Feeling mentally soggy? It could be that your brain has shrunk what with it being winter and all

I wouldn’t have believed that part of the brain can shrink by 40% and then regrow, but exactly that happens to the Etruscan Shrew in the winter. So maybe it’s not you or even COVID19.

It’s a fascinating critter — the world’s smallest mammal, tipping the scales at 1.8 grams (about 6 aspirins). It has a very rapid metabolic rate, eating twice its weight daily. Things get tight in the winter so it shrinks its brain. Remember that even in big and sluggish us, as we sit there reading (or writing) this, our brain is receiving 20% of our cardiac output, despite being 3% or so of our body weight. For more about the Shrew see https://en.wikipedia.org/wiki/Etruscan_shrew

For more detail see https://www.pnas.org/content/pnas/117/50/32136.full.pdf.

What’s really exciting is that the number of neurons increases in the shrew’s brain come summer. Since it’s a mammal, we’re not talking about lizards regrowing limbs, but something evolutionarily close to us. For more detail see https://www.pnas.org/content/pnas/117/50/32136.full.pdf.

There are actually some conditions with reversible cerebral atrophy, and as a neurologist I made sure to look for them.

Here they are

l. Alcoholism

2. Adrenal corticosteroids (exogenous or endogenous)

3. Malnutrition in kids

4. Depakene (valproic acid)

5. Anorexia nervosa.


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  • Christophe L Verlinde  On January 5, 2021 at 10:43 pm

    Is it possible that most of the volume change is due to an alteration of perfusion? It appears that this aspect was not investigated in the study.

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