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PubMed1993

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.

Adult↗
PubMed1994

Mapping P300 waves onto inhibition: Go/No-Go discrimination.

Subjects viewed letters presented at 2 sec intervals and prepared a fast button press whenever an "O" appeared. If the next letter was an "X" the button press was executed (Go signal), but if the letter was a non-X character (T, H, Z) suppression of the response was required (No-Go cue). No-Go signals elicited a P300-like wave that was larger at central and frontal scalp sites contralateral to the prepared movement, compared to P300s elicited by Go cues which were symmetric about the sagittal midline and dominant at parietal sites. Subtraction of preparatory CNVs from the No-Go P300 did not remove differences in scalp topography, or reduce the amplitude of the No-Go P300 to that seen following control letters that required perceptual identification but did not call for suppression of prepared motor responses. Principal components analysis identified a middle positive wave following X-alone control stimuli whose topography resembled the No-Go P300. These findings suggest that the source of augmented No-Go P300s is a generator involved with sensorimotor inhibition. We discuss the mechanism of P300 waves and evidence linking these waves with inhibition in other task arrangements.

Adult↗
PubMed1975

Psychophysiology of sociopathy: electrocortical measures.

The CNV, visual AEP and resting EEG were analyzed in sociopaths and controls matched for age and sex. Twenty-seven male sociopaths were selected by psychiatric interview and special rating scale, restricted to Shipley-Hartford IQs of 115-145 and separated into young (x = 20.5 yr) and older (x = 35.3 yr) age groups. Subjects participated in forewarned reaction-time tasks in which the imperative stimulus was either an innocuous or noxious tone that the subject escaped by pressing a response key. Sociopaths and controls did not differ in reaction time, vertex and occipital AEP amplitude or latency, and power spectral density of the EEG. Contrary to previous findings, there also were no significant differences between sociopaths and controls in overall CNV amplitude or topography. However, while most controls showed increased CNV amplitude in the noxious tone condition as compared to the innocuous tone condition, older sociopaths showed no change, or decreased amplitudes.

Acoustic Stimulation↗
PubMed1975

Selective attention and evoked potentials in humans--a critical review.

Human evoked-potential research on the neurophysiological substrate of selective attention is reviewed. Most of these studies report enhanced amplitudes of potentials evoked by attended (task-relevant, meaningful, important, etc.) stimuli the results of which are generally regarded as providing an electrophysiological correlate for selective attention. In accepting such claims, there appears to be two major procedural problems generally not satisfactorily solved in these studies: (1) the inability to reliably separate the specific and non-specific physiological changes concomitant with selective attention from each other; and (2) inadequacy of peripheral sensory control possibly inducing contaminating changes already at the level of the proximal stimulus. Problem (1) originates from, and the importance of (2) is emphasized by, the temporal stimulus structure of experimental tasks in these studies which allows the subject to predict above the chance level the relevant events and, thus, to differentially prepare himself for these in advance (increased non-specific arousal and selective peripheral sensory orientation, the latter often made possible by insufficient control, have possibly been among these changes). Those studies to which these two (and other) remarks do not apply at all or only to an insignificant degree have generally shown no selective evoked-potential changes (or these changes have occurred only with a long latency ('P3' or 'P300') making their interpretation especially uncertain). There is one exception for this general notion, the reasons for and significance of which are dealt with in detail. Finally, the difficulties and inherent limitations of inferring brain events from scalp-recorded evoked-potential data, especially with respect to the important selective-filter hypothesis of selective attention, are extensively discussed and, in the light of these difficulties, some trends for future research proposed.

Arousal↗
PubMed1977

Event-related brain potentials in selective response.

Event-related potentials were recorded during performance of a simple reaction task and two selective response tasks differing in the intensity of the non-key stimulus. Known differences in reaction between these tasks were confirmed, but there were no corresponding differences in amplitude of the slow potential shift which develops in the EEG in anticipation of the imperative signal. Since this anticipatory potential is not affected by event uncertainty, it seems to be related to motor preparation rather than to expectancy. Performance differences between simple and selective response tasks appear to depend not upon differential preparation, but upon selective processing of the imperative signal, which is reflected in the N120 component of the visual evoked response to that signal.

Brain↗
PubMed1978

Selective attention, cortical evoked responses, and brain function in human subjects: a critical review and theory.

A theoretical framework is proposed to account for the facts of selective attention in terms of cortical redundancy and cortical-subcortical interactions as measured by the Average Evoked Response and the background EEG. The recent research concerning AER correlations of selective attention is reviewed and found to be lacking in methodological coherence. This lack is found to contaminate existing theory regarding selective attention and brain function. An alternative approach is explored and its findings are found to yield the present theory.

Arousal↗
PubMed1978

EEG event-related potentials and signal detection.

The purpose of this study was to determine whether certain previously reported relationships between event-related potentials and measures of signal detection performance occur in vigilance as well as psychophysical settings. In the course of the study, evidence was found which challenges previously proposed psychological correlates of "P300". EEG was recorded while 15 subjects carried out a 40-min signal detection test. CNV was measured between a warning click and the brief offset of a dim light denoting the possible (p = 0.5) occurrence of the signal, a faint tone in the constant background noise. P300 was measured at a point 300 msec following offset of the dim light. As reported previously in psychophysical settings, P300 amplitude was positively related to signal intensity and response confidence, and was larger for correct detections (Hits) than for correct rejections, misses or false alarms. From first to second half of the test both Hits and false alarms fell, response criterion beta rose, and the amplitude of both CNV and P300 fell. The latter negative relationship between beta and P300 contrasted with a positive one when subjects rated their signal reports at three levels of confidence; here the most confident ratings (high beta) were associated with the highest amplitude of P300. CNV reflected individual ability to sustain performance. Results are explained in terms of a two-factor version (Wilkinson, 1976) of the prior state/reactive change hypothesis (Karlin, 1970). It is suggested that time on task constitutes a prior state influence on P300, whereas other variables influence P300 by means of either reactive change or 'real' change in an endogenous P300 component.

Adult↗
PubMed1979

On the independence of P300 and the CNV: a short critique of the principal components analysis of Donchin et al. (1975).

Donchin, Tueting, Ritter, Kutas and Heffley (1975) present evidence from a principal components analysis (PCA) that the CNV and P300 are independent. This short critique points out a number of erros in their PCA and presents a reworking of their analysis. A number of further aspects of Donchin et al.'s paper are also discussed. The general value of this contribution in drawing the attention of EP researchers to potential sources of error in the application of factor analysis is emphasized.

Contingent Negative Variation↗
PubMed1979

The independence of the P300 and the CNV reviewed: a reply to Wastell.

The relationship of P300 to the CNV was investigated by Donchin, Tueting, Ritter, Kutas and Heffley (1975) who concluded that these two components of the event-related brain potential (ERP) are independent. Wastell (1979) questioned the validity of the data analysis procedures and of the experimental design used by Donchin et al. In this report we examine Wastell's criticisms and find them to be unfounded. In support of this conclusion we note the differences between principal component analysis and factor analysis. We clarify points about Donchin et al.'s experimental design, and we review evidence for the independence of the P300 and the CNV that has accumulated since 1975.

Contingent Negative Variation↗
PubMed1980

Brain slow potential changes elicited by missing stimuli and by externally paced voluntary responses.

Brain evoked potential changes were recorded from the scalp of 22 normal subjects and from the cortex of two patients in conditions where expected auditory stimuli were missing. It was found that such stimulus omissions could be used to initiate slow potential shifts (CNVs) in a warned foreperiod response task. Further slow potential shifts with durations of over 3 sec were recorded preceding self-initiated, but externally paced, responses made to one of a train of clicks. The experiments confirmed the cortical origins of the missing stimulus potentials, and illustrated the dependence of the CNV on endogenous factors rather than the physical properties of external stimuli. Contrary to most previous reports the negative component of the missing stimulus potential was in this study virtually identical in latency and amplitude to the N1 component of the click evoked potential. The slow potential shifts observed in the self-initiated condition contained elements of both the CNV and Bereitschaftspotential and appeared to reflect the steadily increasing cortical involvement during preparatory foreperiods.

Auditory Perception↗
PubMedDate not supplied

CNV and EMG preceding a plantar flexion of the foot.

In 25 subjects CNV and EMG were recorded during a reaction time experiment with a fixed 4 sec foreperiod. The response was plantar flexion of the right foot. EEGs were recorded with four electrodes from the central area, two over each hemisphere. CNV amplitudes were larger over the ipsilateral than over the contralateral hemisphere. Amplitudes were smaller in the more lateral derivations. The late component of the CNV showed larger amplitudes when preceding relatively fast responses. EMG activity was recorded from the calf muscles of both legs. In the left leg it was not different during the intertrial interval and the foreperiod. A small but systematic increase in EMG activity was found during the foreperiod in the right leg. The increase was larger preceding fast responses, parallel to the amplitude changes in CNV late waves.

Adolescent↗
PubMedDate not supplied

Slow potential correlates of attention dysfunction in senile dementia: I.

The EEG was recorded within a CNV (S1-S2-MR) paradigm in 10 seniles and 10 normal elderly subjects. The presence of the CNV in senile patients was confirmed. The seniles' CNV amplitude and latency differed from the normals and suggested that the seniles were less able to efficiently maintain and shift preparatory set, and this was also reflected in their much longer reaction time scores. However some adaptation particularly on CNV peak latency was observed in the seniles across trials.

Aged↗
PubMedDate not supplied

Slow potential correlates of attention dysfunction in senile dementia: II.

The CNV was recorded from Fz and Cz placements in five seniles and five normal elderly subjects over two sessions under five ISI levels. In the first session 32 trials each of five foreperiods with 2, 4, 6, 8 and 10 sec ISIs were recorded. The second session involved presentation of 32 trials of five foreperiods with 1.4, 1.8, 2.2, 2.6 and 3.0 sec ISIs. The use of a repeated measures within subjects design was to avoid the confounding effect of between subject variance. The results suggested that difference between groups in preparatory strategies as measured by amplitude and latency of the CNV were exacerbated for longer ISIs. Though the seniles seemed able to 'keep time' with small changes in ISI the effort invested in preparation of response was far lower than that of the normals. CNV amplitude and latency and RT measures showed that for both groups the optimal preparatory interval was around 2 sec, the seniles requiring a slightly shorter interval than the normal to synchronise preparation and response. Cortical topography differences suggested that the seniles' preparatory strategies were predominantly influenced by the extent of their initial frontal orienting response and that the seniles showed less differentiation between frontal and central recordings. The seniles' dependence on frontal orienting suggests that their performance does not benefit from preparatory set and results in a more stimulus bound divisive set. Implications of these qualitative differences in attentional strategy for behavioural management of senile patients are discussed.

Aged↗
PubMed1981

Principal components and varimax-rotated components in event-related potential research: some remarks on their interpretation.

Some properties of principal components analysis (PCA) and simple structure rotation, which are relevant to the study of event-related potentials (ERPs), were examined both in theory and with simulated data. The analysis casts some doubt on whether it is useful and desirable to rotate the loading pattern of a PCA of ERPs to simple structure. The evidence presented is more in favour of the unrotated solution. In particular we were able to demonstrate with simulated data that a solution rotated to simple structure may lead to false conclusions about the functional independence of ERP peaks. Beyond this, the more general question is asked of whether principal components should be accepted as basic waveforms, i.e. as physiologically meaningful entities which, for example, represent different ERP generators.

Contingent Negative Variation↗