Article Figures & Data
Figures
- Figure 1.
Schedule of the experiment. All groups were trained in the localization task, following recovery for lesioned animals. Once trained to criterion, all animals went through the same testing routine, as shown. Each experimental run was followed by a break period. After the final session, lesion animals were killed and the lesions were histologically verified.
- Figure 2.
A, Schematic showing the origins of MOC and LOC fibers in the superior olivary complex, the relative numbers from the ipsilateral and contralateral sides of the brainstem, and the locations of the two types of OC lesions used in the present study. B, Coronal brainstem section stained for AChE, showing a successful lateral lesion. Arrow at right indicates the fibers of the OC bundle. On the corresponding region of the left side, there is an obvious scar (dotted ellipse) where the microknife cut into the floor of the IVth ventricle. MSO, Medial superior olive; LSO, lateral superior olive.
- Figure 3.
Normal variation in OC innervation density along the cochlear spiral, as revealed by immunostaining cochlear whole mounts for synaptophysin, a marker for synaptic vesicles, which are densely packed in efferent terminals. Arrows in the top panel indicate the inner spiral bundle containing the LOC terminals and the row of MOC terminals on outer hair cells from the first row. The three panels show images from a control ear at three locations along the cochlear spiral: regions closer to the base are tuned to higher frequencies. Scale bar in bottom panel applies to all three images.
- Figure 4.
Degree of de-efferentation in each of the OC lesions cases. A–C, Place-matched images of cochlear whole mounts immunostained for synaptophysin. Each row of images shows cochlear regions 25% of the distance from the basal end: Ipsi denotes the ear on the same side as the lateral lesion; contra, the opposite. Each image is the maximum projection of a z-stack of confocal images spanning the entire height of the organ of Corti. Scale bar in C applies to all images. D, E, Quantification of the degree of de-efferentation for the LOC system (D) or the MOC system (E) in each of the cases with an attempted lateral lesion. Total volumes of all labeled terminals were measured in image stacks such as those pictured in A–C: degree of de-efferentation was estimated by dividing the data from place matched image stacks from the two sides of each case.
- Figure 5.
Sound localization by control animals before (preplug), during (plug 1, plug 8), and following (postplug) removal of the first, left earplug; 1 s stimulus duration. A, CoM for each stimulus location (colors) for each animal (different symbols). B, Radar plots showing the absolute accuracy for individual animals (dotted lines) and the mean (bold).
- Figure 6.
Localization by midline lesion animals. A, CoM plots. B, Radar plots. Details as in Figure 5.
- Figure 7.
Localization by lateral lesion animals. A, CoM plots. B, Radar plots. Details as in Figure 5.
- Figure 8.
Schematic representation of the effects of OC bundle lesions on sound localization and learning in ferrets. The vertical axes show the mean CoM(y) for a 1 s stimulus, averaged for left and right earplugs. Lesions affected only the ability to relearn how to localize with altered binaural cues.
