[Cortical mechanisms underlying sensori-motor association and its disorders].
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Contingent Negative Variation↗
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Inhibitory deficits in probable Alzheimer's disease. A study of movement related potentials and EMG response.
We have recently reported contralateral associated EMG responses to voluntary hand movement in Alzheimer's disease. Several aspects of this process were not fully explained in our last paper. In the present one we present data on the register of movement-related potentials (Negative Shift, NS) and Lateralized Readiness Potential (LRP), which have shown a very fine capacity to reveal processes that occur in the motor cortex while movement execution is being prepared. The associated EMG responses (so called by us) have almost all the characteristics of the partial errors revealed by cognitive psychology. First, it is a covert response, so it can only be detected by EMG recording; second, the appearance of this partial error changes the reaction time in the same way as described by Coles: mainly, by increasing reaction time as compared with clear responses. Nevertheless, contrary to partial errors, the associated EMG response does not constantly appear before the correct response. Associated EMG responses always appear after correct responses, with a constant delay of 54 +/- 28 ms. Our results show also an incorrect response preparation related to associated EMG response. We interpreted this specific feature in relation to inhibitory deficits in motor cortex and associated callosal pathways that avoid a correct response performance in Alzheimer patients.
Aged↗
[Reactions in the brainactivity during increased carbondioxyde concentration (author's transl)].
A comparative study of two kinds of respiration (normal air and mixed with 4% CO2) was carried out in 8 healthy students. During the three experiments, each one lasting over 120 min, CO2 or air was inhaled using a mask. Blood samples were taken from the fingers, an average increase of pCO2 of 1.9 mm (p less than 0.01) and pO2 of 7.3 mm (p less than 0.01) was found during CO2-inhalation. The ECG and EEG were recorded and reaction times to tone stimuli in a foreperiod reaction time experiment were measured. During CO2-inhalation a clear reduction of the power in the alpha-band was found in frontal, central and occipital region in the order of 23% (p less than 0.05) and 12% (p less than 0.05) and 22% (p less than 0.01). The heart rate interval decreased significantly by 2.3% (p less than 0.05). No significant changes were found in CNV, reaction time and percentage event-related alpha-desynchronization.
Adult↗
Electroencephalographic and other neurophysiological abnormalities in uremia.
1) Neurophysiological abnormalities in patients with renal failure are being investigated because a) it is the nervous system which preeminently produces the phenomena of clinical uremia that dialysis affects and b) objective quantitative measures of such functions are generally lacking and are needed to provide objective evidence for adequacy of dialysis and other treatment measures in uremic patients. Accordingly, the attempt is warranted to measure in objective terms what renal failure, alternatively maintenance dialysis, does to the patient's nervous system in the comprehensive terms and the several modalities by which the nervous system serves the patient. 2) It is clear from the foregoing presentation that electroencephalographic phenomena including some aspects of the spontaneous EEG and certain event-related potentials can be readily reduced to quantitative terms. Some of these are abnormal in the presence of renal failure, are improved by dialysis treatment, may vary with the frequency of dialysis treatment and are often normalized by renal transplantation. Apparently similar EEG changes may be induced by other intercurrent influences occasionally operating in patients with renal failure. These can usually be readily detected but appear at this time to limit the potential usefulness of the EEG in those instances. However, especially using successive determinations in individual patients, the quantitative measure of slow-wave-associated EEG power is a reasonable candidate-measure of adequacy of dialysis. Other measures should be explored. 3) Quantitative measures of EEG phenomena appear to be superior in speed and objectivity to conventional, descriptive reporting of electroencephalograms, especially for the repetitive comparisons which are necessary for clinical patient monitoring. 4) The data system so far employed to transform EEG phenomena into clinically useful data (Fig. 1) will be greatly simplified as soon as the most informative, sensitive and specific measures are selected from among those being explored. Dedicated micro-processing equipment, for example, can then be expected to replace the much more expensive, multipurpose computer system which is necessary for the initial investigation.
Contingent Negative Variation↗
Medial frontal cortex in action monitoring.
Effective behavior requires continuous action monitoring. Electrophysiological studies in both monkeys and humans have shown activity in the medial frontal cortex that reflects dynamic control and monitoring of behavioral acts. In humans, the centromedial frontal cortex shows an electrical response within 100 msec of an error, the error-related negativity (ERN). The ERN occurs only when subjects are aware of making an error, suggesting that a critical factor may be self-monitoring of the action process. In the present study, we examined late responses in a deadline reaction time task, in which the subject becomes increasingly aware of making an error as the response becomes increasingly late. We found evidence of response conflict before errors defined by late responses but not before errors defined by incorrect responses. The results also show a linear increase in the amplitude of the ERN with increasingly late responses. These data suggest that frontal networks provide dynamic representations that monitor and evaluate the unfolding action plan.
Adolescent↗
The roles of vertex sharp waves and K-complexes in the generation of N300 in auditory and respiratory-related evoked potentials during early stage 2 NREM sleep.
STUDY OBJECTIVES: To determine the scalp topography of the N300 response to stimuli of different modalities and to investigate the relationship of the N300 component to K-complexes and vertex sharp waves seen in the un-averaged EEG. DESIGN: Two experiments were conducted one using auditory; the other using respiratory occlusion stimuli presented during stage 2 sleep. Trials were classified on the basis of whether they produced a K-complex, a vertex sharp wave, or some other response. Auditory stimuli were presented in the form of an oddball paradigm, and averaged separately depending on whether they were "frequent" or "rare". In both experiments, responses were averaged separately based on the appearance of K-complexes, vertex sharps waves, or some "other" response to the stimuli. SETTING: Data were collected in the Melbourne University Sleep Laboratory. PARTICIPANTS: Young healthy male adults, eight in experiment 1 and six in experiment 2. INTERVENTIONS: NA. MEASUREMENTS AND RESULTS: Data were collected from 29 scalp sites. In all cases, N300 amplitude was maximal in the vertex sharp wave averages, despite being clearly present in the averages of K-complexes and "other" responses. The vertex maximal scalp topography of the N300 did not differ across response conditions or as a function of stimulus modality. This is consistent with the N300 being produced by the same intracranial generators in all cases. There were no effects of stimulus or response type on N300 latency. CONCLUSIONS: N300 should be viewed as a multi-modal component with a different underlying generator mechanism than that of the K-complex.
Adult↗
Multimedia stimulation for psychophysiological investigation.
This paper describes a multimedia approach to sensory stimulation in psychophysiological studies. High resolution colour images are presented to a subject by a Delphi stimulus program, controlled by a data acquisition system which concurrently records cognitive Event Related Potentials from the subject. The acquisition PC is linked to the stimulus PC using serial communications and requests slide material using a character based protocol. The sound card in the data acquisition system can present concurrent complex auditory stimuli for multimedia experiments.
Acoustic Stimulation↗
[The bereitschaftspotential. The concept and methodology for acquiring it].
INTRODUCTION: The movement of extension of the index finger in a stereotyped manner, not as a reaction to any external or internal stimulus, is preceded by EEG activity representing activity of the supplementary motor area of the motor cortex. DEVELOPMENT: By averaging retrograde EEG activity prior to movement, the Bereitschaftspotential (BP) may be obtained, using the German nomenclature of the earliest investigators who first described it and its components NS1 and NS2. We include a table with normal values obtained from a group of healthy persons. CONCLUSION: In our study we show the usefulness of off-line methodology with manual adjustment of the start of EMG activity to obtain better morphological definition and greater voltage of the BP. At the same time, continual acquisition with the trigger adjusted to a prefixed threshold (on-line methodology) means that a smaller BP is obtained, especially in persons with difficulty in the organization of this movement.
Adult↗
Rate of force development and the lateralized readiness potential.
We examined the relationship between force and rate of force development aspects of movement dynamics and electroencephalogram motor components as reflected in the lateralized readiness potential (LRP). Using self-paced tasks, in Studies 1 and 3 we investigated whether differential speed and accuracy constraints in discrete and repetitive finger force production tasks influenced the LRP. These studies showed that speed tasks produced larger LRP than accuracy tasks regardless of whether the movement type was discrete or repetitive. In Studies 2 and 4 we studied four conditions with two levels of force and two levels of rate of force development. The largest LRPs were found with the greatest rate of force development. Overall, the four studies demonstrated that preparation for differential rates of force development is a major component reflected in the LRP.
Adult↗
Scalp recorded direct current potential shifts associated with quenching thirst in humans.
As an indicator of cortical excitability, direct current (DC) potentials were recorded from thirsted subjects before, during and after drinking 400 ml of water. Self-rated thirst was distinctly reduced after drinking. Compared with control conditions in which the subjects remained thirsty, during drinking a widespread negative potential shift occurred averaging over -70 microV at Cz. At the transition from the consumatory phase to the postconsumption phase, a slow positive potential shift commenced that was most pronounced over the anterior cortex (averaging over +40 microV at Fz) and persisted for more than 3 min after drinking. Control conditions excluded muscle activity, ocular movements, and changes in body fluid and serum osmolality as possible non-neuronal sources of the DC-potential changes. The sequence of negative and positive potential shifts associated with drinking indicates a coordinate regulation of cortical excitability that may facilitate consumatory behavior and its context-dependent encoding into memory.
Adult↗
Right N170 modulation in a face discrimination task: an account for categorical perception of familiar faces.
Behavioral studies have shown that two different morphed faces belonging to the same identity are harder to discriminate than two faces stemming from two different identities. The temporal course of this categorical perception effect has been explored through event-related potentials. Three kinds of pairs were presented in a matching task: (1) two different morphed faces representing the same identity (within), (2) two other faces representing two different identities (between), and (3) two identical morphed faces (same). Following the second face onset in the pair, the amplitude of the right occipitotemporal negativity (N170) was reduced for within and same pairs as compared with between pairs, suggesting an identity priming effect. We also observed a modulation of the P3b wave, as the amplitude of the responses for within pairs was higher than for between and same pairs, suggesting a higher complexity of the task for within pairs. These results indicate that categorical perception of human faces has a perceptual origin in the right occipitotemporal hemisphere.
Adult↗
Mismatch negativity in children and adults, and effects of an attended task.
Attention has been shown to modulate the amplitude of the mismatch negativity (MMN) elicited by a small deviation in auditory stimuli in adults. The present study examined the effects of attention and deviant size on MMN amplitude in children. Children and adults were presented with sequences of tones containing standards (1000 Hz) and three deviants varying in degree of deviance from the standard (1050, 1200, and 1500 Hz). Tones were presented in three conditions: (1) while participants ignored them; (2) while participants listened to them and responded to all three deviants; and (3) while participants again ignored them. We found that the MMNs elicited by the hard deviant (1050 Hz) were larger when the children were actively discriminating the stimuli than when they were ignoring them. However, the MMNs elicited by the easy and medium deviants (1500 and 1200 Hz, respectively) in the children and by all three deviants in the adults were not affected by attention.
Adult↗
[Negative mismatch of evoked potentials in short-term acoustic stimulation].
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Acoustic Stimulation↗
Motor processes in simple, go/no-go, and choice reaction time tasks: a psychophysiological analysis.
Psychophysiological measures were used to compare the response preparation and response execution processes of modified versions of F. C. Donders's (1868/1969) classic simple, go/no-go, and choice reaction time tasks. On all measures, differences between tasks were minimal prior to test stimulus onset, supporting the idea of equivalent motor preparation for the 3 tasks. In addition, the psychophysiological measures indicated that the time from the onset of motor processing to the keypress response was also approximately constant across tasks. These results support the assumption that the mean duration of motor processes can be invariant across simple, go/no-go, and choice tasks, at least for the present modified versions of these tasks. The findings emphasize the utility of psychophysiological measures for both examining preparatory processes preceding stimulus onset and for localizing effects on reaction time.
Adult↗
Novelty-elicited mismatch negativity in patients with schizophrenia on admission and discharge.
OBJECTIVE: Given recent reports of differences between mismatch negativity (MMN) elicited by always novel sounds (novelty-elicited MMN) and that elicited by repeated rare deviants (conventional MMN), we investigated novelty-elicited MMN and P3a in patients with schizophrenia before and after a nonstandardized inpatient treatment. DESIGN: Electrophysiological and clinical assessment of patients on admission and discharge from hospital. Assessment of control subjects on 2 sessions. SETTING: Inpatient treatment in a psychiatric university hospital. SUBJECTS: 20 patients with schizophrenia and 21 healthy control subjects of similar age and sex. Selection of patients with first- to third-episode schizophrenia. OUTCOME MEASURES: Early and late component MMN amplitudes and latencies, P3a amplitudes and latencies, Positive and Negative Syndrome Scale (PANSS), Global Assessment of Functioning (GAF), Extrapyramidal Symptom Scale (EPS), Abnormal Involuntary Movement Scale (AIMS) and chlorpromazine equivalents. RESULTS: In patients with schizophrenia, novelty-elicited MMN was unimpaired on admission, and there was a statistically significant reduction of the late MMN component with treatment. Improvements in symptom expression were associated with increased latencies of the early MMN component. CONCLUSION: Results indicate differences in information processing between conventional and novelty-elicited MMN. Some components of the novelty-elicited MMN might be more state dependent than those of the conventional MMN.
Adult↗
Mismatch negativity and personality traits in chronic primary insomniacs.
The thalamo-(fronto)cortical circuit is involved in sleep regulation, and its dysfunction might contribute to the pathophysiology of chronic primary insomnia. To obtain more evidence of the involvement of the circuit, we studied 23 patients with chronic primary insomnia and 28 healthy volunteers via the assessment of mismatch negativity (MMN) elicited by tone intensity deviance, and of personality traits measured by Zuckerman's Sensation Seeking Scales, and Zuckerman-Kuhlman's Personality Questionnaire. In insomniacs, MMN amplitude at Fz was significantly larger; Depression, which was measured by Plutchik-van Praag's Depression Inventory, and Neuroticism-anxiety and Impulsivity scores were higher, while the Thrill and adventure seeking score was lower; MMN amplitude was positively correlated with Depression and with Impulsivity. In healthy subjects, MMN amplitude at Fz was positively correlated with Neuroticism-anxiety, but negatively with Experience seeking. The larger MMN and distinct personality traits suggest a hyperactivity in the thalamo-(fronto)cortical neuronal circuit in insomniacs, which is probably the result of weak thalamic gating mechanisms, or an imbalance of several neurotransmitter systems.
Adult↗
The processing of sound duration after left hemisphere stroke: event-related potential and behavioral evidence.
The ability of left-hemisphere stroke patients (n = 8) and healthy control subjects (n = 8) to process sounds preattentively and attentively was studied by recording auditory event-related potentials (ERPs) and behavioral responses. For the right-ear stimulation, the mismatch negativity (MMN) was significantly smaller in the patients than control subjects over both hemispheres. For the left-ear stimuli, the MMN was significantly smaller in the patient group than in the control group over the left hemisphere, whereas no group differences were obtained over the right hemisphere. In addition, the N1 amplitude was reduced bilaterally for the right-ear stimulation (with the reduction being larger over the left hemisphere), whereas no significant effects on the N1 amplitude were found for the left-ear stimulation. Behaviorally, the patients detected significantly fewer deviant tones than did the control subjects irrespective of the stimulated ear. The present results thus suggest that the long-latency ERPs can be used to probe such auditory processing deficits that are difficult to define with behavioral measures. Especially by recording MMN to monaural stimuli, the discrimination accuracy can be separately determined for the left and right temporal lobes.
Acoustic Stimulation↗
Long-term habituation of the speech-elicited mismatch negativity.
A significant issue in the use of the mismatch negativity evoked potential (MMN) concerns its low signal-to-noise ratio (SNR). One can improve the noise level by increasing the number of samples included in the averaged response. However, improvement achieved in this way assumes that the signal, the MMN, remains stable for extended test times, an assumption which has not been tested. If the MMN is not stable, or exhibits habituation over the test session, then SNR would be adversely affected. MMN response magnitude was measured in 5-min intervals over the course of a test session in response to various speech syllable contrasts. Significant long-term habituation of MMN was observed for all three subject populations tested: young adults, school-age children, and guinea pigs. The time course of the habituation and the stimulus conditions under which it occurs have important implications for research and clinical applications of the MMN. Recording procedures that minimize habituation effects may be used to advantage to improve the signal-to-noise ratio of the MMN.
Adolescent↗