Abstract
Sensing interaural time difference (ITD) is essential for azimuthal sound source localization. In birds, bilateral sound signals first converge in nucleus laminaris (NL). NL neurons act as a coincidence detector of bilateral excitatory synaptic inputs, and encode ITD. Thus, the acuity of coincidence detection (CD) in NL neurons is critical for ITD calculation. NL neurons also receive GABAergic inputs, and these inhibitory innervations have been thought to improve the acuity of CD in NL. GABAergic inputs for NL arise mainly from the superior olivary nucleus (SON). SON neurons increase their activity with the increase of sound intensity, but poorly hold timing information. Therefore, SON neurons are thought to supply the tonic inhibition during sound presentation. Consistently, continuous application of GABA for slice preparation increases the shunting conductance of NL neurons, and improves the acuity of CD in NL. On the other hand, the precisely-timed inhibition is proposed to enhance ITD discrimination in mammals, but such inhibition has not been found in NL of birds. In this study, we show the possibility that NL neurons of birds also receive the precisely-timed inhibition, and this inhibition modulates the acuity of CD in NL. [J Physiol Sci. 2008;58 Suppl:S122]
