The analysis of interaural time differences in the chick brain stem

Physiol Behav. 2005 Oct 15;86(3):297-305. doi: 10.1016/j.physbeh.2005.08.003. Epub 2005 Oct 3.

Abstract

The brain stem auditory system of the chick has proven to be a useful model system for analyzing how the brain encodes temporal information. This paper reviews some of the work on a circuit in the brain stem that compares the timing of information coming from the two ears to determine the location of a sound source. The contralateral projection from the cochlear nucleus, nucleus magnocellularis (NM), to nucleus laminaris (NL) forms a delay line as it proceeds from medial to lateral across NL. NL neurons function like coincidence detectors in that they respond maximally when input from the two ears arrive simultaneously. This arrangement may allow NL to code sound space by the relative level of activity across the nucleus. The head anatomy of the chick allows for enhancement of the functional interaural time differences. Comparing the functional interaural time differences to the length of the neural delay line suggests that each NL can encode approximately one hemifield of sound space. Finally it is suggested that inhibitory input into the NM-NL circuit may provide a means to dynamically adjust the gain of the circuit to allow accurate coding of sound location despite changes in overall sound intensity.

Publication types

  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Acoustic Stimulation / methods
  • Animals
  • Auditory Pathways / physiology*
  • Brain Stem / drug effects
  • Brain Stem / physiology*
  • Chickens / physiology*
  • Dose-Response Relationship, Drug
  • Models, Neurological
  • Neurotransmitter Agents / metabolism
  • Sound Localization / physiology*
  • Time Perception / physiology*
  • gamma-Aminobutyric Acid / pharmacology

Substances

  • Neurotransmitter Agents
  • gamma-Aminobutyric Acid