Level-dependent latency shifts quantified through binaural processing.
The mammalian binaural system compares the timing of monaural inputs with microsecond precision. This temporal precision is required for localizing sounds in azimuth. However, temporal features of the monaural inputs, in particular their latencies, highly depend on the overall sound level. In a combined psychophysical, electrophysiological, and modeling approach, we investigate how level-dependent latency shifts of the monaural responses are reflected in the perception and neural representation of interaural time differences. We exploit the sensitivity of the binaural system to the timing of high-frequency stimuli with binaurally incongruent envelopes. Using these novel stimuli, both the perceptually adjusted interaural time differences and the time differences extracted from electrophysiological recordings systematically depend on overall sound pressure level. The perceptual and electrophysiological time differences of the envelopes can be explained in an existing model of temporal integration only if a level-dependent firing threshold is added. Such an adjustment of firing threshold provides a temporally accurate neural code of the temporal structure of a stimulus and its binaural disparities independent of overall sound level.
Siveke
Ida
I
Division of Neurobiology, Department Biologie II, Ludwig-Maximilians-Universität München, Germany.
Leibold
Christian
C
Kaiser
Katharina
K
Grothe
Benedikt
B
Wiegrebe
Lutz
L
D000161:Acoustic Stimulation / Q000379:methods*; D000328:Adult; D000818:Animals; D001306:Auditory Pathways / Q000502:physiology*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D005849:Gerbillinae; D006801:Humans; D008297:Male; D011930:Reaction Time / Q000502:physiology*; D055815:Young Adult