Dr Oliver Finlay
KEY POINTS
· Hormones, neurotransmitters, neurotransmitter modulators and neuropeptides work in symphony, contributing to the neurophysiological processes that influence cognitive performance and brain plasticity.
· Hormones, play a vital role in coordinating and regulating brain function and plasticity over prolonged periods of time.
· Neurotransmitters facilitate rapid communication between neurons, impacting actions over short time periods.
· Neurotransmitter modulators fine-tune brain activity, balancing cognitive flexibility and stability for optimal brain function.
· Neuropeptides facilitate synaptic plasticity, regulating synaptic reorganisation and impact emotional responses.
Introduction
In the intricate world of the brain, four key players - hormones, neurotransmitters, neurotransmitter modulators and neuropeptides - work together, like an orchestra playing a symphony, to influence the neurophysiology shaping cognitive performance and brain plasticity.
Nerve cells, called neurons, use one or more of these chemicals in a process called neuromodulation to regulate other neurons within the central nervous, peripheral nervous and neuromuscular systems.
Examples of these neuromodulation systems include: the norepinephrine system, which governs arousal and reward, suppresses neuroinflammation, stimulates nerve plasticity and consolidates memory; the dopamine system, which influences cognition, reward, endocrine function; the serotonin system which influences behaviour through mood, satiety, body temperature and sleep; and the cholinergic system, which impacts learning, short-term memory, arousal, reward, and the motor control system.
Hormones: The Conductors of Brain Function
Hormones are produced by the endocrine glands and typically influence target cells far removed from the hormone-secreting cell by traveling through the bloodstream. Hormones influence involuntary actions and their effects can last for long periods of time.
Neurohormones are those hormones produced and released by neuroendocrine cells in parts of the brain like the hypothalamus, the adrenal medulla, anterior and posterior pituitaries. Neurohormones can also have dual roles as neurotransmitters and are the conductors of the brain's orchestra. They play a vital role in coordinating and regulating various cognitive functions and processes related to brain plasticity, telling other endocrine glands to make the hormones that affect every aspect of health.
One hormone that stands out in this regard is cortisol. Cortisol is produced by the adrenal glands and is commonly known as the "stress hormone". McEwen (2005) found that elevated cortisol levels, often associated with chronic stress, can impair cognitive performance and hinder neuroplasticity. It can interfere with the brain's ability to form new connections and adapt to changing environments, ultimately impacting learning and memory.
Other examples of hormones that are involved in neurophysiological processes are melatonin, epinephrine, dopamine, serotonin, growth hormone, progesterone, and oestrogen.
Neurotransmitters: The Rapid Messengers
Neurotransmitters are the rapid messengers of our brain, facilitating communication between neurons. In contrast to hormones, neurotransmitters are produced by the nervous system and act over miniscule distances, often across the space between two adjacent neurons (synapse) less than a micrometre away, up to a range of tens of hundreds of micrometres when diffused locally. Neurotransmitters’ actions are fast and short-lived, influencing both voluntary tasks (e.g., eating, mobility) and involuntary tasks (e.g., breathing, blinking).
When it comes to cognitive performance and brain plasticity, one neurotransmitter that plays a starring role is acetylcholine. Acetylcholine is known to significantly enhance attention and memory. Hasselmo & Sarter (2011) found that increased acetylcholine release improved cognitive performance, promoting better attention and memory recall. Furthermore, acetylcholine has been linked to neuroplasticity by influencing synaptic strength and enhancing the formation of new neural connections, crucial for learning and memory.
Examples of other neurotransmitters include norepinephrine, glutamic acid, gamma-aminobutyric acid (GABA), endorphins, histamine, catecholamine, monoamine neurotransmitter,
There are rare examples where peptide hormones, such as oxytocin, dopamine, serotonin, and vasopressin, act as a neurotransmitter in one region of the brain, whilst serving as a hormone elsewhere.
Neurotransmitter Modulators: Fine-Tuning Brain Activity
Neurotransmitter modulators fine-tune the activity of neurotransmitters, influencing cognitive processes and brain plasticity.
An excellent example of a neurotransmitter modulator is serotonin. Serotonin has been shown to modulate the balance between cognitive flexibility and stability (Celada et al., 2001). Optimal serotonin levels are associated with maintaining an adaptive balance between stability, necessary for routine tasks, and flexibility, crucial for adapting to new challenges. This modulation by serotonin is fundamental to cognitive performance and brain plasticity, allowing the brain to learn and adapt while maintaining stability.
Neuropeptides: The Subtle Harmonies in the Brain's Chemical Symphony
In the orchestra of brain chemistry, neuropeptides are like the subtle harmonies that add depth and nuance to the music. They play a crucial neurophysiological role alongside hormones, neurotransmitters, and neurotransmitter modulators in shaping cognitive performance and brain plasticity.
Neuropeptides are molecules that serve as messengers in the brain, much like hormones and neurotransmitters. However, they bring a unique flavour to the musical analogy – while hormones and neurotransmitters are like conductors and rapid messengers, neuropeptides can be considered as the delicate melodies that enhance the emotional depth and subtlety of the performance. They are made up of small chains of amino acids made and released by the nerve cells, often along with other neuropeptides and neurotransmitters to yield a variety of effects.
There are over a hundred known neuropeptides that can influence a wide range of targets, thanks to their diverse chemical structures and ability to diffuse across broad areas without being reabsorbed.
In the realm of neurophysiology, neuropeptides influence various bodily functions and processes. For instance, oxytocin, often referred to as the "love hormone," is a neuropeptide that plays a central role in social bonding and emotional regulation. Oxytocin has been shown to enhance trust and empathy in social interactions, highlighting its importance in shaping neurophysiological responses to social stimuli (Heinrichs et al., 2003).
One neuropeptide that holds great significance in cognitive performance is brain-derived neurotrophic factor (BDNF). BDNF plays a crucial role in promoting synaptic plasticity by enhancing the strengthening of connections between neurons, which is essential for learning and memory (Huang & Reichardt, 2001). In essence, BDNF helps fine-tune the brain's cognitive abilities, making it a key player in the orchestra of cognitive performance.
Neuropeptides also contribute to the orchestra's ability to adapt and change – a hallmark of brain plasticity. Substance P, a neuropeptide found in the brain, has been linked to the regulation of synaptic plasticity. Substance P influences the brain's ability to reorganise and form new connections, a fundamental aspect of brain plasticity (Korol, 2002). These neuropeptides act as gentle whispers guiding the brain's dynamic nature.
Some of the other most influential neuropeptides in neurophysiology are norepinephrine, gamma-aminobutyric acid (GABA), acetylcholine, dopamine, epinephrine and serotonin.
Conclusion: The Neurochemical Orchestra in Action
In summary, our brain operates like a finely tuned orchestra where hormones, neurotransmitters, neurotransmitter modulators and neuropeptides play distinct but interrelated roles in influencing our neurophysiology and shaping cognitive performance, and brain plasticity.
Hormones, such as cortisol, influence brain function and plasticity, with elevated levels negatively impacting cognition. Neurotransmitters, exemplified by acetylcholine, facilitate rapid communication between neurons, enhancing cognitive performance and supporting neuroplasticity. Neurotransmitter modulators like serotonin fine-tune brain activity, balancing cognitive flexibility and stability for optimal brain function.
Neuropeptides add the subtle harmonies to the brain's chemical symphony alongside hormones, neurotransmitters, and neurotransmitter modulators. They are like the melodies that enrich the emotional depth of the music. These subtle notes, while often overlooked, play a crucial role in shaping our neurophysiological responses to various stimuli and influencing our cognitive abilities and brain plasticity.
Understanding this neurochemical orchestra's dynamics provides crucial insights into how our brains operate, adapt, and perform, ultimately contributing to our knowledge of cognitive science and brain health.
References and Evaluation of Scientific Power
Celada, P., Puig, M.V., MartÃn-Ruiz, R., Casanovas, J.M. and Artigas, F., 2002. Control of the serotonergic system by the medial prefrontal cortex: potential role in the etiology of PTSD and depressive disorders. Neurotoxicity Research, 4, pp.409-419.
OVERVIEW: The article delves into the fascinating world of the serotonergic system and its control by a brain region called the medial prefrontal cortex (mPFC). It explores the potential implications of this control in understanding disorders like PTSD (post-traumatic stress disorder) and depression.
STRENGTHS: One of the notable strengths of this article is its in-depth exploration of the neurobiology of the serotonergic system. The authors provide a clear overview of how the mPFC influences serotonin, a neurotransmitter linked to mood regulation. They offer compelling evidence from animal studies and neural activity observations, supporting their claims. Additionally, the article discusses the potential clinical relevance of this research, shedding light on the aetiology (causes) of PTSD and depressive disorders. This connection between basic science and clinical applications is a strong point, making the research more meaningful.
LIMITATIONS: The research primarily relies on animal models, and translating findings from animals to humans can be complex. While the article hints at the potential relevance for PTSD and depression, it doesn't provide concrete clinical data or human studies to directly link mPFC control of serotonin to these disorders. Furthermore, the article doesn't thoroughly explore the complexities of PTSD and depression, which involve multiple factors beyond serotonin regulation.
CONCLUSION: The article offers valuable insights into the role of the medial prefrontal cortex in controlling the serotonergic system. It provides a strong foundation for understanding the neurobiology of mood regulation. However, its true clinical implications in the aetiology of PTSD and depression require further research and human studies for a more comprehensive understanding.
SCIENTIFIC POWER: MODERATE - While it presents a well-structured and informative exploration of the topic, it primarily relies on animal studies and theoretical connections to human disorders. To reach a stronger scientific power rating, the research would need to include more direct clinical evidence and human studies to firmly establish the link between mPFC control of serotonin and PTSD and depression.
Hasselmo, M.E. and Sarter, M., 2011. Modes and models of forebrain cholinergic neuromodulation of cognition. Neuropsychopharmacology, 36(1), pp.52-73.
OVERVIEW: The article explores cholinergic neuromodulation in the forebrain, specifically how the neurotransmitter acetylcholine influences cognitive functions like memory and attention.
STRENGTHS: The article provides a comprehensive examination of the role of acetylcholine in the brain. The authors provide a clear and detailed overview of how acetylcholine impacts cognition. They discuss various modes of cholinergic neuromodulation, explaining how acetylcholine influences the brain's performance in different ways. The article also presents models and theories that help us understand the complex workings of acetylcholine in cognition. These models are particularly helpful for grasping the concept.
LIMITATIONS: The article is quite theoretical in nature. While it offers models and theories, it doesn't provide concrete experimental data or results from human studies. This means that the ideas presented are largely conceptual, and their practical applications or direct implications for clinical use are not discussed in-depth. Additionally, some readers may find the detailed neural mechanisms and terminology challenging to follow without prior knowledge in the field.
CONCLUSION: The article provides a thorough exploration of cholinergic neuromodulation and its role in cognition. It offers valuable theoretical insights that contribute to our understanding of how acetylcholine influences memory and attention. However, it's important to remember that the article primarily focuses on theories and models, and further experimental research would be needed to validate these concepts and translate them into practical applications.
SCIENTIFIC POWER: MODERATE - While it provides a comprehensive and well-structured overview of the topic, it leans heavily on theoretical models and lacks empirical data from human studies or clinical applications. To reach a stronger scientific power rating, the research would need to incorporate more concrete experimental evidence and demonstrate the practical relevance of these theories in real-world cognitive scenarios.
McEwen, B.S., 2005. Glucocorticoids, depression, and mood disorders: structural remodeling in the brain. Metabolism, 54(5), pp.20-23.
OVERVIEW: The article discusses the relationship between glucocorticoids, which are stress hormones, and mood disorders, especially depression. It explores how these hormones can lead to structural changes in the brain, which might be linked to mood disorders.
STRENGTHS: The article clearly explains how stress hormones, specifically glucocorticoids, can affect the brain's structure. The author presents a concise overview of the role of these hormones in the brain. The article highlights the idea that chronic stress and high levels of glucocorticoids can lead to changes in the brain's architecture, potentially contributing to mood disorders like depression. This insight is valuable for understanding the biological basis of depression.
LIMITATIONS: The article primarily discusses the theoretical aspects of how stress hormones may relate to mood disorders. While it provides a compelling hypothesis, it doesn't offer concrete experimental data or results from clinical studies. The connection between structural brain changes and mood disorders is complex and multifaceted, and this article doesn't delve deeply into the specifics or nuances of this relationship.
CONCLUSION: The article provides an informative introduction to the potential connection between glucocorticoids and mood disorders like depression. It offers a valuable theoretical framework for understanding how stress hormones might contribute to changes in the brain. Nonetheless, it's essential to acknowledge that this is a theoretical discussion, and further empirical research is required to substantiate these ideas and explore their practical implications.
SCIENTIFIC POWER: MODERATE - While it provides a clear and informative overview of the topic, it is primarily theoretical and lacks empirical evidence from human studies or clinical applications. To achieve a higher scientific power rating, the research would need to incorporate concrete experimental findings and demonstrate the direct link between glucocorticoids, structural brain changes, and mood disorders in real-world scenarios.
Heinrichs, M., Baumgartner, T., Kirschbaum, C. and Ehlert, U., 2003. Social support and oxytocin interact to suppress cortisol and subjective responses to psychosocial stress. Biological Psychiatry, 54(12), pp.1389-1398.
OVERVIEW: The article explores how social support and the hormone oxytocin work together to reduce stress responses, specifically cortisol levels and subjective stress experiences, during social challenges.
STRENGTHS: The article investigates the complex interplay between social support, oxytocin, and stress responses. The authors provide a clear explanation of how oxytocin, often called the "love hormone," and social support can work together to reduce the body's stress reactions. They conducted experiments involving participants subjected to social stressors and measured not only cortisol levels (a stress hormone) but also subjective stress experiences, making their findings more comprehensive. The article highlights the importance of social relationships in managing stress, which is relevant and relatable to everyday life.
LIMITATIONS: The research primarily focuses on controlled laboratory experiments, which may not fully capture the complexities of real-world stress. The article does not delve deeply into the potential variations in individual responses to social support and oxytocin, which can differ from person to person. Additionally, while the findings are intriguing, they might not cover all the factors that contribute to stress or fully explain the intricacies of social support's impact on stress.
CONCLUSION: The article provides valuable insights into how social support and oxytocin can interact to reduce stress responses, both in terms of hormones and subjective experiences. It underscores the significance of social connections in managing stress, a topic of relevance to everyone. However, it's important to remember that this research primarily stems from controlled experiments, and real-life stress is influenced by numerous factors beyond what this study covers.
SCIENTIFIC POWER: MODERATE to STRONG - It conducts controlled experiments, which are a robust scientific approach, and includes measurements of both hormonal and subjective stress responses. However, to reach a stronger scientific power rating, future research might consider incorporating a more diverse range of stressors and accounting for individual differences in stress responses to provide a fuller picture of this complex phenomenon.
Huang, E.J. and Reichardt, L.F., 2001. Neurotrophins: roles in neuronal development and function. Annual review of neuroscience, 24(1), pp.677-736.
OVERVIEW: The article focusses on neurotrophins, which are proteins that play crucial roles in the development and functioning of neurons in the brain.
STRENGTHS: The article offers a comprehensive and in-depth overview of neurotrophins, providing a clear explanation of their roles in the nervous system. The authors present a substantial amount of research evidence from various studies, helping readers grasp the importance of neurotrophins in neuronal development and function. Moreover, the article effectively discusses the mechanisms through which neurotrophins influence neurons, making it easier for readers to understand complex biological processes. This thorough exploration contributes significantly to our knowledge of neuroscience.
LIMITATIONS: While the article provides a wealth of information, it can be quite dense and technical, which may be challenging for readers without a strong background in neuroscience. Additionally, the research primarily focuses on basic science and may not provide direct insights into clinical applications or specific neurological disorders. It's also worth noting that the article covers a vast range of neurotrophins and their functions, and some readers may find it overwhelming due to the sheer volume of information.
CONCLUSION: The article offers a robust and informative overview of the roles of neurotrophins in neuronal development and function. It serves as an excellent resource for those interested in the intricacies of neuroscience. However, readers should be prepared for the technical nature of the content and understand that the article is more focused on fundamental science rather than clinical applications.
SCIENTIFIC POWER: MODERATE to STRONG - It presents a comprehensive review of the topic, relying on a substantial body of research evidence. However, the article's complexity and the absence of clinical applications may slightly lower its scientific power for readers seeking practical insights into neurological disorders. Nonetheless, it remains a valuable resource for understanding the foundational aspects of neurotrophins in neuroscience.
Korol, D. L., 2002. Enhancing cognitive function across the life span. Annals of the New York Academy of Sciences, 959(1), pp.167-179.
OVERVIEW: The article explores the enhancement of cognitive function throughout our lives. It explores various factors and strategies that can help us maintain and even improve our cognitive abilities as we age.
STRENGTHS: The article provides a clear and informative overview of cognitive function across the lifespan, making it accessible to readers with varying levels of scientific background. Korol discusses the importance of factors like physical activity, nutrition, and mental stimulation in maintaining cognitive health. The article also touches on the role of hormones like oestrogen, which is particularly relevant for understanding cognitive changes in aging women. These insights are practical and relatable, making the article valuable for anyone interested in optimising their cognitive abilities.
LIMITATIONS: While the article highlights the importance of these factors, it doesn't delve deeply into the specific mechanisms or provide detailed recommendations for improving cognitive function. Additionally, the research mentioned often leans toward animal studies, which may not perfectly translate to human experiences. It's essential to recognise that enhancing cognitive function is a complex and multifaceted topic, and individual responses can vary.
CONCLUSION: The article provides a valuable overview of factors that can influence cognitive function throughout our lives. It emphasises the significance of lifestyle choices and hormonal changes in shaping cognitive health. However, it offers more of a broad perspective rather than in-depth strategies, and readers should be aware that individual results may differ.
SCIENTIFIC POWER: MODERATE - It presents a well-structured and accessible overview of the topic, making it suitable for a wide audience. However, the reliance on animal studies and the lack of specific recommendations for cognitive enhancement slightly lower its scientific power. To reach a stronger scientific power rating, the article could incorporate more human-based research and practical strategies for cognitive improvement. Nonetheless, it serves as a valuable starting point for understanding the fundamentals of cognitive function across the lifespan.