title: Spatial tuning of neurons in the inferior colliculus of the big brown bat: effects of sound level, stimulus type and multiple sound sources.
abstract: We examined factors that affect spatial receptive fields of single units in the central nucleus of the inferior colliculus of Eptesicus fuscus. Pure tones, frequency- or amplitude-modulated sounds, or noise bursts were presented in the free-field, and responses were recorded extracellularly. For 58 neurons that were tested over a 30 dB range of sound levels, 7 (12%) exhibited a change of less than 10 degrees in the center point and medical border of their receptive field. For 28 neurons that were tested with more than one stimulus type, 5 (18%) exhibited a change of less than 10 degrees in the center point and medial border of their receptive field. The azimuthal response ranges of 19 neurons were measured in the presence of a continuous broadband noise presented from a second loudspeaker set at different fixed azimuthal positions. For 3 neurons driven by a contralateral stimulus only, the effect of the noise was simple masking. For 11 neurons driven by sound at either side, 8 were unaffected by the noise and 1 showed a simple masking effect. For the remaining 2, as well as for 5 neurons that were excited by contralateral sound and inhibited by ipsilateral sound, the peak of the azimuthal response range shifted toward the direction of the noise.
authors.affiliation: Zoologisches Institut, Universität München, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Grothe
authors.forename: E
authors.initials: E
authors.lastname: Covey
authors.forename: J H
authors.initials: JH
authors.lastname: Casseday
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D002685:Chiroptera / Q000502:physiology*; D007245:Inferior Colliculi / Q000166:cytology / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D009622:Noise; D013017:Sound Localization / Q000502:physiology*