Wednesday, 23 July 2014

Resilient or depressed? Neurons in the brain make the difference

Many of us go through major or minor crises in our lives. These could be unemployment, a serious disease or accident, a divorce, or many others. But why is it that some people cope with such crises surprisingly well and are even stronger than before, whereas others end up in a depression? A recent study reveals the mechanisms involved in our brain.

Minghui Wang and colleagues from the Cold Spring Harbor Laboratory in New York used a learned helplessness paradigm in their study: This involves teaching animals that they cannot control a situation by e.g. exposing them to electric shocks and not giving them the opportunity to avoid these. Learned helplessness occurs when afterwards animals endure the aversive stimuli although being given back the opportunity to escape from them. In their study the researchers used mice that were exposed to electric bolts. Resilient mice escaped the bolts once given the opportunity. However, helpless mice did not. What the researchers could see in those mice that had become helpless as opposed to the resilient ones was that in the former there was enhanced neural activity in a brain region called the medial prefrontal cortex. There was less activity in the respective region in the resilient mice. When they artificially enhanced the activity of neurons in this region in previously resilient mice these mice became helpless as well and remained where they are when exposed to the electric shocks even though they had the opportunity to escape. Thus, they concluded that activity in the medial prefrontal cortex is related to learned helplessness.

The original study was published in the Journal of Neuroscience. There is an outline of the study on the IFLScience Blog and another one including some background information on the Washington Post homepage.

Now what does learned helplessness have to do with depression and what can we conclude from the study? Learned helplessness is a key symptom of depression: Depressed people are unable to avoid or improve aversive situations even though they might be able to. Thus, understanding the mechanisms behind this behaviour is important for understanding and (hopefully) curing the mental illness. And there is in fact research indicating that stimulating certain regions of the brain can be used for treating depression [http://www.iflscience.com/brain/brain-stimulation-may-treat-severe-depression-better-meds]. What is interesting here is that it is enhanced activity (in the brain) that leads to (physical) inactivity and the reverse. Thus, inhibition and inactivity seem to be very meaningful for understanding the brain as well. Maybe it is a bit like when looking at the representation of expertise in the brain: One could say that overall there is less activity in an expert’s brain when completing the task he or she is an expert in. Thus, the best behavioural outcomes seem to be achieved by targeted and efficient functioning of the brain.

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