Elsevier

Neuroscience

Volume 154, Issue 1, 12 June 2008, Pages 397-408
Neuroscience

The changing auditory system: Development, learning, aging and disease
Sound localization behavior in ferrets: Comparison of acoustic orientation and approach-to-target responses

https://doi.org/10.1016/j.neuroscience.2007.12.022Get rights and content

Abstract

Auditory localization experiments typically either require subjects to judge the location of a sound source from a discrete set of response alternatives or involve measurements of the accuracy of orienting responses made toward the source location. To compare the results obtained by both methods, we trained ferrets by positive conditioning to stand on a platform at the center of a circular arena prior to stimulus presentation and then approach the source of a broadband noise burst delivered from 1 of 12 loudspeakers arranged at 30° intervals in the horizontal plane. Animals were rewarded for making a correct choice. We also obtained a non-categorized measure of localization accuracy by recording head-orienting movements made during the first second following stimulus onset. The accuracy of the approach-to-target responses declined as the stimulus duration was reduced, particularly for lateral and posterior locations, although responses to sounds presented in the frontal region of space and directly behind the animal remained quite accurate. Head movements had a latency of ∼200 ms and varied systematically in amplitude with stimulus direction. However, the final head bearing progressively undershot the target with increasing eccentricity and rarely exceeded 60° to each side of the midline. In contrast to the approach-to-target responses, the accuracy of the head orienting responses did not change much with stimulus duration, suggesting that the improvement in percent correct scores with longer stimuli was due, at least in part, to re-sampling of the acoustical stimulus after the initial head turn had been made. Nevertheless, for incorrect trials, head orienting responses were more closely correlated with the direction approached by the animals than with the actual target direction, implying that at least part of the neural circuitry for translating sensory spatial signals into motor commands is shared by these two behaviors.

Section snippets

Experimental procedures

All procedures involving animals were performed following local ethical review committee approval and under license from the UK Home Office in accordance with the Animal (Scientific Procedures) Act (1986). Every effort was made to minimize the number of animals used and their suffering. The data for the present study were collected from ten adult pigmented ferrets (Mustela putorius furo) from our breeding colony, which also contributed to other behavioral studies. The apparatus and methods used

Results

All naïve animals typically learned the approach to target task within a week of commencing training, after which we started the data collection. The results presented here are based on the analysis of 43,776 approach-to-target trials that each yielded a good head tracking signal.

Discussion

We have examined the accuracy with which ferrets localize broadband sounds of varying level and duration presented from 1 of 12 loudspeakers within the horizontal plane. We analyzed both the initial head orienting response toward the source of the sound and the subsequent locomotor behavior as the animals approached the speaker from which the stimulus had been presented in order to receive a water reward. Although both measures can be regarded as part of the natural response to sounds presented

Acknowledgments

We are grateful to Susan Spires, Jenny Bizley, Rob Campbell and Dan Kumpik for assistance with the data collection. This study was supported by the Wellcome Trust through a Wellcome Principal Research Fellowship to A. J. King and BBSRC grant BB/D009758/1 to J. W. Schnupp and A. J. King.

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    Present address: School of Medicine, University of Western Sydney, Narellan Road, Campbelltown, New South Wales 2560, Australia.

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