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P Ullsperger

Publications and source records attributed to P Ullsperger.

62 records · Page 4Linked to original sources
PubMed1975

[Analysis of variance delimitation of factors influencing studies of acoustic evoked potentials].

The effect of the variables "stimulus intensity", "residual effect of previous stimulus intensity", "period effect" and "subject effect" on the amplitudes and on the peak latencies of the N1 and P1 components of the acoustical EEG evoked potentials was studied in human subjects with the use of an orthogonal experimental design. The stimulus intensity (30, 50 and 80 dB) accounts for the greatest part of the total variance of the amplitudes and of the peak latencies of N1.-The existence of a totalvariance component due to differences between the subjects is also statistically significant (P equals 5%), As far as the period effect (habituation effect) is concerned, only its effect on the amplitude of N1 - P2 is statistically significant. - The residual effect of the stimulus intensity used in the previous series was not significant.

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↗