Gene expression and signal classification in the auditory system of bats

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DESCRIPTION (provided by applicant): Little brown bats (Myotis lucifugus) have exquisite ability to echolocate; they can utilize their sonar system to navigate, and detect, identify, locate and track prey, in darkness. Their echolocation signals have been studied in detail but their communication calls are less well characterized despite the widespread use during their social interactions, e.g. in mother-young interactions, and in defending or advertising feeding areas. The goals of this study are to characterize, and determine the behavioral relevance of, sound communication signals of little brown bats, as well as to investigate the anatomical substrates for processing of these calls. The communication calls of M. lucifugus will be recorded from individual bats overnight, and an automatic classification algorithm will be developed to objectively classify the recorded calls. To study the anatomical structures involved in processing of the communication signals, the immediate early gene ZENK (zif268, egr1, NGFI-A, krox-24) will be used as a molecular marker for brain activation. In songbirds, after exposure to the bird's own songs or conspecific songs (i.e., songs within their species), ZENK is upregulated in specific brain areas involved in processing of these songs. A recent study in frogs also showed that ZENK displays call-dependent activation in isolated regions of the frog auditory midbrain. These studies demonstrate that ZENK can be used to elucidate the anatomical substrates of processing of communication signals. To determine the behavioral relevance of each call type, individual calls will be played back to a bat, and the bat's response investigated audio-visually. The bat auditory system has served as a useful model for studying speech processing (due to the similarities in sound features between bat's echolocation [and communication] calls and human speech sounds, and in structural and functional organizations of their auditory systems). The proposed study would shed light on the neural processing of complex natural sounds.