Activity evoked in cortical association areas of cats

Abstract

1. Responses arising in different parts of the association cortex to photic, acoustic and cutaneous stimulation in cats under chloralose anesthesia (70 mg/kg) show similarity but also certain differences in the three areas examined. Photic stimulation activates the anterior marginal gyrus more strongly, as is shown by the appearance of a response here with larger amplitudes and shorter latent periods than in other parts. Acoustic stimulation activates mainly the posterior part of the middle suprasylvian gyrus, while cutaneous stimulation activates sometimes one, sometimes the other part (or both equally) of the middle suprasylvian gyrus. 2. Another difference is that an initial negative spike is observed systematically in the responses of all parts of the association cortex to photic stimulation and to cutaneous stimulation of the contralateral limb. It coincides in time with the primary cutaneous stimulation of the ipsilateral limb are absent. The initial negative wave thus reflects activation of neurons of the primary sensory area. 3. It may be concluded: a) that the anterior marginal gyrus is probably the zone of preferential projection of the visual system and the place of integration of visual impulses with impulses of the other afferent systems, b) that the posterior part of the suprasylvian gyrus is the site of preferential projection of auditory impulses and the region of interaction between them and impulses of the other modalities, whereas, c) integration of somatosensory activity with that from other sources may take place in either the posterior or the anterior part (or both parts simultaneously) of the middle suprasylvian gyrus.