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Background. The functional integration (»binding«) of different brain areas, for example as a possible mechanism for stimulus perception, may be mediated by the synchronizing oscil­latory activity of neuronal populations, which can be determined by electroencephalographic coherence analysis. Visuomotor integration in a visuomotor task requires functional coop­eration between the motor and visual cortical areas. Unilateral limb movements are based on the activation of contralateral primary motor cortex and bilateral activation of premotor cortices.

Aim. Our main aim was to introduce a new method of coherence analysis and to com­pare our results obtained using an established model of the visuomotor task with other comparable studies, thereby assessing the validity of this method. The changes in coherence and power spectra of the left and right hemispheres of the brain were then compared while the subjects performed the visuomotor task with the right or with the left hand.

Hypothesis. It was assumed that the coherence between the visual and motor areas of the cortex would increase for the visuomotor task compared to the control tasks. It was also hypothesized that an increase in coherence and a decrease in the power spectrum while per­forming the task with the right hand would be greater in the left hemisphere and vice versa.

Methods. 6 healthy, right-handed subjects were tested and their electroencephalograms were recorded while they performed 4 different tasks: a visuomotor task with the right and the left hand (which required good coordination between visual and motor brain areas), a visu­al task, a motor task and a visual and motor task (which required independent activation of the visual and motor areas). For coherence and spectral analysis, a special computer program was designed using Matlab software. The results were statistically analysed with two-way analy­sis of variance, one-way analysis of variance and post hoc t-tests with Bonferroni correction.

Results. A statistically significant increase in coherence (p<0.05) was demonstrated for the visuomotor task compared to other tasks in alpha and beta 1 frequency bands. There were no significant differences in coherence values depending on the hand used. The changes of coherence between the two hemispheres were symmetrical.

Conclusions. In accordance with previous studies, a specific increase of coherence for the visuomotor task was demonstrated and it was shown that there are no conclusive asymme­tries when the task is performed with the right or with the left hand. This can be explained by proposing that the increase in coherence reflects a cooperation between more complex visual and motor brain areas.