Temporal Damping in Response to Broadband Noise. I. Inferior Colliculus

• Published in: Journal of neurophysiology 2005-04, Vol.93 (4), p.1857-1870
• Main Authors: Joris, Philip X, Van De Sande, Bram, van der Heijden, Marcel
• Format: Article
• Language: English
• Subjects: Acoustic Stimulation - methods; Action Potentials - physiology; Animals; Cats; Inferior Colliculi - physiology; Noise; Time Factors
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.00962.2004

1 Laboratory of Auditory Neurophysiology, K.U. Leuven, Medical School, Campus Gasthuisberg, Leuven, Belgium; and 2 Department of Physiology, University of Wisconsin, Medical School, Madison, Wisconsin Submitted 15 September 2004; accepted in final form 30 November 2004 Many cells in the inferior colliculus (IC) are sensitive to interaural time differences (ITDs), in the form of an oscillatory dependency of average firing rate on ITD. We studied the degree of damping in such binaural responses, recording from neurons in the inferior colliculus of pentobarbital-anesthetized cats to binaural broadband noise and tones. Noise-delay functions and composite curves were characterized by computing the difference between responses to correlated and anticorrelated stimuli. We use a new metric, based on the envelope of this difference, to quantify damping. There is a clear relationship between damping and characteristic frequency (CF), but even neurons of the same CF can differ in their damping. For individual cells, damping can be stronger to tones or to noise; at the population level the two are positively correlated and are scarcely affected by SPL. The frequencies that dominate ITD sensitivity are near the CF in response to noise, but are often below CF in response to tones. These findings qualify conclusions from earlier reports but overall they support the conclusion that, at a population level, basic aspects of binaural responses to wideband noise are consistent with summed responses to pure tones. Address for reprint requests and other correspondence: P. X. Joris, K.U. Leuven, Laboratory of Auditory Neurophysiology, Gasthuisberg O&N bus 801, Herestraat 49, B-3000 Leuven, Belgium (E-mail: philip.joris{at}med.kuleuven.ac.be )