Single unit studies on the dorsal and intermediate acoustic striae

Abstract

Studies were made of the fiber composition and of single unit discharge characteristics in the dorsal and intermediate acoustic striae. Counts of fibers and cells revealed more than twice as many fibers as cochlear nucleus cells of the types known to contribute axons to these tracts. Recordings were made in the striae to confirm the classes of discharge patterns which are transmitted from the posterior cochlear nucleus to more central structures and to seek evidence for descending activity entering the cochlear nucleus through the striae. Discharge patterns of the majority of units resembled those seen in previous studies when recordings were made from regions of the cochlear nucleus which are known to contribute fibers to the striae. Some patterns, however, were unlike any which have been reported in the cochlear nucleus on the same side as the recording site, but resembled activity of other auditory structures, suggesting that these were descending inputs. To confirm the presence of descending activity, recordings were made in the dorsal acoustic stria at a point medial to where the stria had been completely severed. Recordings made under these conditions demonstrated the presence of descending activity. The physiological findings help explain the disparity between the counts of fibers and cells, and point out a need for more detailed descriptions of the origins of descending inputs through the striae.