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Proceedings Paper

Information encoding in the temporal characteristics of auditory-evoked neuromagnetic fields
Author(s): Timothy P. L. Roberts
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Paper Abstract

Imaging data, provided by functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) has allowed insights into spatial organization of human cortical brain function. In the auditory system, a spatially-organized 'tonotopic' representation of frequency has been proposed. To provide an additional dimension to the description of functional organization, this study investigates the temporal signature of neuronal responses to auditory stimuli, detected using magnetoencephalography (MEG), to identify and characterize temporal encoding of stimulus attributes such as pitch and timbre. Stimuli elicited neuromagnetic fields with distinct peaks approximately 100 ms post-stimulus (M100). For sinusoidal tones frequency-dependent variation of the M100 latency was observed. This was mimicked using triangle and square waveforms, although the magnitude of the latency shift was attenuated. Amplitude-modulated tones and speech sounds demonstrated M100 latencies dominated by the carrier frequency and formats, and secondarily influenced by modulation frequency and fundamental, respectively. Information is encoded in the time domain of neuronal responses to auditory stimulation. Both the fundamental frequency and the timbre of a stimulus influence the specific latency of neuronal coherence. High temporal resolution recording of electromagnetic activity induced by stimuli allows new insights into the brain's functional encoding of presented information.

Paper Details

Date Published: 3 July 1998
PDF: 10 pages
Proc. SPIE 3337, Medical Imaging 1998: Physiology and Function from Multidimensional Images, (3 July 1998); doi: 10.1117/12.312566
Show Author Affiliations
Timothy P. L. Roberts, Univ. of California/San Francisco School of Medicine (United States)

Published in SPIE Proceedings Vol. 3337:
Medical Imaging 1998: Physiology and Function from Multidimensional Images
Eric A. Hoffman, Editor(s)

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