Role of centrifugal pathways to cochlear nucleus in determination of critical bandwidth.

Atropine sulfate was applied locally to the cochlear nucleus of three unanesthetized cats in order to block the cholinergic centrifugal innervation of the nucleus. The critical bandwidth was measured behaviorally from the masked thresholds of 1-kHz tone pips in different bandwidths of masking noise. Atropine increased the critical bandwidth markedly. This suggests that normally the centrifugal pathways influence the critical bandwidth. Saline solutions alone had no effect, and if the cannula was not accurately implanted over the cochlear nucleus, atropine had no effect either.