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PubMed2003

Electroencephalograph effects of single doses of Ginkgo biloba and Panax ginseng in healthy young volunteers.

Both Ginkgo biloba and Panax ginseng exert a number of physiological effects and have been shown to modulate aspects of cognitive performance. Whilst a number of studies have examined ginkgo's effects on electroencephalograph (EEG) recordings, to date, none have investigated the EEG effects of ginseng. In this double-blind, placebo-controlled, balanced crossover experiment, the effects of single doses of G. biloba (360 mg GK501), P. ginseng (200 mg G115), and an identical placebo, on auditory-evoked potentials, contingent negative variation (CNV), and resting power within the delta, theta, alpha, and beta wavebands, were assessed in 15 healthy volunteers. Each participant was assessed on three separate occasions 4 h after consuming that day's treatment. The order of presentation of the treatments was dictated by a Latin square with 7 days between testing sessions. The results showed that ginseng led to a significant shortening of the latency of the P300 component of the evoked potential. Both ginseng and ginkgo also led to significant reductions in frontal 'eyes closed' theta and beta activity, with additional reduction for ginseng in the alpha waveband. These findings demonstrate for the first time that P. ginseng can directly modulate cerebroelectrical activity, and that these effects are more pronounced than those following G. biloba.

Adult↗
PubMed2004

Valence-related vigilance biases in anxiety studied through event-related potentials.

INTRODUCTION: Behavioral experiments on reaction time indicate that anxious subjects' vigilance-related attention is biased towards threatening words, though direct data on cerebral activity associated to this bias are conspicuously scarce. METHODS: In the present study, event-related potentials (ERPs) were recorded from 30 subjects, grouped according to their scores in trait and state anxiety questionnaires. The specific role of the arousal and valence content of the stimulation in the vigilance bias was investigated by blocking the arousal content. Stimulation with high biological significance was employed. An S1 (sound)-S2 (emotional picture) task ensured that subjects were vigilant towards positive, negative or control (neutral) images. RESULTS: Only subjects presenting high state scores and high state-trait combination scores showed significantly higher amplitudes in the Early Contingent Negative Variation during vigilance towards negative stimuli. This ERP component typically appears between S1 and S2 and reflects the intensity of vigilance. CONCLUSIONS: ERP activity detects cerebral indices that confirm the presence of valence-related vigilance biases in anxiety.

Adult↗
PubMed1997

Slow brain potentials in a visual-spatial memory task: topographic distribution and inter-laboratory consistency.

Slow brain electrical potentials (SPs) were investigated in a visual-spatialmemory task. Two issues were addressed: (1) the nature and topographic distribution of the potentials obtained under such conditions; and (2) the consistency of the SPs when recorded in six identically configured laboratories. Fifteen young male subjects were studied at each laboratory (total n = 90). The paradigm entailed presentations of paired-visual patterns (S1 and S2), to which subjects responded with a choice reaction time response indicating whether or not the two patterns matched. A biphasic contingent negative variation (CNV) was produced which consisted of an early symmetric component with bilateral foci at posterior temporal sites and a subsequent mid-parietal dominant wave later in the retention interval. Although the CNVs from all laboratories were similar in waveform and in topographic distribution, there were significant inter-laboratory differences in amplitude of the slow potential components. The topographic distributions of the components and the possible role of sampling effects are discussed.

Adult↗
PubMed1997

Magnetic fields from human prefrontal cortex differ during two recognition tasks.

The present study represents our second successful use of magnetoencephalography to identify different sources of human prefrontal activity corresponding to subjects' engagement in different tasks. We used two visual recognition tasks: a familiar person recognition and an abstract pattern recognition task in the context of a design suitable for eliciting Contingent Negative Variations (CNVs) and their concurrent slow magnetic fields in this preliminary study of 5 subjects. Each trial of either task was started by one of two specific warning symbols (S1), indicating whether a person's picture or an abstract pattern should be attended during the presentation of a second stimulus (S2), and compared to the corresponding person's picture or pattern contained in the third stimulus, (S3) that followed. The S2 and S3 stimuli were common to both tasks, and were composed of patterns made with four line traces superimposed on photographs of persons familiar to each subject. Subjects responded with a right hand button press, following S3, indicating their judgments regarding the identity of the patterns or persons' pictures contained in the S2 and the S3 stimuli, for the two tasks, respectively. Results showed that the sources of the CNV equivalent magnetic fields were localized in different cortical regions depending on the task and that this difference was consistent across all subjects. The sources were localized in the right hemisphere, in medial areas of the prefrontal cortex for the person recognition task and in the dorsolateral prefrontal cortex for the pattern recognition task. The same degree of consistency was not found for the left hemisphere sources. Moreover, as in our previous study, we found no difference between the sources active during the first and the second CNV periods (occurring during the S1-S2 and the S2-S3 intervals, respectively), within each task condition.

Adult↗
PubMed2000

Near-infrared spectroscopy: does it function in functional activation studies of the adult brain?

Changes in optical properties of biological tissue can be examined by near-infrared spectroscopy (NIRS). The relative transparency of tissues including the skull to near-infrared light is the prerequisite to apply the method to brain research. We describe the methodology with respect to its applicability in non-invasive functional research of the adult cortex. A summary of studies establishing the 'typical' response in NIRS vascular parameters, i.e. changes in the concentration of oxygenated and deoxygenated haemoglobin, over an activated area is followed by the validation of changes in the cytochrome-oxidase redox state in response to a visual stimulus. Proceeding from these findings a rough mapping of this metabolic response over the motion-sensitive extrastriate visual area is demonstrated. NIRS measures concentration changes in deoxygenated haemoglobin [deoxy-Hb] which are assumed to be the basis of fMRI BOLD contrast (blood oxygenation level-dependent). The method is therefore an excellent tool to validate assumptions on the physiological basis underlying the fMRI signal, due to its high specificity as to the parameters measured. Questions concerning the concept of 'activation'/'deactivation' and that of the linearity of the vascular response are discussed. To challenge the method we finally present results from a complex single-trial motor paradigm study testing the hypothesis, that premotor potentials (contingent negative variation) can be examined by functional techniques relying on the vascular response. Some of the work described here has been published elsewhere.

Adult↗
PubMed2000

The application of electroencephalographic techniques to the study of human olfaction: a review and tutorial.

The use of a variety of electrophysiological techniques to determine the effects of odor on the nervous system is reviewed. Methods and problems associated with the collection of on-going EEG, chemosensory event-related potentials, and contingent negative variation data are discussed in depth as is the use of odors as modulators of brain potentials produced by other senses. In addition, the advantages of several seldom used EEG analysis techniques are discussed with respect to the unique problems of understanding olfaction.

Electroencephalography↗
PubMed2001

Error-negativity and positivity as they relate to other ERP indices of attentional control and stimulus processing.

We compared individual differences in the ERP associated with incorrect responses in a discrimination task with other ERP components associated with attentional control and stimulus discrimination (N2, P3, CNV). Trials with errors that are detected by the subject normally produce a negativity (N(E)) immediately following the response followed by a positivity (P(E)). The morphology of the N(E) and the P(E) is similar to that of the standard N2-P3 complex on correct discrimination trials. Our findings suggest that the P(E) is a P3 response to the internal detection of errors. The N(E), however, appears to be distinct from the N2. Finally, even though both the contingent negative variation (CNV) and the N(E) are associated with prefrontal cortex and the allocation of attention to response accuracy, the N(E) and CNV did not relate to one another.

Adult↗
PubMed2002

Differential effects of the hiba odor on CNV and MMN.

The aim of this study was to objectively measure some psychophysiological effects of odors, particularly the effects of odors on the contingent negative variation (CNV) and the mismatch negativity (MMN). It is generally believed that CNV reflects arousal processes and MMN reflects activity in an automatic detection system. Sixteen females were exposed to the odor of Thujopsis dolabrata (hiba), a conifer. CNV was obtained with a foreperiod of 2 s in a traditional click-flash reaction-time (RT) paradigm. Auditory MMN was measured while the subject was reading a book with SOA fixed at 500 ms. The amplitude of the early and late CNV components were significantly larger and RT to the imperative stimulus (IS) was shorter in the aroma condition than in the absence-of-odor condition, but there was no significant difference in the amplitude of MMN obtained in the two conditions. Our results indicate that the odor generates a high level of arousal within the nervous system but does not have a significant effect on automatic information processing.

Adult↗
PubMed2003

Gender differences in response to pictures of nudes: a magnetoencephalographic study.

The magnetic equivalent of the contingent negative variation (CMV) and visual evoked magnetic fields (VEF) in anticipation of pictures of opposite-sex nude, same-sex nude, and neutral photographs has been recorded with whole-head MEG in 12 males and 12 females. Subjective ratings of valence indicated a strong gender effect. While females rated both male and female nudes as neutral, males rated male nudes similar to neutrals but female nudes received higher scores of pleasantness. Gender differences were also found for ratings of picture-induced arousal. While females rated male and female nudes as equally arousing, males attributed more arousal to opposite-sex nudes. The CMV instead revealed, for both male and female participants, higher amplitudes for opposite-sex nudes. VEF in response to nudes revealed two components with mean latencies of 126 and 203 ms. The amplitude of the first component was stronger in males than in females, and only in males the magnetic activity was increased in response to male and female nudes compared to neutral pictures. For the second component the mean magnetic activity was higher in response to nudes than to neutral contents for both male and female participants. The results are discussed in terms of an evolutionary view of sexual selection, which predicts a greater response in male subjects to stimuli relevant for mate choice.

Adult↗
PubMed2000

Role of frontal cortex in memory for duration: an event-related potential study in humans.

Event-related potentials were recorded in order to determine how brain activity is lateralized during the encoding and the recognition of visual durations (700 and 2500 ms ranges). It is assumed in the Hemispheric Encoding Retrieval Asymmetry model that the encoding of words, faces and odours involves left frontal areas whereas their recognition involves right frontal areas. The present results indicate that, for temporal information, the hemispheric bias is different: a negativity developed over right frontal electrodes for both encoding and recognition, and for both duration ranges. Thus, the involvement of right frontal areas appears critical for time perception. Conversely to what was expected, contingent negative variation during recognition was large over both left and right frontal electrodes. These results suggest that the involvement of both hemispheres is necessary for recognition of temporal information.

Adult↗
PubMed1999

C- and A delta-fiber components of heat-evoked cerebral potentials in healthy human subjects.

Feedback-controlled laser heat was used to stimulate the hairy skin of the hand dorsum and forearm, and heat-evoked cerebral potentials were recorded at midline (Fz, Cz, Pz) and temporal (T3, T4) scalp positions. Based on data from primary afferent electrophysiology a stimulus level (40 degrees C) was chosen, which is above C-fiber heat threshold, but clearly below A delta-nociceptor heat threshold in order to excite selectively C-fibers without concomitant excitation of A delta-fibers. Feedback-controlled stepped heat stimuli to 40 degrees C elicited ultralate laser evoked potentials (LEPs) at the vertex in a high proportion of experiments (90%). Estimates of conduction velocity calculated from latency shifts between the hand and forearm sites of ultralate LEPs (2.4 m/s) and of reaction times (2.8 m/s) confirmed mediation of ultralate potentials by unmyelinated nerve fibers (nociceptors and/or warm fibers). The ultralate LEP could be differentiated from resolution of contingent negative variation (CNV), an endogenous potential related to expectation and response preparation, by its scalp topography. Strong heat stimuli of 48 degrees C, which is suprathreshold for most A delta- and C-fiber nociceptors, elicited the well-known late LEPs mediated by nociceptive Adelta-fibers confirming previous studies. The LEP waveform to strong heat stimuli also contained an ultralate component reminiscent of an ultralate LEP following the late LEP. Ultralate and late LEP had identical scalp topography. In conclusion, the method of temperature-controlled laser heat stimuli allows the selective and reliable examination of A delta- and C-fiber-mediated afferent pathways and the related cortical processing without the complication of dissociating A-fiber nerve blocks.

Adult↗
PubMedDate not supplied

[Alertness and attention: recent theoretical perspectives and new areas of exploration (author's transl)].

Long considered only under the aspects of a level of alertness, attention has also to be considered under its directional aspects which imply attentive focalization and selection of information. The present paper reviews data and hypotheses concerning attention as a level of alertness, selective attention, slow cortical phenomena (negative contingent variation and evoked potentials), and attention as a motor program.

Arousal↗
PubMed1982

[Positron tomographic study of the behavior of 13N-labeled nitrous oxide in the human brain].

The synthesis of 13N-labelled nitrous oxide was made following NICKLES' method. After a partial denitrogenisation by breathing pure oxygen for 3 min, the subject inhaled a bolus of 13N-labelled nitrous oxide diluted in 2 l of oxygen (a mixture of 5% 13N2O and 95% O2). After an apnea of 30 sec the subject began to breathe in a closed respiratory system containing a mixture of 10% N2O and 90% O2. Eight images of the brain taken at level OM + 3 in 4 subjects showed an important uptake in the cerebellum and in the frontal and temporal cortex. Six min after inhalation of the bolus, the radioactivity in the cerebellum showed a clear decrease, whereas little decrease was observed in the frontal cortex and only a slight decrease in the temporal cortex. In order to suppress the activity due to the vascular comportment, an experiment was performed under the same conditions as the previous one, but using sodium pyrophosphate containing tin and 25 mCi of Tc-99m pertechnetate. The correction factors vary from 0.394 to 0.894 depending on the R.O.I. The activity curves after correction showed a predominance in the frontal cortex. It can therefore be concluded that some specific zones of the brain are receptive to N2O and in particular the frontal cortex. These results were compared with the data obtained from the electrophysiological recording of the frontal region of the brain (C.N.V.: Contingent Negative Variation).

Adult↗
PubMed2001

Antisocial personality disorder and cocaine dependence: their effects on behavioral and electroencephalographic measures of time estimation.

The present study examined time estimation performance and concurrently-recorded electroencephalographic activity among 57 residential treatment program patients previously dependent on either cocaine or cocaine and alcohol. The patients were assigned to one of two subgroups based upon the presence (n=20) versus absence (n=37) of a comorbid diagnosis of Antisocial Personality Disorder (APD). Twenty-six subjects, who had no history of substance abuse and no diagnosis of APD, were also examined. All subjects performed a psychomotor task in which they were asked to press a response key exactly 2 s after the onset of a visual cue. Analyses revealed that cocaine-dependent patients with APD were often premature in their behavioral estimates of time passage. The analysis of a slow EEG potential, viz. the Contingent Negative Variation, recorded over the 2 s time estimation interval, also suggested premature response preparation in the cocaine-dependent, APD-positive group. Correlational analyses revealed that the number of conduct problems reported prior to age 15 was a better predictor of both premature responding and CNV amplitude than either severity of cocaine dependence, alcohol use, or anxious or depressed mood. The potential relevance of these findings for studies of future time orientation and delay discounting behavior are discussed.

Adult↗
PubMed2003

Neurophysiology of Tourette's syndrome: pathophysiological considerations.

At present the neurophysiology of Tourette's syndrome (TS) has been investigated largely from two perspectives; one for evaluation of the dysfunction of the cerebral cortex and the other for clarification of the neuronal mechanisms that underlie tics and related symptoms. For the former the following examinations have been conducted: quantitative analyses of scalp electroencephalography (EEG), premovement EEG potentials, contingent negative variation, transcranial magnetic stimulation, and neuroimaging studies, including echo-planar images and positron emission tomography scans. These explorations have revealed the likely involvement of the subcortical and the cortical structures, particularly of the basal ganglia, in the pathophysiology of TS. For the latter, surface electromyography, evoked potentials, saccadic eye movements, and polysomnographies have been performed, and again have suggested a dysfunction of the basal ganglia and the brainstem neurons in TS patients. These neurophysiological studies suggest dysfunction of both motor and non-motor basal ganglia-thalamocortical circuitries in TS patients, which is hypothesized to be caused by hypofunction of the dopamine (DA) neurons associated with DA receptor supersensitivity, a well as hypofunction of the serotonergic neurons of the brainstem. Polysomnographical examination suggests that the dysfunction of the nigrostriatal (NS)-DA neurons is not a progressive process, but that the dysfunction is closely associated with an early occurrence of the developmental decrement of the activities of the NS-DA system to mature in a normal fashion. The associated DA receptor supersensitivity is assumed to be a consequence of this developmental abnormality and not due to denervation supersensitivity.

Basal Ganglia↗
PubMed1985

Benign (nonparoxysmal) familial chorea of early onset: an electroneurophysiological examination of two families.

A nonparoxysmal nonprogressive autosomal dominant choreatic disorder of early onset is described in two families. Laboratory investigations of blood, urine and cerebrospinal fluid were normal. Extensive electroneurophysiological examinations did not reveal evident abnormalities. The contingent negative variation was also normal, except for a P500. These electroneurophysiological data are the opposite of what can be found in cases of Huntington's chorea.

Child↗
PubMed2000

Electrophysiological evidence for reduced latent inhibition in schizophrenic patients.

The present study examined latent inhibition (LI) effects in 17 acute and 16 partially remitted schizophrenic patients, and in 20 healthy controls, by measuring manual response latencies and event-related potentials (ERPs) during an association learning task. ERPs were recorded to elucidate the role of attention in the LI effect. Subjects performed a go/no-go task with an auditory conditional stimulus predicting a visual go command. Half of the subjects in each diagnostic group were pre-exposed to the conditional stimulus which had been used as an irrelevant distractor in a preceding discrimination task. Independent of diagnostic group membership, pre-exposed subjects showed slower manual responses to go stimuli than non-pre-exposed subjects, reflecting a robust LI effect. The N100 wave after the conditional stimuli, however, showed a differential pattern: pre-exposure increased N100 amplitudes in acute schizophrenics, whereas pre-exposed control subjects showed a trend for decreased N100. The amplitude of the contingent negative variation (CNV) was unaffected by pre-exposure. The ERP results suggest that acute schizophrenics have a deficit in learned inattention to irrelevant stimuli. However, the intact LI effect in schizophrenics at the motor speed level shows that human LI is a complex phenomenon depending on the tasks and measures used.

Acute Disease↗
PubMed2001

Gender and activation level in smokers.

Studies on the enhancing effects of nicotine on performance are usually pharmacological challenges using deprived male smokers. However, gender may be a factor that influences nicotine/smoking effects upon information processing. We investigated gender differences in contingent negative variation (CNV) amplitude in non-deprived dependent smokers performing a go-no go reaction time paradigm. Female smokers did not differ from female non-smokers in both early and late CNV, whereas male smokers presented greater early and late CNV compared to male non-smokers and an alteration in inhibiting processes responsible for CNV development in the no go condition. Consistent with the evidence of gender differences in nicotine/smoking sensitivity, these preliminary results emphasize the need for taking into account gender in psychophysiological research of nicotine/smoking effects.

Arousal↗