vendredi 16 août 2013

Allez vous balader

Nicholas Spitzer est professeur de neurosciences à l'université de Californie à Berkeley. The Economist lui a demandé ce qu'il faisait pour protéger son cerveau. Il a répondu gymnastique, escalade et escalade sur glace. Okay, et les mots croisés? Et la lecture? Selon Spitzer c'est bien si vous voulez devenir un champion de mots croisés mais ça ne développe pas dans votre cerveau de nouvelles fonctions cognitives, alors que le sport et en particulier l'escalade, oui!

Doing crosswords isn’t good for your brain?

It is good for improving your crossword skills but does it lead on to other kinds of advanced cognitive function? No. There is no translation of the crossword skills to other skill categories. That shouldn’t discourage anyone, they are a lot of fun, but a vigorous hike will do more for your cognitive function.

Autres idées de M. Spitzer, sur la dépression saisonnière par exemple :

Our experiments have mainly been done on adult rats. A finding that is directly related to the human condition is that putting the animals on different photoperiods [day and night cycles] changes the neurotransmitter identity in the hypothalamus [a part of the brain] and this changes the animal’s behaviour. When animals are on a short day (rats are nocturnal so a short day is good) they make dopamine, the reward chemical. On the long day the neurons switch from dopamine to somatostatin, which retards growth.
We test the behaviour with a simple maze that has a dark side and a light arm. When they have the dopamine from the short day they waltz around in the light arm, but during the long-day cycle they hide out in the dark side. Their anxiety or confidence depends on the neurotransmitters which, in turn, depend on the light experience.
We think this is related to Seasonal Affective Disorder. (I did my PhD in London and remember the short winter days very well!) The treatment for SAD is no longer drug therapy, but light.

Why do humans become depressed when it gets dark?

We have to speculate a bit here, but the idea is that during the winter months back in the days when we had a very seasonally driven existence it was perhaps useful to be quiet, withdrawn and sleeping a lot. In the summer months when the spring arrives you want to run outside and be active.

So we are conserving energy and not consuming our resources?

Exactly. There is evolutionary rationale for this kind of change in the brain. The rewiring of the brain can occur in seconds as we change the neurotransmitters and neuromodulators, such as dopamine and serotonin. The metaphor that’s useful is a railway switching yard—the trains come into the yard and depending on the switch they can go off to Manchester or down to Bangor. These neuromodulators route the brain’s electrical activity. The circuitry doesn’t change but the route does.