The effects of noise upon the electrical activity of the cat cortex

Short periods of high intensity noise (100 db) were applied to cats under barbiturate or chloralose anesthesia and to some awake animals immobilized with gallamine. In the animals under barbiturate anesthesia, the noise increased the mean frequency of the ECG spindles recorded in the suprasylvian cortex. The cortical evoked responses to somatic and visual stimulation were modified in their late components during the noise periods. These late waves became more apparent and seemed to prolong the duration of those evoked responses. The changes in the cortical evoked responses were observed not only on those of the primary somatosensory and visual areas but also in those of the suprasylvian cortex.