How Stress Affects Memory
Posted on 16th August 2018 at 20:54
In numerous different animals, cognitive ability, including learning and memory, is often negatively affected by stress. But not all individuals of a particular species are equally good at cognitive tasks to begin with, and they respond to the effects of stress in different ways.
Take pond snails – specifically Lymnaea stagnalis – for example. They, just like other animals (including humans), remember things about different aspects of their environment. They remember smells that are associated with good things to eat, for instance, as well as negative experiences which may be associated with the risk of being eaten themselves. But not all snails are equally good at remembering. Some snail populations, originating from different rivers or ditches, are much better at forming memories than others.
Research has found that a 30-minute operant conditioning training session – whereby a stimulus is applied each time an animal performs a specific behaviour, in this case a gentle poke – produces a memory of the stimulus lasting about three hours in snails from some populations, and 24 hours (which is long term memory for snails) in others. We also found that two 30-minute training sessions result in a memory lasting a day in snail populations with weak memories, and seven days in populations with strong memories. So it seems some populations are "smarter" than others when it comes to forming memories of the training.
"smart" pond snails also appear to be more robust to some types of stress. Smart snails still form long-term memory following two training sessions. But long-term memory is blocked in snail populations which form a weak memory.
However, not all types of stress can be considered equal. Each type can have a different effect on an animal. In humans, for example, different types of stress can cause short term emotional problems while others can lead to long term physical health issues. And in snails, we have found that one type of stress – social isolation, or loneliness – can change the way that they form memories.
This research raises two important considerations when looking at the cognitive differences among individuals of any species. First, that the social environment doesn't affect all individuals in the same way. Not all will experience the same levels of stress when isolated. Second, that our conclusions about which individuals are "smart" may be highly dependent on the environment in which they are tested.
Though this study was focused on snails, it tells us a lot about memory in all kinds of other animals and humans, too. Snail memory is affected by environment in the same way as a lot of other species. For example, things that are beneficial to memory formation in mammals, such as plant flavonols found in red wine and dark chocolate, also improve snail memory. Similarly, different types of stress that negatively affect memory in mammals, including social isolation, also have negative effects on snails' memory.
If you think that stress is affecting you or your employees, there are simple tools and tecniques that you can implement in your everyday life that can build your resilience to stress. Book a discovery session for you or your team to find out just what harm stress is doing and receive the training you need to be resilient to the effects of stress.
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