A Radical New Model of the Brain Illuminates Its Wiring
IN MID-19TH CENTURY Europe, a debate was raging among early brain scientists. Strangely, this academic disagreement had its roots in the pseudoscience of phrenology, the practice of measuring bumps on the skull to determine someone’s personality. Phrenology had found purchase at fairs and was quite popular with the general public, but it had been roundly rejected by most scholars.
For others, though, this carnival trick held a pearl of inspiration. Phrenology depended on the assumption that different parts of the brain are associated with different traits and abilities, a position called “localizationism.” And the absurdity of skull-measuring did not necessarily invalidate this notion.
But others disliked the stench of charlatanism that clung to any ideas associated with phrenology. This second camp contended that capacities are evenly distributed throughout the brain, and so damage to any one brain region would have the same effect as damage to any other. The debate between these groups raged until 1861, when Paul Broca, a French neurologist, reported on a patient with a bizarre set of symptoms.
Though this man could not speak, he was entirely capable of understanding language, and his intelligence seemed unaffected. When the patient died and Broca dissected his brain, he discovered a lesion, or site of severe damage, low on the left side of his brain. Here was an individual who had sustained brain damage in a specific area and had lost a very specific ability—while the rest of his functions remained intact! Localizationism had been vindicated. For the next 150 years, it would be the dominant position in brain science.