4pAB10. An acoustic perception model for echolocation signals.

Session: Thursday Afternoon, May 16

Time: 4:05

Author: Mathew J. Palakal
Author: Uday Murthy
Location: Dept. of Comput. Sci. IUPUI, 723 W. Michigan St., SL 280, Indianapolis, IN 46202
Author: Donald Wong
Location: Indiana Univ., Indianapolis, IN 46202


Bats that echolocate using biosonar pulses perceive their target as an auditory image by extracting acoustic cues conveyed in the target-reflected echoes. Neurophysiological studies suggest that a large majority of cortical neurons found in FM bats are delay sensitive. Moreover, these neurons are tonotopically organized and have a best delay (BD) at which they respond maximally to an input stimulus. In order to understand the role of these neurons during pulse-echo processing, a mathematical model capturing the functionality of delay sensitive neurons (DSN) has been developed. As a first approximation, response to a pulse-echo pair of a DSN is derived as, y(t)=exp[-i*((beta)-(delta))[sup 2]/2*(sigma)[sup 2]], where (beta) is best delay of the neuron, (delta) is arrival time of the echo, i is neural spikes, and (sigma) is delay range of the neuron. A two-dimensional cortical response map (CORMAP) of DSNs is then developed based upon the best frequencies and the above stated response property with varying BDs. The CORMAP is then simulated using phantom targets containing multiple echoes. Once a pulse is sent and as the echoes begin to arrive for every (delta)[inf k], the CORMAP generates a response map as the DSNs fire. The firing patterns occur at various (delta)[inf k] can be analyzed to estimate target distance and structural information. [Work supported by NSF.]

from ASA 131st Meeting, Indianapolis, May 1996