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G Junghanns

Publications and source records attributed to G Junghanns.

3 recordsLinked to original sources
PubMed1989

The P300 amplitude of the event-related brain potential indicates changes within a frame-of-reference.

The starting point of this study was the fact that investigations in the frame-of-reference research were mostly performed on the behavioural level. The present study aimed at studying behaviour of P300 amplitude of the event-related brain potential in a frame-of-reference investigation. Ten healthy volunteers participated in the investigation. Test material consisted of horizontal bars of different lengths presented successively on a screen. Each bar (serial stimulus) was preceded by a prestimulus (anchor) of constant length. Each serial stimulus was to be evaluated according to a 9 step rating scale. There were no significant differences in the overt length judgements of the serial stimuli depending on the 3 different anchor lengths. However, the mean P300 amplitude increased with growing dissimilarity between the length of the anchor and serial stimulus length. Thus, it is assumed that the adaptation level on the internal dimension of stimulus length, which was assumed to be influenced by the anchor stimuli, led to the different behaviour of P300 amplitude.

Adult↗
PubMedDate not supplied

[Adaptation to the complexity of a task (a P300 study)].

In numerous studies the P300 component of the event-related brain potential (ERP) has been shown to occur in connection with stimulus evaluation processes. 10 healthy right-handed volunteers (3 women, 7 men) aged from 25 to 30 years (mean age 27.8 years) participated in the experiments. One of 5 equiprobably occurring two-letter strings appeared on the screen always at the same central location. The strings informed the subjects about the difficulty of subsequently presented mental arithmetic tasks. After the letter strings vanished from the screen the subjects were to press the space-bar whereby a mental arithmetic task was presented corresponding in difficulty to the preceding message. The EEG was recorded by means of Ag/AgCl electrodes from frontal (F zeta), central (C zeta) and parietal (P zeta) midline electrodes referenced to linked earlobes. EEG and EOG were sampled 1200 ms, starting 200 ms prior to string onset. P300 peak latencies, peak amplitudes and areas in the time range 300 to 900 ms were measured in ERPs averaged selectively for the 5 strings. The main finding was that the P300 amplitude in ERPs to the 5 different strings varied in a U-shaped trend as a function of announced task difficulty. This result gives further evidence that the P300 amplitude reflects distance between incoming information and current adaptation level at the inferred internal dimension, i.e. task difficulty in this experiment.

Adaptation, Physiological↗