[Changes in the late components of evoked cortical potentials during the human solving of a visual-spatial task]

The ability of mental construction of easily verbalized geometric figures was studied in 20 healthy subjects by means of recording of the evoked potentials of the cerebral cortex. Fragments of geometric figures were presented with the intervals of 80 and 500 ms. To one half of the subjects the stimuli were presented unilaterally (both fragments to one and the same visual field, to the left or to the right one) and to the second half of the subjects--bilaterally (the first fragment--to one visual field and the second one--to the other). It was established that the latency of the wave P300 was shorter and the amplitude--greater at correct decisions of the visual-spatial task than at false ones, both at unilateral and bilateral fragments presentation. At a great interval (500 ms), when the effects of masking became significantly weaker, a predominant activation of the left hemisphere was observed: the latency of the late components was shorter and the amplitude--greater, when the information came "directly" to the left hemisphere. The obtained results testify once more to a great variability, dynamic interhemispheric relations, impossibility of connecting the realization of some functions with one of the hemispheres.