Evolutionary aspects of bat echolocation.
This review is yet another attempt to explain how echolocation in bats or bat-like mammals came into existence. Attention is focused on neuronal specializations in the ascending auditory pathway of echolocating bats. Three different mechanisms are considered that may create a specific auditory sensitivity to echos: (1). time-windows of enhanced echo-processing opened by a corollary discharge of neuronal vocalization commands; (2). differentiation and expansion of ensembles of combination-sensitive neurons in the midbrain; and (3). corticofugal top-down modulations. The second part of the review interprets three different types of echolocation as adaptations to ecological niches, and presents the sophisticated cochlear specializations in constant-frequency/frequency-modulated bats as a case study of finely tuned differentiation. It is briefly discussed how a resonant mechanism in the inner ear of constant-frequency/frequency-modulated bats may have evolved in common mammalian cochlea.
Department of Biology II, University of Munich (LMU), Luisenstrasse 14, 80333 München, Germany. neuweil@zi.biologie.uni-muenchen.de
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D000161:Acoustic Stimulation; D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D001306:Auditory Pathways / Q000502:physiology*; D005075:Biological Evolution; D001921:Brain / Q000502:physiology; D002685:Chiroptera / Q000502:physiology*; D003051:Cochlea / Q000502:physiology*; D004455:Echolocation / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology; D009474:Neurons / Q000502:physiology; D014828:Vocalization, Animal / Q000502:physiology