Magneto-encephalographic correlates of the lateralized readiness potential.
To determine the onset of movement-related EEG activity accompanying stimulus-induced movements, it is commonly isolated from overlapping stimulus-related activity by a subtraction procedure, yielding the lateralized readiness potential (LRP). In order to elucidate the generation of the LRP and to explore whether magnetoencephalographic (MEG) measures have advantages over the LRP as a measure of response selection, MEG activity was recorded in four healthy adults during self-paced and stimulus-induced hand movements. Self-paced movements were preceded by readiness fields in all subjects, explained by sources in contralateral and (for 2/8 response sides) also ipsilateral hemispheres. Movement-related activity preceding stimulus-induced movements could only be modeled adequately when stimulus-related activity was removed by subtracting MEG signals for left and right hand movements. Thus identified source locations showed no systematic deviation from the sources for readiness fields, supporting a generation of the movement-related activity in primary motor cortex. The corresponding source waveforms allowed latency determinations of motor cortex activity as markers for response-choice timing. MEG thus provides information on the time course of hand-specific motor cortex activation for each hemisphere separately, where the electro-encephalographic LRP provides a composite measure for both hemispheres.
Department of Neurology, Heinrich-Heine Universität, Düsseldorf, Germany. p.praamstra@czzoknf.azn.nl
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Praamstra
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Schmitz
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Freund
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Schnitzler
D000328:Adult; D003265:Contingent Negative Variation; D004569:Electroencephalography; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D009044:Motor Cortex / Q000502:physiology; D009068:Movement / Q000502:physiology*; D011930:Reaction Time