Corticofugal modulation of peripheral auditory responses.
The auditory efferent system originates in the auditory cortex and projects to the medial geniculate body (MGB), inferior colliculus (IC), cochlear nucleus (CN) and superior olivary complex (SOC) reaching the cochlea through olivocochlear (OC) fibers. This unique neuronal network is organized in several afferent-efferent feedback loops including: the (i) colliculo-thalamic-cortico-collicular; (ii) cortico-(collicular)-OC; and (iii) cortico-(collicular)-CN pathways. Recent experiments demonstrate that blocking ongoing auditory-cortex activity with pharmacological and physical methods modulates the amplitude of cochlear potentials. In addition, auditory-cortex microstimulation independently modulates cochlear sensitivity and the strength of the OC reflex. In this mini-review, anatomical and physiological evidence supporting the presence of a functional efferent network from the auditory cortex to the cochlear receptor is presented. Special emphasis is given to the corticofugal effects on initial auditory processing, that is, on CN, auditory nerve and cochlear responses. A working model of three parallel pathways from the auditory cortex to the cochlea and auditory nerve is proposed.
Programa de Fisiología y Biofísica, ICBM, Facultad de Medicina, Universidad de Chile Santiago, Chile.
Gonzalo
G
Terreros
Programa de Fisiología y Biofísica, ICBM, Facultad de Medicina, Universidad de Chile Santiago, Chile ; Departamento de Otorrinolaringología, Hospital Clínico de la Universidad de Chile Santiago, Chile.
Paul H
PH
Delano
auditory efferent; corticofugal; descending projections; neural network; olivocochlear; top-down