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| Research article summary (published 29 Nov 2002): |
The representation of peripheral neural activity in the middle-latency evoked field of primary auditory cortex in humans(1).
Full Abstract
Short sweeps with increasing instantaneous frequency (up-chirps) designed to compensate for the propagation delay along the human cochlea enhance the magnitude of wave V of the auditory brainstem responses, while time reversed sweeps (down-chirps) reduce the magnitude of wave V [Dau, T., Wegner, O., Mellert, V., Kollmeier, B., J. Acoust. Soc. Am. 107 (2000) 1530-1540]. This effect is due to synchronisation of frequency channels along the basilar membrane and it indicates that cochlear phase delays are preserved up to the input of the inferior colliculus. The present magnetoencephalography study was designed to investigate the influence of peripheral synchronisation on the activation in primary auditory cortex. Spatio-temporal source analysis of middle-latency auditory evoked fields (MAEFs) elicited by clicks and up- and down-chirps showed that up-chirps elicited significantly larger MAEF responses compared to clicks or down-chirps. Both N19m-P30m magnitude and its latency are influenced by peripheral cross-channel phase effects. Furthermore, deconvolution of the empirical source waveforms with spike probability functions simulated with a cochlear model indicated that the source waves for all stimulus conditions could be explained with the same unit-response function, i.e. a far field recorded cortical response of a very small cell assembly along the medio-lateral axis of Heschl's gyrus that receives input from a small number of excitatory fibres. The conclusion is that (i) phase delays between channels in the auditory pathway are preserved up to primary auditory cortex, and (ii) MAEFs can be described by a convolution of a unit-response function with the summary neural activity pattern of the auditory nerve.
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Author information
Author/s: Rupp, André (A); Uppenkamp, Stefan (S); Gutschalk, Alexander (A); Beucker, Roland (R); Patterson, Roy D (RD); Dau, Torsten (T); Scherg, Michael (M);
Affiliation: Section of Biomagnetism, Department of Neurology, Universität Heidelberg, 69120, Heidelberg, Germany. andre.rupp@urz.uni-heidelberg.de
Journal and publication information
Publication Type: Journal Article; Research Support, Non-U.S. Gov't
Journal: Hearing research (Hear Res), published in Netherlands. (Language: eng)
Reference: 2002-Dec; vol 174 (issue 1-2) : pp 19-31
Dates: Created 2002/11/15; Completed 2003/05/02; Revised 2006/11/15;
PMID: 12433393, status: MEDLINE (last retrieval date: 11/6/2008)
Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.
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