Instantaneous movement-unrelated midbrain activity modifies ongoing eye movements

Abstract

At any moment in time, new information is sampled from the environment and interacts with ongoing brain state. Often, such interaction takes place within individual circuits that are capable of both mediating the internally ongoing plan as well as representing exogenous sensory events. Here we investigated how sensory-driven neural activity can be integrated, very often in the same neuron types, into ongoing oculomotor commands for saccades. Despite the ballistic nature of saccades, visually-induced action potentials in the superior colliculus (SC), a structure known to drive eye movements, not only occurred intra-saccadically, but they were also associated with highly predictable modifications of the ongoing eye movements. Such modifications were also possible by peri-saccadically injecting single, double, or triple electrical microstimulation pulses into the SC. Our results suggest instantaneous readout of the SC map during movement generation, irrespective of activity source, and explain a significant component of kinematic variability of motor outputs.