Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published September 1, 1993 | Published
Journal Article Open

Bilateral inhibition generates neuronal responses tuned to interaural level differences in the auditory brainstem of the barn owl


I investigated the neural algorithms by which neurons gain selectivity for interaural level difference in the brainstem of the barn owl (Tyto alba). Differences in the timing and in the level of sounds at the ears are used by this owl to encode, respectively, azimuthal and vertical position of sound sources in space. These two cues are processed in two parallel neural pathways. Below the level of the inferior colliculus, all neurons in the pathway that processes level differences show responses to this cue that are monotonic, and thus not selective for a particular level difference. Only in the inferior colliculus, which contains a map of auditory space, are neurons sharply tuned to specific interaural level differences. How are these response properties generated from those of the nuclei that provide input to the inferior colliculus? I show that the posterior subdivision of the nucleus ventralis lemnisci lateralis (VLVp) projects bilaterally to the lateral shell of the central nucleus of the inferior colliculus, the input stage to the map of auditory space. Both these nuclei are part of the pathway that processes interaural level differences. Manipulations of the responses in VLVp affected the responses to level differences in the inferior colliculus; responses to time differences were unaffected. By systematically increasing or decreasing neural activity in VLVp, I show that the VLVp on each side provides inhibition to the colliculus at large level differences. This results in a peaked response that is tuned to level differences in the inferior colliculus. Some cells in the lateral shell of the inferior colliculus appear to receive direct GABAergic inhibition from VLVp. I suggest that this circuitry and the algorithms it supports are the neural substrates that allow the barn owl to exploit level differences for computation of sound source elevation.

Additional Information

© 1993 Society for Neuroscience. Received Sept. 25, 1992; revised Feb. 24, 1993; accepted Mar. 1, 1993. I thank J. Mazer, E. Knudsen, J. Pearson, T. Takahashi, and M. Konishi for comments on a previous version of the manuscript, and M. Konishi for helpful suggestions on later drafts. The manuscript benefitted from the criticisms of two anonymous reviewers. T. Takahashi, S. Volman, and M. Konishi provided help and encouragement at various stages of the experiments. J. Mazer wrote all the computer programs for stimulus presentation and analysis on the Masscomp 5600 computer. R.A. is a Howard Hughes Medical Institute Fellow. This work was in part supported by NIH Grant DC00134-14 to M. Konishi.

Attached Files

Published - 3647.full.pdf


Files (3.1 MB)
Name Size Download all
3.1 MB Preview Download

Additional details

August 20, 2023
October 18, 2023