The Journal of Neurophysiology Vol. 80 No. 3 September 1998, pp. 1302-1316
Copyright ©1998 The American Physiological Society

Physiological Studies of the Precedence Effect in the Inferior Colliculus of the Cat. II. Neural Mechanisms

Ruth Y. Litovsky and Tom C. T. Yin

Department of Neurophysiology, University of Wisconsin, Madison, Wisconsin 53706

Litovsky, Ruth Y. and Tom C. T. Yin. Physiological studies of the precedence effect in the inferior colliculus of the cat. II. Neural mechanisms. J. Neurophysiol. 80: 1302-1316, 1998. We studied the responses of neurons in the inferior colliculus (IC) of cats to stimuli known to evoke the precedence effect (PE). This paper focuses on stimulus conditions that probe the neural mechanisms underlying the PE but that are not usually encountered in a natural situation. Experiments were conducted under both free-field (anechoic chamber) and dichotic (headphones) conditions. We found that in free field the amount of suppression of the lagging response depended on the location of the leading source. With stimuli in the azimuthal plane, the majority (84%) of units showed stronger suppression of the lagging response for a leading stimulus placed in the cell's responsive area as compared with a lead in the unresponsive field. A smaller number of units showed stronger suppression for a lead placed in the unresponsive field, and a few showed little effect of the lead location. In the elevational plane, there was less sensitivity of the leading source to changes in location, but for those cells in which there was sensitivity, suppression was always stronger when the lead was in the cell's responsive area. Studies on stimulus locations also were conducted under dichotic conditions by varying the interaural differences in time (ITD) of the leading source. Results were consistent with those obtained in free field, suggesting that ITDs play an important role in determining the amount of suppression that was observed as a function of leading stimulus location. In addition to location and ITD, we also studied the effect of varying the relative levels of the lead and lag as well as stimulus duration. For all units studied, increasing the level of the leading stimulus while holding the lagging stimulus constant resulted in increased suppression. Similar effects of leading source level were observed in azimuth and elevation. The effect of varying the duration of the leading source also showed that longer duration stimuli produce stronger suppression; this finding was observed both in azimuth and elevation. We also compared the suppression observed under binaural and monaural contralateral conditions and found a mixed effect: some neurons show stronger suppression under binaural conditions, others to monaural contralateral conditions, and still others show no effect. The results presented here support the hypothesis that the PE reflects a long-lasting inhibition evoked by the leading stimulus. Five possible sources for the inhibition are considered: the auditory nerve, intrinsic circuits in the cochlear nucleus, medial and lateral nuclei of the trapezoid body inhibition to the medial superior olive, dorsal nucleus of the lateral lemniscus (DNLL) inhibition to the ICC, and intrinsic circuits in the ICC itself.

This article has been cited by other articles:

				Y. Gutfreund and E. I. Knudsen Adaptation in the Auditory Space Map of the Barn Owl J Neurophysiol, August 1, 2006; 96(2): 813 - 825. [Abstract] [Full Text] [PDF]

				M. W. Spitzer and T. T. Takahashi Sound Localization by Barn Owls in a Simulated Echoic Environment J Neurophysiol, June 1, 2006; 95(6): 3571 - 3584. [Abstract] [Full Text] [PDF]

				J. Zhang, K. T. Nakamoto, and L. M. Kitzes Modulation of Level Response Areas and Stimulus Selectivity of Neurons in Cat Primary Auditory Cortex J Neurophysiol, October 1, 2005; 94(4): 2263 - 2274. [Abstract] [Full Text] [PDF]

				S. Furukawa, K. Maki, M. Kashino, and H. Riquimaroux Dependency of the Interaural Phase Difference Sensitivities of Inferior Collicular Neurons on a Preceding Tone and Its Implications in Neural Population Coding J Neurophysiol, June 1, 2005; 93(6): 3313 - 3326. [Abstract] [Full Text] [PDF]

				D. J. Tollin, L. C. Populin, and T. C. T. Yin Neural Correlates of the Precedence Effect in the Inferior Colliculus of Behaving Cats J Neurophysiol, December 1, 2004; 92(6): 3286 - 3297. [Abstract] [Full Text] [PDF]

				M. W. Spitzer, A. D. S. Bala, and T. T. Takahashi A Neuronal Correlate of the Precedence Effect Is Associated With Spatial Selectivity in the Barn Owl's Auditory Midbrain J Neurophysiol, October 1, 2004; 92(4): 2051 - 2070. [Abstract] [Full Text] [PDF]

				D. J. Tollin and T. C.T. Yin Psychophysical Investigation of an Auditory Spatial Illusion in Cats: The Precedence Effect J Neurophysiol, October 1, 2003; 90(4): 2149 - 2162. [Abstract] [Full Text] [PDF]

				R. Y. Litovsky and B. Delgutte Neural Correlates of the Precedence Effect in the Inferior Colliculus: Effect of Localization Cues J Neurophysiol, February 1, 2002; 87(2): 976 - 994. [Abstract] [Full Text] [PDF]

				R. M. Burger and G. D. Pollak Reversible Inactivation of the Dorsal Nucleus of the Lateral Lemniscus Reveals Its Role in the Processing of Multiple Sound Sources in the Inferior Colliculus of Bats J. Neurosci., July 1, 2001; 21(13): 4830 - 4843. [Abstract] [Full Text] [PDF]

				R. A. Reale and J. F. Brugge Directional Sensitivity of Neurons in the Primary Auditory (AI) Cortex of the Cat to Successive Sounds Ordered in Time and Space J Neurophysiol, July 1, 2000; 84(1): 435 - 450. [Abstract] [Full Text] [PDF]

				D. McAlpine, D. Jiang, T. M. Shackleton, and A. R. Palmer Responses of Neurons in the Inferior Colliculus to Dynamic Interaural Phase Cues: Evidence for a Mechanism of Binaural Adaptation J Neurophysiol, March 1, 2000; 83(3): 1356 - 1365. [Abstract] [Full Text] [PDF]

				A. V. Galazyuk, D. Llano, and A. S. Feng Temporal Dynamics of Acoustic Stimuli Enhance Amplitude Tuning of Inferior Colliculus Neurons J Neurophysiol, January 1, 2000; 83(1): 128 - 138. [Abstract] [Full Text] [PDF]

				A. Klug, E. E. Bauer, and G. D. Pollak Multiple Components of Ipsilaterally Evoked Inhibition in the Inferior Colliculus J Neurophysiol, August 1, 1999; 82(2): 593 - 610. [Abstract] [Full Text] [PDF]

				R. Y. Litovsky and T. C. T. Yin Physiological Studies of the Precedence Effect in the Inferior Colliculus of the Cat. I. Correlates of Psychophysics J Neurophysiol, September 1, 1998; 80(3): 1285 - 1301. [Abstract] [Full Text] [PDF]