What can one neuron tell us about brain function? It can tell if we are looking at a picture of Jennifer Aniston. Brain surgeon and researcher Itzak Fried, in 2005, was probing a certain brain region in patients with epilepsy to pinpoint the source of their seizures. This is open brain surgery done while the patient is conscious (the brain doesn’t have pain receptors). These patients agreed to additional probing in the interest of science. Fried was showing patients pictures, some of famous people, and kept running into neurons that would fire to multiple representations of the same person or object, and to nothing else (within the limited but large set of images used). “The first time we saw a neuron firing to seven different pictures of Jennifer Aniston–and nothing else–we literally jumped out of our chairs,” recalled R. Quian Quiroga, who did subsequent work on the phenomenon with Fried.
In a study by Quiroga, Fried and others, severe epilepsy patients each had 64 tiny probes implanted in different parts of the brain, to study how the seizures manifested. The patients also agreed to view sets of images while the probes were monitored. A number of invariant responses (the same neuron firing to multiple views of the same person/thing) were found. “In some patients, Jennifer Aniston neurons would also fire to her fellow actresses in Friends, … But they would never fire to other similar-looking, but otherwise unconnected, actresses” (Nature Magazine). Either way, a connection was made between a concept and a single neuron. Finding connections between a specific neuron and one specific memory has been going on for seven decades, and single neuron stimulation has triggered laughter, remembered childhood scenes or hearing snippets of music, but this association, apparently with the concept of a certain person, instantly became and remains a major focus of brain research.
