Stress and memory, a love/hate relationship?

Last update: February 20, 2024
Reading time: 3 minutes
By Brain Matters

You have just finished reviewing the entire material for the third time, you know everything by hearth. You’re definitely ready for your exam. The next morning, your bus is canceled, and you have to run to the university to avoid being late. You arrive just on time, but you’re the last one to enter the room. Your heart is racing, your hands are clammy, and you suddenly remember how important this exam is for your future career… We can probably all agree that these circumstances aren’t ideal for passing an exam. The likelihood of not being able to recall the information studied for the exam, even though it’s there, stored in some drawer of our mind, is greater than when we feel calm, rested and focused. However, sometimes stress helps us with remembering things. For instance, most people say they remember vividly the birth of their child, the loss of a close acquaintance, or some other dramatic event of their life such as 11.09.2001. I therefore wonder, can we conclude that the combination of stress with memory always leads to a messy outcome? Let’s delve into the different memory processes to see if we can shed some light on the role of stress for memory.

Learning and temporal dynamic of stress effect on memory

Learning is a complex and time-consuming activity that can be divided into three memory stages; encoding, consolidation, and retrieval. As explained in Brain basics: Learning - Brain Matters, a memory can be seen as a road between neurons, and the more this road is used, the bigger and more effective it will become. Conversely, if the road is deserted, it will eventually disappear. This is a very basic definition of the concept of neuroplasticity, which is also described in this statement by Donald Hebb “Neurons that fire together, wire together”. Thus, the encoding of a new memory can be seen as the first way we have to make through a dense forest. Consolidation refers to the subsequent reuse of this path after initial encoding in order to, first, prevent its natural disappearance over time, and second, to make it bigger and more accessible. Then, the retrieval reflects the process of walking back the path to bring the previously stored information to our consciousness. The following question is then, how does stress affect the traffic on these neuronal roads?

The biological components of the stress response, among them, adrenaline, noradrenaline, and cortisol, can be seen as traffic controllers, whose mission is to modulate the accessibility of different roads of the brain depending on the state of the individual. For instance, if you see a gun pointed at you, the brain will command, via a hormonal cascade (called the HPA axis), the release of adrenaline and noradrenaline from the adrenal glands. They are responsible for many physiological changes such as increased blood pressure and muscle tension, in order to prepare the individual for a fight or flight response. In addition, they will also affect the brain by increasing the construction of new roads, enhancing the encoding process of memory formation. While doing so, they also restrict the accessibility of other pre-established roads to save energy and allow a full orientation of the attentional resources to the threatening event. This makes sense from an evolutionary point of view; when dealing with an unexpected and possibly dangerous situation, humans developed this stress response as a way to react quickly to the threat with a “flight or fight” response. Furthermore, if the person survived this event, it would be beneficial to remember what happened. We are more likely to remember what happened to prevent the manifestation of similar threatening occurrences in the future. This is why, when we experience a stressful event, we are more likely to remember this compared to a random everyday situation, and are more prone not to be able to retrieve previously stored information from our memories.

To sum up, when you are stressed before your exam, your brain probably interprets this inner physiological activation as an indicator of some sort of dangerous situation, or at least one “worth paying attention to”. Hence, it may direct its resources to the encoding process, which can be done more easily by partly impeding the retrieval process, although you would want the opposite to happen.

Author: Pablo de Chambrier

If you wish to learn more about the temporal dynamics of stress and the specific actions over time of the biological components of the stress response, this article offer details explanation:

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