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No evidence for ITD-specific adaptation in the frequency following response

Research output: Contribution in Book/Report/ProceedingsChapter

Published

Publication date2013
Host publicationBasic aspects of hearing: physiology and perception
EditorsBrian C. J. Moore, Roy D. Patterson, Ian M. Winter, Robert P. Carlyon, Hedwig E. Gockel
Place of publicationNew York
PublisherSpringer
Pages231-238
Number of pages8
ISBN (Electronic)9781461415909
ISBN (Print)9781461415893
Original languageEnglish

Publication series

NameAdvances in Experimental Medicine and Biology
PublisherSpringer
Volume787
ISSN (Print)0065-2598

Abstract

Neurons sensitive to interaural time differences (ITDs) in the fine structure of low-frequency signals have been found in binaurally responsive auditory nuclei in a wide range of species. The present study investigated whether the frequency following response (FFR) would show evidence for neurons “tuned” to ITD in humans. The FFR is a scalp-recorded measure of sustained phase-locked brainstem activity that has been shown to follow the frequency of low-frequency tones. The magnitude of the FFR often decreases over time for tones of long duration. The present study investigated whether this adaptation effect is ITD specific.The FFR to a 100-ms, 80-dB SPL, 504-Hz target tone was measured for ten subjects. The target was preceded by a 200-ms, 80-dB SPL, 504-Hz adaptor. The target always led by 0.5 ms in the left ear. The adaptor led either in the left ear or in the right ear by 0.5 ms. Stimuli (adaptor + target = pair) were presented in alternating polarity at a rate of 1.81 Hz. We used a “vertical” montage (+Fz, – C7, ground = Fpz) for which the FFR is assumed to reflect phase-locked neural activity from rostral generators in the brainstem. The averaged FFR waveforms for each polarity were subtracted, to enhance temporal fine structure responses. The results showed significant adaptation effects in the spectral magnitude of the FFR. However, adaptation was not larger when the adaptor had the same ITD as the target than when the ITD of the adaptor differed from that of the target. Thus, the current data provide no evidence that the spectral magnitude of the scalp-recorded FFR provides a non-invasive indicator of ITD-specific neural activation.