Steven P. Dear
James A. Simmons
Dept. of Neurosci., Box 1953, Brown Univ., Providence, RI 02912
A previous study demonstrated that a subpopulation of cortical neurons comprised a multiresolution decomposition of target range information in the big brown bat [Dear et al., Nature 364, 620--622 (1993)]. Given the strong relationship between a multiresolution decomposition and wavelets, it was wondered if acoustic information is represented as wavelets in the auditory cortex. Here, the existence of Daubechies wavelets in the auditory cortex in response to multiharmonic FM sweeps simulating the type of signals used by the big brown bat for echolocation is reported. The Daubechies wavelets exist as continuous analog voltages that appear to be evoked by a local ensemble of cortical neurons. The wavelets are sensitive to manipulations of multiple synthetic echoes and suggest an orthogonal representation of acoustic echo information in the auditory cortex. [Work supported by NSF.]