Preparation- or Intention-To-Act, in Relation to Pre-Event Potentials Recorded at the Vertex

  • Benjamin Libet
  • Elwood W. WrightJr.
  • Curtis A. Gleason
Part of the Contemporary Neuroscientists book series (CN)


A slow negative shift in potential, recordable extracranially, appears during the second or so preceding a signal to which a subject is supposed to respond. The ’ contingent negative variation’ (CNV) was the first discovered example of this (Walter et al. 1964). Similar pre-event potentials were found in a variety of delayed reaction paradigms, in both man (Low et al. 1966a; Donchin et al. 1971, 1972; Kutas and Donchin 1980; Rohrbaugh et al. 1980; Sanquist et al. 1981; Libet et al. 1982) and monkeys (Low et al. 1966b; Rebert 1972; Rosen and Stamm 1972). Several classes of processes may be reflected in these pre-event potentials: (1) a non-motor process; suggestions for this have included expectancy or anticipation (Walter et al., 1964), or an orienting or possibly more ‘general response to salient or novel stimuli’ (see Rohrbaugh and Gaillard, 1983) which may involve a shift in attentive or arousal state (Desmedt 1981) and leads to some behavioral/mental response (Donchin et al. 1971, 1972); (2) a general cerebral motor process, as represented in the readinesspotential (RP), that leads to the response (e.g., Rohrbaugh et al. 1980; Sanquist et al. 1981); (3) a combination of (1) and (2) (see Kutas and Donchin 1980; Rohrbaugh and Gaillard 1983); (4) a conative process of preparing or intending to act, independent of any actual movement (e.g., Low et al. 1966a; Libet et al. 1982). The present work helps to distinguish more definitively among these alternatives for the case of vertex-recorded potentials. The same human subject was tested with closely related procedures all of which developed mental sets of strong expectancy, orientation and attentiveness but differed in whether motor or non-motor responses were required. The study utilizes the subjects’ introspective reports, in conjunction with the behavioral tasks, to define the mental sets in question.


Supplementary Motor Area Contingent Negative Variation Readiness Potential Introspective Report Vertex Potential 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer Science+Business Media New York 1993

Authors and Affiliations

  • Benjamin Libet
    • 1
  • Elwood W. WrightJr.
    • 2
  • Curtis A. Gleason
    • 2
  1. 1.Department of PhysiologyUniversity of CaliforniaSan FranciscoUSA
  2. 2.Neurological Institute, Department of NeuroscienceMount Zion Hospital and Medical CenterSan FranciscoUSA

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