[Spatiotemporal study of event-related desynchronization during self-paced movement]

The desynchronization of Alpha band components during a self-paced movement of the thumb was studied in 7 subjects. The EEG was recorded from 23 electrodes located on the frontocentral, central, and parietocentral regions, referred to the right mastoïde, 4 s before and 2 s after movement onset. The data were then transformed to obtain 11 source derivations. The temporal evolution of the power of the signal within the Alpha band, every 250 ms, associated to the non parametric statistic test of Wilcoxon, authentifies the event-related desynchronization (ERD). The spatiotemporal analysis of ERD underlines on the central regions, two principal locations of ERD: one controlateral to the movement, starting more than 1 s before the movement; the other, ipsilateral, shorter, during the movement. However, no significance desynchronization was underlined on the vertex. The ANOVA used to analyse these results confirms the principal location of ERD on the central region, and seems to indicate a right lateralisation during the right or the left movement.

Bereitschaftspotential: is there a contribution of the supplementary motor area?

Bereitschaftspotentials (BPs) preceding simple repetitive finger movements were recorded in 11 normal volunteers. By modeling the recorded data with multiple equivalent dipoles we found that bilateral sources in the motor cortex were the best fitting hypothesis for the early BP. The activity of the source contralateral to the moving finger was increased during the steep slope of the late BP before and during the motor potential. Around and after electromyogram (EMG) onset, separate sources were detected for the motor potential close to the anterior wall of the central sulcus, and for the reafferent somatosensory potential in the postcentral gyrus. Their source wave forms showed short transient deflections peaking about 10 msec and 100 msec, respectively, after EMG onset. No evidence was found for significant source currents in the supplementary motor area (SMA), which has been suggested as the main generator of the BP. Placing probe dipoles arbitrarily into the region of the SMA did not result in the detection of a large source activity. Therefore, we conclude that the SMA does not provide a major contribution to the scalp BP during simple repetitive finger movements.

Bereitschaftspotential in idiopathic and symptomatic restless legs syndrome

Patients with idiopathic and symptomatic restless legs syndrome (RLS) suffer from "dyskinesia while awake" or "daytime myoclonus" when at rest preceded by sensory symptoms. In order to characterise the RLS either as reflex movement or as voluntary movement we measured movement-related cortical potentials in 5 idiopathic and 8 uraemic RLS patients. Movements from both legs were polygraphically recorded concomitantly with cortical activity 2000 msec before to 500 msec after onset of EMG activity. These data were compared with a voluntary simulation of each patient's movement pattern and with 5 age-matched controls performing dorsiflexion of the right, left and both feet. Cortical activity preceding daytime myoclonus was absent in RLS patients whereas self-initiated leg movements in patients elicited onset times (1180-1380 msec) and amplitudes of Bereitschaftspotential (readiness potential) not significantly different from readiness potentials in control subjects (P > 0.05). Lack of movement-related potentials in myoclonus and/or dyskinesias during daytime in RLS patients is compatible with an involuntary mechanism of induction and points towards a subcortical or spinal origin of RLS.

CNV-like potentials on the cortical surface associated with conditioning in head-restrained rats

Head-restrained rats were conditioned to perform a CNV task: to press a lever in response to an imperative auditory stimulus (S2) given 1.5 sec after a warning stimulus (S1) for a drop of jelly food. With an electrode on the surface of the forelimb cortex, (1) sharp wave complexes immediately after S1 and S2, and (2) a negative slow potential (SP) between S1 and S2, on which early and late components were discernible, were recorded in association with performance of this task. With the electrode at a depth of 2 mm in the same cortical area, the corresponding field potential showed a long-lasting positive shift in addition to the components of the surface potential. These monopolar recordings were obtained with respect to a common reference at the frontal sinus. The surface-minus-depth potential (the transcortical potential), consequently, showed a surface-negative tonic wave, confirming Pirch's report (1980). During extinction of this conditioning, the SP between S1 and S2 disappeared, while the sharp waves following S1 and S2 remained with little modification, suggesting that the sharp waves are a kind of evoked potential (EP) elicited by the stimuli. Recording from 5 surface electrodes set in an array over the left hemisphere contralateral to the used forelimb during development of the conditioning revealed not only a spatial distribution of the SP but also a transition of the potentials. As the conditioning progressed, the negativity of the early SP component tended to increase, while that of the late component tended to decrease and was confined to the sensorimotor cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

The modulation of somatosensory evoked potentials during the foreperiod of a forewarned reaction time task

During the foreperiod of a forewarned reaction time (RT) task reflexes in the executing limb increase to a lesser extent than those in the contralateral limb. This is possibly due to input modulation. The present study investigates the possibility of cutaneous sensory modulation during motor preparation by studying the amplitudes of somatosensory evoked potentials (SEPs). Eighteen subjects performed a forewarned RT task with the same fingers as the ones which were electrically stimulated. SEPs evoked during the 4 sec preparatory period were compared to those evoked during movement execution and during the resting period after the motor response respectively. During response execution most SEP components showed smaller amplitudes, i.e., they were gated, which agrees with other studies. In the first part of the foreperiod no SEP modulation was observed. Towards the end of the foreperiod, 500 msec before the response stimulus (RS), the amplitude of the contralateral parietal N70-P100 was significantly decreased, while the P45-N70 showed a similar tendency. However, at the same time the P100-N140 was increased in amplitude. The decrease of the intermediate latency components towards the end of the foreperiod is discussed in terms of gating, while the increase in the long latency component is discussed with respect to a decrease in RT on trials where the fingers were stimulated just before the RS, pointing to the role of attentional mechanisms.

Self-regulation of slow cortical potentials in psychiatric patients: alcohol dependency

Ten unmediated alcohol-dependent male inpatients participated in a Slow Cortical Potential (SCP) self-regulation task utilizing biofeedback and instrumental conditioning. These patients were hospitalized for treatment of alcohol dependency after chronic abuse of alcoholic beverages. Somatic withdrawal symptomatology had occurred recently and the patients were free of any withdrawal symptoms of the autonomic nervous system. Immediately after hospitalization patients were unable to control their SCPs without the reinforcement of immediate feedback across 4 sessions. Seven patients participated in a fifth session an average of 4 months later. Six out of these 7 patients had not had a relapse at the follow-up. In the fifth session these patients were immediately able to differentiate between the required negativity and negativity suppression, whereas the seventh patient, who had relapsed, was unable to control his brain potentials successfully. Results are further evidence that some of the frontocortical dysfunctions in alcohol-dependent patients are reversible. This could covary with a morphological restitution of the cortex.

Is increased amplitude of contingent negative variation in migraine due to cortical hyperactivity or to reduced habituation?

The aim of this study was to compare the habituation kinetics of contingent negative variation (CNV) between 12 migraineurs without aura and matched healthy controls. CNV was studied with a 3 sec interval between the warning stimulus (WS) and the imperative stimulus (IS). The data from (a) the total interval (WS-IS), (b) early component, and (c) late component were analyzed. During successive trials the habituation kinetics were determined using regression analysis. On CNV averaged over 32 trials, migraine patients had a significantly higher negativity in the total interval compared to controls. When sequential blocks of four trials were analyzed, the most significant finding in migraineurs was lack of habituation of the early CNV component. The present study indicates that a delayed habituation, rather than a general increased cortical activity, is responsible for the CNV abnormalities in migraine without aura. We suggest that migraineurs between attacks not only have a cortical hyperexcitability, but also a lack of cortical inhibition causing delayed habituation.

Contingent negative variation--findings and perspectives in migraine

Contingent negative variation (CNV) is a negative cerebral potential which is related to attention and arousal. CNV occurs during an experimental situation in which stimuli and responses are serially organized. Between attacks migraine patients have on average higher negative amplitudes compared to healthy controls or patients with tension-type headache. Successful treatment with beta-blocking agents decreases CNV amplitudes. In spite of encouraging findings in neurological disorders, CNV is not widely used. In this review some possible reasons for this are pointed out.

Contingent negative variation in childhood migraine

Adult migraineurs without aura have an increased amplitude of the Contingent Negative Variation (CNV) between attacks. Given the potential diagnostic importance of this finding and the difficulties associated with diagnosing migraine in childhood it seemed important to assess CNV in children suffering from this disorder. Ninety-seven children aged between 8 and 14 years were recruited. Forty-two suffered from migraine, 34 from tension-type headache. Twenty-one healthy controls were also studied. CNV was recorded from Fz, Cz and Pz referenced to linked earlobes during 20 trials consisting of two tones of moderate intensity with an interstimulus interval (ISI) of 4 sec and an intertrial interval (ITI) of 10 to 14 sec. The second tone of each trial required a button press. EOG was recorded from the left eye. The 10 CNV responses with the least EOG artefact were selected and averaged. Children with migraine had a highly significantly more negative mean CNV amplitude at all three electrode sites than children with tension-type headache and also a more pronounced Post-Imperative-Negative-Variation (PINV). Migrainous children differed from controls only at Cz (ISI). There was also a highly significant increase of mean CNV amplitude and PINV at all three electrode sites in the control group compared to the tension headache group.

Contingent negative variation: methods and potential interest in headache

Contingent negative variation (CNV) is an event-related slow cerebral potential which has been found abnormal in migraine. Its methodology is described. Contrary to other neurophysiological techniques, CNV needs special equipment and expertise. On average, CNV amplitude is increased and its habituation is lacking in migraine without aura between attacks, but not in migraine with aura. The sensitivity of CNV as a diagnostic tool is low, but its specificity is high. CNV amplitude normalizes after treatment with beta-blockers. The CNV abnormalities in migraine might be due to hyperreactivity of central catecholaminergic pathways.

A possible masking effect of tinnitus. Evaluation of CNV audiometry

To determine whether tinnitus has a masking effect similar to that of general external sounds, the hearing threshold shift when the tinnitus was changed by intravenous administration of lidocaine was measured by contingent negative variation (CNV) audiometry. In a preliminary study, the reliability of CNV audiometry was evaluated in 12 patients with tinnitus. The reproducibility of CNV audiometry was confirmed, based on repeated measurements of CNV audiometry at the tinnitus frequency. The threshold difference between CNV audiometry and pure tone audiometry was -0.76 +/- 1.35 dB, and a high statistical correlation between the threshold of CNV audiometry and pure tone audiometry was evident. The CNV threshold shift at tinnitus frequency after lidocaine injection was measured in 89 ears. In the tinnitus-decreased group, the CNV threshold decreased (4-6 dB) in 22% of cases; however, in the tinnitus-unchanged group, the CNV threshold was little changed. These findings suggest that tinnitus may have a masking effect as is the case with external sounds.

Altered fronto-central PINV topography and the primary negative syndrome in schizophrenia

Postimperative negative variation (PINV) was recorded during a warned reaction time paradigm in 16 chronic DSM-IIIR schizophrenics in remission. Clinical symptoms were assessed by BPRS, SANS and the anhedonia scale of the Chapman Questionnaire. Ten healthy controls were studied in the same manner. Over the fronto-central area we found a significantly elevated PINV amplitude with an altered topographical distribution in the patient group. The difference values 'PINV Cz-PINV Fz' were correlated negatively with primary negative symptoms of schizophrenia.

Sensory-evoked potentials as indices of neurotoxicity in the rat: effect of 4-tert-butyltoluene

The use of evoked potentials to measure neurotoxicity was evaluated using 4-tert-butyltoluene (TBT) as a test compound. Male Wistar rats were habituated to the recordings of auditory- and flash-evoked potentials until the combined waveform of the evoked potentials reached a steady state. The rats were then divided into three groups and exposed to 0, 50 and 150 ppm TBT for 6 h, and the auditory- and flash-evoked potentials were measured for up to 288 h after exposure. Event-related potentials specifically associated with the temporal pairing of auditory and visual stimuli were not apparent in the recordings. The peak-to-peak values of selected components, integrated amplitude and power spectra of the waveforms in exposed rats were significantly different from control values for at least 288 h in the group exposed to 150 ppm TBT and for 120 h in the group exposed to 50 ppm TBT. It is concluded that evoked potentials may be used for detection and characterization of minor neurofunctional changes due to low-dose exposure to chemicals.

Relationship between CNV asymmetries and individual differences in cognitive performance, personality and gender

This study used verbal and spatial variants of a cognitive 'match/mismatch' paradigm to explore relationships between functional brain asymmetries and individual differences in cognitive performance, personality and gender. Contingent negative variation (CNV) elicited in the 'match/mismatch' paradigm was recorded from central (Cz, C3 and C4) derivations in two male and one female samples. Results indicated gender differences in both the degree and direction of CNV asymmetries. Males showed a left hemisphere asymmetry in the verbal task and a right hemisphere asymmetry in the spatial task, with significant laterality (C3-C4) differences between tasks across the foreperiod. Females showed a left hemisphere asymmetry in both tasks with laterality differences between tasks confined to the early part of the foreperiod. CNV amplitude in the verbal task correlated with verbal memory performance and verbal I.Q. CNV amplitude in the spatial task correlated with visuospatial memory performance. Social extraversion was associated with greater left-hemisphere asymmetry in both tasks, while behavioural extraversion was associated with left-hemisphere asymmetry in the verbal task only, and with smaller verbal than spatial CNVs.

Postimperative negative variation and skin conductance response in chronic DSM-III-R schizophrenia

The hypothesis was tested that there are relationships between schizophrenic negative or deficit symptoms, the skin conductance nonresponding and an elevated amplitude of the postimperative negative variation (PINV). These variables were recorded in 16 chronic schizophrenics and 10 healthy controls. Clinical symptoms were assessed by the Brief Psychiatric Rating Scale, Scale for the Assessment of Negative Symptoms, Frankfurt Complaint Questionnaire 3 and Chapman Questionnaire. In the patient group we found a significantly elevated PINV at Fz. Surprisingly, only one patient was a skin conductance nonresponder. PINV amplitude at Fz and the number of skin conductance responses to habituation were not correlated with negative or deficit symptoms inclding anhedonia. The hypothesis thus had to be rejected.

Abnormal premovement brain potentials in schizophrenia

We assessed scalp-recorded movement related potentials (MRPs) generated prior to voluntary movements in chronic, medicated schizophrenics (n = 9) and age matched normal controls (n = 9). MRPs were recorded in a self-paced button press task in which subjects pressed a button with either their right, left or both thumbs (experimental condition I, II and III respectively). Controls generated a slowly rising readiness potential (RP) at about 1000 ms, a negative shift (NS') at about 450 ms and a motor potential (MP) at about 100 ms prior to movement. The initial MRP components (RP and NS') were reduced in schizophrenics indicating an impairment of the voluntary preparatory process in schizophrenia. Results of the present study indicate a similarity of MRP findings in schizophrenics and reported MRPs (Singh and Knight, 1990) in patients with unilateral lesions of the dorsolateral prefrontal cortex. These findings provide further support for frontal lobe dysfunction in schizophrenia.

Dependence of presaccadic cortical potentials on the type of saccadic eye movement

Premovement cortical potentials were studied with 4 types of saccadic eye movement: (a) visually triggered saccades of normal reaction time (RT; regular saccades); (b) visually triggered saccades of extremely short RT (express saccades); (c) saccades towards predicted target locations (anticipatory saccades); (d) saccades back towards predicted location of fixation point (refixation saccades). With all 4 saccade types a "presaccadic negativity" with the maximum at the vertex (Cz) was observed. A bilaterally symmetrical component contained in this potential (being smallest with almost unconsciously performed refixation saccades and smaller in trained than in naive subjects) appeared to be related mainly to the subjects' volitional effort. In addition, anticipatory and refixation saccades were preceded by an early, widespread contralateral negativity, which we relate to cortical activities that prepare, in general terms, action within or towards the hemifield containing the saccade goal. During the 60 msec before anticipatory saccades, a negativity occurred over the contralateral central lead, which may reflect neural activation in the frontal eye field (FEF) and premotor cortex. In contrast, regular saccades were preceded 30 msec before onset by a negativity over the contralateral parietal cortex, which probably reflects an activation of parietal visuo-motor neurons. No lateralization of the cortical potentials was observed before express saccades, which suggests that these saccades are generated in a reflex-like way mainly by subcortical mechanisms.

Contingent negative variation as an indicator of sexual object preference: revisited

This study attempted to replicate the finding of Costell et al. (1972) that contingent negative variation (CNV) in anticipation of opposite sex nudes is of greater amplitude than CNV in anticipation of same sex nudes. In order to control for variation in level of attention, which may have accounted for the result of Costell et al., a 'match/mismatch' CNV paradigm was used in which S2 was either identical to S1 or differed from it. Subjects (n = 6 males) were required to indicate a same/different judgement by button pressing at S2 offset. CNV in anticipation of opposite sex nudes was of significantly greater amplitude than CNV in anticipation of same sex nudes, confirming the finding of Costell et al. This offers encouragement for the application of CNV to the assessment of sexual object preference in sex offenders.

Rare events and the CNV--the oddball CNV

Event-related brain potentials (ERPs), such as Nd and P300, change as a function of the proportion of time if a rare, significant, stimulus occurs. This 'oddball' paradigm has had a significant influence on the interpretation of ERPs in terms of the psychological and information-processing functions they reflect. Interpretations of transient components have differed considerably from that of the sustained potential known as the Contingent negative Variation (CNV), the latter appearing to reflect proactive rather than reactive brain processes. However, experiments in monkeys indicated that the CNV was also sensitive to the oddball effect. The purpose of this experiment was to replicate that finding in humans. The CNVs and P300s of five male and five female college students were studied under three conditions involving different proportions of two types of warning stimuli in a cued reaction time task (paired tone and light). The proportions of one of the warning stimuli, with respect to the total number of trials, were 0.10, 0.30 and 0.50. P300s were larger when elicited by rare warning tones only in the 0.10 condition with maximum P300 amplitude at the parietal site. CNVs at frontal and central areas were larger when the warning cue was the rare event, but there was no effect at the parietal site. These findings may require a rethinking of specific information processing interpretations of other endogenous ERPs, although the results also indicate that the 'oddball' effect on the P300 and CNV was distinctive in terms of scalp distributions and sensitivity to the manipulation.

[Event-related negativity and alpha band desynchronization in motor reactions]

The foreperiod of a motor reaction to an impending stimulus is accompanied by a slow negative wave of the event-related potential, the "contingent negative variation" (CNV), when the imperative stimulus follows at a fixed interval to a warning stimulus. Using similar experimental paradigms, an event-related desynchronization (ERD) in the alpha range occurs indicating cortical activation before and during motor acts. Both EEG-parameters were quantified for four subjects using the following experimental design: One second after a non-informative warning signal (WS) a cue was presented that indicated by which hand the subject had to respond quickly after presentation of a reaction stimulus (RS); subjects were requested to respond by pressing a button with their left or right thumb. EEG-signals were recorded unipolarly from 17 electrodes. Average ERPs and ERD were computed for all electrode sites for trials with left and right hand movements, respectively, and topographically displayed in simultaneous amplitude and ERD-maps. CNV and ERD could be observed simultaneously over similar brain regions, namely central over the motor cortex, frontal with possible location over the supplementary motor area (SMA) and also covering the parietal region. While the CNV had a interindividually different and wide distribution, the ERD calculated for the upper alpha band mapped focally over the electrode sites C3 and C4 overlaying primary sensorimotor structures, with a contralateral dominance. In contrast to the negativity which is terminated following delivery of the response stimulus, the ERD persisted during the motor reaction showing a similar pattern some hundreds of milliseconds before and after movement onset.(ABSTRACT TRUNCATED AT 250 WORDS)

[The dependence of late evoked cortical potentials on a complex of cognitive factors]

The formation of late evoked cortical responses, N150 and P300, correlates with some factors determining cognitive activity (selective attention, different types of memory, decision making process). Influence of different significance stimuli in a particular situation results in creation of an integral "psychonervous image" reflecting a context of these stimuli, whole complex of cognitive tasks to be solved. It influences significantly on the magnitude of cortical evoked reactions to different stimuli that allows to make a correspondence with the "psychological set" phenomenon and its role in the evaluation of the perceived stimuli.

[Electrophysiologic investigations in migraine]

This article is a critical review of standard electroencephalography (EEG), brain mapping, evoked potential, and electromyography (EMG) studies carried out in various forms of migraine during and between attacks. With the exception of contingent negative variation, the exteroceptive silent period of the temporalis muscle, and possibly fast activity in response to visual stimuli, which are useful for the differential diagnosis of functional headache, the main value of electrophysiologic studies is to provide insight into the pathophysiology of the disease. Results of the different methods consistently indicate that the brain of migraine patients is characterized by hypersensitivity to some forms of stimuli between attacks and by, often focal, hypoactivity during attacks.

Changes in bit-mapped contingent negative variation (CNV) activity due to initial normal involutional processes of the human brain

Bit-color mapped multicomponent CNV complexes and RTs to S2 evoked with a simple warned CNV/RT paradigm were recorded and measured in 20 selected right-handed very healthy volunteers (10 young adults and 10 presenile subjects, mean age 28.3 and 59.6, respectively). EEG and CNV components (post S1, N1, P2, P3; early CNV; N1200; late CNV; CNV resolution) were recorded from Fz, C3, Cz, C4, P3, Pz, and P4 referenced to linked mastoid electrodes. EOG, RT and stimuli were also recorded. The presenile group differed significantly from the younger group in the auditory post-S1 N1 and early (O-wave) and late (P-wave) CNV complex components. A progressive amplitude reduction limited to frontal leads between O-wave and P-wave, the lowest point being reached in the P-wave, was characteristic in the presenile group. Moreover, presenile subjects showed relatively flat CNV waveshapes of low amplitude and, on the whole, performed a little less well than young ones. This finding suggests that the statistically significant changes in auditory post-S1 N1 and CNV activity recorded in our presenile subjects, without any appreciable deficits in behavioral or mental performance, could be alerting signs of early brain involutional processes related to minimal and subclinical decline in orienting, attentiveness and response preparation capabilities. If such is the case, and it could be confirmed in a larger sample of very healthy subjects, these age-related changes in the presenium might prove to be of considerable practical importance for clinical research.