Nucleus Laminaris

In all vertebrates, distinct neural circuits within the central nervous system are responsible for binaural auditory processing. These circuits are highly specialized for the temporal processing of sound at the network, synaptic, and cellular levels. This chapter focuses on important structural and functional specializations of the avian nucleus laminaris (NL), an auditory brainstem structure responsible for encoding the difference in arrival of sounds between the two ears, i.e., interaural time difference (ITD). Unique structural features, such as a bipolar dendritic configuration and axonal input delay lines, provide the fundamental anatomic substrate for optimal ITD coding. Individual neurons in NL act as coincidence detectors, responding maximally when sound arrives from the two ears simultaneously. Several physiological mechanisms account for such coincidence optimization and allow NL neurons the ability to code ITDs in the microsecond range, a process critical for sound localization.