Whether it occurs temporarily or sustainably, the physiological stress response alters memory, causing difficulties in retaining new information and recovering already consolidated memories.
Nevertheless, The effects of stress on memory can be somewhat contradictory and they differ depending on whether we are talking about acute or chronic stress.
When the demands of the situation in which we find ourselves exceed our physical and/or cognitive capabilities, our body activates the stress response. This consists of the release of glucocorticoids, stress hormones, into the bloodstream.
Glucocorticoids cause different effects in the body, among which are the increase in heart rate and respiratory rate, the reduction of gastrointestinal activity and the release of stored glucose reserves in order to use them as a source of energy.
If their concentration is excessive, glucocorticoids, among which cortisol stands out, can have a negative effect on the functions of the hippocampus, a brain structure that is associated with the formation and retrieval of memories. This is partly because glucocorticoids redirect glucose from the hippocampus to nearby muscles.
Two types of stress have been described depending on their origin: extrinsic and intrinsic. Extrinsic stress is caused by non-cognitive factors, such as those that come from a specific situation, while intrinsic stress is related to the level of intellectual challenge that a task requires. Some people have chronic intrinsic stress.
Stress interferes with both our ability to retain new information and to retrieve memories and knowledge, causing memory loss. Furthermore, extrinsic stress seems to affect spatial learning. In the following sections we will describe these effects in more detail.
The Yerkes-Dodson law states that stress does not always negatively interfere with cognition, but a moderate degree of brain activation improves memory and performance on intellectual tasks. On the other hand, excessive increases in stress levels worsen cognitive functions.
This gives rise to the so-called “inverted U effect”: if our body responds to environmental demands with mild or moderate stress responses, the effectiveness of our productivity increases until it reaches a threshold (the ideal activation point) from from which performance progressively decreases and memory leaks occur.
Too intense stress responses interfere with the performance of intellectual tasks because they are associated with physical and cognitive symptoms such as concentration difficulties, tachycardia, sweating, dizziness or hyperventilation.
Effects of acute or transient stress
When we find ourselves in a stressful situation, our attention focuses on the most salient stimuli, while we pay less attention to the rest; This phenomenon is known as “tunnel vision” and facilitates the consolidation of some memories while interfering with others, causing memory loss.
Acute stress can have beneficial effects on some types of memory but only under certain conditions. In this sense, the Yerkes-Dodson law should be mentioned again; besides, Some studies have shown that glucocorticoids improve the formation of new memories but they worsen the recovery of other already existing ones.
Furthermore, emotionally relevant stimuli are better remembered if the stress response has occurred previously, if the retrieval of the information takes place shortly after encoding, and if the memory situation is similar to the learning situation.
Other research suggests that, under conditions of stress, we learn and remember to a greater extent information and situations that cause us emotional discomfort. This fact is associated with the mood congruency effect described by Gordon H. Bower, who describes similar results in relation to depression.
Consequences of chronic stress
The stress response not only involves changes in memory at the time it occurs, but if maintained chronically it can cause long-term damage to the brain. Since the body consumes many resources and reserves in the activation of these physiological processes, Chronic stress is significantly more harmful than acute stress.
After situations of acute or transient stress our body recovers homeostasis, that is, physiological balance; On the other hand, chronic stress prevents the body from reaching homeostasis again. Therefore, if stress continues, it unbalances the body’s responses.
From a physiological point of view, this facilitates the appearance of symptoms such as abdominal, back and headache pain, chronic difficulties in concentrating and falling or staying asleep, anxiety attacks, etc. Furthermore, continued stress is associated with social isolation, depression and the development of cardiovascular diseases.
Regarding memory loss, chronic stress increases the risk of suffering from dementia in older people. These effects are probably related to glucocorticoid activity in the hippocampus and other brain regions on which memory and cognition in general depend.
