| Visual evoked potential interhemispheric transfer time in different frequency bands. | |
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MedLine Citation:
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PMID: 10348323 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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OBJECTIVE: Visual evoked potentials (VEP) have been used to estimate interhemispheric transfer time (IHTT). However, the complex wave of VEP is most probably formed by different generators of neural populations that act through different frequency channels. If the main peaks of VEP are established by different types of generators, which can also be connected to each other by a different type of callosal fibres, we would be able to estimate a wide range of various IHTT by measuring the latency between time-locked peaks of narrow band-pass filtered VEP. This research aimed to test this hypothesis. METHODS: Nine right-handed men were presented with a reversal of a checkerboard pattern as stimuli at RVF or LVF, and EEG was recorded at O1, O2, P3, P4. The grand-averaged VEPs were transformed to the frequency domain by means of the fast Fourier transform to obtain the amplitude frequency characteristics. Band-pass filters were chosen adequately, according to tuning frequencies indicated by clear peaks in the amplitude frequency characteristics. The chosen band pass filters (4-8 Hz, 8-15 Hz, 15-20 Hz, 20-32 Hz) were applied to the VEP of the subjects, and 4 different components of VEPs for each VEP were obtained. The latency of P100 and N160 of unfiltered VEP was measured. In the band-pass digital filter applied VEPs, positive and negative peaks, which are consistent with P100 and N160, were measured for each subject. Latency differences between hemispheres for digitally unfiltered and filtered VEPs were computed to estimate IHTT. RESULTS: In the different frequency bands, different IHTTs were estimated, ranging from 3 ms to 30 ms. Approximately 16 ms for theta band, 11 ms for alpha band, 6 ms for 15-20 Hz and 3 ms for 20-32 Hz bands were found. CONCLUSIONS: Our findings support the hypothesis which states that unfiltered VEPs provide us with only a rough estimation of IHTT. Also, they are consistent with anatomical findings that describe callosal fibres of varying dimensions, predicting various velocities between hemispheres. |
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Authors:
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E Nalcaci; C Basar-Eroglu; M Stadler |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology Volume: 110 ISSN: 1388-2457 ISO Abbreviation: Clin Neurophysiol Publication Date: 1999 Jan |
Date Detail:
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Created Date: 1999-06-01 Completed Date: 1999-06-01 Revised Date: 2008-09-10 |
Medline Journal Info:
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Nlm Unique ID: 100883319 Medline TA: Clin Neurophysiol Country: NETHERLANDS |
Other Details:
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Languages: eng Pagination: 71-81 Citation Subset: IM |
Affiliation:
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Physiology Department of Medical Faculty, University of Ankara, Turkey. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Adult Brain / physiology* Corpus Callosum / physiology* Electroencephalography Evoked Potentials, Visual / physiology* Humans Male Photic Stimulation Time Factors |
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