Biomedical subjects

T Winker

Publications and source records attributed to T Winker.

4 recordsLinked to original sources

PubMed1992

Changes in cortical negative DC shifts due to different motor task conditions.

The experiments were performed to study the relationship between motor performance and DC potential curves recorded by scalp electrodes. Accordingly, we studied the influence of different movements (e.g., unilateral versus bilateral, simple versus complex, active versus passive, phasic versus tonic muscle activity) on negative DC potentials. Our results confirm that spatial distributions of DC potential maxima can be used as an indicator of the activation of distinct cortical areas. Furthermore, evidence is presented that some motor tasks have a greater influence on the magnitude of surface electronegativity than others. (1) Phasic muscle activity revealed a significantly larger potential size than tonic. (2) Performance of a complex finger movement task elicited an increased surface electronegativity compared with performance of a simple task. (3) No significant differences in potential size were found between left (untrained) and right (skilled) hand use during the performance of the same complex motor task. (4) This was also true for the performance of an active and a passive finger movement task, indicating that, at least in simple motor tasks, somatosensory afferents significantly contribute to the recorded potential curve.

Adolescent↗

PubMed1991

Changes of slow cortical negative DC-potentials during the acquisition of a complex finger motor task.

To study whether electrophysiological correlates of increasing motor skill can be demonstrated in man, we recorded cortical negative DC-potentials during the acquisition of a complex finger movement in 21 subjects. The movement consisted in moving a matchstick to and fro between the index finger (II) and the little finger (V). Cortical negative DC-potentials were recorded at Fz, Cz, C1, C2 and Pz. As a control a simple finger movement was performed during the same session by 7 of the Ss. Both tasks were repeated 60-80 times and averages of the first and the last 15 artifact-free single runs were compared. Whereas only a slight, inconstant decrease in surface electronegativity during the simple motor task was observed, a significant reduction in potential size occurred during the complex task at Cz (maximum), C1, C2 and Pz but not at Fz. In addition, a significant difference in the decrease of surface electronegativity between various electrode positions was observed. We suggest that these changes in potential size during the process of motor learning may reflect an altered cortical organisation of movement control during the acquisition of a complex motor task.

Adult↗

PubMed1990

Statistical evaluation of slow brain potentials on the basis of single trials.

The amplitude of slow brain potentials is related to the complexity of the task performed. Therefore, the large potentials related to the processing of complex tasks (tracking, writing, mental acts) may be analysed statistically on a single trial basis. This opens up a range of new facilities for within-session tests of significance. Prior to evaluation, signals are passed through several automatic error compensation routines: smoothing, trend removal, subtraction of eye artifacts, rejection of trials with random artifacts. The shape of the task potential approximates well to a rectangular elevation of cortical negativity, with the mean amplitude over a pre-event baseline being used as the main statistical parameter. Non-parametric statistical tests are preferred for evaluation. Application of the method is demonstrated for a tracking paradigm.

Electroencephalography↗

PubMed1989

Premotor programming and cortical processing in the cerebral cortex. Electrophysiological correlates of hemispheric dominance.

Slow brain potentials were averaged from 12-15 EEG records (t = DC or 5 s) before and during voluntary hand movements and writing, spatial vision, language, and calculation tasks without vocalization and with visual fixation. EOG and writing pressure or EMG were recorded simultaneously. Skilled actions caused largest negative potentials in the contralateral sensorimotor hand area. Left-sided lateralization or bilaterally equal surface-negative potential shifts appeared during language and calculation tasks in 90% of the right-handers and in 75% of the left-handers. Right-sided lateralizations occurred during the viewing of perspective Necker figures or random-dot stereograms in the large majority of all subjects.

Adolescent↗