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Contingent negative variation (CNV) is a type of event-related potential, associated with focused attention, consisting of a large negative change in potential voltage across the cerebral cortex, especially in the frontal lobe. It develops slowly when a person is actively anticipating the occurrence of a significant stimulus requiring a response and is observable as an evoked potential occuring within 1–2 seconds of a warning signal being given.
Voluntary movements can be classified into two categories depending on their mode of initiation, i.e., whether they are initiated internally or triggered or paced by external stimuli. The central neuronal mechanisms involved in those preparations and executions can be reflected by Bereitschaftspotential (BP) and contingent negative variation (CNV), respectively.
CNV is a wide and prolonged negative potential recorded during simple warned reaction time paradigms from central and parietal scalp sites. The Bereitschaftspotential or readiness potential is a slow potential which precedes a voluntary movement, and was reported for the first time by Kornhuber and Deecke. Its scalp distribution is fairly wide, always begins bilaterally, symmetrically at the midline of the precentral-parietal regions, about 1000–1500 ms before movement.
The clinical application of CNV is for the evaluation of the correlation of potential changes with changes in cognitive functions occurring in various diseases. Numerous studies have confirmed the applicability of CNV on the diagnosis of dementia, Parkinson's disease, epilepsy, schizophrenia, anxiety states, chronic pains, including migraine.
W. Grey Walter et al. (1964) in Nature.