Drifting population dynamics with transient resets characterize sensorimotor transformation in the monkey superior...

Sensorimotor transformation, the process of converting sensory input signals into a movement command, is essential for mediating goal-directed movements. Neural correlates of sensorimotor transformation were assessed in the delay period activity of superior colliculus (SC) neurons recorded simultaneously in three male monkeys generating saccades to visual targets. We applied dimensionality reduction on the SC population response and used a proximity index to quantify the relative, probabilistic closeness of the evolving delay period activity to the visual- and motor-dominant subspaces associated with the sensation and action states. Here, we show that sensorimotor transformation is achieved through a drift in population activity from a visual-like to a motor-like representation during the delay period, with transient visual resets following microsaccades. Also, the proximity index was correlated to reaction time throughout the delay period, suggesting a similar movement preparation mechanism is conserved across the skeletomotor and oculomotor systems.