Effects of stress on memory

The effects of stress on memory include interference with a person's capacity to encode memory and the ability to retrieve information.^[1][2] Stimuli, like stress, improved memory when it was related to learning the subject.^[3] During times of stress, the body reacts by secreting stress hormones into the bloodstream. Stress can cause acute and chronic changes in certain brain areas which can cause long-term damage.^[4] Over-secretion of stress hormones most frequently impairs long-term delayed recall memory, but can enhance short-term, immediate recall memory. This enhancement is particularly relative in emotional memory. In particular, the hippocampus, prefrontal cortex and the amygdala are affected.^[5][6] One class of stress hormone responsible for negatively affecting long-term, delayed recall memory is the glucocorticoids (GCs), the most notable of which is cortisol.^[1][6][7] Glucocorticoids facilitate and impair the actions of stress in the brain memory process.^[8] Cortisol is a known biomarker for stress.^[9] Under normal circumstances, the hippocampus regulates the production of cortisol through negative feedback because it has many receptors that are sensitive to these stress hormones. However, an excess of cortisol can impair the ability of the hippocampus to both encode and recall memories.^[2] These stress hormones are also hindering the hippocampus from receiving enough energy by diverting glucose levels to surrounding muscles.^[2]

Stress affects many memory functions and cognitive functioning of the brain.^[10] There are different levels of stress and the high levels can be intrinsic or extrinsic. Intrinsic stress level is triggered by a cognitive challenge whereas extrinsic can be triggered by a condition not related to a cognitive task.^[8] Intrinsic stress can be acutely and chronically experienced by a person.^[8] The varying effects of stress on performance or stress hormones are often compared to or known as "inverted-u"^[10] which induce areas in learning, memory and plasticity.^[8] Chronic stress can affect the brain structure and cognition.

Studies considered the effects of both intrinsic and extrinsic stress on memory functions, using for both of them Pavlovian conditioning and spatial learning.^[8] In regard to intrinsic memory functions, the study evaluated how stress affected memory functions that was triggered by a learning challenge. In regard to extrinsic stress, the study focused on stress that was not related to cognitive task but was elicited by other situations. The results determined that intrinsic stress was facilitated by memory consolidation process and extrinsic stress was determined to be heterogeneous in regard to memory consolidation.^{[clarification needed]} Researchers found that high stress conditions were a good representative of the effect that extrinsic stress can cause on memory functioning.^{[8][clarification needed]} It was also proven that extrinsic stress does affect spatial learning whereas acute extrinsic stress does not.^{[8][clarification needed]}