title: Sound-intensity-dependent compensation for the small interaural time difference cue for sound source localization.
abstract: Interaural time difference (ITD) is a major cue for sound source localization. However, animals with small heads experience small ITDs, making ITD detection difficult, particularly for low-frequency sound. Here, we describe a sound-intensity-dependent mechanism for compensating for the small ITD cues in the coincidence detector neurons in the nucleus laminaris (NL) of the chicken aged from 3 to 29 d after hatching. The hypothesized compensation mechanisms were confirmed by simulation. In vivo single-unit recordings revealed an improved contrast of ITD tuning in low-best-frequency (<1 kHz) NL neurons by suppressing the firing activity at the worst ITD, whereas the firing rate was increased with increasing sound intensity at the best ITD. In contrast, level-dependent suppression was so weak in the middle- and high-best-frequency (> or =1 kHz) NL neurons that loud sounds led to increases in firing rate at both the best and the worst ITDs. The suppression of firing activity at the worst ITD in the low-best-frequency neurons required the activation of the superior olivary nucleus (SON) and was eliminated by electrolytic lesions of the SON. The frequency-dependent suppression reflected the dense projection from the SON to the low-frequency region of NL. Thus, the small ITD cues available in low-frequency sounds were partly compensated for by a sound-intensity-dependent inhibition from the SON.
authors.affiliation: Departments of Physiology and Morphological Brain Science, Faculty of Medicine, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Eri
authors.initials: E
authors.lastname: Nishino
authors.forename: Rei
authors.initials: R
authors.lastname: Yamada
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kuba
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hioki
authors.forename: Takahiro
authors.initials: T
authors.lastname: Furuta
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kaneko
authors.forename: Harunori
authors.initials: H
authors.lastname: Ohmori
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000200:Action Potentials / Q000502:physiology; D000222:Adaptation, Physiological / Q000502:physiology*; D000367:Age Factors; D000818:Animals; D001306:Auditory Pathways / Q000378:metabolism / Q000502:physiology; D001309:Auditory Threshold / Q000502:physiology; D001522:Behavior, Animal; D002645:Chickens; D003198:Computer Simulation; D003463:Cues; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology / Q000528:radiation effects; D007839:Functional Laterality; D007266:Inhibition, Psychological; D008954:Models, Biological; D009687:Nuclear Proteins / Q000378:metabolism; D018408:Patch-Clamp Techniques / Q000379:methods; D011601:Psychophysics; D011930:Reaction Time / Q000502:physiology*; D013016:Sound; D013017:Sound Localization / Q000502:physiology*; D013997:Time Factors; D050495:Vesicular Inhibitory Amino Acid Transport Proteins / Q000378:metabolism
chemical_list: D009687:Nuclear Proteins; D050495:Vesicular Inhibitory Amino Acid Transport Proteins; C493406:vesicular GABA transporter