Sound-Intensity-Dependent Compensation for the Small Interaural Time Difference Cue for Sound Source Localization

• Published in: The Journal of neuroscience Vol. 28; no. 28; pp. 7153 - 7164
• Main Authors: Nishino, Eri, Yamada, Rei, Kuba, Hiroshi, Hioki, Hiroyuki, Furuta, Takahiro, Kaneko, Takeshi, Ohmori, Harunori
• Format: Journal Article
• Language: English
• Published: United States Soc Neuroscience 09.07.2008; Society for Neuroscience
• Subjects: Acoustic Stimulation - methods; Action Potentials - physiology; Adaptation, Physiological - physiology; Age Factors; Animals; Auditory Pathways - metabolism; Auditory Pathways - physiology; Auditory Threshold - physiology; Behavior, Animal; Chickens; Computer Simulation; Cues; Excitatory Postsynaptic Potentials - physiology; Excitatory Postsynaptic Potentials - radiation effects; Functional Laterality; Inhibition (Psychology); Models, Biological; Nuclear Proteins - metabolism; Patch-Clamp Techniques - methods; Psychophysics; Reaction Time - physiology; Sound; Sound Localization - physiology; Time Factors; Vesicular Inhibitory Amino Acid Transport Proteins - metabolism
• ISSN: 0270-6474; 1529-2401
• DOI: 10.1523/JNEUROSCI.4398-07.2008

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.