Accumulation of Neural Activity in the Posterior Insula Encodes the Passage of Time

Abstract

AbstractThe experience of time, i.e. the estimation of duration, is fundamental for perception and behavior and, therefore, essential for the survival of the individual organism. Over the last decades, neuroimaging, neurophysiological and clinical neuropsychological studies have pointed to many different brain areas involved in the processing of time. However, the core neural substrates and the processes accounting for the encoding of duration, which could form a timekeeping mechanism (essentially, a neural clock), are still unknown. Here we present evidence of neurophysiological activity in circumscribed areas of the human brain that is involved in the encoding of duration. Time-activity curves of neural activation derived from event-related functional magnetic resonance imaging (fMRI) during a time estimation task show that bilateral posterior insula as well as superior temporal and inferior parietal cortices build up activation when individuals are presented with 9 or 18 seconds tone intervals. Since the build up of neuronal activation peaks at the end of the interval, it appears that this accumulator-type activity encodes duration. Because of the close connection between posterior insula and ascending internal body signals, the accumulation of physiological changes in body states might constitute our experience of time. These results could be the starting point for a neural model of human time perception in the multiple-seconds range in which specific brain regions accumulate brain activity for the representation of duration.