The Auditory Thalamus in Bats

Abstract

During the past several years, studies of the auditory cortex in bats have revealed striking examples of functional specializations in the analysis of biosonar pulses and echoes (see O’Neill, Chapter 9). By means of sharp timing or frequency selectivities, some bat cortical neurons encode particular features of sonar targets, and these features are mapped across the cortical surface. Target range is one such feature. Much of the cortical analysis of sonar signals may depend on neural interactions that occur in the medial geniculate body (MGB), the thalamic relay in the ascending pathway to the auditory cortex. For example, combination-sensitive neurons, selective for combinations of spectrally or temporally distinct signal elements in the sonar pulse and echo, have been well described in regions of the auditory cortex; physiological studies suggest that these responses may be created in the medial geniculate body (Olsen and Suga 1991a,b). Thus, the auditory thalamus in bats may provide new insights into the processing of complex sounds, as well as furthering our understanding of biosonar mechanisms in these animals.