Microsecond Precision of Phase Delay in the Auditory System of the Barn Owl

1 Institute for Biology II, Rheinisch-Westfölische Technische Hochschule Aachen, Aachen, Germany; 2 Department of Biology, University of Maryland, College Park, Maryland; and 3 Institute for Theoretical Biology, Humboldt University Berlin, and Neuroscience Research Centre, Charité Medical Faculty of Berlin, and Bernstein Center for Computational Neuroscience, Berlin, Germany Submitted 1 December 2004; accepted in final form 7 April 2005 The auditory system encodes time with sub-millisecond accuracy. To shed new light on the basic mechanism underlying this precise temporal neuronal coding, we analyzed the neurophonic potential, a characteristic multiunit response, in the barn owl's nucleus laminaris. We report here that the relative time measure of phase delay is robust against changes in sound level, with a precision sharper than 20 µs. Absolute measures of delay, such as group delay or signal-front delay, had much greater temporal jitter, for example due to their strong dependence on sound level. Our findings support the hypothesis that phase delay underlies the sub-millisecond precision of the representation of interaural time difference needed for sound localization. Address for reprint requests and other correspondence: H. Wagner, Institut für Biologie II, RWTH Aachen, Kopeinikusstra e 16, D-52074 Aachen