Chronotopic maps in human premotor cortex

Abstract

Time is the most elusive dimension of everyday experiences. We cannot see or touch time nevertheless we clearly sense its flow and adjust our behavior accordingly. The neuronal mechanism underlying our capacity to perceive time remains yet unknown. Single-neuron recordings in animals suggest that the encoding of temporal information in the millisecond/second range is achieved via duration tuning mechanisms. The existence of such mechanisms has never been reported in the human brain. Here, in two independent visual duration-discrimination experiments, using ultra-high-field (7-Tesla) functional magnetic resonance imaging, we found duration-related activations in the medial premotor cortex and the posterior parts of the left parietal lobule of the human brain. More specifically, in the supplementary motor area (SMA), we identified a topographic organization of duration selective voxels i.e., chronotopic maps. Voxels sensitive to the shortest duration were mainly located in the anterior premotor cortex while those responsive to the longest duration in the posterior premotor cortex. This rostro-caudal direction of chronotopic organization was consistent in both experiments. We also showed that the hemodynamic response of each portion of the chronotopic map was enhanced by the preferred and its' neighboring durations and inhibited by non-preferred durations represented in distant portions of the map. These findings identify, for the first time in the human brain, duration-sensitive tuning as a neural mechanism underlying the active recognition of time and demonstrate that the adaptive representation of an abstract feature such as time can be achieved by a topographical arrangement of duration-sensitive neural populations similar to that observed in several cortical and subcortical structures for the processing of sensory and motor signals.

Meeting abstract presented at VSS 2018