Monday, June 28, 2021

In our brains everything changes

Sometimes learning the hard neuroscience of how our brains work leaves me feeling a bit queasy. The first time this happened was when I learned about the Libet experiments that showed that cells in our motor cortex start a movement well before we ‘decide’ to initiate it. “We” think we are initiating a movement when in fact “it” (those brain cells) are already well on their way to doing it. So what happened to my ‘free will’? Well...there is a work around for that problem that I explain in my “I Illusion” and subsequent web lectures. 

 A further uncomfortable jolt comes on seeing evidence the brain cells that become active during a familiar experience can change over time. Each instance of the recall of an important event can recruit a different group of nerve cells, because each time the memory is fetched from the neuronal ‘library’ it gets put back, sometimes slightly altered, in different nerve cell collections and connections. A very striking example of this has been provided by Schoonover et al. Who show that the network of nerve cells active when a particular smell triggers a specific behavior changes over time, moving to different brain areas. This is an example of ‘representational plasticity’ which is discussed in a review article by Rule et al. 

This conflicts with our common sense view of how our minds should work. If you have an experience and then later remember it, you must have put it somewhere in your brain’s library of nerve cell connections, like a book on a library shelf, so that all you have to do to remember something is go fetch it. If the experience is an emotional one it couples with a hard wired circuit for that emotion. This essentialist view of how our minds work is being thoroughly displaced as experimental evidence continues to accumulate showing that in each moment we are constructing our experience anew - reminding of the Buddhist saying that the river you view flowing past is never the same twice. The series of MindBlog posts (starting here) on the work and ideas of Barrett covers this material. 

It is from constant change and flux in our evolved neuroendocrine circuitry that we generate the illusion of certainty or constancy - expectations of selves, rules, objects, and emotions that stay in place. We model the world we expect to see before each moment we are about to enter. If our expectations are not met, then our brains perk up to adjust them appropriately.  


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