Journal of Comparative Physiology A

, Volume 178, Issue 4, pp 499–512

Responses to simulated echoes by neurons in the barn owl's auditory space map

  • C. H. Keller
  • T. T. Takahashi
Original Paper

Abstract

The natural acoustical environment contains many reflective surfaces that give rise to echoes, complicating the task of sound localization and identification. The barn owl (Tyto alba), as a nocturnal predator, relies heavily on its auditory system for tracking and capturing prey in this highly echoic environment. The external nucleus of the owl's inferior colliculus (ICx) contains a retina-like map of space composed of “space-specific” auditory neurons that have spatially limited receptive fields. We recorded extracellularly from individual space-specific neurons in an attempt to understand the pattern of activity across the ICx in response to a brief direct sound and a simulated echo. Space-specific neurons responded strongly to the direct sound, but their response to a simulated echo was suppressed, typically, if the echo arrived within 5 ms or less of the direct sound. Thus we expect there to be little or no representation within the ICx of echoes arriving within such short delays.

Behavioral tests using the owl's natural tendency to turn their head toward a sound source suggested that owls, like their space-specific neurons, similarly localize only the first of two brief sounds. Naive, untrained owls were presented with a pair of sounds in rapid succession from two horizontally-separated speakers. With interstimulus delays of less than 10 ms, the owl consistently turned its head toward the leading speaker. Longer delays elicited head turns to either speaker with approximately equal frequency and in some cases to both speakers sequentially.

Key words

Binaural Inferior colliculus Nucleus mesencephalicus laterale pars dorsalis Precedence effect Sound localization 

Abbreviations

IC

inferior colliculus

ICx

external nucleus of the inferior colliculus

ITD

interaural time difference

ISI

interstimulus interval

LS

left speaker

RS

right speaker

CS

centering speaker

RF

receptive field

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Copyright information

© Springer-Verlag 1996

Authors and Affiliations

  • C. H. Keller
    • 1
  • T. T. Takahashi
    • 1
  1. 1.Institute of Neuroscience, University of Oregon EugeneUSA

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