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Stress, a ubiquitous experience, significantly impacts the hippocampus, a brain structure crucial for memory formation.[1] Uncontrollable stress, in particular, can lead to a cascade of effects on the hippocampus, influencing behavior, neural activity, and structure.[1]
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The impact of stress on the hippocampus is multifaceted, affecting memory at various levels.[1] Behaviorally, stress often impairs hippocampal-dependent memory tasks.[1] Neurally, stress alters synaptic plasticity and the firing properties of hippocampal neurons.[1] Structurally, stress can change neuronal morphology, suppress neuronal proliferation, and reduce hippocampal volume.[1]
The glucocorticoid hypothesis suggests that the sustained elevation of adrenal hormones, such as cortisol, is a key mediator of stress effects on the hippocampus.[1] The hippocampus is densely concentrated with receptors for corticosteroids, making it susceptible to heightened cortisol action.[1] Studies have shown that exposures to stress or elevated levels of cortisol impair performance on memory tasks dependent on the hippocampus.[1]
Chronic stress can lead to dendritic retraction in the CA3 region of the hippocampus, which is associated with impaired spatial ability and increased vulnerability to neurotoxic challenges.[2] This structural remodeling is a key indicator of a chronic stress history.[2] Furthermore, the Glucocorticoid Vulnerability Hypothesis posits that a history of chronic stress, which includes repeated elevation of glucocorticoids, may make the hippocampus vulnerable to potential injury.[2]
The hippocampus is also affected by aging, and memory impairment is seen in rats as they age, with a link between rising glucocorticoid levels, EAAs, and memory impairment.[3]
The effects of stress on the hippocampus are also linked to changes in the amygdala and prefrontal cortex (PFC).[1] The amygdala, which enhances glucocorticoid secretion in response to stress, undergoes stress-induced changes in LTP and cytoarchitecture.[1] The PFC, particularly the medial PFC (mPFC), is implicated in regulating the stress effects on the hippocampus.[1]
Authoritative Sources
- Kim, J. J., & Diamond, D. M. (2002). The stressed hippocampus, synaptic plasticity and lost memories. Nature Reviews Neuroscience, 3(6), 453–462. [https://pmc.ncbi.nlm.nih.gov/articles/PMC4561403/]↩
- Conrad, C. D. (2009). Chronic stress endangers the hippocampus: The glucocorticoid vulnerability hypothesis. Neurobiology of Aging, 30(10), 1665–1674. [https://pmc.ncbi.nlm.nih.gov/articles/PMC2746750/]↩
- McEwen, B. S., & Sapolsky, R. M. (1995). Stress and cognitive function. Current Opinion in Neurobiology, 5(2), 205–216. [www.nature.com/articles/npp2015171]↩
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