Under times of increased stress, the body secretes epinephrine, norepinephrine, and cortisol from the adrenal glands. These act on the neurotransmitters of the brain that can result in long-term damage to brain cells that are involved in memory production.
The Impact of Glucocorticoids
The glucocorticoids (mainly cortisol) are believed to negatively affect memory. Cortisol impairs the brain’s ability to function in its memory processes.
Cortisol is one of the major biomarkers for stress. Under healthy circumstances, it is the hippocampus of the brain that takes short-term memory and translates it into long-term memory.
There are many brain receptors in the hippocampus that are sensitive to cortisol and other stress hormones. An increase in cortisol impairs the hippocampus’s ability to recall and encode short-term memory into long-term memory.
Cortisol can also block the hippocampus from getting the energy it needs because it shunts blood away from the hippocampus toward the external muscles.
Stress has an effect on the various memory and cognitive functions of the brain. There are various levels of stress; high levels of stress can be extrinsic or intrinsic. External stress is related to anything unrelated to the performance of cognitive functioning.
Intrinsic stress is related to cognitive challenges occurring within the brain. Intrinsic stress can be acute or chronic.
The Brain and the Effects of Stress
The different effects of stress on the brain include the induction of learning problems, memory processes and the plasticity of the brain. Chronic stress can negatively affect the structures of the brain and the ability of the brain to do cognitive tasks.
Pavlovian conditioning and spatial memory have been studied as to the effects of stress on memory functions, including intrinsic and extrinsic memory. With regard to intrinsic memory, it was found that stress affected the function of memory triggered by some type of learning task.
When looking at extrinsic stress, research has focused on stress elicited by environmental situations. It was found that both intrinsic stress and extrinsic stress affected the consolidation of memory in the hippocampus of the brain.
Very high levels of stress represented the impact that extrinsic stress has on the function of memory. Extrinsic stress has an impact on spatial learning but acute extrinsic stress has no impact on spatial learning.
What exactly happens with stress and memory?
When a person encounters a stressful situation, the stress hormones are secreted into the blood stream by the adrenal glands. Epinephrine begins the process and acts in the “fight or flight” response, which is a part of the sympathetic nervous system. It helps the body react to a real or perceived stressor.
This, in turn, causes a rise a person’s blood pressure, heart rate, and breathing rate. The kidneys give off glucose for energy to be used to fight or to flee from the stressful event.
The Axes Responsible for the Stress Response:
- There are three biochemical axes or cycles responsible for the brain’s reaction to memory and stress. These are the vasopressin axis, the adrenocorticotropic axis, and the thyroxine axis:
- The vasopressin axis. Vasopressin is produced by the brain and regulates the amount of fluid lost by the kidneys. This affects the blood pressure in the body. If the stress is elevated chronically, the muscles will tire and hypertension can occur.
- The adrenocorticotropic axis. When under stress, the anterior hypothalamus is sent a signal to release corticotrophin-releasing factor. This stimulates ACTH in the pituitary gland that releases cortisol. Cortisol acts directly on the brain, reducing its ability to remember things.
- The thyroxine axis. This is another response to stress. Thyrotropic hormone releasing factor is released by the hypothalamus and this results in the release of T3 and T4 from the thyroid gland. This increases the metabolic rate, which actually enhances memory.
The Effect of Chronic Stress on Memory
Chronic stress is any stressor that goes on for a long time period. The body is constantly aroused and this can affect our ability to learn new things and to remember them. This has been borne out by studies in rats.
Chronic stress has an effect on one’s cognitive function. This effect is different for people who are cognitively impaired already. The higher the stress, the greater was the effect on memory in those people with cognitive impairment.
The Effect of Acute Stress on Memory
An acute stress is any stressor that is seen as an immediate threat. This type of stress does not last long and the effect on the body is less.
The effect of acute stress on memory is mixed. Some studies show a worsening of memory under acute stress, while other studies indicate that acute stress actually improves memory.