Models of the Neuronal Mechanisms of Target Localization of the Barn Owl
Final rept. 11 Sep 90-20 Sep 1993
DAVID SARNOFF RESEARCH CENTER PRINCETON NJ
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Models of the computation of sound direction in the brainstem and midbrain of the barn owl tyto alba were developed. Nucleus laminaris is the first site of interaural time-delay ITD processing. It was shown that standard neuron models would have to have unrealistically fast time constants in order to match the 10 micro-second ITD resolution characteristic of laminaris neurons. Three physiological reasonable, qualitatively distinct alternatives, were developed. Nucleus ventralis lemnisci lateralis pars posterior VLVP and the lateral shell of the central nucleus of the inferior colliculus ICL are the first two stages of interaural level differences ILD processing. It was shown how a thermometer code of ILD could be formed in VLVp through competitive dynamics, and how the ILD-tuned responses of ICL neurons could derive from the VLVp through lateral inhibition. It was shown how this architecture could be modified to achieve near independence from the average binaural level. Experimentalists are now checking the predictions of these models of ILD and ITD processing.
- Anatomy and Physiology