Anatomical and Physiological Properties of GABAergic Inputs to n. Laminaris from the Superior Olivary Nucleus of the Chick

Monday, March 8, 1999 - 1:15pm - 2:00pm
Keller 3-180
Edwin Rubel (University of Washington)
Joint work with Pablo Monsivais and Lichuan Yang.

Neurons in nucleus laminaris (NL) of the avian brainstem receive spatially segregated binaural excitatory projections from the two ears, via the neurons of n. laminaris. It has been known for many years that the axonal delay line innervating the contralateral n. laminaris provides the anatomical substrate for an ordered set of coincidence detectors capable of signaling the range of interaural time differences (ITDs) as a sound source is moved in azimuth. In this presentation, we will discuss the possible roles played by the other major input to NL neurons, GABAergic axons from the superior olivary nucleus (SON). In vitro slice preparations were used to study the anatomy and cellular physiology of SON neurons, and to study the effects of activating the SON neurons on physiological properties of NL neurons. We will show that activation of SON causes a temporally summated depolarizing potential in NL that leads to decreased input resistance and decrease in the amplitude and duration of psp�s evoked by n. magnocellularis. These changes may lead to a �sharpening� of the time constraints required for coincidence detection by NL neurons.

Supported by NIH grants DC00395 and DC00312.