Overdispersion: Navigating Noise, Learning and Remembering

I recount the personal and professional circumstances that contributed to recognizing overdispersion in the discharge of hippocampal place cells. Place cell overdispersion describes the general fact that when a rodent passes through the cell's place field, action potential discharge is often surprisingly excessive or inadequate relative to expectations from the cell's firing rate map. These large deviations from place tuning are far beyond what random noise can explain. Instead, overdispersion indicates that there are additional extrapositional signals in place cell discharge, not merely place. I discuss that the finding might have been initially ignored because we did not identify a specific source of extrapositional information, and that today many have been identified. The narrative focuses on the overall importance of recognizing that there must be extrapositional signals (i.e., mixed selectivity) to the intellectual evolution of my research program.