Hemispheres of influence

Discover Magazine has an interesting Carl Zimmer article on one of the most intriguing questions in neuroscience – why do we have two cortical hemispheres? And why are they not quite the same?

It turns out that the 'brain of two halves' is incredibly common in the animal kingdom and that many creatures also show the behavioural lateralisation that we most readily see in humans as someone being left or right handed.

But it's no entirely sure why we, or indeed, or animal compatriots, have evolved this way, although various theories are kicking around:

David Stark of Harvard Medical School recently found additional clues about lateralization in his studies of 112 different regions in the brains of volunteers. He and his collaborators discovered that the front portions of the brain are generally less tightly synchronized across the hemispheres than are the ones in the back. It may be no coincidence that the highly synchronized back regions handle basic functions like seeing.

To observe the world, it helps to have unified vision. At the front of the hemispheres, in contrast, we weave together streams of thought to produce complex, long-term plans for the future. It makes sense that these areas of the brain would be more free to drift apart from their mirror-image partners.

Zimmer goes on to puncture the myth of 'left brained' and 'right brained' people, or indeed, thinking styles, erroneously labelled with these pseudoscientific terms.

While certain cognitive styles have been correlated to greater activation in the left or right hemisphere, to describe a whole class of problems of thinking methods like this is nonsensical because the two hemispheres of the brain work together.

It's like claiming someone is a good cook solely because they come from Italy. The generalisation is so broad it just doesn't apply to individual people or situations.

Anyway, the Discover article is an excellent whistle-stop tour through the curious world of brain lateralisation.

Link to Discover on the brain of two hemispheres (via @mocost).