Hemispheric EEG slow-potential asymmetry (SPA) during a one-dimensional horizontal tracking task was recorded over Oi, O2, C3 and C4 electrode positions. The time instants of tracking error occurrences (CXJT events) and their corrections (IN events) were used as synchronization events in selected EEG epochs. The central values (medians) of amplitudes in the averaged 500 ms EEG epochs were used for SPA description. Significant negative correlations between medians calculated for the time epochs prior to and after the events were found indicating a specific influence of these events on SPA. Prior IN events the left hemisphere (represented by Oi and C3 positions only) was more negative than the right one, while it was significantly more positive after the same type of events. An opposite relationship was suggested for OUT events.
Tracing movements (hand-following the stationary contours of three two-dimensional figures: square, triangle and circle by means of a computer mouse-operated lightspot) were analyzed during five consecutive days. All three figures consisting of four (square, circle) or three (triangle) segments had the same circumference. Three parameters were chosen to express the tracing efficiency: average error, average time and performance quotient (average error per time unit) either for individual segments or the whole figures. The performance quotient was the best for the square and the worst for the circle, yielding better values for horizontal (than for others) segment orientation for the square and triangle. On the contrary, vertical segment orientation was found to be the best for the circle. The performance quotient and average error yielded better values in triangle segments when the right hand was used (all subjects were right-handed). However, considering the whole figures all three parameters displayed better values for the right hand. No differences were found with respect to the direction of tracing movements (clockwise or counter-clockwise). During the first three days both average error and time decreased, the change in later performance is caused by shortening of the average time only.