A neural model of medial geniculate body and auditory cortex detecting target distance independently of target velocity in echolocation

Using frequency-modulated (FM) ultrasonic pulses, echolocating bats detect with a high accuracy the arrival time differences between emitted pulses an d their echos generated by targets, even though the targets are moving. We propose a neural mechanism by which the bat may detect the time differences independently of the target velocity using FM ultrasonic pulses. The neura l processing model presented consists of the networks in MGB for calculatin g the temporal correlation between pulse and echo for each frequency and th e network of AC for integrating the calculated results over the frequency r ange used by bat. We found that the key factor generating the detection ind ependent of target velocity is the value of frequency modulation rate of ab out 6 kHz. (C) 2000 Published by Elsevier Science B.V. All rights reserved.