Localized Responses in Auditory Cortex to Brief Tones in High Level Noise

Abstract

By observing the evoked potentials at 50 electrodes on the MES auditory cortex, essentially the same foci of response for P pulses of different frequencies were found in the presence of high level thermal noise as at the absolute threshold. The wide band thermal noise produced a linear threshold shift for the P pulse response foci. The best representation of frequency was obtained for signal to noise ratios of 0 to 20 db. The masking effect or threshold shift was primarily confined to the ear in which the P pulse was delivered. Under these conditions, it is expected that the information storage capacity of the MES area for spectra would remain essentially the same for a 20-db signal to noise ratio at any level of thermal noise. Also, because of the absence of contralateral masking, the representation for both ears could be maintained at an optimum in spite of high level noise in one ear.