Neurobiological specializations in echolocating bats

Abstract

Although the bat's nervous system follows the general mammalian plan in both its structure and function, it has undergone a number of modifications associated with flight and echolocation. The most obvious neuroanatomical specializations are seen in the cochleas of certain species of bats and in the lower brainstem auditory pathways of all microchiroptera. This article is a review of peripheral and central auditory neuroanatomical specializations in echolocating bats. Findings show that although the structural features of the central nervous system of echolocating microchiropteran bats are basically the same as those of more generalized mammals, certain pathways, mainly those having to do with accurate processing of temporal information and auditory control of motor activity, are hypertrophied and/or organized somewhat differently from those same pathways in nonecholocating species. Through the resulting changes in strengths and timing of synaptic inputs to neurons in these pathways, bats have optimized the mechanisms for analysis of complex sound patterns to derive accurate information about objects in their environment and direct behavior toward those objects.

Distribution and morphology of cholinergic, catecholaminergic and serotonergic neurons in the brain of Schreiber's long-fingered bat, Miniopterus schreibersii

“…While major works have been undertaken on the structural anatomy of the brain of numerous microbat species (Baron et al, 1996a,b,c; reviewed by Reep and Bhatnagar, 2000) and a great deal of research undertaken on the neurobiology of the echolocation system (e.g. Suga, 1989;Moss and Sinha, 2003;Covey, 2005), work on other aspects of the brain are not so numerous (e.g. Wise et al, 1986;Pettigrew et al, 1989;Hof et al, 1999;Manger et al, 2001).…”

Stimulus-specific adaptation in specialized neurons in the inferior colliculus of the big brown bat, Eptesicus fuscus

“…Echolocating bats have developed functional specializations of the central auditory system, including neurons that respond exclusively to specific spectrotemporal patterns similar to those contained in echolocation signals (Covey, 2005). In previous studies of the IC in Eptesicus, approximately 22% of IC neurons were found to respond exclusively to sinusoidally frequency modulated (SFM) signals, and 14% to single frequency modulated (FM) sweeps (Yue et al, 2007;Casseday and Covey, 1992).…”

Sound localization in common vampire bats: Acuity and use of the binaural time cue by a small mammal

“…The MSO of the mouse is the smallest relative to its brain size among 53 mammals (Glendenning and Masterton, 1998). The big brown bat's MSO is also very small, with only about half of the cells receiving binaural input, and its output is bilateral rather than ipsilateral (Covey, 2005;Grothe et al, 2001;Huffman and Covey, 1995)-all of which are atypical features that call into question its participation in a binaural time analysis for localization. Finally, the MSO of the shorttailed fruit bat, although described as "prominent," is based on its microscopic appearance; its physiology and anatomical connections are unknown (Hutson, 2000), leaving open the question of whether it is homologous to that of species known to use time cues.…”