The impact of warning signal intensity on reaction time and components of the contingent negative variation.

Slow EEG potentials were recorded during performance of a simple reaction task in which warning signal intensity was varied from trial to trial under foreperiod durations of 1, 3 and 8 sec. As shown by speed of reaction, the warning signal had an activating effect which increased with its intensity and decreased with foreperiod duration. This effect was related to the amplitude of a slow potential which appears in the EEG shortly after presentation of the warning signal. This potential is interpreted as a component of the orienting response regulating sensitivity to subsequent stimulation, so that reaction time is affected through change in the effective intensity of the imperative signal.     

Planning of visually guided reach-to-grasp movements: inference from reaction time and contingent negative variation (CNV)

We performed electroencephalogram (EEG) recording in a precuing task to investigate the planning processes of reach-to-grasp movements in human. In this reaction time (RT) task, subjects had to reach, grasp, and pull an object as fast as possible after a visual GO signal. We manipulated two parameters: the hand shape for grasping (precision grip or side grip) and the force required to pull the object (high or low). Three seconds before the GO onset, a cue provided advance information about force, grip, both parameters, or no information at all. EEG data show that reach-to-grasp movements generate differences in the topographic distribution of the late Contingent Negative Variation (ICNV) amplitude between the 4 precuing conditions. Along with RT data, it confirms that two distinct functional networks are involved with different time courses in the planning of grip and force. Finally, we outline the composite nature of the lCNV that might reflect both high- and low-level planning processes.     

The contingent negative variation in an odor labeling paradigm

Fifteen subjects participated in an experiment designed to assess the contingent negative variation (CNV) during the labeling of odors and shapes. Odors or shapes were presented (SI) and followed 3 s later by a lexical label (A, B, or C) (S2). In 75% of the trials, the S2 was the correct label for the odor or shape. In the remaining trials, the S2 was an incorrect label. Subjects' olfactory performance was correlated with both the CNV during in the S1/S2 interval and also the P300 following the S2 stimulus. The CNV over the left frontal area was significantly larger in the olfactory phase of the experiment. CNV activity also correlated with olfactory performance such that subjects with the largest odor-related CNVs had the best olfactory performance. Although P300 differed as a function of label matches versus mismatches, no odor-specific effects or correlations were found.     

Serotonergic-1a activity and contingent negative variation

While cholinergic, dopaminergic, noradrenergic, and gabaergic effects on contingent negative variation (CNV) have been largely described, little is known about serotonergic influence. Therefore, the relationship between CNV and serotonergic activity as reflected by prolactin (PRL) response to flesinoxan, a 5-HT(1A) full agonist, has been investigated in 28 healthy volunteers. To investigate the clinical implications of the relationship between CNV and serotonergic-1a activity, a group of 43 depressed patients was included in the study. Results among healthy volunteers showed a significant negative relationship between PRL response to flesinoxan and CNV amplitude at Fz, but no relationship for the other electrodes (Cz and Pz). In depressed patients, the relationships were not significant. Overall, this study does not support serotonergic effects on CNV. However, this information is indirect (correlations) and is limited to 5-HT(1A) activity.     

Fear conditioning, preparedness, and the contingent negative variation

Psychophysiological research on preparedness has previously focused on autonomic nervous system parameters. The present study used electrocortical indices of fear conditioning. Subjects (n= 10) were tested under fear-relevant and fear-irrelevant conditions (1 week apart, order of conditions counterbalanced). Each condition comprised acquisition and extinction sessions. The contingent negative variation (CNV) was elicited in anticipation of forewarned slides (fear relevant: small animals; fear irrelevant: landscapes). In acquisition, reinforced conditioned stimulus (CS+) (but not nonreinforced conditioned stimulus [CS-]) slides were followed by white noise as an unconditioned stimulus (UCS). In extinction, the UCS was omitted. In the fear-relevant condition, CNV amplitude was significantly larger for CS+ than CS- in both acquisition and extinction. In the fear-irrelevant condition, CNV differentiation between CS+ and CS- was weak in both sessions. CNV was significantly larger in the fear-relevant than in the fear-irrelevant condition, for CS+ but not CS-. The findings are consistent with a preparedness interpretation and suggest that CNV under such circumstances may represent an automatic affective response to fear-relevant stimuli. Electrocortical measures could be particularly useful in examining information processing mechanisms in phobia and cognition-affect relationships generally.     

Selective attention, contingent negative variation and the evoked potential

Contingent negative variation (CNV), N1-P2 amplitude of the evoked potential (EP), and positivity at 300, 400 and 500 msec latency (P300, P400 and P500) were measured in relation to task relevant (R) or irrelevant (I) tones presented alternately or unpredictably at 1 sec intervals. High concordance of P300, 400 and 500 indicated a slow, relatively unpeaked wave thought to be the CNV resolution. Both N1-P2 and P300 appeared small only when stimuli were both irrelevant and predictably so. With predictable presentation correlations were observed between CNV, N1-P2 and P300 in terms of both absolute level and, particularly, relevant/irrelevant difference. Holding CNV constant statistically, and to a lesser extent P300, reduced these correlations. It is suggested that CNV resolution in the post-stimulus trace reflects selective attention paid to the stimulus, and may be responsible, through summation, for claims that N1-P2, and sometimes P300, does so.     

The effects of a depressant and a stimulant drug on the contingent negative variation

Three groups, each comprising eight subjects, were twice tested with an interval of one week: one group receiving 10 and 20 mg chlordiazepoxide, another group receiving 150 and 300 mg caffeine and a control group receiving placebo and 'no-drug' treatment. During each session the CNV was determined five times: one pre-drug and four post-drug measurements, each divided in a condition with and one without 'white noise'. Based on Eysenck's theory it was predicted that the CNV would increase after administering chlordiazepoxide and would decrease after administering caffeine. Furthermore it was expected that 'white noise' would attenuate the CNV of introverts and would enhance the CNV of extraverts. The first hypothesis was significantly verified comparing the chlordiazepoxide group with the caffeine group. However, making comparisons within groups, only the decrease between the measurement before taking caffeine and the first one after administering was significant. The second hypothesis could be supported for introverts only.     

The relationship between waking time and urinary epinephrine in bed-rested humans under conditions involving minimal stress

The correlation between urinary excretion of epinephrine and percent of waking time during time allotted for sleep was evaluated for both daytime and nighttime bed-rest under minimally stressful conditions. The experiment was performed on 6 male subjects. Polysomnographic recordings were made throughout each 8-h bed-rest period, and free epinephrine excretion was measured at intervals of 2.5 h. Epinephrine excretion showed a strongly positive correlation with percent of waking time during bed-rest in the daytime and at night (average correlation coefficient: day: r = 0.89, P less than 0.001; night: r = 0.68, P less than 0.001). The possibility that levels of epinephrine excretion could be used as an indicator of sleep disturbance is discussed.     

The relationship between reaction time and response variability and somatosensory No-go potentials

We investigated the relationship between reaction time (RT) and response variability and somatosensory Go/No-go potentials. Event-related potentials following electrical stimulation of the second (Go stimulus) or fifth (No-go stimulus) digit of the left hand were recorded from 16 subjects, and Go and No-go stimuli were presented at an even probability. The subjects were instructed to respond to the Go stimuli by pushing a button with their right thumb. We analyzed the correlation between RT and the N140 and P300 components, and between the standard deviation (SD) of RT and the N140 and P300. Neither the amplitude nor latency of the No-go-N140 (N140 evoked by No-go stimuli) or the Go-N140 (N140 evoked by Go stimuli) related significantly with RT and the SD of RT. There was a significant negative correlation between RT and the amplitude of the No-go-P300 (P300 evoked by No-go stimuli) at Fz and C3, indicating that subjects with a shorter RT had a No-go-P300 of larger amplitude. The latency of the Go-P300 (P300 evoked by Go stimuli) at Pz and C3 showed a significant correlation with RT. The SD of RT was significantly correlated with the amplitudes of the No-go-P300 at C3 and Go-P300 at Pz and C4, and the latency of the No-go-P300 at Cz and Go-P300 at Fz, Cz, Pz, C3, and C4. Our results suggest that response speed and variability for the Go stimulus in Go/No-go paradigms affect No-go-related neural activity for the No-go stimulus.     

The contingent negative variation (CNV) to fear-related stimuli in acquisition and extinction

Contingent Negative Variation (CNV) in anticipation of phobic and neutral slide material was recorded in Acquisition of a learned association between tone pitch and slide type, and in Extinction (following removal of slide presentation). In phobic volunteers, no clear CNV differentiation between 'phobic' and control condition was apparent in either Acquisition or Extinction. For Control subjects, a different pattern entirely has been demonstrated, with anticipation of the neutral condition giving rise to a larger CNV than anticipation of the 'phobic' condition (in Acquisition). In addition, Extinction led to a reversal of this CNV amplitude relationship, with the tone previously associated with the phobic slide producing a DC-shift which was larger than that following the tone previously paired with the neutral slide. The results are compatible with a dynamic model of CNV generation according to which CNV amplitude is positively related to an expectancy for reward or non-punishment but inversely related to an expectancy for punishment or non-reward.     

Effects of warning-signal modality on the contingent negative variation (CNV).

CNVs were recorded during the S1-S2 interval of a prolonged simple reaction task. In the task, a warning stimulus S1 is followed by an imperative stimulus S2, to which the subject makes a motor response. The differential effects of a visual and an auditory S1 were investigated under two interstimulus interval (ISI) durations (1 and 3 sec). Under the 3 sec ISI condition, the form of the slow negative wave demonstrated clearly a biphasic character: an orientation wave (O wave) following S1 with a peak latency at about 650 msec and an expectancy wave (E wave), which reaches its largest amplitude towards the end of the ISI. Under the 1 sec ISI condition the two components of the CNV are confounded. The O wave had a fronto-central distribution, while the E wave was located precentrally. The O wave was enhanced after an auditory S1, as compared to a visual S1.     

The effect of warning stimulus novelty on the P300 and components of the contingent negative variation

This experiment evaluated the effects of stimulus and response probability on the P300 and components of the contingent negative variation (CNV) in three different reaction tasks. In the first task the warning stimulus (S1) indicated that the imperative stimulus (S2) would require either a left or a right button press response; in the two other tasks the S1 indicated that S2 would either require a button press response or not. The a priori probability of S1 and the response to S2 were independently varied. The results show that a novel S1 significantly increased the amplitude and latency of the P300 and early CNV component: the late CNV component, however, increased significantly when a motor response to S2 was required. Early and late CNV components also differed in midline distribution. It is concluded that the early CNV can be viewed as the slow wave part of the event-related potential to S1, while the late CNV is an event preceding shift that strongly relates to the motor requirements of S2. It is finally suggested that both the P300 and early CNV reflect an orienting response to S1.     

The contingent negative variation (CNV) and speech production: Slow potentials and the area of Broca

The lateral distribution of the CNV was investigated during conditions that required normal male and female subjects to vocalize simple English words in a CNV paradigm. In addition to a non-verbal or comparison condition (Tone-Clicks/Button Press), two word conditions presented stimulus words in either S₁ or S₂ positions (Word-Tone/Speak; Tone-Word/Speak) and a third condition required a one-word association to the stimulus words (Word-Tone/Speak Association). Monopolar scalp activity was collected from sites that included a location approximating Broca's speech area on the left hemisphere, a homologous comparison site on the right hemisphere, frontal sites (F₃, F₄) and the vertex (C_z). Although several subjects showed some asymmetrical activity in some of the word conditions, amplitude measures baed on CNV averages indicated no consistent lateralization effects over the left hemisphere prior to word vocalization. Negative pretrial shifting was suspected in those conditions in which words appeared as S₁ signals.     

The effects of eye fixation and stimulus and response location on the contingent negative variation (CNV)

Vertex and parietal cortical slow waves and horizontal and vertical eye movement were recorded from 16 male subjects. Each subject was run in four constant-foreperiod reaction time conditions, in which the location of the auditory stimulus (speaker position above or below; to the subject's left or right) and the presence or absence of an eye focusing light was varied. Eye movements were unrelated to stimulus location, but were correlated with the position of the response key. Eye fixation resulted in reduced eye movement; however, it markedly reduced the cortical potential (CNV), unless the fixation light also served as the imperative stimulus. The relationship of eyeblinks and eye movement to the CNV was shown to be complex, and no method provided perfect correction for this artifact. The study also demonstrated the biphasic character of the cortical potential during the RT foreperiod. An early negative phase is apparently related to signal stimulus orientation, and habituates over trials; a separate, later negativity, appearing just before the imperative stimulus, appears to be the true CNV.     

Early contingent negative variation of the EEG and attentional flexibility are reduced in hypotension.

This study explored the question as to whether hypotension is related to decreased attentional performance and reduced cortical activation. A total of 50 females aged 19-44 years participated in the study. Attentional performance was assessed using three subtests of the Attentional and Cognitive Efficiency (ACE) battery. Contingent negative variation (CNV) as a measure of cortical activation was registered during a constant fore-period reaction time paradigm: two conditions were defined using tones as S1 (80 or 60 dB) and S2 (70 dB). The following results were obtained. Hypotensive patients performed significantly more poorly on one subtest of the ACE, which indicates a reduced speed for switching from a routine to a controlled response (quantifying attentional flexibility). They also had longer reaction times and revealed a significantly smaller amplitude of the early CNV component. In addition, a significant correlation was observed between systolic blood pressure and the amplitude of the early CNV component. The data support previous findings that hypotension can be related to lowered cortical activation and indicate that specific aspects of attentional performance might be negatively affected by hypotension.     

The relationship between reaction time, error rate and anterior cingulate cortex activity.

Current concepts of cognitive control suggest that the anterior cingulate cortex (ACC) is involved in performance monitoring. This idea is supported by the finding that increased ACC activity is found in situations in which errors are likely to occur, even if none are actually made. In addition, recent results suggest that increased ACC activity is negatively correlated with reaction time. We have now compared the error rates and the ACC activity of healthy subjects with short (n=19) vs. long reaction times (n=17) in an auditory choice reaction paradigm and analysed the current density differences in the ACC in the time range of the N1 component with low resolution electromagnetic tomography. Subjects with short reaction times showed significantly more ACC activation (Brodmann Area 24) and an increased error rate. This finding suggests that increased ACC activity is associated with a gain in reaction speed at the expense of correctness and is discussed in the context of current concepts about the role of the ACC in cognitive functions.     

Effects of warning-signal duration on the early and late components of the contingent negative variation.

Slow EEG potentials were recorded from three sites on the scalp (Fz, Cz and Pz) during a simple reaction time task in which the duration of the warning signal was either 0.5 or 2 sec. The duration of the foreperiod was held constant, and order of conditions was varied according to a latin square design. As predicted, the longer warning signal evoked increased amplitude of the early component of the contingent negative variation (CNV). These results confirm the interpretation of that wave as an orienting response. In contrast, the duration of the warning signal did not affect the second CNV component or reaction time latency. Additional dissociation between the two CNV components was evident in their distribution on the scalp. The early component was smallest at Pz, whereas the late component attained its lowest amplitude at Fz. Concurrently recorded palmar skin potentials exhibited different polarity and latency from the CNV.     

Two phases of the contingent negative variation in humans: Association with motor and mental functions

The question of the relationship between contingent negative variation and the mechanisms controlling motor and mental functions has received inadequate study. The aims of the present work were to investigate the relationship between the early and late phases of contingent negative variation and the state of motor and mental functions in patients with Parkinson’s disease and to study the effects of levodopa on contingent negative variation. Patients with Parkinson’s disease showed significant decreases in the amplitudes and areas of both phases of contingent negative variation as compared with subjects of similar age. Correlation analysis demonstrated a negative relationship between the extent of impairment of coordinatory muscle interactions and the amplitudes of both phases of this variation (p < 0.01). There was a positive relationship between the magnitudes of both phases and the state of mental functions, particularly memory (p < 0.05). Treatment of patients with Parkinson’s disease with levodopa was followed by a significant increase in the late phase (p < 0.05). The results obtained here provide evidence for the important role of structures supporting both direct motor control and mental functions in forming both phases of contingent negative variation. The greater effect of levodopa on the late phase of contingent negative variation suggests that the efferent system of the basal ganglia has a greater role in generating the late phase than in organizing the early phase of the variation. __________ Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 91, No. 4, pp. 364–373, April, 2005     

Effects of experimentally induced low back pain on the sit-to-stand movement and electroencephalographic contingent negative variation

It is becoming increasingly evident that people with chronic, recurrent low back pain (LBP) exhibit changes in cerebrocortical activity that associate with altered postural coordination, suggesting a need for a better understanding of how the experience of LBP alters postural coordination and cerebrocortical activity. To characterize changes in postural coordination and pre-movement cerebrocortical activity related to the experience of acutely induced LBP, 14 healthy participants with no history of LBP performed sit-to-stand movements in 3 sequential conditions: (1) without experimentally induced LBP; NoPain1, (2) with movement-associated LBP induced by electrocutaneous stimulation; Pain, and (3) again without induced LBP; NoPain2. The Pain condition elicited altered muscle activation and redistributed forces under the seat and feet prior to movement, decreased peak vertical force exerted under the feet during weight transfer, longer movement times, as well as decreased and earlier peak hip extension. Stepwise regression models demonstrated that electroencephalographic amplitudes of contingent negative variation during the Pain condition significantly correlated with the participants’ change in sit-to-stand measures between the NoPain1 and Pain conditions, as well as with the subsequent difference in sit-to-stand measures between the NoPain1 and NoPain2 conditions. The results, therefore, identify the contingent negative variation as a correlate for the extent of an individual’s LBP-related movement modifications and to the subsequent change in movement patterns from before to after the experience of acutely induced LBP, thereby providing a direction for future studies aimed to understand the neural mechanisms underlying the development of altered movement patterns with LBP.