Event-related potentials associated with judgment: comparison of S1- and S2-choice conditions in a contingent negative variation (CNV) paradigm

Postural control and contingent negative variation during transient floor translation while standing with the ankle fixed

Background

Adaptation changes in postural muscle activity and anticipatory attention were investigated with the ankle joint fixed to change postural control strategies during transient floor translation.

Methods

For 15 healthy young adults, 40 transient floor translations (S2) in the anterior direction were applied 2 s after an auditory warning signal (S1), under conditions with or without fixation of the ankle. Activity of the frontal postural muscles (tibialis anterior (TA), rectus femoris (RF), rectus abdominis) and contingent negative variation (CNV, brain potential) were analyzed for 20 trials each of the early and latter halves under each fixation condition.

Results

With fixation, peak amplitude of muscle activity after S2 was significantly decreased in TA and increased in RF. These muscles showed marked adaptive decreases. The early component of CNV reduced with adaptation, particularly under fixation condition. Only in RF, background activity increased just before S2, with adaptation under fixation. A significant correlation was found between timings of CNV peak and RF activation just before S2 only after adaptation under fixation.

Conclusion

These results suggest that the main activation muscle changes from TA to RF with fixation. Under such condition, attention would be focused on the knee with adaptation, and the need for heightening attention in the early stage may have declined. Correspondingly, the timing to heighten stiffness of the RF became later, and attention would have been paid to RF activation just before S2.

Adaptation changes in dynamic postural control and contingent negative variation during repeated transient forward translation in the elderly

BACKGROUND

Adaptation changes in postural control and contingent negative variation (CNV) for the elderly were investigated during repeated forward floor translation.

METHODS

Fifteen healthy elderly persons, living in the suburban area of Kanazawa City, Japan, underwent backward postural disturbance by a forward-floor translation (S2) 2 s after an auditory warning signal (S1). A set with 20 trials was repeated until a negative peak of late CNV was recognized in the 600-ms period before S2, and the last set was defined as the final set. Electroencephalograms, center of foot pressure in the anteroposterior direction (CoPap), and electromyograms of postural muscles were analyzed.

RESULTS

CoPap displacement generated by the floor translation was significantly decreased until the twelfth trial in the first set, and mean CoPap displacement was smaller in the second and final sets than in the first set. The mean displacement was significantly smaller in the final set than the previous set. A late CNV with a negative peak was not recognized in the first and second sets. However, most subjects (13/15) showed a negative peak by the fourth set, when the late CNV started to increase negatively from about 1,000 ms after S1 and peaked at about 300 ms before S2. At about 160 ms before the CNV peak, the CoPap forward shift started. The increase in timing of the gastrocnemius activity related to the CoPap shift was significantly correlated with the CNV peak timing (r = 0.64). After S2, peak amplitudes of the anterior postural muscles were significantly decreased in the final set compared to the first set.

CONCLUSIONS

It was demonstrated that even for the elderly, with so many repetitions of postural disturbance, a late CNV with a negative peak was recognized, leading to accurate postural preparation. This suggests the improvement of frontal lobe function (e.g., anticipatory attention and motor preparation) in the elderly.

Dissociation of preparatory attention and response monitoring maturation during adolescence

OBJECTIVE

Substantial brain development occurs during adolescence providing the foundation for functional advancement from stimulus-bound "bottom-up" to more mature executive-driven "top-down" processing strategies. The objective was to assess development of EEG markers of these strategies and their role in both preparatory attention (contingent negative variation, CNV) and response monitoring (Error Related Negativity, ERN, and Correct Related Negativity, CRN).

METHODS

CNV, ERN and CRN were assessed in 38 adolescents (18 girls), age 11-18 years, using a variation of a letter discrimination task.

RESULTS

Accuracy increased with age and developmental stage. Younger adolescents used a posterior attention network involved in inhibiting irrelevant information. Activity in this juvenile network, as indexed by a posteriorly-biased CNV and CRN decreased with age and advancing pubertal development. Although enhanced frontal CNV, known to be predictive of accuracy in adults, was not detected even in the older adolescents, top-down medial frontal response monitoring processes (ERN) showed evidence of development within the age-range studied.

CONCLUSIONS

The data revealed a dissociation of developmental progress, marked by relatively delayed onset of frontal preparatory attention relative to error monitoring.

SIGNIFICANCE

This dissociation may render adolescents vulnerable to excessive risk-taking and disinhibited behavior imposed by asynchronous development of component cognitive control processes.

Differential effects of age and executive functions on the resolution of the contingent negative variation: a reexamination of the frontal aging theory

The "frontal aging theory" assumes the deterioration of executive/inhibitory functions as causal factors for the cognitive decline in human aging. The contingent negative variation resolution (CNV-R) is an electroencephalographic potential elicited after the second (informative) stimulus in warned Go/NoGo tasks requiring a response to one type of stimulus (Go) but not to the other (NoGo). Whereas the CNV-R across conditions is a measure of executive functions, the augmented potential in the NoGo condition is a specific measure of inhibitory processes. The aim was to examine the presumed linkage between executive processes and the CNV-R with special regard to inhibition in the NoGo condition, and to test whether any effects of age on this potential can be explained by a failure of (inhibitory) executive functions. Nineteen young and 15 elderly non-demented healthy volunteers were examined in a Go/NoGo CNV-R paradigm and on a test of executive functions focussed on set shifting (Trail Making test). Results showed: (1) Better executive functions are associated with higher amplitudes of the CNV-R across conditions. (2) The CNV-R is higher for elderly than younger subjects; this increment is much stronger in the NoGo condition. In conclusion, the CNV-R across conditions reflects executive processes such as the shift of motor set. A higher CNV-R for elderly subjects (particularly of the inhibition-related NoGo CNV-R) indicates that this group is not impaired in the available amount of executive control but may exert such control for task demands where young subjects do not require it.

Oscillatory changes related to the forced termination of a movement

OBJECTIVE

Stimulus-induced movements are accompanied by a definite pattern of oscillatory changes, that include a frontal 15 Hz synchronization, a central peri-movement desynchronization, and a contralateral beta rebound after the movement. Our aim was to study the oscillatory changes related to the forced termination of a single complex motor program (signature) and compare them with those observed after the normal termination of the movement.

METHODS

Fifty-eight reference-free EEG channels were analyzed in 10 healthy subjects. A 2000 Hz tone (S1, go signal) indicated the subject to begin to write his/her complete signature. A second 2000 Hz tone 0.8 s afterwards (50% probability: S2, stop signal) indicated the subject to stop immediately. Movement-related energy changes were evaluated by means of time-frequency (Gabor) transforms.

RESULTS

A frontal 15 Hz synchronization was observed after S1, but not after S2. The amplitude of the post-movement beta increase was significantly lower when the movement was abnormally terminated (p=0.005), while the peri-movement decrease was similar.

CONCLUSIONS

The forced termination of a motor program reduces significantly the amplitude of the post-movement beta increment, conserving its temporal pattern. Also, the presence of the 15 Hz frontal synchronization only after S1, together with the results of previous studies, suggests that the frontal mechanisms involved in go/no go and stop signals are very different.

SIGNIFICANCE

Our results indicate that the beta rebound is an active process, independent of the peri-movement beta decrease, which is influenced by how the movement is terminated.

Contingent negative variation elicited before jaw and tongue movements

Contingent negative variation (CNV) is a negative brain potential occurring between two successive stimuli when the first stimulus is a warning and the second stimulus requires a motor response. The CNV is interpreted as an expression of the cognitive processes in preparation for a response directed to a purpose. Using 19 electrodes we recorded CNVs for mouth opening, closing and lateral movements, tongue protrusion and hand extension in 10 healthy subjects. The aim of the study was to examine the motor control mechanism underlying jaw and tongue movements in a cognitive paradigm. The first stimulus (S1) served as a preparatory warning signal for the imperative stimulus (S2) 2 s after the S1. The subject performed the experimental tasks after the S2. The grand average CNVs for jaw and tongue movements showed a bilaterally widespread negativity with the maximum in the vertex region (Cz). The early CNV was identified about 400 ms after the S1 and its amplitude was highest at the midline-frontal area. The late CNV started approximately 1000 ms after the S1 with the maximum at Cz. The mean amplitude was significantly lower for hand extension than for the other tasks, and significantly higher for lateral movement than for mouth closing, suggesting that the CNV amplitude can be affected by the complexity of the task. The CNV recording may provide a means to study the neuronal activity necessary for the sensorimotor integration of jaw and tongue movements.

Patients with Right Frontal Lesions are Unable to Assess and Use Advice to Make Predictive Judgments

Frontal lobe damage impairs decision-making. Most studies have employed gambling and probabilistic tasks, which have an emotional (reward-punishment) component and found that patients with ventromedial sector lesions have exceptional difficulty performing normally on these tasks. We have recently presented an economic decision-making task to patients and normal volunteers that required them to not only forecast an economic outcome but also to weigh advice from four advisors about the possible outcome across 40 trials. We studied 20 patients with right frontal lobe lesions and 9 patients with parietal lobe lesions and compared their performance to 20 matched controls. Frontal lobe lesion patients were inconsistent at using advice and their forecasts were poor. Patients with dorsolateral but not orbito-frontal lesions showed some ability to assess advice. Patients with parietal lobe lesions were good at assessing advice but were slow at doing so; they were consistent but poor at using advice and their use of advice was unrelated to their forecasting. All three patient groups were overconfident in their own performance. In contrast, controls could both use and assess advice, their ability to use advice was mediated by their ability to assess it, and they were not overconfident. Group differences on an overall measure of accuracy on this task were associated with an ability to accurately plan. Differences in ability to assess and forecast were associated with planning and working memory performance. These findings indicate that patients with both right dorsolateral and orbito-frontal lesions may be impaired when required to make complex decisions related to forecasting and judgment. Our findings enlarge the scope of decision-making deficits seen in patients with frontal lobe lesions and indicate additional circumstances in which patients with frontal lobe lesions will have difficulty in deciding.

High resolution spatiotemporal analysis of the contingent negative variation in simple or complex motor tasks and a non-motor task

OBJECTIVES

Since the characteristics of the Bereitschaftspotential (BP) - voluntary movement paradigm of internally-driven movements - have been established recently by our group using high resolution DC-EEG techniques, it was of great interest to apply similar techniques to the other slow brain potential--contingent negative variation (CNV) of externally-cued movements--with the same motor tasks using the same subjects.

METHODS

The CNV for simple bimanual sequential movements (task 1), complex bimanual sequential movements (task 2) and a non-motor condition (task 3) was recorded on the scalp using a 64 channel DC-EEG in 16 healthy subjects, and the data were analyzed with high resolution spatiotemporal statistics and current source density (CSD).

RESULTS

(1) The CNV was distributed over frontal, frontocentral, central and centroparietal regions; a negative potential was found at the frontal pole and a positive potential was found over occipital regions. (2) CNV amplitudes were higher for task 2 than for task 1, and there was no late CNV for task 3. (3) A high resolution spatiotemporal analysis revealed that during the early CNV component, statistical differences existed between the motor tasks (tasks 1 and 2) and the non-motor task (task 3), which occurred at frontocentral, central, centroparietal, parietal and parieto-occipital regions. During the late CNV component, additional significant differences were found not only between the motor tasks and the non-motor task but also between motor task 1 and task 2 at frontocentral, central and centroparietal regions. (4) Comparison of the CNV between the frontomesial cortex (situated over the supplementary/cingulate areas, SCMA) and both lateral pre-central areas (situated over the primary motor areas, MIs) showed that there was no statistically significant difference between the two cortical motor areas except for the early CNV. (5) Comparison of the CNV between the 3 tasks over the cortical motor areas showed that there were significant differences between the motor tasks and the non-motor task regarding the auditory evoked potential (AEP) and the early CNV component, and between all 3 tasks in the late CNV, the visual evoked potential (VEP(2)) and the N-P component. (6) The ranges and the densities of the CSD maps were larger and higher for complex than for simple tasks. The current sinks of the AEP and the early CNV were located at Fz, the late CNV at FCz and surrounding regions. As to be expected, current sources of the VEPs were located at the occipital lobes. The CNV was a current sink (negative) except for the VEP's main component which was a current source (positive).

CONCLUSIONS

(1) The CNV topography over the scalp varied with the complexity of motor tasks and between motor and non-motor conditions. (2) The origin of the early CNV may rest in the frontal lobes, while the late CNV may stem from more extensive cortical areas including SCMA, MIs, etc. (3) The late CNV component is not identical with the BP.

Abnormal contingent negative variation in writer's cramp

OBJECTIVE

To investigate the physiological abnormality in writer's cramp, a focal dystonia which specifically affects writing.

METHODS

We recorded brain potentials that precede hand and neck movements (contingent negative variation or CNV) in 11 patients and 11 age-matched normal subjects. A 1000 Hz tone burst (S1) was delivered to the right or left ear in random sequence, and 2 s after, a 2000 Hz tone burst (S2) was delivered to both ears simultaneously. For the response task to S2, the subjects were instructed to extend their fingers ipsilateral to the ear to which S1 was given in one experiment or to rotate the head to the side of the S1 presentation in another. All the patients had symptoms in the right hand only, and performed both tasks normally. CNV amplitudes were compared between normals and patients using unpaired t test.

RESULTS

They showed normal CNV for neck movement but significantly decreased CNV amplitudes for movements both in the affected and unaffected hands.

CONCLUSIONS

Our findings suggest that motor programming is specifically abnormal for the affected body part, including the asymptomatic contralateral limb, and that the clinical symptom may result from a deficient compensatory mechanism for abnormal motor programs or subroutines.