Effects of visual attention on tone burst evoked auditory potentials

Abstract

Tone burst evoked potentials were recorded from unanesthetized cats with electrodes chronically implanted in the auditory cortex, cochlear nucleus, and round window. The tone bursts (irrelevant stimuli) were presented continuously (85 db SPL, 1 s ) as background before, during, and after the presentation of a visual discrimination task (relevant stimuli) which was used as a means of altering the attentive state of the animals. At the auditory cortex and cochlear nucleus, the mean peak-to-peak amplitudes of tone burst evoked potentials were significantly reduced during attention to the visual discrimination stimuli compared to the pretest and post-test control periods. However, at the round window (cochlear microphonic) no significant differences in amplitude were observed. Although the amplitudes of the tone burst evoked potentials were reduced at all frequencies during visual attention, much greater suppression occurred at the middle frequencies (700 to 5000 Hz) than at higher or lower frequencies. The results support the hypothesis that during visual attention a central inhibitory mechanism suppresses irrelevant tone burst evoked potentials, presumably via the olivocochlear bundle.