When I learned neuroanatomy at Medical School I was taught that the two cerebral hemispheres were symmetrical. There was no mention at all that they were in any way different. But look at this image above. (This is referred to as Yakovlevian Torque)
Clearly, the two hemispheres are NOT identical. In particular the right one is bigger at the front, and sits just a bit in front of the left, and the left one is bigger at the back, and sits just a little further back than the right.
Why might that be? Why the larger frontal area on the right, and occipital (back) area on the left?
Iain McGilchrist nicely summarises it by pointing out that how the left hemisphere approaches the world is by trying to grasp it. We try to make sense of the world by literally getting a hold of it – we want to understand it, to measure it, to predict what it going to happen by matching the patterns we see to those we have already learned from our experience, and we try to manipulate or control it. This is what the left hemisphere is really great at doing. Interestingly, the areas at the back of the brain are primarily for processing the outside world (our visual and auditory areas are toward the back, and the cerebellum which helps us to know whether we are standing up or falling over by orientating where we are in 3D space, is also to the back). The right hemisphere majors in making connections and maps. It has a significant role to play in all the skills we need to act as social animals.
So, one nice summary of why there might be this asymmetry in the brain, is to enable us to both grasp the world and to be social creatures. Amongst all the creatures on this planet we are probably the most able to manipulate our environment and the most developed as social animals.
There’s a huge amount more to this left brain/right brain understanding but I do think this is a fabulous starting point. Oh, and by the way, look at this
Interesting, huh? And how come this has been pretty much completely ignored for so long?
Well, Iain McGilchrist’s theory, written up in full in The Master and His Emissary, or summarised in the Kindle Single, The Divided Mind, is that we have over developed the left hemisphere approach so much that we have developed the tendency to see only what we have already “learned” – so if we were taught that it was symmetrical, and we haven’t explored the differences between the two hemispheres, then we’ve become a bit blind. Time to start using our whole brains?
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