Investigating Cortical Descending Control of the Peripheral Auditory System
Corticofugal projections may modulate auditory signal processing at all levels of the ascending auditory system. The final link in this pathway, extending descending control to the cochlea, is the olivocochlear bundle, which originates in the olivary complex and consists of lateral and medial (MOC) systems. Classically, activation of the MOC system leads to an increase in cochlear microphonic and a decrease in cochlear action potential amplitudes.
Here, we investigated the effect of reversible cortical inactivation on the guinea pig cochlea. During cortical inactivation, CM and CAP amplitudes were decreased to varying extents. Reactivation of the cortex led to a recovery to control levels. These results indicate that even in the anaesthetized animal, the cortex is exercising control over the function of the cochlea.