CAUTIONARY NOTE: RESEARCH STUDIES RELATING TO THIS COMPLEX FIELD OF NEUROPHYSIOLOGY ARE SUBJECT TO UNIQUE CHALLENGES AND EVEN THE MOST RIGOROUS STUDIES HAVE PRESENTED DIFFERING OUTCOMES. PLEASE BE AWARE THAT CURRENT EVIDENCE, WHILE PROMISING, IS NOT FULLY CONCLUSIVE.
What is Neurogenesis?
Neurogenesis, the process of generating new neurons, is a fascinating area of neuroscience that has the potential to reshape our understanding of the brain's ability to adapt and evolve throughout an individual's life. Once believed to cease after childhood, recent research indicates that neurogenesis may continue into adulthood, offering potential pathways for enhancing brain health and treating neurological disorders.
Research into this important area of neurophysiology is not yet mature and there have been conflicting studies. There is nevertheless growing evidence that neurogenesis does continue, albeit at a declining rate, into old age. Moreover, as with other key aspects of human health, acceptance is growing of the idea that modifications to environmental and lifestyle factors can influence the extent to which neurogenesis is able to occur in adult humans.
Where does Adult Neurogenesis take place?
Neurogenesis primarily occurs in two regions of the adult brain: the subgranular zone (SGZ) of the dentate gyrus in the hippocampus and the subventricular zone (SVZ) lining the lateral ventricles. This process involves several stages, starting from the proliferation of neural stem cells, followed by their differentiation into immature neurons, and finally, the integration and survival of these neurons as they mature and form synaptic connections.
The Hippocampus and Cognitive Function
The hippocampus, a crucial area for learning and memory, is significantly impacted by neurogenesis. The generation of new neurons in this region is associated with improved learning processes, memory formation, and emotional regulation. Neurogenesis in the hippocampus is believed to contribute to the flexibility of cognitive functions, allowing for the adaptation to new information and environments.
Beyond the Brain: The Central Nervous System
While most research has focused on the brain, some studies suggest neurogenesis may also occur in other parts of the central nervous system (CNS), albeit at a much lower rate. The discovery of neural stem cells in the spinal cord, for instance, opens up potential avenues for regenerative therapies targeting spinal cord injuries and neurodegenerative diseases.
Factors Influencing Neurogenesis
Positive Factors
High Quality Diet:
A diet rich in the Omega-3 PUFAs DHA and EPA, antioxidants and flavonoids appears to be beneficial for neurogenesis. Foods high in flavanoids, such as blueberries and chocolates, and in Omega 3 PUFAs, especially fatty fish, have been linked to increased neural growth. Resveratrol, found in red wine as well as red grapes, has been shown as a positive factor which might, to at least some extent, offset the negative impact of alcohol.
Blueberry juice, in addition to its beneficial flavanoid content, has been shown to increase blood flow in the brain.
Intermittent Fasting:
Restricting the intake of food to shorter windows of, say, six to eight hours each day may support neurogenesis.
Exercise:
Regular physical activity, especially aerobic exercise such as running and sports which include running, has been shown to significantly enhance the production of new neurons in the hippocampus.
Learning and Cognitive Engagement:
Engaging in new learning experiences and cognitive tasks promotes neurogenesis, suggesting that maintaining mental activity is crucial for brain health.
Sleep:
Adequate sleep supports the consolidation of new memories and facilitates the neurogenesis process.
Negative Factors
Stress:
Chronic stress and high levels of cortisol, the stress hormone, are detrimental to neurogenesis, reducing the production of new neurons, particularly in the hippocampus.
Aging:
The rate of neurogenesis declines with age, contributing to decreased cognitive flexibility and memory capacity in older adults.
Poor Diet and Lifestyle:
Diets high in processed foods (especially ultra processed products), poor quality fats (especially processed vegetable oils which have been transformed by heat and pressure), sugar, starch can all negatively impact neurogenesis, as can excessive alcohol consumption and smoking.
Lack of Physical and Mental Exercise:
Leading a sedentary life devoid of physical activity and mental stimulation is likely to impact neurogenesis adversely.
The Impact of Neurogenesis on Health
Enhanced neurogenesis is associated with improved cognitive function, mood regulation, and resilience to stress and depression. Conversely, reduced neurogenesis is linked to cognitive decline, mood disorders, and impaired recovery from neurological conditions. By understanding and influencing the factors that affect neurogenesis, there is potential for therapeutic interventions targeting a range of mental health conditions, including depression, anxiety, and Alzheimer's disease.
Improving Neurogenesis: Practical Measures
Based on the positive and negative factors outlined above, it is suggested that attention to the following lifestyle-related activities could be helpful in improving neurogenesis. It is perhaps not coincidental that these are similar to the types of interventions that have been shown to constructively impact other key aspects of health such as insulin resistance and inflammation. This observation highlights the degree to which all aspects of human health may be interconnected, with a relatively small number of fundamental themes having a very wide relevance in terms of their ability to affect outcomes over protracted periods of time.
Regular Exercise:
Incorporating aerobic exercise into daily routines can significantly boost neurogenesis.
Healthy Eating:
Adopt a diet that restricts processed foods, sugar and starch while emphasising omega-3 PUFAs and other beneficial fats, whole fruits, vegetables, and whole grains, can enhance the production of new neurons.
Cognitive Training:
Engaging in activities that challenge the brain, such as learning a new language or instrument, puzzles, and memory exercises, can promote neurogenesis.
Stress Management:
Techniques such as meditation, yoga, and mindfulness can reduce stress and its harmful effects on neurogenesis.
Quality Sleep:
Ensuring sufficient and quality sleep is essential for supporting the processes underlying the generation of new neurons.
How does Neurogenesis support Neural Plasticity?
Neurogenesis plays an important role in neural plasticity, the brain's remarkable ability to reorganise and adapt in response to new information, experiences, and environments. This adaptability is crucial for learning, memory formation, and recovery from brain injuries. The generation of new neurons, particularly in the hippocampus, a region vital for memory and learning, allows the brain to form new connections and pathways. These new neurons integrate into existing neural circuits, contributing to the synaptic plasticity that underlies learning and memory consolidation. This process extends beyond simply adding more neurons into enhancing the brain's capacity to remodel itself in response to the demands placed upon it, whether through everyday experiences, learning new skills, or recovering from traumatic events.
Moreover, neurogenesis and neural plasticity together form a synergistic combination that supports cognitive flexibility and emotional resilience. The birth of new neurons can help mitigate the effects of stress and aging on the brain, potentially offsetting cognitive decline and mood disorders such as depression and anxiety, which are often characterised by impaired plasticity. By fostering a more adaptable and resilient neural network, neurogenesis enhances the brain's ability to navigate complex cognitive tasks and emotional landscapes, underscoring its critical role in maintaining mental health and cognitive function throughout life.
Conclusion
Neurogenesis offers a promising frontier in understanding how brain function can be maintained through the aging process and the potential for treating neurological conditions. Through lifestyle modifications and interventions aimed at enhancing the generation of new neurons, individuals can potentially improve their cognitive health and resilience to brain aging and neurological diseases. As research continues to explore the intricacies of neurogenesis and its implications for health, the hope is that new strategies will emerge for preventing and treating cognitive decline, harnessing the brain's innate ability to regenerate and adapt.
Resources
The Journal of Neuroscience: Evidences for Adult Hippocampal Neurogenesis in Humans
Dr Sandrine Thuret (Kings College London) with Dr Rangan Chatterjee: How to Grow New Brain Cells