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H G Gille

Publications and source records attributed to H G Gille.

16 recordsLinked to original sources
PubMed1990

Amplitude variations in P300 component due to unpredictable stepwise change of stimulus probability.

The present study investigates whether the amplitude of the P300 in 'normal' subjects adapts to unexpected changes in global stimulus probability. The adaptation level (AL) metrics (in terms of Helson's [1964] theory) was applied to explain the variations in the P300 amplitude. In an oddball paradigm the probability of the deviant tone (target 1000 Hz, 80 dB, 50 ms) occurring randomly in a train of standard ones (non-target 1100 Hz, 80 dB, 50 ms) was changed in a stepwise way from 0.5 to 0.3 and then to 0.1 in 3 blocks without interruption of the stimulus presentation. Two experiments were performed. In the first one the subjects did not receive any prior information about the changes in the stimulus probability, whereas in the second experiment they were aware of such changes. The task always required the subject to silently count the deviants. EEG was recorded monopolarly from Fz, Cz and Pz in a total of 15 subjects. The block averaged P300 increased monotonically with probability, the increase being larger in Expt. II. In contrast to the block averaged P300, the variations in the P300 amplitude following the abrupt change in probability showed a non-linear dependency. On the basis of the AL a simulation of the time course of the P300 variations with probability was performed and a clear similarity between the simulated P300 and the experimental data was found. Some properties of the AL model are discussed.

Acoustic Stimulation↗
PubMed1990

A new approach to cerebral asymmetry: RT differences in simultaneous bimanual finger movement during verbal and nonverbal tasks.

This study was aimed at testing a new approach for examination of functional laterality based on hemispheric specialization. The subjects had to perform verbal (words/nonwords) and nonverbal (similar/different patterns) discrimination. The separation of the two hemispheres during information processing was realized by requiring a simultaneous response of both index fingers. The obtained over-all reaction times (RT) were faster for verbal than for pattern tasks. Considering the RTs for solely the particular, faster response of one or the other index finger, the right index finger turned out to be faster on verbal tasks whereas the left one dominated on pattern tasks. According to the hypothesis that the faster hand indicates the more active (contralateral) hemisphere, it can be assumed that words are responded to more quickly when processed in the left hemisphere. On the other hand, patterns are responded to more quickly when the right hemisphere is active. These results suggest that each hemisphere may be capable of processing verbal and nonverbal material; the speed of information processing, however, is faster in the more adept one.

Adult↗
PubMed1990

Psychophysiological assessment of transcutaneous electric nerve stimulation (TENS) effects upon orofacial pain.

Fear of pain in dentistry may be one reason why preventive care is avoided by a number of individuals. Therefore, measures which reduce painful experiences may be beneficial for patients' attitudes towards medical interventions. Using conservative dental treatment as a model situation, we studied effects of transcutaneous electric nerve stimulation (TENS) upon acute orofacial pain in three experiments. In the first experiment, pain thresholds (electric tooth stimulation) were found to be increased under TENS. In the second experiment, electric brain potentials (ERP) were evoked by electric tooth stimulation. The ERP amplitude is intensity-dependent and revealed a marked decrease as a consequence of TENS. Finally, TENS was applied during real treatment, and subjective estimates confirm its beneficial effect upon pain and stress.

Adult↗
PubMed1988

The late positive component of the ERP and adaptation-level theory.

Relationships between the P300 component of the event-related potential (ERP) and processes of evaluation and categorization of events have been demonstrated in numerous investigations. On the other hand, these same processes have also been studied extensively by means of rating scale procedures within the framework of the psychological Adaptation-Level Theory. Recently, it has been suggested that the P300 amplitude reflects the distance between the adaptation level and the event that elicits the ERP. In this study we explored this suggestion by examining the effects of stimulus categorization on P300. Seven healthy adult subjects had to judge the length of five letter strings which were presented equiprobably in a randomized sequence. The ERPs (Fz, Cz, Pz derivations) elicited by string presentation were selectively averaged according to the five categories of string length. U-shaped trends of P300 amplitude changes were found. Minimum amplitudes were elicited by strings of medium length consistent with the inferred adaptation level. The data provide further evidence that P300 amplitude reflects the mental distance to adaptation level.

Adaptation, Physiological↗
PubMed1987

P300 and anticipated task difficulty.

Recently, it has been shown that P300 measures depend on stimulus evaluation processes. This paper explores the effect of messages informing about the degree of difficulty of subsequent tasks on the P300 component. Ten healthy volunteers were asked to solve mental arithmetic tasks of graduated difficulty. The degree of difficulty was announced by messages which preceded the tasks and which were used as P300 eliciting stimuli. Measurements of the amplitude and latency of P300 components from 3 brain regions (Fz, Cz, Pz) were collected selectively for each category of task difficulty announced. Subjective ratings of difficulty and the frequency of errors confirmed the monotonic increase of task difficulty from categories I to VI. The mean P300 amplitude in categories I-VI showed a U-shaped trend, i.e. the highest amplitude occurred in the extreme categories 'extremely easy' and 'very difficult'. No significant effect of stimulus categories on P300 peak latencies was found. It is concluded that the P300 amplitude reflects an evaluation in the sense of distance judgements on an internal scale which in this study concerned the task difficulty.

Adult↗
PubMed1985

[The P300 component of the event-related brain potential as an indicator in the study of information processing].

Event-related bioelectrical brain activity plays an important role in psychophysiological investigations of mental processes. One of the so-called endogenous components of ERP, the P300, occurring in the time range from 300 ms to 800 ms after stimulus presentation accompanies the selective call on cognitive processing of stimulus information. An overview of some influencing factors and of hypotheses according functional significance of P300 is given. Although functional significance of P300 is only partly known there are interesting possibilities of application, e.g. in Neurology, Psychiatry and Occupational medicine.

Arousal↗
PubMed1983

Changes in EEG power density spectrum during static muscle work.

Changes in parameters of the EEG power density spectrum were demonstrated in four healthy male subjects during fatiguing static muscle contractions (M. biceps brachii dexter). For the following EEG frequency bands (delta 1-4 Hz, theta 4-8 Hz, alpha 8-13 Hz, beta 13-20 Hz), the relative power and the peak frequencies were determined. A significant increase in the alpha peak frequency was observed during muscle work. This trend was evident in both the central leads (C3-A1, C4-A1) and the occipital (O1-A1), particularly when the subjects had their eyes closed. These changes in peak frequency might be connected with an increase in central nervous activation.

Adult↗
PubMed1976

[Activation-dependent characteristics of the electroencephalogram during visual information--processing: Results of an automatic interval analysis (author's transl)].

EEG signal from fronto-occipital derivation was recorded in 16 Ss during a mental performance test (modified "Konzentrations-Leistungs-Test" including four levels of performance). A balanced changer-over design was used. Interval histograms in four frequency bands (theta, alpha, beta-1 and beta-2 bands) were determined on the basis of peak detection. A total of 44 characteristics were derived and tested (multi-factor analyses of variance, multiple mean comparison and rank tests). Twenty eight of these characteristics were proved to be dependent on activation. In the visual information-processing performances chosen, it could be demonstrated that the intraindividual changes of the spontaneous EEG activity were related predominantly to the perceptual components of the performance. On the other hand, the influence of the performance rate and of the mental-arithmetic itself was of minor relevance. During higher activation an increase in the relative abudance of the theta-band activity was also observed.

Adult↗