PHYSIOLOGICAL-STUDIES OF THE PRECEDENCE EFFECT IN THE INFERIOR COLLICULUS OF THE KITTEN

The precedence effect (PE) is a perceptual phenomenon that reflects li steners' ability to suppress echoes in reverberant environments. The P E is not present at birth and appears only several months postnatal. R ecent physiological studies have demonstrated correlates of the PE in the central nucleus of the inferior colliculus (ICC) of adult animals. The present study extended the same techniques to search for similar correlates in the ICC of kittens during the first postnatal month. Sti muli consisted of pairs of clicks or noise bursts presented from diffe rent locations in free fielder with different inter-aural differences in time (ITD) under headphones, with an inter-stimulus-delay (ISD) bet ween their onsets. Results suggest that a physiological correlate of t he PE, i.e. suppression of responses to the second source, is present as early as 8 days postnatal, and occurs at similar ISDs to those reco rded in adult cats. Suppression in kitten neurons varies with stimulus level, duration, and azimuthal position, in a similar manner to that in adult neurons. The age at which correlates of the PE in the kitten can be found precedes the age at which kittens can localize sound sour ces effectively, and presumably before the age at which they would dem onstrate the PE behaviorally. Thus, the neural mechanisms that might b e involved in the first stages of processing PE stimuli may be in plac e well before the behavioral correlate develops. (C) 1998 Acoustical S ociety of America.