Proprioceptive effects on evoked responses to sounds in the cat auditory cortex

With a view to analyse the influence of neck proprioceptors on directional hearing, evoked potentials (EPs) to dichotically or monaurally presented clicks were recorded from the auditory cortex of cats under deep Nembutal anaesthesia with their head pointing to the front, and then to the right or to the left side at 45 degrees. The change in the head position produced considerable changes in the amplitude of the two primary EP components and in their thresholds. The changes were of two kinds: either decrease or increase of the amplitude. At symmetrical points of the auditory cortex they went in the same direction. The also appeared in the associative zone with the same sign. With monaurally presented clicks, the change of the side of stimulation for the most part resulted in a reversal of the sign of the proprioceptive effect. Similar proprioceptive influences were recorded when the clicks were presented not through earphones but in an open acoustic field.