ABSTRACT
The mouse, like all vertebrates, critically examines acoustic patterns that reveal where events arise in the environment and what they represent. A central question concerns what are the important features of sounds for the detection, localization, and interpretation of external events and how those features are detected by the nervous system. Incoming sound is transformed by the sensory epithelium of the cochlea into temporal firing patterns across the tonotopic array of auditory nerve fibers. The cochlear nucleus, the obligate terminal for auditory nerve fibers, serves as the initial platform to begin deciphering this code, a duplex of time and frequency, and rebuilding its elements into a coherent image of the external world. Whereas much is known about auditory behaviors and abilities in mice (e.g., Chapters 1 through 7), we can also look to behavioral/psychophysical studies in other mammals to help interpret results obtained with
in vitro
methods in the mouse auditory system. For example, bats with a similar head size and audiogram to the mouse, can precisely localize and orient toward prey during flight; and in discriminating among prey, they rely on patterns of frequency and amplitude modulations, similar to those measured in natural speech signals (reviewed in Moss and Schnitzler, 1996). These behaviors suggest that mammals have evolved sophisticated mechanisms for examining spatiotemporal firing patterns to interpret sounds before choosing an appropriate response. The circuitry of the cochlear nuclei described in this chapter is the foundation of those mechanisms.
