ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

3aPP4. A bridge between place and time. I. The peripheral/central origins of frequency analysis.

Steven Greenberg

Int. Comput. Sci. Inst., 1947 Center St., Berkeley, CA 94704

Auditory theory has traditionally pitted ``place'' (the tonotopically organized spatial pattern of excitation) versus ``time'' (the temporal pattern of discharge) with respect to the neural representation underlying specific attributes of acoustic sensation. This long-standing controversy has been of particular significance for models of pitch and frequency analysis, but casts its theoretical shadow over the discipline as a whole. A potential resolution of this historical opposition is proposed, in which place and time are viewed as flip sides of a complex representational matrix of neural activity, bound together through the mechanics of the cochlear traveling wave and its interaction with central loci of coincidence detection and inhibition. Frequency analysis is viewed as possessing two components. One is excitatory, based on spatially circumscribed patterns of temporally coherent peripheral activity and processed by central coincidence-sensitive neural elements. The other involves central inhibitory elements driven by nonsynchronous activity distributed over a broad tonotopic domain. Together, these two components can account for the preservation of frequency selectivity across a wide range of frequencies and sound-pressure levels, despite dramatic changes in the average-rate-based profile of neural activity.