Stress and adolescent hippocampal neurogenesis: diet and exercise as cognitive modulators

Abstract

Adolescence is a critical period for brain maturation. Deciphering how disturbances to the central nervous system at this time affect structure, function and behavioural outputs is important to better understand any long-lasting effects. Hippocampal neurogenesis occurs during development and continues throughout life. In adulthood, integration of these new cells into the hippocampus is important for emotional behaviour, cognitive function and neural plasticity. During the adolescent period, maturation of the hippocampus and heightened levels of hippocampal neurogenesis are observed, making alterations to neurogenesis at this time particularly consequential. As stress negatively affects hippocampal neurogenesis, and adolescence is a particularly stressful time of life, it is important to investigate the impact of stressor exposure at this time on hippocampal neurogenesis and cognitive function. Adolescence may represent not only a time for which stress can have long-lasting effects, but is also a critical period during which interventions, such as exercise and diet, could ameliorate stress-induced changes to hippocampal function. In addition, intervention at this time may also promote life-long behavioural changes that would aid in fostering increased hippocampal neurogenesis and cognitive function. This review addresses both the acute and long-term stress-induced alterations to hippocampal neurogenesis and cognition during the adolescent period, as well as changes to the stress response and pubertal hormones at this time which may result in differential effects than are observed in adulthood. We hypothesise that adolescence may represent an optimal time for healthy lifestyle changes to have a positive and long-lasting impact on hippocampal neurogenesis, and to protect against stress-induced deficits. We conclude that future research into the mechanisms underlying the susceptibility of the adolescent hippocampus to stress, exercise and diet and the consequent effect on cognition may provide insight into why adolescence may be a vital period for correct conditioning of future hippocampal function.

Hippocampal subfields alterations in adolescents with post‐traumatic stress disorder

“…However, despite this plasticity, some studies consider that the adolescent brain is more vulnerable to the effects of stress exposure than adults (Holder & Blaustein, ; Romeo, ). In addition, a stress perceived during adolescence could negatively affect hippocampal maturation and cause negative long‐term effects which could last into adulthood (Holder & Blaustein, ; Hueston, Cryan, & Nolan, ). Therefore, further studies are required to: (1) understand if the vulnerability to the effects of stress exposure on the brain during adolescence can be a risk factor to develop PTSD; and (2) investigate the effects of the development of PTSD on the maturation of hippocampal subfields.…”

Born this way: Hippocampal neurogenesis across the lifespan

“…Similarly, radiation therapy for children and adolescents with cancer is associated with lasting changes in intelligence quotient (IQ) scores and cognitive performance (Rodgers, Trevino, Zawaski, Gaber, & Leasure, ). Defective hippocampal neurogenesis during adolescence has been suggested as a contributing factor to the onset and development of neuropsychiatric disorders (reviewed by Hueston, Cryan, & Nolan, ), which in combination with the fact that adolescence is a period of dramatic vulnerability to the effect of extrinsic influences, means that it is imperative to expand our understanding of how positive and negative regulators of hippocampal neurogenesis such as stress and exercise influence the brain during this critical period.…”

Deletion of TLX and social isolation impairs exercise‐induced neurogenesis in the adolescent hippocampus

“…Adolescence is a critical phase of development associated with plasticity‐driven organization of neural circuits in the hippocampus, prefrontal cortex, and amygdala (Pattwell, Bath, Casey, Ninan, & Lee, ; Selemon, ). It is also a key period for susceptibility to stress and the emergence of neurobiological disorders such as schizophrenia, depression, and anxiety (Green & Nolan, ; Hueston, Cryan, & Nolan, ; O'Connor & Cryan, ; Paus, Keshavan, & Giedd, ). By approximately postnatal day (P) 30 in rodents, dentate gyrus (DG) formation, cerebellar neurogenesis, and myelogenesis are completed, and neurogenesis (the birth of new neurons) is restricted to the niches of the brain where the process persists through adulthood—the subgranular zone (SGZ) of the DG of the hippocampus and the subventricular zone (Lemasson, Saghatelyan, Olivo‐Marin, & Lledo, ; Li, Mu, & Gage, ).…”