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Quantification of the cortical silent period evoked via transcranial magnetic brain stimulation
Author(s) -
Clark Brian C,
Hoffman Richard L.,
Damron Leatha A.
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.946.5
Subject(s) - silent period , transcranial magnetic stimulation , motor cortex , stimulus (psychology) , neuroscience , audiology , stimulation , coefficient of variation , evoked potential , psychology , medicine , mathematics , statistics , cognitive psychology
A magnetic pulse to the motor cortex during a muscle contraction produces a motor evoked potential (MEP) followed by electrical quiescence before activity resumes (cortical silent period [CSP]). The CSP is used clinically and scientifically despite little consensus on how to best assess and quantify it. In this study we assessed the stability and reliability of different CSP quantification methods by recording the CSP from 7 humans at 3 stimulus intensities (10, 20 and 30% active motor threshold [AMT]) and quantifying it based on 5 commonly used onset points (see figure). Inter‐rater reliability of CSP quantification was high (r≥0.95). The coefficient of variation (CV) was reduced when the reference point used to demarcate the CSP onset was earliest in the temporal occurrence of events (range 14–33%). The lower stimulus intensities (10 and 20% AMT) exhibited high CV's (>20%), and random error (LOA Ratio: 73–98), whereas the amount of variability evident at 30% was not associated with the length of the CSP (systematic bias <1‐ms). These results suggest that CSP studies should utilize a stimulus intensity ≥30% AMT and define the onset of the CSP at the MEP onset.