Mind Is Flat by Nick Chater

Author:Nick Chater
Language: eng
Format: epub, azw3
Publisher: Yale University Press
Published: 2018-08-06T16:00:00+00:00

PRODDING THE CONSCIOUS BRAIN

The eminent neurosurgeon Wilder Penfield pioneered brain investigations and brain surgery on people who were wide awake.5 From the patient’s point of view, a little local anaesthetic to deal with any pain of the incision through the skull is all that is required. Though the brain detects pains of many and varied types throughout the body (pokes, abrasions, twists, excesses of heat and cold), the brain has no mechanism for detecting damage to itself. So Penfield’s brain operations were entirely painless for his patients.

The purpose of Penfield’s surgery was to relieve severe epilepsy by attempting to isolate, and remove, portions of the brain from which the seizures originated. In an epileptic attack, the cells across large areas cease any complex cooperative computation to solve the problem of the moment and start instead to ‘fire’ in slow synchronized waves and hence, being entrained by each other, become disengaged from their normal information-processing function. A slightly fanciful parallel is to imagine the population of a busy city suddenly dropping their varied and highly interconnected activities (buying, selling, chatting, building, making) to join in a single, continuous, coordinated, but entirely involuntary Mexican wave – wherever the wave spreads, work will come to a complete halt. In severe epileptic attacks, the whole, or large areas of, the cerebral cortex become entrained and hence entirely non-functional, until the brain is somehow able to reset itself; people with severe epilepsy can suffer such debilitating attacks many times each day. The entrainment in epilepsy typically starts in a specific region of the cortex. It is as if the inhabitants of one district are particularly prone to spontaneously launching into Mexican waves – and the nearby neighbourhoods are then drawn in, and the wave spreads inexorably across the city. Penfield’s logic was that, if only the troublesome district could somehow be isolated from the rest of the city, the Mexican wave would be unable to spread – and normal life would continue unhindered. In practice, Penfield found that the most effective treatment often turned out to be rather extreme: rather than a few subtle surgical cuts to key regions of the cortex, the equivalent of closing a few bridges or main roads, Penfield was often driven to remove large regions of the cortex, analogous to flattening huge areas of a city (see Figure 28).

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