ASA 125th Meeting Ottawa 1993 May

3aMU3. Anomalies in the neural tonotopic-synchrony pattern as the basis for the segregation of tones.

William Morris Hartmann

Dept. of Phys., Michigan State Univ., East Lansing, MI 48824

It is possible to envision a comprehensive model for the segregation and integration of tones based upon synchrony and asynchrony of neural excitation patterns. Evidence for this model comes from experiments on mistuned harmonic matching, simultaneous and sequential octave tuning, and FM incoherence detection with harmonic and inharmonic tones. Such a model has the conceptual advantage of unifying temporal effects and mistuning effects upon segregation. A central remaining question in the formulation of this model is the role of tonotopic analysis. There is, in fact, tonal segregation attributable entirely to tonotopic oddity. More than that, there are tonotopic effects on the processing of synchrony anomalies. These can be seen in mistuned harmonic detection experiments with neighboring harmonics removed, or with added constant remote inharmonic confuser, or with several mistuned harmonics that are themselves either mutually synchronous or asynchronous. Such experiments have suggested a tuned-autocorrelator model with a bandwidth of about two critical bands. Tonotopically based synchrony models are, in turn, challenged by experiments on cross-channel interaction where excitation at intervening tonotopic sites has been deliberately squelched. [Work supported by the NIDCD, DC 00181.]