(Response to an article in Nautilus, 14th October 2020, in which David Eagleman is interviewed by Steven Paulson)
The ‘plasticity’ of the brain: We use the term ‘plasticity’ to suggest that something can be moulded into a particular shape, a plastic duck, box, bag and a million other things in our modern world. David Eagleman does not like the term ‘plasticity’ used in connection with the brain. Plastic objects have been given a firm and fixed shape. But the brain is not like that, he argues, but rather in a constant state of flux: ‘You’ve got 86 billion neurons and a fraction of a quadrillion connections between them. These vast seas of connections are constantly changing their strength, and they’re unconnecting and reconnecting elsewhere. It’s why you are a slightly different person than you were a week ago or year ago. When you learned that my name is David, there’s a physical change in the structure of your brain. That’s what it means to remember something.’
The brain is also very adept and resourceful. In some cases if one area is lost or damaged and can no longer fulfil its usual function, another part of the brain will take over that function. He cites as an example studies of the brains of nuns who had donated them to science. From the evidence of examination of their brains, some of these nuns had Alzheimer’s disease. But the challenging fact is that in spite of this when they were alive their illness had not been apparent. Eagleman attributed this fact to their lifestyle, their regular duties and constant interactions with one another. The significant point, however, is this: ‘Even though their brains were physically getting chewed up by the disease, they were constantly building new roadways in the brain.’
Another example of this self-maintenance activity in the brain is taken from blind people. Scans have shown that in some of them the unused or little used visual cortex at the back of the brain begins to be encroached upon by areas which deal with touch and hearing. In short, redundant parts of the brain are appropriated to carry out different functions.
He adds, interestingly, that of course the brain is not working to a conscious plan. Inside the brain all the different experiences we call seeing, imagining, remembering, thinking and so on are correlated (in some mysterious way) with electrochemical activity. ‘The brain doesn’t know if the data come from photons or air compression waves picked up by the ears or mixtures of molecules picked up by the nose or mouth. It just figures out (my italics) how to establish feedback loops to send commands to muscles that change the input in a particular way.’ ‘Figure out’, difficult to avoid the language of agency and thought to describe the sort of physical activity that is goal oriented.
How strange that within the mechanistic cause and effect physical world, which, of course, includes the brain, are collections of atoms and molecules which pursue ends, try to preserve and even repair themselves.
Consciousness and Other Matters 