PT  - JOURNAL ARTICLE
AU  - Nishino, Eri
AU  - Yamada, Rei
AU  - Kuba, Hiroshi
AU  - Hioki, Hiroyuki
AU  - Furuta, Takahiro
AU  - Kaneko, Takeshi
AU  - Ohmori, Harunori
TI  - Sound-Intensity-Dependent Compensation for the Small Interaural Time Difference Cue for Sound Source Localization
AID  - 10.1523/JNEUROSCI.4398-07.2008
DP  - 2008 Jul 09
TA  - The Journal of Neuroscience
PG  - 7153--7164
VI  - 28
IP  - 28
4099  - http://www.jneurosci.org/content/28/28/7153.short
4100  - http://www.jneurosci.org/content/28/28/7153.full
SO  - J. Neurosci.2008 Jul 09; 28
AB  - 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 (≥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.