Multiplicity of inputs in the afferent path to cat auditory cortex neurons revealed by tone-on-tone masking

This report presents preliminary evidence on the effect of continuous tonal maskers on the responses of single primary auditory cortical neurons in anesthetized cats to tonal signals across their effective frequency ranges 10 dB above characteristic frequency threshold. Tonal maskers had three kinds of effects. In many cells, the masker produced a generalized suppression of responses to tones across the response area. In some neurons, typically those with monotonic intensity profiles, tonal maskers on one side of the response area produced a selective suppression of responses to tone signals on the same side as the masker. This differential sensitivity to the masker is evidence of independent inputs to those neurons on the high- and low-frequency sides of their excitatory response areas. Finally, in non-monotonic neurons, tonal maskers at the high-frequency edge of the excitatory response area produced enhanced responses to tonal signals on the same side of the response area as the masker. We interpret this as a release from the effect of an inhibitory input located at the high-frequency edge of the response area.