Understanding the neurological basis for déjà vu would certainly help scientists pin down its trigger, but neural connections are only partially understood. For a long time, one popular theory held that delayed neurological transmission was responsible. When we perceive, pieces of information from different neuronal paths enter the processing centers of the cerebrum and must, of course, blend together to consistently produce a uniform impression. It would make sense that any delay in some aspect of transmission could be muddled and set off déjà vu.
In 1963 Robert Efron, then at the Veterans Administration Hospital in Boston, tested this general notion. His experiments led him to conclude that the temporal lobe of the brain’s left hemisphere was responsible for the punctual sorting of incoming data. He also found that this location received signals coming over visual pathways twice, within milliseconds of one another—once directly and once via a normal detour through the right hemisphere. If, for some reason, a delay were to occur in the detoured transmission, the left temporal lobe would register a time lapse on the second arrival and could interpret the visual scene as having already happened.
After a long break, I experienced déjà vu, about two weeks ago. I savored it, relishing each microsecond. If only I could recapture the existential terror of contemplating infinity once again.