Auditory- and movement-related neural activity interact in the pulvinar of the behaving rhesus monkey

We recorded the activity of 101 pulvinar nucleus neurons in a rhesus monkey performing an auditory discrimination task. The monkey was trained to push a lever to the left after hearing a noise burst and to the right after hearing a tone. When the stimulus was presented every 3 s the auditory evoked potentials (AEPs) habituated very rapidly to about 10% of initial height. With a stimulation rate of 1 every 15 s, however, the AEPs maintained full amplitude. A movement-related increase in firing rate was recorded in 81 units (80%) and could usually be detected 100-200 ms before onset of arm EMG. A stimulus-related firing was detected in 70 units (69%). Most of the stimulus-driven units (65/70) were also movement-driven. No responses correlated to the movement or to the sound stimuli were seen during passive conditions, i.e. when the monkey was not engaged in task performance. The occurrence of both stimulus- and movement-related activity in single pulvinar units suggests sensory-motor interaction possibly related to the decision to perform a certain movement.