Document Detail

A convenient method for detecting electrolyte bridges in multichannel electroencephalogram and event-related potential recordings.
MedLine Citation:
PMID:  11222978     Owner:  NLM     Status:  MEDLINE    
Dense electrode arrays offer numerous advantages over single channel electroencephalogram/event-related potential (EEG/ERP) recordings, but also exaggerate the influence of common error sources arising from the preparation of scalp placements. Even with conventional low density recordings (e.g. 30-channel Electro-Cap), over-application of electrode gel may result in electrolyte leakage and create low impedance bridges, particularly at vertically-aligned sites (e.g. inferior-lateral). The ensuing electrical short produces an artificial similarity of ERPs at neighboring sites that distorts the ERP topography. This artifact is not immediately apparent in group averages, and may even go undetected after visual inspection of the individual ERP waveforms. Besides adding noise variance to the topography, this error source also has the capacity to introduce systematic, localized artifacts (e.g. add or remove evidence of lateralized activity). Electrolyte bridges causing these artifacts can be easily detected by a simple variant of the Hjorth algorithm (intrinsic Hjorth), in which spatial interelectrode distances are replaced by an electrical analog of distance (i.e. the variances of the difference waveforms for all pairwise combinations of electrodes). When a low impedance bridge exists, the Hjorth algorithm identifies all affected sites as flat lines that are readily distinguishable from Hjorth waveforms at unbridged electrodes.
C E Tenke; J Kayser
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology     Volume:  112     ISSN:  1388-2457     ISO Abbreviation:  Clin Neurophysiol     Publication Date:  2001 Mar 
Date Detail:
Created Date:  2001-03-06     Completed Date:  2001-04-12     Revised Date:  2008-09-10    
Medline Journal Info:
Nlm Unique ID:  100883319     Medline TA:  Clin Neurophysiol     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  545-50     Citation Subset:  IM    
Department of Biopsychology, Unit 50, New York State Psychiatric Institute, 1051 Riverside Drive, New York, NY, USA.
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MeSH Terms
Brain / physiology
Electroencephalography / methods*
Electrolytes / metabolism*
Evoked Potentials / physiology*
Grant Support
Reg. No./Substance:

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