ASA 127th Meeting M.I.T. 1994 June 6-10

2aPP20. Evidence for physiological correlates of the precedence effect in the inferior colliculus of kittens.

Ruth Y. Litovsky

Dept. of Neurophysiol., Univ. of Wisconsin, 1300 University Ave., Madison, WI 53706

Physiological correlates of the precedence effect (PE) were studied by recording from single cells in the inferior colliculus of young kittens and adult cats. This effect is interesting from a developmental perspective since it appears to be absent in newborn animals including human infants and dogs, but develops after the first few months of life [Clifton, in Auditory Development in Infancy (Plenum, New York, 1985)]. Experiments were conducted in an anechoic chamber. PE stimuli were generated by presenting two successive clicks from two different speakers, with a variable time delay between them. Kittens were studied at the ages of 5--28 days postnatal. At all ages, most units displayed ``echo suppression;'' they responded to both the leading and lagging sounds at long delays (>30--60 ms), with a suppressed response to the lagging sound at short delays. There seem to be no differences in the physiological manifestations of the PE between kittens and adult cats. Correlates of psychophysics related to the PE, which were found in the responses of adult neurons, were also present in kitten neurons. It seems that the neural circuitry involved in the initial stages of the PE may develop very early in life, prior to the onset of corresponding behaviors. [Work supported by NIH.]