Kelly Clancy in Nautilus:
My father, a neurologist, once had a patient who was tormented, in the most visceral sense, by a poem. Philip was 12 years old and a student at a prestigious boarding school in Princeton, New Jersey. One of his assignments was to recite Edgar Allan Poe’s The Raven. By the day of the presentation, he had rehearsed the poem dozens of times and could recall it with ease. But this time, as he stood before his classmates, something strange happened. Each time he delivered the poem’s famous haunting refrain—“Quoth the Raven ‘Nevermore’ ”—the right side of his mouth quivered. The tremor intensified until, about halfway through the recitation, he fell to the floor in convulsions, having lost all control of his body, including bladder and bowels, in front of an audience of merciless adolescents. His first seizure.
When my father heard this story, he decided to try an experiment. During Philip’s initial visit, he handed the boy a copy of The Raven and asked him to read it aloud. Again, at each utterance of the raven’s gloomy prophecy, Philip stuttered. His teeth clenched and his lips pulled sideward as though he were disagreeing with something that had been said. My father took the poem away before Philip had a full-blown fit. He wrote a note to the boy’s teacher excusing him from ever having to recite another piece of writing. His brain, my father explained, had begun to associate certain language patterns with the onset of a seizure.
The power of the nervous system lies in this ability to learn, even through adulthood. Networks of neurons discover new relationships through the timing of electrochemical impulses called spikes, which neurons use to communicate with one another. This temporal pattern strengthens or weakens connections between cells, constituting the physical substrate of a memory. Most of the time, the upshot is beneficial. The ability to associate causes with effects—encroaching shadows with dive-bombing falcons, cacti with hidden water sources—gives organisms a leg up on predators and competitors.
But sometimes neurons are too good at their jobs. The brain, with its extraordinary computational prowess, can learn language and logic. It can also learn how to be sick.