Overlap between P300 and movement-related-potentials: a response to Verleger.
In reply to Verleger's commentary, I first clarify what the term "MRP overlap" implies; by means of a simple additive simulation it is shown that overlap between a stable P300 and a MRP that moves in time with reaction-time, may cause two types of artefacts--amplitude reduction and double peaking of P300. Following Verleger's suggestion, it is then argued that the effects of stimulus-degradation on P300 amplitude in our experiments was, at least in part, due to overlap with negative components of the MRP (in the go-intact condition), and with positive CNV return (in the nogo-intact condition). It is concluded that MRP overlap is not only an artefact but also a useful index of motor-preparation in reaction tasks, and that more refined methods should be developed in future research for accurate estimation of MRP overlap in stimulus-locked ERP waveforms.
Kok
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Psychology Department, University of Amsterdam, The Netherlands.
D001143:Arousal / Q000502:physiology*; D001288:Attention / Q000502:physiology*; D002540:Cerebral Cortex / Q000502:physiology; D003265:Contingent Negative Variation; D004569:Electroencephalography; D005074:Evoked Potentials, Visual; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology