Emotion and Cognition 2: literature summary
Churchill et al. (2002): Exercise, experience, and the aging brain
The goal of this study was to investigate how animal and human studies contribute to
understanding plasticity during aging.
Research suggests that during aging a decline in various perceptual, cognitive, and action-
related processes occurs. Older adults tend to perform more poorly compared to younger
adults in terms of response delay and accuracy on tasks. In general, there is a consensus
regarding the fact that life-time aerobic exercise may help preserving cognitive abilities in
older adults. However, results about the effects of short-term exercise are still unclear. Other
studies have shown how physical activity enhances performance on spatial learning task in
rodents, and others have observed how cortical volume changes can be altered by rearing
animals in enriched environments compared to impoverished. The same concept of using
complex environments to mitigate age-related neural declines has been adopted in other
studies.
Synaptogenesis
Certain areas of the cortex appeared to be heavier and thicker in rats exposed to complex
environments. This is thought to be due to the expansion of contacts made by existing cells
with surrounding neurons. Results suggest that the level of neuropil expansion positively
correlates with the degree of environmental complexity.
Neurogenesis
Thanks to new detection methods it was possible to establish that certain regions of the brain
can respond to environmental stimuli by forming new neurons. In rodents, neurogenesis has
been observed in the hippocampus, olfactory bulb, and cerebral cortex, as well as in primates.
Moreover, it was demonstrated that exercise on a running wheel inreased the rate of neuron
proliferation in the rodent dentate gyrus when compared to both learning and inactive
controls, thus, there may be (even if still vague) evidence suggesting that exercise aid
neurogenesis. One possible explanation for this could be the secretion of serotonin that
increases during exercise, while decreases in serotonin have been associated to decrease
neuron proliferation. Another component is the brain-derived neurotrophic factor mRNA,
which is up-regulated in response to exercise and seems to be associated with increased
neurogenesis.
Glial plasticity
Other studies have shown the effects of physical activity in non-neural elements in the brain.
à astrocyte process surface density is approximately 20% greater per neuron in the visual
cortex of rats reared in complex environments, compared to inactive rat.
Two aspects related to living in a complex environment could influence brain function:
1) Learning
2) Neuronal activity driven by peripheral stimulation
• Using rats exposed to either motor learning, exercise, or inactive conditions, it
was observed that the of astrocytes processes in the cerebellar cortex of
“motor learning” rats was highly correlated with synapse number per neuron,
indicating that astrocytic plasticity is not limited to development.
• Not only that, but oligodendrocytes exhibit similar plastic responses to
experience
Vascular plasticity
, As one ages there is a significant deterioration of the brain’s vasculature, including loss of
vessels, changes in the wall’s characteristic of vessels, deposition of collagen and other
material, declines in blood flow, oxygen extraction and glucose transport. Although still
unclear, these deteriorating processes may play a role in the cognitive impairment observed
during aging. Increasing evidence supports the observation that manipulating blood flow to
the brain alters behavioral performance on a variety of tasks. Results show that not only the
administration of certain substances enhances cognitive performance in rodents, but
behavioral strategies may also be capable of increasing blood flow and consequently,
cognition. It is likely that prolonged exercise and the concomitant neural activity associated
with it have significant long-term consequences for behavioral and neural plasticity.
McKercher et al. (2013): Physical activity patterns and risk of depression in young
adulthood: a 20-year cohort study since childhood
This study aimed at investigating how physical activity patterns during childhood and
adolescence are associated with risk of depression by examining both prospective and
retrospective associations between leisure physical activity patterns from childhood to
adulthood and risk for depression in young adulthood over a 20-year follow-up.
From childhood to adulthood, the lifetime prevalence of MD increases à 20% of people
experience at least a depressive episode before young adulthood. Interestingly, the levels of
physical activities tend to decline between childhood and young adulthood. Moreover, studies
not only have shown that habitual physical activity reduces the risk for depression in adults,
but they also observed an effect in adults who already experience depression. However, few
studies focus on these possible effects in childhood and adolescence.
Results showed that increasing or maintaining activity from childhood to adulthood
decreased the risk of depression in adulthood. This was observed more strongly in men.
Sherder et al. (2014): Executive functions of sedentary elderly may benefit from
walking: a systematic review and meta-analysis
The goal of this study was to investigate in a meta-analysis the association between leisure
physical activities walking and executive function. The study took into account other multiple
studies with different and sometimes even contrasting findings. For example, one study
suggests that both vigorous and non-vigorous physical activity predicted cognitive
functioning in old age. However, another study observed that self-reported weekly physical
activity was not associated with cognition, nor the risk of Alzheimer.
Sherder’s study thus, sought to investigate this issue and expected that maintaining or
improving the level of executive function as long as possible by regular physical activity may
postpone the onset of dementia.
Results showed that walking interventions improve executive functioning of older sedentary
persons without cognitive impairment. However, no significant effect of walking on
executive func- tions in older persons with cognitive impairment was found.
Verburgh et al. (2013): Physical exercise and executive functions in preadolescent
children, adolescents and young adults: a meta-analysis
The purpose of this study was to combine different results regarding the effects of physical
exercise on executive functions in preadolescent children (6-12 y/o), adolescents (13-17 y/o)
