussed.

Moreover, natural environments provide exposure to clean air, which can positively impact cognitive performance. Whilst air pollution has been linked to a variety of negative health outcomes, including impaired cognitive function, exposure to natural environments has been shown to reduce exposure to air pollution.

Exposure to excessive noise levels has been linked to impaired cognitive performance because noise can lead to increased stress levels and distract the brain from tasks at hand. Chronic exposure to noise has been linked to negative impacts on attention, memory, and other cognitive functions. On the other hand, exposure to natural environments can help mitigate the negative impact of noise on cognitive performance. Natural environments, such as forests and green spaces, can help mask and reduce the levels of noise pollution, leading to improved cognitive function.

Natural environments provide opportunities for restorative experiences, such as listening to birds singing or water flowing. These experiences can have a positive impact on cognitive function by reducing stress and promoting a sense of calm.

Conclusion

In conclusion, cognition is a complex process that occurs in various regions of the brain, primarily the prefrontal, parietal, temporal, and occipital cortices. External factors, such as sleep, stress, nutrition, exercise, and environmental characteristics, can significantly impact cognitive performance. It is essential to maintain healthy habits and reduce distractions to optimize cognitive function.

References & Evaluation of Scientific Power

Abreu, R.V., Silva-Oliveira, E.M., Moraes, M.F.D., Pereira, G.S. and Moraes-Santos, T., 2011. Chronic coffee and caffeine ingestion effects on the cognitive function and antioxidant system of rat brains. Pharmacology Biochemistry and Behavior, 99(4), pp.659-664.

OVERVIEW: Abreu et al. investigated the long-term effects of coffee and caffeine ingestion on the cognitive function and antioxidant system in rat brains. They examined whether chronic consumption of coffee and caffeine could cause oxidative stress and impair cognitive function in rats.

STRENGTHS: The study conducted a comprehensive assessment of the cognitive function and antioxidant system in the rat brain after long-term coffee and caffeine ingestion. The researchers used several behavioural and biochemical tests to assess cognitive function and oxidative stress. The study provides valuable information about the long-term effects of coffee and caffeine on the brain.

LIMITATIONS: The study was conducted in rats, and the results may not be applicable to humans. The study only examined the effects of coffee and caffeine on cognitive function and antioxidant system in the brain. Other potential effects of coffee and caffeine, such as cardiovascular effects, were not assessed.

SCIENTIFIC POWER: MODERATE - The researchers used a comprehensive approach to assess the cognitive function and antioxidant system in the rat brain. However, the study was conducted on rats, and further research is needed to determine whether the findings are applicable to humans.

Agustí, A., García-Pardo, M.P., López-Almela, I., Campillo, I., Maes, M., Romaní-Pérez, M. and Sanz, Y., 2018. Interplay between the gut-brain axis, obesity and cognitive function. Frontiers in Neuroscience, 12, p.155.

OVERVIEW: Agustí et al. explored the interplay between the gut-brain axis, obesity, and cognitive function. They investigated how gut microbiota could affect cognitive function and how obesity could affect the gut microbiota and cognitive function.

STRENGTHS: The study provides a comprehensive understanding of the interplay between the gut-brain axis, obesity, and cognitive function. The researchers used several behavioural and biochemical tests to assess cognitive function and gut microbiota. The study provides valuable information about the role of the gut-brain axis in cognitive function.

LIMITATIONS: The study only examined the association between the gut microbiota, obesity, and cognitive function. The study does not establish a causal relationship between these variables.

SCIENTIFIC POWER: STRONG - The researchers used a comprehensive approach to assess the gut microbiota and cognitive function in humans. However, the study only establishes an association between the variables and does not establish causality. Further research is needed to determine the causal relationship between the gut-brain axis, obesity, and cognitive function.

Bae, J.H. and Song, W., 2019. Brain and Brawn: Role of Exercise-Induced Myokines. Journal of Obesity & Metabolic Syndrome, 28(3), p.145.

OVERVIEW: This scientific article explores the relationship between exercise and the brain through the release of chemicals called myokines. Myokines are produced in muscles during exercise and can enter the bloodstream to affect other parts of the body, including the brain. The authors discuss the potential benefits of myokines for brain function, including improving mood and cognitive abilities.

STRENGTHS: The article provides a clear explanation of the relationship between exercise and the brain, as well as the role of myokines in this relationship. The authors provide evidence from previous studies to support their claims about the benefits of myokines for brain function.

LIMITATIONS: The article does not discuss potential negative effects of exercise on the brain or the release of myokines. Additionally, the article does not address how different types or intensities of exercise may affect myokine release and subsequent brain function.

SCIENTIFIC POWER: MODERATE - The article provides a good overview of the current understanding of the relationship between exercise and the brain, but its focus on myokines as the main mechanism for this relationship may oversimplify a complex system.

Barnes, J.N., 2015. Exercise, cognitive function, and aging. Advances in physiology education, 39(2), pp.55-62.

OVERVIEW: This article discusses the relationship between exercise and cognitive function as people age. The author explains how physical activity can help maintain brain health and cognitive abilities as people age, including improving memory and attention.

STRENGTHS: The article provides a thorough review of previous studies on the relationship between exercise and cognitive function. The author explains the potential mechanisms for this relationship, including changes in brain structure and function, and provides evidence to support these claims.

LIMITATIONS: The article does not address how different types of exercise may affect cognitive abilities. Additionally, the article primarily focuses on the effects of exercise on aging adults and does not discuss how exercise may affect cognitive function in younger populations.

SCIENTIFIC POWER: STRONG - The article provides a comprehensive review of previous research on the relationship between exercise and cognitive function, and the author presents evidence-based explanations for this relationship.

Bowman, G.L., Silbert, L.C., Howieson, D., Dodge, H.H., Traber, M.G., Frei, B., Kaye, J.A., Shannon, J. and Quinn, J.F., 2012. Nutrient biomarker patterns, cognitive function, and MRI measures of brain aging. Neurology, 78(4), pp.241-249.

OVERVIEW: This study investigates the relationship between nutrient biomarker patterns and cognitive function, as well as brain aging as measured by magnetic resonance imaging (MRI). The researchers collected blood samples and MRI scans from 104 healthy older adults and analysed the levels of various nutrient biomarkers in their blood. They then assessed the participants’ cognitive function through various tests. The study found that certain nutrient biomarker patterns were associated with better cognitive function and less brain aging.

STRENGTHS: One strength of this study is that it used a large sample size of healthy older adults, which makes the findings more generalisable to the population. The use of MRI scans to assess brain aging also adds to the strength of the study, as it provides a more objective measure of age-related changes in the brain. Additionally, the study utilized sophisticated statistical methods to analyse the complex relationships between nutrient biomarkers, cognitive function, and brain aging.

LIMITATIONS: One limitation of this study is that it was cross-sectional, meaning that the researchers only measured the nutrient biomarkers and cognitive function at one point in time. This makes it difficult to determine causality or the direction of the relationship between nutrient biomarkers and cognitive function. Additionally, the study only assessed a limited number of nutrient biomarkers and did not account for other factors that may affect cognitive function, such as exercise or medication use.

SCIENTIFIC POWER: MODERATE to STRONG - While the study used a large sample size and objective measures of brain aging, the cross-sectional design limits the ability to establish causality and other factors that could influence cognitive function were not accounted for.

Bressler, S.L. and Menon, V., 2010. Large-scale brain networks in cognition: emerging methods and principles. Trends in Cognitive Sciences, 14(6), pp.277-290.

OVERVIEW: This article discusses the importance of studying large-scale brain networks in understanding cognition. The authors review emerging methods and principles used in studying these networks and discuss how they have improved our understanding of the brain's complex functioning.

STRENGTHS: The authors provide a comprehensive review of the different methods used in studying large-scale brain networks, including functional and structural connectivity measures. They also discuss the benefits and limitations of each method, which can help researchers in selecting the appropriate method for their study. The article also provides examples of how these methods have been used to study specific brain networks involved in various cognitive functions, such as attention and memory.

LIMITATIONS: One limitation of the article is that it is a review article and does not present new empirical data. However, it does provide an important synthesis of the current state of knowledge on large-scale brain networks in cognition. Another limitation is that the article is technical in nature and may be challenging for readers who do not have a strong background in neuroscience.

SCIENTIFIC POWER: MODERATE to STRONG - The authors are highly regarded experts in the field of cognitive neuroscience and provide a thorough review of the current state of knowledge on large-scale brain networks in cognition. The article is published in a highly respected journal in the field, which adds to its credibility. However, as a review article, it does not present new empirical data and may not provide as much scientific power as a primary research article.

Calderón-Garcidueñas, L., Mora-Tiscareño, A., Styner, M., Gómez-Garza, G., Zhu, H., Torres-Jardón, R., Carlos, E., Solorio-López, E., Medina-Cortina, H., Kavanaugh, M. and D'Angiulli, A., 2012. White matter hyperintensities, systemic inflammation, brain growth, and cognitive functions in children exposed to air pollution. Journal of Alzheimer's Disease, 31(1), pp.183-191.

OVERVIEW: This article explores the effects of air pollution on the developing brains of children. The study shows that children exposed to air pollution have an increased number of white matter hyperintensities (WMHs) in their brains, which is associated with systemic inflammation and a reduction in cognitive function.

STRENGTHS: The study is unique in that it investigates the effects of air pollution on the developing brains of children. The use of magnetic resonance imaging (MRI) to detect WMHs provides an objective measure of brain damage. The study also includes a large sample size of children from Mexico City, a highly polluted urban area.

LIMITATIONS: While the study shows a correlation between air pollution and WMHs, it cannot establish causality. Additionally, the study does not explore the specific pollutants that may be responsible for the observed effects.

SCIENTIFIC POWER: MODERATE to STRONG - The study has a large sample size and uses objective measures to detect brain damage. However, it is limited by its correlational design and the lack of investigation into specific pollutants.

Chen, W., Wang, L., You, W. and Shan, T., 2021. Myokines mediate the cross talk between skeletal muscle and other organs. Journal of Cellular Physiology, 236(4), pp.2393-2412.

OVERVIEW: This article examines the role of myokines, proteins released by skeletal muscle during exercise, in communicating with other organs in the body. The study explores how myokines can influence metabolism, immune function, and brain health.

STRENGTHS: The study provides a comprehensive review of the current literature on myokines and their potential roles in various physiological processes. The authors also propose a model for how myokines can mediate communication between skeletal muscle and other organs.

LIMITATIONS: The study is primarily a review of existing literature and does not present any new experimental data. The proposed model for myokine communication is speculative and requires further investigation.

SCIENTIFIC POWER: MODERATE - While the study does not present any new experimental data, it provides a thorough review of the current literature and proposes a novel model for myokine communication. However, further experimental studies are needed to validate the proposed model.

Coelho-Júnior, H.J., Oliveira Gonçalves, I.D., Sampaio, R.A.C., Sampaio, P.Y.S., Lusa Cadore, E., Calvani, R., Picca, A., Izquierdo, M., Marzetti, E. and Uchida, M.C., 2020. Effects of combined resistance and power training on cognitive function in older women: a randomized controlled trial. International Journal of Environmental Research and Public Health, 17(10), p.3435.

OVERVIEW: The study aimed to investigate the effects of resistance and power training on cognitive function in older women. The study involved 38 older women, who were randomly assigned to either the training or control group. The training group underwent 12 weeks of combined resistance and power training, while the control group received no intervention. Cognitive function was assessed using neuropsychological tests before and after the intervention.

STRENGTHS: The study used a randomised controlled trial design, which is considered a gold standard for evaluating the efficacy of an intervention. The neuropsychological tests used to assess cognitive function were standardised and validated, enhancing the reliability of the results. Additionally, the study focused on a population group (older women) that is at high risk for cognitive decline, making the findings particularly relevant.

LIMITATIONS: The study had a relatively small sample size, which could limit the generalisability of the findings to the wider population. Additionally, the study only focused on women, so it is unclear whether the findings can be applied to men. The study did not assess the long-term effects of the intervention on cognitive function.

SCIENTIFIC POWER: MODERATE - The randomised controlled trial design and the use of standardised and validated neuropsychological tests to assess cognitive function are positive. However, the small sample size and the lack of long-term follow-up limit the generalisability and applicability of the findings.

Davenport, M.H., Hogan, D.B., Eskes, G.A., Longman, R.S. and Poulin, M.J., 2012. Cerebrovascular reserve: the link between fitness and cognitive function? Exercise and Sport Sciences Reviews, 40(3), pp.153-158.

OVERVIEW: The study aimed to investigate the relationship between cerebrovascular reserve (the ability of blood vessels to maintain adequate blood flow to the brain) and cognitive function in older adults. The study involved 11 older adults (age 66-73), who underwent tests to assess cerebrovascular reserve, cardiovascular fitness, and cognitive function.

STRENGTHS: The study used objective measures to assess cerebrovascular reserve and cardiovascular fitness, enhancing the reliability of the results. The study also used standardised tests to assess cognitive function, enhancing the validity of the results. The study focused on a population group (older adults) that is at high risk for cognitive decline, making the findings particularly relevant.

LIMITATIONS: The study had a very small sample size, which could limit the generalisability of the findings to the wider population. Additionally, the study only focused on older adults, so it is unclear whether the findings can be applied to younger populations. The study did not assess the long-term effects of cerebrovascular reserve and fitness on cognitive function.

SCIENTIFIC POWER: LOW to MODERATE - Overall, the study has low to moderate scientific power due to the very small sample size and the lack of long-term follow-up. However, the use of objective measures and standardised tests enhances the reliability and validity of the findings.

de Oliveira, J., Engel, D.F., de Paula, G.C., Dos Santos, D.B., Lopes, J.B., Farina, M., Moreira, E.L. and de Bem, A.F., 2020. High cholesterol diet exacerbates blood-brain barrier disruption in LDLr–/–mice: impact on cognitive function. Journal of Alzheimer's Disease, 78(1), pp.97-115.

OVERVIEW: In this scientific article, researchers investigate the relationship between a high-cholesterol diet, blood-brain barrier (BBB) disruption, and cognitive function in mice. The study aims to understand how a high-cholesterol diet affects the brain's health and function. The authors also explore potential mechanisms that contribute to these effects.

STRENGTHS: The study used a mouse model, which allows for precise control of experimental conditions and the ability to investigate mechanisms that are not feasible in human studies. The authors employed various tests to evaluate cognitive function, including the Morris water maze and fear conditioning, which are well-established tests of learning and memory. The study also included an assessment of BBB permeability using Evans blue dye, which allows for visualization of areas of BBB disruption. The authors analysed several signalling pathways involved in BBB disruption and cognitive function, which provides insights into the underlying mechanisms involved.

LIMITATIONS: The study was conducted on mice, so it is unclear how well the findings translate to humans. Additionally, the study only evaluated the effects of a high-cholesterol diet and did not investigate other dietary factors or lifestyle factors that may contribute to cognitive function.

SCIENTIFIC POWER: MODERATE - Overall, this study provides valuable insights into the relationship between a high-cholesterol diet, BBB disruption, and cognitive function in mice. The study used multiple measures to evaluate cognitive function and BBB permeability and identified potential mechanisms underlying these effects. However, because the study was conducted in mice, further research is needed to determine the relevance of these findings to human health. Additionally, future studies should investigate other factors that may impact cognitive function in humans, such as diet and lifestyle factors.

Ding, Q., Vaynman, S., Akhavan, M., Ying, Z. and Gomez-Pinilla, F., 2006. Insulin-like growth factor I interfaces with brain-derived neurotrophic factor-mediated synaptic plasticity to modulate aspects of exercise-induced cognitive function. Neuroscience, 140(3), pp.823-833.

OVERVIEW: This scientific article investigates how exercise impacts cognitive function through the interaction of two signalling molecules, insulin-like growth factor I (IGF-I), and brain-derived neurotrophic factor (BDNF). The study aims to understand how exercise-induced increases in these molecules can enhance cognitive function.

STRENGTHS: The study utilised a rat model, which allows for precise control of experimental conditions and enables investigation of mechanisms that are not feasible in human studies. The authors employed various cognitive tests, including the Morris water maze and the passive avoidance test, which are well-established tests of learning and memory. The authors also analysed multiple signalling pathways involved in cognitive function to provide insights into the mechanisms of exercise-induced cognitive enhancement.

LIMITATIONS: The study was conducted on rats, so it is unclear how well the findings translate to humans. Additionally, the study only investigated the effects of exercise on IGF-I and BDNF signalling and did not explore other potential mechanisms that may contribute to exercise-induced cognitive enhancement.

SCIENTIFIC POWER: MODERATE to STRONG - Overall, this study provides valuable insights into the mechanisms underlying exercise-induced cognitive enhancement through the interaction of IGF-I and BDNF signalling pathways. The study utilised multiple measures to evaluate cognitive function and signalling pathways, and the results suggest that exercise-induced increases in IGF-I and BDNF can enhance cognitive function. However, because the study was conducted on rats, further research is needed to determine the relevance of these findings to human health. Additionally, future studies should investigate other potential mechanisms that may contribute to exercise-induced cognitive enhancement.

Donohoe, R.T. and Benton, D., 1999. Cognitive functioning is susceptible to the level of blood glucose. Psychopharmacology, 145, pp.378-385.

OVERVIEW: This study investigated the effect of blood glucose levels on cognitive function in humans. Participants completed cognitive tasks after consuming a drink with either a high or low level of glucose. The study found that cognitive function was better in the high glucose condition compared to the low glucose condition.

STRENGTHS: This study used a randomised, double-blind design, which helps to control for confounding variables. The cognitive tasks used were standardised and validated, which increases the reliability of the findings. The study also included a large sample size of 82 participants.

LIMITATIONS: The study only examined the acute effects of glucose on cognitive function, and the long-term effects are unknown. The cognitive tasks used were limited to a few specific areas, and the study did not investigate the effects of glucose on other cognitive domains. The study only included healthy young adults, so the findings may not generalise to other populations.

SCIENTIFIC POWER: MODERATE to STRONG -While this study had some limitations, it used rigorous methods and a large sample size, which increases the strength of the findings.

Ferris, L.T., Williams, J.S. and Shen, C.L., 2007. The effect of acute exercise on serum brain-derived neurotrophic factor levels and cognitive function. Medicine & Science in Sports & Exercise, 39(4), pp.728-734.

OVERVIEW: This study investigated the effect of acute exercise on cognitive function and levels of a protein called brain-derived neurotrophic factor (BDNF) in the blood. Participants completed cognitive tasks before and after either cycling or resting for 30 minutes. Blood samples were taken to measure BDNF levels. The study found that cognitive function improved and BDNF levels increased in the exercise group compared to the rest group.

STRENGTHS: This study used a randomised, controlled design, which helps to control for confounding variables. The cognitive tasks used were standardised and validated, which increases the reliability of the findings. The study also included a large sample size of 31 participants.

LIMITATIONS: The study only examined the acute effects of exercise on cognitive function and BDNF levels, and the long-term effects are unknown. The study only included healthy young adults, so the findings may not generalise to other populations. The study did not investigate the effects of different types or intensities of exercise on cognitive function.

SCIENTIFIC POWER: MODERATE to STRONG - While this study had some limitations, it used rigorous methods and a large sample size, which increases the strength of the findings. The use of a control group also increases the reliability of the findings.

Gareau, M.G., 2014. Microbiota-gut-brain axis and cognitive function. Microbial endocrinology: The microbiota-gut-brain axis in health and disease, pp.357-371.

OVERVIEW: The article explores the relationship between gut bacteria and cognitive function, also known as the microbiota-gut-brain axis. The article highlights how the trillions of bacteria in our gut, collectively known as the microbiome, may play an important role in the communication between our gut and brain. The article discusses research that suggests that the composition of the microbiome can influence brain function and behaviour, including cognitive processes such as learning and memory.

STRENGTHS: The article provides a clear and concise overview of the current understanding of the microbiota-gut-brain axis and how gut bacteria can influence cognitive function. It also discusses potential mechanisms for how this communication may occur, such as through the immune system, neural pathways, and the production of neurotransmitters.

LIMITATIONS: The article is a review of existing research and does not present any new empirical findings. It also focuses primarily on animal studies, and it is unclear how applicable these findings are to humans. Additionally, the article does not provide any recommendations for how to improve gut health to promote cognitive function.

SCIENTIFIC POWER: MODERATE to STRONG - The article presents a well-supported hypothesis based on existing research, but further empirical research is needed to fully understand the relationship between gut bacteria and cognitive function in humans.

Glisky, E.L., 2007. Changes in cognitive function in human aging. Brain Aging, pp.3-20.

OVERVIEW: The article explores the changes in cognitive function that occur as we age. The article describes how aging can affect different cognitive domains, such as attention, memory, and executive function. It also discusses how changes in brain structure and function may contribute to these changes in cognitive function.

STRENGTHS: The article provides a comprehensive overview of the current understanding of cognitive changes that occur with aging. It covers a range of cognitive domains and provides detailed explanations of the underlying changes in brain structure and function.

LIMITATIONS: The article is a review of existing research and does not present any new empirical findings. It also focuses primarily on age-related changes in healthy adults and does not discuss cognitive changes associated with dementia or other neurological disorders. Additionally, the article does not provide any recommendations for how to prevent or mitigate age-related cognitive decline.

SCIENTIFIC POWER: MODERATE to STRONG - The article presents a well-supported hypothesis based on existing research, but further empirical research is needed to fully understand the mechanisms underlying age-related cognitive changes and to develop effective interventions.

Guxens, M., Lubczyńska, M.J., Muetzel, R.L., Dalmau-Bueno, A., Jaddoe, V.W., Hoek, G., van der Lugt, A., Verhulst, F.C., White, T., Brunekreef, B. and Tiemeier, H., 2018. Air pollution exposure during foetal life, brain morphology, and cognitive function in school-age children. Biological Psychiatry, 84(4), pp.295-303.

OVERVIEW: This study investigates the relationship between air pollution exposure during foetal life, brain structure, and cognitive function in school-age children. The researchers used magnetic resonance imaging (MRI) to measure brain morphology and cognitive tests to evaluate cognitive function in the children. They found that exposure to air pollution during foetal life was associated with reductions in certain brain structures and poorer cognitive performance.

STRENGTHS: The study used a large sample size of over 2,000 children and controlled for various confounding factors such as maternal education and smoking. The use of MRI and cognitive tests provides objective measures of brain structure and function. The study design was longitudinal, allowing for the examination of the effects of air pollution exposure during foetal life on later cognitive function.

LIMITATIONS: The study did not measure air pollution exposure after birth, which limits the ability to assess the relative contributions of prenatal and postnatal exposure. The study also did not measure the exact timing or duration of air pollution exposure during foetal life, which may be important for understanding the effects on cognitive function. Although the study controlled for various confounding factors, it is still possible that other unmeasured factors may have influenced the results.

SCIENTIFIC POWER: MODERATE to STRONG - The large sample size, longitudinal design, and objective measures of brain structure and cognitive function are strengths of the study. However, the lack of detailed information on the timing and duration of air pollution exposure during foetal life and the potential influence of unmeasured confounding factors are limitations. Overall, the study provides evidence for the detrimental effects of air pollution exposure during foetal life on cognitive function, but more research is needed to establish causality and to identify the specific mechanisms underlying this association.

Hamilton, G.F. and Rhodes, J.S., 2015. Exercise regulation of cognitive function and neuroplasticity in the healthy and diseased brain. Progress in Molecular Biology and Translational Science, 135, pp.381-406.

OVERVIEW: This review article discusses the effects of exercise on cognitive function and neuroplasticity in both healthy and diseased brains. The authors review various studies that have examined the effects of exercise on brain structure and function, including animal studies, neuroimaging studies, and clinical trials. They conclude that exercise can improve cognitive function and promote neuroplasticity in both healthy individuals and those with neurological disorders.

STRENGTHS: The review includes a comprehensive analysis of various types of studies, providing a broad perspective on the effects of exercise on cognitive function and neuroplasticity. The authors provide detailed explanations of the underlying mechanisms involved in these effects, such as changes in neurotransmitter levels and growth factors. The review also discusses the potential clinical implications of exercise for the prevention and treatment of various neurological disorders.

LIMITATIONS: The review does not provide a systematic meta-analysis of the various studies, which may limit the ability to draw firm conclusions about the magnitude of the effects of exercise. The authors do not discuss potential limitations of the individual studies included in the review, such as differences in study design and participant characteristics. The review focuses mainly on animal and neuroimaging studies, which may not fully reflect the effects of exercise on cognitive function and neuroplasticity in humans.

SCIENTIFIC POWER: MODERATE to STRONG - The review provides a comprehensive analysis of various types of studies, including animal studies, neuroimaging studies, and clinical trials, which strengthens the evidence for the effects of exercise on cognitive function and neuroplasticity. However, the lack of a systematic meta-analysis and the potential limitations of the individual studies reviewed must be considered.

Hashimoto, T., Tsukamoto, H., Ando, S. and Ogoh, S., 2021. Effect of exercise on brain health: The potential role of lactate as a myokine. Metabolites, 11(12), p.813.

OVERVIEW: This article explores the potential link between exercise and brain health, specifically examining the role of lactate as a myokine. Myokines are signalling molecules that are released from muscles during exercise and may have positive effects on brain health. The authors discuss the current research on this topic and provide suggestions for future studies.

STRENGTHS: The article provides a comprehensive overview of the current research on the topic and highlights potential mechanisms for how exercise may impact brain health. The discussion of the role of lactate as a myokine is particularly interesting and could have important implications for future studies. The article is also well-written and easy to understand.

LIMITATIONS: The article does not present any new research or findings, but rather summarizes existing studies. Additionally, while the authors provide suggestions for future studies, there is still much that is unknown about the potential link between exercise and brain health.

SCIENTIFIC POWER: MODERATE to STRONG - The article is based on a thorough review of existing research and provides a well-supported argument for the potential link between exercise and brain health. However, as the article does not present any new research or findings, its scientific power is limited.

Hoffmann, C. and Weigert, C., 2017. Skeletal muscle as an endocrine organ: the role of myokines in exercise adaptations. Cold Spring Harbor Perspectives in Medicine, 7(11), p.a029793.

OVERVIEW: This article explores the role of skeletal muscle as an endocrine organ and how it communicates with other organs and tissues through the release of myokines. The authors discuss the different types of myokines and their potential effects on various physiological processes, including exercise adaptations.

STRENGTHS: The article provides a comprehensive overview of the role of myokines in exercise adaptations and highlights the potential implications of this research for human health. The discussion of the different types of myokines and their effects on various physiological processes is informative and well-supported by existing research.

LIMITATIONS: This article does not present any new research or findings, but rather summarizes existing studies. Additionally, the role of myokines in exercise adaptations is still a relatively new area of research, and there is much that is still unknown about how these molecules function in the body.

SCIENTIFIC POWER: MODERATE - While the article provides a thorough overview of the role of myokines in exercise adaptations, its scientific power is limited by the fact that it does not present any new research or findings. However, the article's focus on an emerging area of research makes it an important contribution to the field.

Kamijo, K., Hayashi, Y., Sakai, T., Yahiro, T., Tanaka, K. and Nishihira, Y., 2009. Acute effects of aerobic exercise on cognitive function in older adults. Journals of Gerontology: Series B, 64(3), pp.356-363.

OVERVIEW: This article investigated the acute effects of aerobic exercise on cognitive function in older adults.

STRENGTHS: This study involved a randomised controlled trial with a relatively large sample size (n=48) of healthy older adults. The study used a battery of cognitive tests to assess various aspects of cognitive function, including attention, memory, and processing speed. The study also used a well-established exercise protocol to ensure consistency in the exercise intervention.

LIMITATIONS: The study only investigated the acute effects of a single bout of aerobic exercise on cognitive function, so it is unclear whether these effects persist over time or with repeated exercise. Additionally, the study did not investigate the underlying mechanisms of the observed effects.

SCIENTIFIC POWER: MODERATE - The study design and methods were sound, but the limited scope of investigation and lack of exploration of underlying mechanisms lower its scientific power.

Kim, S., Choi, J.Y., Moon, S., Park, D.H., Kwak, H.B. and Kang, J.H., 2019. Roles of myokines in exercise-induced improvement of neuropsychiatric function. Pflügers Archiv-European Journal of Physiology, 471, pp.491-505.

OVERVIEW: This article explored the roles of myokines, molecules produced by skeletal muscles during exercise, in exercise-induced improvement of neuropsychiatric function.

STRENGTHS: This review article provides a comprehensive overview of the current knowledge on the roles of myokines in exercise-induced improvement of neuropsychiatric function. The article highlights potential mechanisms through which myokines may exert their effects, such as promoting neurogenesis and modulating neurotransmitter function.

LIMITATIONS: As a review article, this study did not involve original data collection or analysis. Therefore, the conclusions drawn are limited by the quality of the studies included in the review.

SCIENTIFIC POWER: MODERATE to STRONG - While not an original study, this review article provides a comprehensive summary of the current state of knowledge on the topic, which is a strength. However, the conclusions drawn are still limited by the quality of the studies included in the review.

Kramer, A.F., Colcombe, S.J., McAuley, E., Eriksen, K.I., Scalf, P., Jerome, G.J., Marquez, D.X., Elavsky, S. and Webb, A.G., 2003. Enhancing brain and cognitive function of older adults through fitness training. Journal of Molecular Neuroscience, 20, pp.213-221.

OVERVIEW: This study examined the effects of a fitness training program on the cognitive and brain functions of older adults. The participants underwent six months of aerobic exercise, strength training, or balance and toning exercises. The study found that fitness training improved the participants' cognitive abilities and brain functions, such as attention, memory, and executive control.

STRENGTHS: This study had a rigorous design and used objective measures to assess cognitive and brain function. The study also had a large sample size and a control group, which allowed for a comparison of the effects of different types of exercises.

LIMITATIONS: The study did not examine the long-term effects of fitness training on cognitive function. The study also did not investigate the mechanisms by which fitness training improved cognitive and brain function.

SCIENTIFIC POWER: MODERATE to STRONG - This study had a well-designed randomised controlled trial and used objective measures to assess cognitive and brain function, which increases the scientific power of the study.

Leisman, G., Moustafa, A.A. and Shafir, T., 2016. Thinking, walking, talking: integratory motor and cognitive brain function. Frontiers in Public Health, p.94.

OVERVIEW: This review article explored the connection between motor and cognitive functions in the brain. The authors suggest that motor and cognitive functions are closely intertwined, and that activities that involve both, such as walking and talking, can have positive effects on brain health and cognitive function.

STRENGTHS: This article provides a comprehensive overview of the current research on the relationship between motor and cognitive functions. The authors draw from a variety of studies and disciplines to support their argument. The article also highlights the potential benefits of integrative activities on brain health and cognitive function.

LIMITATIONS: The article does not provide a clear explanation of the mechanisms by which motor and cognitive functions are connected. The authors also suggest that future research is needed to fully understand the relationship between motor and cognitive functions.

SCIENTIFIC POWER: MODERATE - This article provides a comprehensive review of the current research on the topic, but it does not present any original research or experiments. The article's conclusions are based on the findings of other studies, which may have varying degrees of scientific power.

Li, L., Wang, Z. and Zuo, Z., 2013. Chronic intermittent fasting improves cognitive functions and brain structures in mice. PloS One, 8(6), p.e66069.

OVERVIEW: This study aimed to investigate the effect of chronic intermittent fasting (CIF) on cognitive function and brain structures in mice. The researchers used various behavioural tests and brain imaging techniques to compare the cognitive abilities and brain structures of mice that underwent CIF with those that did not.

STRENGTHS: This study is valuable because it provides evidence that CIF can improve cognitive function and brain structures in mice. It also used multiple behavioural tests and imaging techniques to ensure accurate results.

LIMITATIONS: The study only used mice as subjects, so it is unclear if the same results would be found in humans. Additionally, the study did not investigate the long-term effects of CIF on cognitive function and brain structures.

SCIENTIFIC POWER: MODERATE - This study provides strong evidence that CIF can improve cognitive function and brain structures in mice, but it is unclear if these findings can be translated to humans.

Lieberman, H.R., 2003. Nutrition, brain function and cognitive performance. Appetite, 40(3), pp.245-254.

OVERVIEW: This article explores the relationship between nutrition and cognitive performance. It discusses how different nutrients, such as carbohydrates, proteins, and fats, affect brain function and how inadequate nutrition can lead to cognitive deficits.

STRENGTHS: This article is important because it highlights the crucial role of nutrition in cognitive performance. It also provides a comprehensive overview of how different nutrients affect brain function.

LIMITATIONS: The article focuses mainly on the effects of inadequate nutrition on cognitive function and does not provide much information on how optimal nutrition can enhance cognitive performance.

SCIENTIFIC POWER: MODERATE - This article provides valuable information on the relationship between nutrition and cognitive performance, but it is mostly based on observational studies and does not provide conclusive evidence.

Manolio, T.A., Olson, J. and Longstreth Jr, W.T., 2003. Hypertension and cognitive function: pathophysiologic effects of hypertension on the brain. Current Hypertension Reports, 5(3), pp.255-261.

OVERVIEW: Hypertension, or high blood pressure, is a common condition that affects many people worldwide. This article explores the connection between hypertension and cognitive function, or how well the brain processes information. It describes the various ways in which hypertension can damage the brain and lead to cognitive impairment.

STRENGTHS: The article provides a comprehensive overview of the relationship between hypertension and cognitive function, including the different ways in which hypertension affects the brain. It discusses the various mechanisms that can lead to cognitive decline, such as reduced blood flow to the brain and damage to brain cells.

LIMITATIONS: The article does not provide a detailed analysis of the specific types of cognitive deficits that can result from hypertension. Additionally, it focuses primarily on the pathophysiology of hypertension and does not delve deeply into the psychological or social factors that may influence the relationship between hypertension and cognitive function.

SCIENTIFIC POWER: MODERATE to STRONG - The article provides a thorough overview of the research on hypertension and cognitive function, but its lack of detail regarding specific cognitive deficits limits its scientific power.

Marsland, A.L., Gianaros, P.J., Kuan, D.C.H., Sheu, L.K., Krajina, K. and Manuck, S.B., 2015. Brain morphology links systemic inflammation to cognitive function in midlife adults. Brain, Behavior, and Immunity, 48, pp.195-204.

OVERVIEW: This article investigates the relationship between systemic inflammation and cognitive function in midlife adults. It discusses how chronic inflammation, which can result from various factors such as stress and poor diet, can damage the brain and impair cognitive abilities.

STRENGTHS: The article provides a detailed analysis of the link between inflammation and cognitive function, including the mechanisms by which inflammation can lead to brain damage. It also discusses the implications of this research for understanding age-related cognitive decline and for developing interventions to improve cognitive function.

LIMITATIONS: The study relies on cross-sectional data, which means that it cannot establish a causal relationship between inflammation and cognitive function. Additionally, the study does not consider other potential factors that could be contributing to cognitive decline in midlife adults, such as genetic or environmental factors.

SCIENTIFIC POWER: MODERATE - While the article provides a thorough analysis of the relationship between inflammation and cognitive function, the limitations of the study design and the lack of consideration for other potential factors limit its scientific power.

Moheet, A., Mangia, S. and Seaquist, E.R., 2015. Impact of diabetes on cognitive function and brain structure. Annals of the New York Academy of Sciences, 1353(1), pp.60-71.

OVERVIEW: Diabetes is a chronic metabolic disorder that affects multiple organ systems in the body, including the brain. This review article examines the impact of diabetes on cognitive function and brain structure. The authors discuss the mechanisms through which diabetes can damage the brain, such as through changes in blood sugar levels and insulin resistance. They also explore the effects of diabetes on brain structure, including alterations in brain volume and white matter integrity. The article concludes with a discussion of the potential treatments for cognitive dysfunction in diabetes, such as blood sugar control and lifestyle modifications.

STRENGTHS: The article provides a comprehensive overview of the impact of diabetes on cognitive function and brain structure. The authors summarise the available evidence from both animal and human studies. They also discuss potential mechanisms through which diabetes can lead to cognitive dysfunction and brain changes.

LIMITATIONS: The article does not discuss the impact of different types of diabetes on cognitive function and brain structure. Additionally, the authors do not discuss the potential role of medications used to treat diabetes on cognitive function.

SCIENTIFIC POWER: MODERATE - The review article provides a comprehensive overview of the available evidence on the topic of diabetes and cognitive function. However, it does not provide new research data, and some areas are not covered in depth.

Nyberg, F. and Hallberg, M., 2013. Growth hormone and cognitive function. Nature Reviews Endocrinology, 9(6), pp.357-365.

OVERVIEW: Growth hormone (GH) is a hormone that is primarily produced by the pituitary gland and plays a crucial role in growth and development. This review article examines the relationship between GH and cognitive function. The authors discuss the potential mechanisms through which GH can affect cognitive function, such as through changes in brain structure and function. They also explore the effects of GH on specific cognitive domains, such as memory and attention. The article concludes with a discussion of the potential clinical applications of GH for cognitive dysfunction.

STRENGTHS: The article provides a comprehensive overview of the relationship between GH and cognitive function. The authors summarise the available evidence from both animal and human studies. They also discuss potential mechanisms through which GH can affect cognitive function and explore the effects of GH on specific cognitive domains.

LIMITATIONS: The article does not provide a detailed analysis of the potential side effects of GH therapy for cognitive dysfunction. Additionally, the authors do not discuss the potential limitations of using GH as a treatment for cognitive dysfunction.

SCIENTIFIC POWER: MODERATE - The review article provides a comprehensive overview of the available evidence on the topic of GH and cognitive function. However, it does not provide new research data, and some areas are not covered in depth.

Pang, T.Y. and Hannan, A.J., 2013. Enhancement of cognitive function in models of brain disease through environmental enrichment and physical activity. Neuropharmacology, 64, pp.515-528.

OVERVIEW: This article discusses the potential benefits of environmental enrichment and physical activity in improving cognitive function in animal models of brain diseases, such as Alzheimer's disease and Parkinson's disease. The authors examine the effects of enriched environments, such as larger cages and access to toys, and physical activity on brain structure, neurotransmitter levels, and cognitive performance.

STRENGTHS: The article provides a comprehensive review of studies that demonstrate the positive effects of environmental enrichment and physical activity on cognitive function in animal models of brain diseases. The authors highlight the potential mechanisms underlying these effects, including changes in neurotransmitter levels and brain plasticity. The article also discusses the potential implications of these findings for human health and disease.

LIMITATIONS: While the studies reviewed in the article demonstrate the positive effects of environmental enrichment and physical activity on cognitive function, the authors note that it is still unclear how much of these benefits can be translated to human populations. Additionally, the specific mechanisms underlying the observed effects are not fully understood, and more research is needed to better understand how these interventions affect brain function and structure.

SCIENTIFIC POWER: MODERATE to STRONG - The article provides a thorough review of studies demonstrating the positive effects of environmental enrichment and physical activity on cognitive function in animal models of brain diseases, and the authors provide a detailed discussion of the potential underlying mechanisms. However, the translation of these findings to humans is still uncertain, and more research is needed to fully understand the observed effects.

Parletta, N., Milte, C.M. and Meyer, B.J., 2013. Nutritional modulation of cognitive function and mental health. The Journal of Nutritional Biochemistry, 24(5), pp.725-743.

OVERVIEW: This article discusses the role of nutrition in cognitive function and mental health. The authors review studies examining the effects of various nutrients, including omega-3 fatty acids, vitamins, and minerals, on cognitive function and mental health outcomes such as depression and anxiety.

STRENGTHS: The article provides a comprehensive review of studies examining the effects of nutrition on cognitive function and mental health outcomes. The authors discuss potential mechanisms underlying these effects, including the effects of nutrients on brain structure and function. The article also provides practical recommendations for improving nutrition and promoting cognitive function and mental health.

LIMITATIONS: While the studies reviewed in the article demonstrate the positive effects of nutrition on cognitive function and mental health, the authors note that more research is needed to fully understand the observed effects and to identify the optimal dietary patterns for promoting cognitive function and mental health. Additionally, the studies reviewed in the article vary in their methodologies, making it difficult to draw clear conclusions.

SCIENTIFIC POWER: MODERATE to STRONG - The article provides a comprehensive review of studies examining the effects of nutrition on cognitive function and mental health outcomes. The authors provide a detailed discussion of potential underlying mechanisms and practical recommendations for improving nutrition. However, more research is needed to fully understand the observed effects and to identify the optimal dietary patterns for promoting cognitive function and mental health.

Ploughman, M., 2008. Exercise is brain food: the effects of physical activity on cognitive function. Developmental Neurorehabilitation, 11(3), pp.236-240.

OVERVIEW: This article focuses on how exercise affects cognitive function, which refers to mental abilities such as memory, attention, and reasoning. The author explains that physical activity can improve cognitive function in people of all ages and provides evidence from studies conducted on animals and humans to support this claim. The article also discusses the underlying mechanisms behind how exercise enhances cognitive function and how it may protect the brain against degenerative diseases.

STRENGTHS: The article provides a clear and concise overview of the current research on how exercise affects cognitive function. It offers evidence from various studies conducted on different populations, including animals and humans, to support its claims. The author also explains the underlying mechanisms behind how exercise improves cognitive function, such as increased blood flow and the release of growth factors, making it easy for readers to understand.

LIMITATIONS: While the article provides a good overview of the current research, it does not discuss the limitations of the studies it cites. For example, some studies may have had small sample sizes or may not have considered other factors that could have influenced the results.

SCIENTIFIC POWER: MODERATE to STRONG - The article provides a good overview of the current research on how exercise affects cognitive function, and it provides evidence from various studies conducted on different populations, which strengthens its claims. However, the article does not discuss the limitations of the studies it cites, which could weaken its scientific power.

Poulose, S.M., Miller, M.G., Scott, T. and Shukitt-Hale, B., 2017. Nutritional factors affecting adult neurogenesis and cognitive function. Advances in Nutrition, 8(6), pp.804-811.

OVERVIEW: This article examines how nutritional factors affect adult neurogenesis, which is the process of generating new neurons in the adult brain, and cognitive function. The authors explain the importance of nutrition in maintaining cognitive function and how different nutrients, such as omega-3 fatty acids and polyphenols, can affect neurogenesis and cognitive function. The article also discusses the potential benefits of using dietary interventions to prevent or treat cognitive decline.

STRENGTHS: The article provides a comprehensive overview of the research on how nutritional factors affect neurogenesis and cognitive function, citing numerous studies conducted on animals and humans. It also provides an explanation of the underlying mechanisms behind how different nutrients affect the brain, making it easy for readers to understand.

LIMITATIONS: While the article provides a good overview of the research, some of the studies cited may not have been conducted on humans or may have had small sample sizes, which could limit the applicability of the findings.

SCIENTIFIC POWER: MODERATE - The article provides a comprehensive overview of the research on how nutritional factors affect neurogenesis and cognitive function, and it cites numerous studies conducted on animals and humans. However, some of the studies cited may not be directly applicable to humans, which could limit its scientific power.

Power, M.C., Adar, S.D., Yanosky, J.D. and Weuve, J., 2016. Exposure to air pollution as a potential contributor to cognitive function, cognitive decline, brain imaging, and dementia: a systematic review of epidemiologic research. Neurotoxicology, 56, pp.235-253.

OVERVIEW: This article is a systematic review that explores the relationship between exposure to air pollution and cognitive function, cognitive decline, brain imaging, and dementia. The authors gathered data from various epidemiological studies and analysed the evidence to determine if there is a link between air pollution and cognitive function.

STRENGTHS: The article includes a comprehensive review of the available literature and uses rigorous methodology to identify and evaluate studies. The authors also use a variety of outcome measures, including cognitive function tests and brain imaging, to examine the relationship between air pollution and cognitive health. The article is well-organised and provides a clear summary of the findings.

LIMITATIONS: One limitation of this study is that it relies solely on observational studies, which cannot establish causality. Additionally, the studies included in the review used different air pollution measures and cognitive function tests, which may limit comparability across studies.

SCIENTIFIC POWER: MODERATE - The systematic review is a powerful tool to evaluate the available literature on a specific topic, but the authors only rely on observational studies, which may not prove causality. Overall, the article provides strong evidence that exposure to air pollution may be linked to cognitive decline and dementia, but further research is needed to establish causality and to better understand the specific mechanisms involved.

Radák, Z., Kaneko, T., Tahara, S., Nakamoto, H., Pucsok, J., Sasvári, M., Nyakas, C. and Goto, S., 2001. Regular exercise improves cognitive function and decreases oxidative damage in rat brain. Neurochemistry International, 38(1), pp.17-23.

OVERVIEW: This article examines the impact of regular exercise on cognitive function and oxidative damage in the rat brain. The authors conducted experiments on rats to explore the effects of physical exercise on cognitive function and the levels of oxidative damage in the brain.

STRENGTHS: The article uses a well-designed experimental study with a control group to examine the impact of regular exercise on cognitive function and oxidative damage in the rat brain. The authors used a variety of cognitive tests and biochemical measures to evaluate the effects of exercise. The study is well-documented and uses a sample size large enough to support the conclusions.

LIMITATIONS: One limitation of this study is that the findings may not be directly generalisable to humans, as rat models may not perfectly mimic human physiology. Additionally, the study only looks at the effects of exercise on oxidative damage and cognitive function in the short term, and it is unclear whether the effects would persist over a longer period.

SCIENTIFIC POWER: MODERATE to STRONG - The article uses an experimental study with a control group to examine the impact of physical exercise on cognitive function and oxidative damage in the rat brain, which is a powerful design. However, the findings may not be directly generalisable to humans, and the study only examines short-term effects. Overall, the article provides evidence that physical exercise may improve cognitive function and decrease oxidative damage in the brain, but further research is needed to better understand the mechanisms involved and to confirm these findings in humans.

Sarter, M., Berntson, G.G. and Cacioppo, J.T., 1996. Brain imaging and cognitive neuroscience: Toward strong inference in attributing function to structure. American Psychologist, 51(1), p.13.

OVERVIEW: This article discusses the use of brain imaging techniques to study cognitive function and neuroscience. The authors argue that by combining different types of brain imaging methods, researchers can more accurately attribute cognitive functions to specific brain structures.

STRENGTHS: The article provides a clear overview of the benefits and limitations of different brain imaging techniques, including positron emission tomography (PET) and magnetic resonance imaging (MRI). The authors also highlight the importance of experimental design in cognitive neuroscience research, emphasizing the need for strong inference and carefully controlled studies.

LIMITATIONS: The article is somewhat technical in nature and may be difficult for readers without a background in neuroscience to fully understand. Additionally, the authors do not discuss the potential limitations of brain imaging techniques, such as their high cost and the difficulty of interpreting complex data.

SCIENTIFIC POWER: MODERATE - The article is well-written and provides a useful overview of brain imaging techniques in cognitive neuroscience. However, it does not present any new experimental data or significantly advance the field.

Sellbom, K.S. and Gunstad, J., 2012. Cognitive function and decline in obesity. Journal of Alzheimer's Disease, 30(s2), pp.S89-S95.

OVERVIEW: This article explores the relationship between obesity and cognitive function, focusing on the potential for obesity to contribute to cognitive decline and dementia in later life.

STRENGTHS: The article draws on a large body of previous research and provides a comprehensive overview of the current state of knowledge on the relationship between obesity and cognitive function. The authors also highlight the potential mechanisms through which obesity may contribute to cognitive decline, such as inflammation and oxidative stress.

LIMITATIONS: While the article presents a convincing case for the negative impact of obesity on cognitive function, it does not explore potential confounding variables or alternative explanations for the observed association. Additionally, the article does not provide any original experimental data or offer potential interventions for preventing cognitive decline in obese individuals.

SCIENTIFIC POWER: MODERATE - The article provides a useful summary of the current state of research on the relationship between obesity and cognitive function. However, it does not present any new experimental data or significantly advance the field.

Titova, O.E., Ax, E., Brooks, S.J., Sjögren, P., Cederholm, T., Kilander, L., Kullberg, J., Larsson, E.M., Johansson, L., Åhlström, H. and Lind, L., 2013. Mediterranean diet habits in older individuals: associations with cognitive functioning and brain volumes. Experimental Gerontology, 48(12), pp.1443-1448.

OVERVIEW: This study examined the association between Mediterranean diet (MD) and cognitive function in older individuals. The researchers collected data from 70 individuals aged 60-96 years and measured their cognitive function and brain volumes using magnetic resonance imaging (MRI). The participants also completed a food frequency questionnaire to determine their MD habits.

STRENGTHS: The study is one of the few that investigated the effects of MD on cognitive function in older individuals. The use of MRI to measure brain volumes and the inclusion of confounding variables such as age, education, and physical activity levels are also strengths of the study.

LIMITATIONS: The small sample size of the study limits the generalisability of the findings. The cross-sectional design of the study also does not allow for causality to be established between MD and cognitive function. The use of self-reported dietary information may also introduce bias.

SCIENTIFIC POWER: MODERATE to STRONG - While the sample size is small and the study design is cross-sectional, the inclusion of MRI to measure brain volumes and the control for confounding variables increases the validity of the study.

Yehuda, S., Rabinovitz, S. and Mostofsky, D.I., 1999. Essential fatty acids are mediators of brain biochemistry and cognitive functions. Journal of Neuroscience Research, 56(6), pp.565-570.

OVERVIEW: This article reviews the evidence for the role of essential fatty acids (EFAs) in brain biochemistry and cognitive function. The authors discuss the importance of EFAs in the formation and maintenance of cell membranes in the brain and how they affect the production of neurotransmitters and other signalling molecules.

STRENGTHS: The article provides a comprehensive review of the current literature on the topic of EFAs and brain function. The authors provide clear explanations of complex concepts, making the article accessible to a wide audience.

LIMITATIONS: The article is a review and does not include any original data. As a result, the conclusions drawn are based on the studies included in the review and may be subject to bias and limitations of those studies.

SCIENTIFIC POWER: MODERATE - While the article is a review and does not provide any original data, the authors provide a thorough and well-supported argument for the role of EFAs in brain biochemistry and cognitive function based on the available literature.

Walther, K., Birdsill, A.C., Glisky, E.L. and Ryan, L., 2010. Structural brain differences and cognitive functioning related to body mass index in older females. Human Brain Mapping, 31(7), pp.1052-1064.

OVERVIEW: This study investigated whether there is a relationship between body mass index (BMI) and brain structure and cognitive function in older women. The researchers used magnetic resonance imaging (MRI) to scan the brains of 95 women between the ages of 65 and 75 and conducted cognitive tests to measure memory and attention.

STRENGTHS: The study had a relatively large sample size and used advanced imaging techniques to analyse the brain structure. The researchers also controlled for important variables such as age, education, and physical activity levels.

LIMITATIONS: The study only included women, so the results may not be generalisable to men or younger individuals. Additionally, the study only looked at BMI as a measure of obesity, which may not be the most accurate or comprehensive measure.

SCIENTIFIC POWER: MODERATE - While the study had a good sample size and controlled for important variables, the use of only BMI as a measure of obesity may have limited the results. However, the use of advanced imaging techniques added strength to the findings.

Wärnberg, J., Gomez‐Martinez, S., Romeo, J., Díaz, L.E. and Marcos, A., 2009. Nutrition, inflammation, and cognitive function. Annals of the New York Academy of Sciences, 1153(1), pp.164-175.

OVERVIEW: The study reviews the literature on the relationship between nutrition, inflammation, and cognitive function. The study examines the role of various nutrients, such as omega-3 fatty acids and antioxidants, in reducing inflammation and improving cognitive function. The study also discusses the potential mechanisms underlying this relationship, such as the impact of nutrients on the immune system and oxidative stress.

STRENGTHS: The study provides a comprehensive overview of the current research on the relationship between nutrition, inflammation, and cognitive function. The review is based on a large number of studies, which increases the statistical power of the results. The study also discusses potential mechanisms underlying the relationship, which can help inform future research.

LIMITATIONS: The study is a review of existing research and does not present new empirical data. The studies reviewed in the article had varying designs and methodologies, which can affect the comparability of the results. The study does not provide a clear synthesis of the existing research, making it difficult to draw definitive conclusions.

SCIENTIFIC POWER: MODERATE to STRONG - The study's comprehensive review of the literature and consideration of potential mechanisms underlying the relationship between nutrition, inflammation, and cognitive function increase the internal validity of the study. However, the lack of new empirical data and variability in the design and methodologies of the studies reviewed limits the study's external validity.

Warren, R.E. and Frier, B.M., 2005. Hypoglycaemia and cognitive function. Diabetes, Obesity and Metabolism, 7(5), pp.493-503.

OVERVIEW: Hypoglycaemia, a condition characterised by low blood glucose levels, is common among people with diabetes and can lead to cognitive impairment. This article reviews the current understanding of how hypoglycaemia affects cognitive function.

STRENGTHS: The article provides a comprehensive overview of the mechanisms through which hypoglycaemia affects cognitive function, including changes in brain metabolism and neurotransmitter function. The authors also summarise the existing evidence linking hypoglycaemia to cognitive impairment.

LIMITATIONS: The article primarily focuses on the effects of hypoglycaemia in people with diabetes and does not consider other causes of hypoglycaemia or their potential effects on cognitive function. Additionally, the article does not explore potential treatments or interventions for hypoglycaemia-related cognitive impairment.

SCIENTIFIC POWER: MODERATE - The article provides a thorough review of the existing literature and summarises the current understanding of the mechanisms through which hypoglycaemia affects cognitive function. However, the article is limited by its focus on a specific population (people with diabetes) and does not provide a comprehensive review of the potential causes and treatments of hypoglycaemia-related cognitive impairment.

Wersching, H., Duning, T., Lohmann, H., Mohammadi, S., Stehling, C., Fobker, M., Conty, M., Minnerup, J., Ringelstein, E.B., Berger, K. and Deppe, M., 2010. Serum C-reactive protein is linked to cerebral microstructural integrity and cognitive function. Neurology, 74(13), pp.1022-1029.

OVERVIEW: C-reactive protein (CRP) is a marker of inflammation and is associated with an increased risk of cognitive decline and dementia. This study examines the relationship between CRP levels, cerebral microstructure, and cognitive function.

STRENGTHS: The study utilises advanced imaging techniques to assess cerebral microstructure and identify potential changes associated with inflammation. The study also measures cognitive function using standardised tests and controls for potential confounding variables, such as age and sex.

LIMITATIONS: The study is cross-sectional, which means that it cannot establish causality between CRP levels, cerebral microstructure, and cognitive function. Additionally, the study only examines a single marker of inflammation (CRP) and does not consider other potential markers or mechanisms of inflammation.

SCIENTIFIC POWER: MODERATE - The study utilises advanced imaging techniques to assess cerebral microstructure and provides a comprehensive assessment of cognitive function. However, the cross-sectional design limits the ability to establish causality, and the study only considers a single marker of inflammation.