Contingent Negative Variation - O-wave and E-wave

O-wave and E-wave

Most researchers agree that the CNV component has been associated with information processing and response preparation. The main controversy is whether the CNV is composed of more than one component. After discovery of the CNV, researchers were able to distinguish between two main components of the CNV. Loveless and Sanford (1975) and Weerts and Lang (1973) increased the interstimulus interval to greater than 3 seconds and showed that two components can be visually distinguished from the CNV. The first wave followed the warning stimulus and was called the O wave, or orienting wave. This wave showed enhanced amplitude in the frontal regions. The second wave preceded the imperative stimulus and was called the E wave, or expectancy wave. A study conducted by Gaillard (1976) provided further evidence that the O wave was frontally distributed and was more strongly affected by auditory stimuli rather than visual stimuli.

A related, important issue has been the question of whether all or part of the CNV corresponds to the readiness potential. The readiness potential is the neural preparation for motoric responses. Both components have a similar scalp distribution with a negative amplitude and are associated with a motor response. In fact, many researchers claimed that the terminal CNV, or E wave, was in fact the readiness potential, or bereitschaftspotential. This was the general consensus until other work provided evidence that the CNV can be distinguished from the RP. First, the RP is usually lateralized to the contralateral side of the motoric response, while the CNV is usually bilateral. Second, the CNV can occur even when a motor response is not required. Third, a RP occurs without any external stimuli. This shows that the RP occurs for motor responses while the CNV occurs when two stimuli are contingent with each other.