Dynamics of motor direction representation in the primate premotor and primary motor cortices during sensorimotor learning

Sensorimotor learning requires reorganization of neuronal activity in the premotor cortex (PM) and primary motor cortex (M1). However, how PM- and M1-specific reorganization occurs in primates remains unclear. We conducted calcium imaging of these areas in common marmosets while they learned a two-target reaching (pull/push) task. Throughout learning, the dorsorostral PM (PMdr) showed peak activity earlier than the dorsocaudal PM (PMdc) and M1. PMdr showed decreased representation of newly introduced (push) movement, whereas PMdc and M1 maintained high representation. Many task-related neurons in PMdc and M1 exhibited a strong preference to either movement direction. PMdc neurons dynamically switched their preferred direction, whereas M1 neurons stably retained their preferred direction. Differences in preferred direction between adjacent neurons in PMdc increased during learning. These results suggest that in primate sensorimotor learning, dynamic motor representation in PMdc converts the cognitive sensorimotor signals of PMdr to stable and specific motor representation of M1.