Christian Jarrett, Wired
The newspapers love using neuroscience findings to make us feel bad about our less salubrious habits. Earlier this year they had a field day with a study that purported to show time spent watching online porn shrinks the brain.
Even more recently, we were warned about multi-tasking with our digital devices: “Multi-tasking makes your brain smaller,” exclaimed the Daily Mail. Similar claims have been made for video gaming and junk food. The message is usually the same – you already knew porn/junk food/gaming etc was bad, well now scientists tell us it ACTUALLY SHRINKS YOUR BRAIN, as if this is the final definitive proof for the evilness of the deeds in question.
What none of these news reports tell you is that brain shrinkage can be a good thing. Indeed, it’s a mistake to think that bigger means better when it comes to brain power (this is “Myth 21″ in my new book Great Myths of the Brain). Elephants and whales have massive brains, but they’re not the cleverest animals on the planet; bees have tiny brains and are very smart. Moreover, localised brain shrinkage can be a sign of increased neural efficiency. Also it’s worth remembering how, through adolescence, our brains don’t just keep getting bigger and bigger; rather they undergo a massive pruning back of excess grey matter.
The idea that localised brain shrinkage isn’t necessarily bad is brought home wonderfully by a new brain scanning study of elite chess players. Jürgen Hänggi took structural MRI scans and diffusion tensor imaging scans of 20 male expert players (including three grandmasters and seven international masters) and compared them with 20 male inexpert players. This is only the second study ever to look at the structural brain differences characteristic of elite chess players, and the first ever to also include a measure of white matter tracts (provided by the diffusion tensor scans).
So, did the elite chess players have huge bulbous temporal lobes for remembering all those chess formations? Did they have massively engorged frontal gyri for considering multiple moves at once? Actually no. There were few structural brain differences between the elite and non-elite players, and those differences that were observed all pointed in the same direction – to localised shrinkage in the brains of the grandmasters and their ilk.
Specifically, the elite players showed reduced grey matter volume in the occipital-temporal junction (OTJ; where the occipital lobe at the back of the head, and the temporal lobes at the side of the head, meet). The OTJ is known to be involved in representing objects and their relations to each other. Elite players also showed reduced “diffusivity” in parts of the superior longitudinal fasciculus. This is a major communication tract in the brain, sending information from visual areas to executive areas. Diffusivity is a technical word for “bushiness”, so elite players showed more pruning along this major communication pathway. Also, the more years experience a player had, the smaller their caudate nucleus volume tended to be (the caudate has many functions, among them decision making).
What to make of these areas of reduced brain volume in the expert chess players? The researchers are admirably honest. The findings are “difficult to explain on the basis of current knowledge” they write, “since it is not clear how cortical thickness and grey matter volume are related to performance in psychological tasks.”
That is a line you won’t find very often in the Daily Mail or other tabloids! Brain science is complex (who knew?), still in its infancy, and it really is difficult to interpret structural brain differences. It’s clear that a simple rule – shrinkage is bad / growth is good – just doesn’t work. To provide you with a little wider context of the conflicting picture, there is research suggesting that practice leads to localised thickening of neural matter – for example, musicians often have more neural matter dedicated to the control of their hands and fingers than do non-musicians. Also, cortical thickness shrinks with ageing and tends to correlate with a loss of cognitive performance. But on the other hand, people who are tone deaf (they have “amusia”) have been shown to have extra thick neural matter in their auditory cortex, so thicker doesn’t always mean better. And this new chess study isn’t the first to associate expertise with less brain power or brain usage. For example, earlier this year, a functional brain imaging study showed how little brain activity was exhibited by the Brazilian soccer player Neymar da Silva Santos Júnior when he controlled his foot.