Contingent Negative Variation Amplitude Research Articles

The contingent negative variation during a memory retrieval task

Evoked potentials were recorded from the human scalp during performance of a memory retrieval task modeled after a paradigm originated by Sternberg (1966). Subjects were required to decide whether a probe digit was contained in a series of one to four target digits presented a few seconds before. The amplitude of the contingent negative variation (CNV) preceding the probe digit and the speed of CNV resolution after the probe varied as a function of target set size. CNV amplitude was greatest when the set size was one. The smaller the set size, the more positive the evoked potential 300 msec after the probe, regardless of whether a motor response was required.

Spatial distribution of the contingent negative variation (CNV) and the relationship between CNV and reaction time.

ABSTRACTMultichannel recording of scalp CNV (Contingent Negative Variation) and RT (Reaction Time) was carried out on 12 normal adult Ss in a fixed foreperiod RT experiment. Single trial responses were stored on digital tape and averaged off‐line. Strict control over eye movement artifact was exerted through fixation techniques coupled with mechanical and electro‐oculographic monitoring of movement. Analysis of single‐trial data gave an intra‐individual picture of correlation apparently in conflict with the across picture gained from averages. A rationalization is attempted of these results and some evidence is offered that, in the individual S, a negative and probably nonlinear relationship holds between CNV amplitude and RT. Analysis of average data demonstrates the distribution of CNV across the scalp and shows a lack of correlation between CNV and RT in prefrontal areas, in contrast with that found in central‐parietal areas. It is suggested that the CNV is an index of functionally different processes in these areas.

Prevalence and methods of control of the cephalic skin potential EEG artifact.

ABSTRACTPrevalence of the cephalic skin potential (CSP) artifact was studied in 21 Ss during EEG recording of the Contingent Negative Variation (CNV), averaged evoked response (AER), and verbal free association test. Skin potential response and electro‐oculogram (EOG) were also recorded. Subdermal pin electrodes and local anesthesia infusion were employed to eliminate the CSP artifact in the EEG.Results indicated that EEG recorded from subdermal pin electrodes or from locally anesthetized scalp was free of CSP artifact. The EEG recorded from subdermal pin electrodes demonstrated spontaneous potential shifts but appeared adequate for EEG recording of the CNV or the AER.Significant CSP artifact was demonstrated in the EEG of 10 of 21 Ss, both evoked by stimuli (10 Ss) and spontaneous (3 Ss). CSP artifact significantly increased CNV amplitude. CSP artifact significantly increased the AER late positive wave (P3) to infrequent tones.Studies of CNV and AER can be confounded by CSP artifact. Above techniques appear promising for recording EEG free of CSP artifact.

Anxiety, stress, and the contingent negative variation.

Two groups of 26 male college students, one scoring in the upper 10% and one scoring in the lower 10% of the Bendig test of emotionality (original sample, N = 200), were studied under a low-stress and a high-stress condition. Contingent negative variations (CNV) and galvanic skin responses (GSR) were recorded in a differential reaction time paradigm. Under low stress (flash-flash, response) both groups demonstrated equal CNV amplitudes. Under high stress (flash-intense electrical shock, response) the high emotionality group had smaller CNVs when response was made to intense shock than did the low emotionality group. Neither anticipatory GSRs nor reaction times differentiated the groups. The data are interpreted as suggesting a higher basal cortical negativity in the high emotionality group which prevented CNVs from reaching values beyond a physiologically determined maximum value.

The contingent negative variation related to preparatory set in a reaction time situation with variable foreperiod

It is well established that when the foreperiod varies over a short range from trial to trial, simple reaction time decreases as foreperiod duration increases. An experiment was conducted to relate this development of preparatory set to the slow change of cortical potential known as the contingent negative variation (CNV). Ten subjects were presented with an auditory warning signal and a visual reaction signal, with interstimulus intervals of 500, 600, 700, 800 and 900 msec arranged in random order. The hypotheses that reaction time decreases and CNV amplitude increases as monotonic functions of foreperiod duration were upheld. These data combine with those already in the literature to suggest that the form of the CNV reflects the development of preparatory set.

Slow potential changes and choice reaction time as a function of interstimulus interval

Slow potential changes were recorded over the vertex (C z) during a choice reaction task. The constant interstimulus interval (ISI) between the visual warning (S 1) and the visual imperative signal (S 2) was either 200, 400, 1000 or 2000 msec. The contingent negative variation (CNV) was not only measured between S 1 and S 2 (CNV 2), but also before S 1 (CNV 1). The main results were: (1) The CNV 2 amplitude showed significant variation as a function of ISI. It reached its maximum with an ISI of 1000 msec. (2) CNV 1 developed only before the short ISIs (200 and 400 msec). (3) When CNV 1 and CNV 2 were summed the differences in CNV amplitudes and durations between different ISIs became smaller. (4) The peak-to-peak amplitude P 1-N 1 of the potential evoked by S 1 was enhanced with short ISIs. (5) The correlations between mean CNV and median reaction time (RT) were low but significant for ISIs of 400, 1000 and 2000 msec. When, however, the effect of subjects was partialized out these correlations were drastically reduced, whereas the partialization of session and block effects had no noticeable influence on these correlations. (6) The correlations between single RT and single CNV (measured for the ISI of 1000 msec, individually for two subjects) were weak or even completely lacking. The main conclusion was that CNV coincides with preparedness to react to a stimulus in a choice RT-task, but its amplitude at the moment of onset of the imperative stimulus does not reflect, or reflects weakly, the degree of preparedness (as indicated by RTs) at that moment.

Task initiation and amplitude of the contingent negative variation (CNV)

When a subject is allowed to initiate the occurrence of the S 1 − S 2 sequence in a CNV experiment, significantly smaller CNVs are generated than when the experimenter initiates the trials. It is hypothesized that the decrement in CNV amplitude is due to a pre-S 1 negative shift in the DC level of the brain which limits subsequent negativity.

Subjective and response-related determinants of CNV amplitude.

ABSTRACTThe effect on contingent negative variation (CNV) of varying the difficulty of obtaining reaction time (RT) feedback and the relationship of CNV and RT were studied. Subjects (Ss) were run in a reaction‐time‐foreperiod experiment with 4 conditions of varying RT feedback duration. Subjective reactions to the experiment were recorded by Ss on a questionnaire and were divided by the experimenters into two highly significant sets of mean CNVs based on the most “positive’ and most “negative’ responses to the conditions. CNVs and their associated RTs were analyzed, and a significant rank order correlation over all Ss showed there was a trend for individuals with faster RTs to have larger CNVs. Individual correlations were low and highly variable. Only the very slowest RTs were associated with small CNVs. The failure of explicit RT feedback to have any effect upon CNV amplitude is in agreement with previous studies, and the significant association of CNV amplitude with written reactions of Ss might prove a useful tool for further CNV analysis. The RT data indicated that CNVs and RTs reflect relatively independent functions and that very slow RTs may reflect qualitative changes in S's psychological state which affect both RT and CNV; and such trials might appropriately be eliminated from CNV data analysis.

Contingent negative variation as an indicator of sexual object preference.

The contingent negative variation (CNV) was recorded in the interval between paired visual exposures of male nudes, female nudes, and sexually "neutral" silhouettes. Groups of 12 male and 12 female subjects viewing 50 randomized presentations from each stinmulus category responded with averaged CNV amplitudes proportional to the predicted degree of sexual interest in the stimulus classes.

The contingent negative variation: some methodological problems in the recording of shifts in steady potentials.

ABSTRACTThe various methods that have been used in recording of the Contingent Negative Variation (CNV) were examined with reference to developing selection criteria. Findings revealed that chopper amplifiers with condenser‐coupled input circuits and DC amplifiers with zero‐suppression circuits between stages showed shifts in output level which were the result of changes in resistance of the input circuit. As these artifacts were not negligible with reference to commonly‐reported CNV amplitudes, it was concluded that the two methods should be avoided in recording of low‐level shifts in steady potentials like the CNV.

Contingent negative variation and individual differences. A new approach in brain research.

Contingent negative variation (CNV) is a slow surface-negative cortical potential in the human brain that is related to individual differences in psychological functions. Major sources of interindividual variability in CNV development among normal adults, children, and psychiatric patients involve attention and arousal functions. Consequently, a two-process theoretical model is postulated to account for individual differences in CNV, namely, that CNV amplitude is positively and monotonically related to attention functions and nonmonotonically (inverted- U ) related to arousal functions. CNV also appears to be reflecting motor processes. Although CNV is a potentially useful tool in psychiatric research, eye movements can drastically alter CNV and are a serious methodological problem requiring further study. The neurophysiological genesis of CNV involves both cortical (apical dendrites in upper layers of frontal cortex) and subcortical (brain stem reticular formation) mechanisms.

Interaction of electro-ocular potentials with the contingent negative variation.

ABSTRACTThe contingent negative variation (CNV) was recorded from the vertex in forty‐five subjects during a two‐stimulus expectancy paradigm under varying conditions of eye closure and fixation. Simultaneously averaged electro‐oculograms (EOG) were recorded as a measure of eye movement. The amplitude of both CNV and EOG responses was significantly greater for the eyes closed and eyes open unfixated conditions as compared to the eyes fixated condition. CNV and EOG responses were often highly similar in terms of waveform. For the eyes fixated condition three patterns of CNV–EOG interaction were observed. Eighteen subjects demonstrated a CNV response of low amplitude in the absence of detectable EOG responses. Twenty‐three subjects showed a predominant pattern in which CNV responses of high amplitude and EOG responses were present. Four subjects failed to show either a CNV or EOG response. There was considerable within subject variability in the pattern of response with replicated blocks of trials. Thus contamination of the CNV by EOG potentials is reduced by eye fixation but not eliminated because of subject variability in control of eye movement.

Slow potential changes recorded from human brain during learning of a temporal interval

The contingent negative variation (CNV), a cerebral DC shift in man, has been linked in the literature to the psychological concept “expectancy.” In a study of the relationship between developing accuracy of interval estimation and CNV amplitude, absolute error of interval estimation was found to decrease exponentially while CNV amplitude could best be described by a quadratic (inverted-U) function. It was concluded that the relationship between CNV amplitude and “expectancy” is not one-to-one, and that these data, with those from a number of other investigations, support the hypothesis that the various portions of the brain act differentially and at various times during learning.