THE EEG FREQUENCY BANDS DURING PERCEPTION AND MENTAL ROTATION OF 2-DIMENSIONAL AND 3-DIMENSIONAL OBJECTS

The EEG spectral power in 4 frequency ranges (8-13, 15-25, 25-35, and 35-45 Hz) was studied during mental rotation of two-and three-dimensio nal objects. Only those EEG segments were analyzed which corresponded to the tasks with similar time of solving. The EEG spectral power of t he alpha range was higher under control conditions than during task so lving. The spectral power in the range of 15-45 Hz was higher under th e operation than under the control conditions. This finding confirms t he assumption that EEG desynchronization in the alpha range is accompa nied by the high-frequency synchronization The EEG high-frequency powe r was higher during mental rotation of two-dimensional objects than th ree-dimensional ones. Since the angular difference between the two-dim ensional objects was larger than between the three-dimensional ones, t he rotation angle rather than the ''depth'' of space increased cortica l activation. Under experimental conditions, EEG spectral power in the range of 15-45 Hz was always the highest in the occipital areas, whic h was associated with the visual modality of stimuli. The EEG spectral power in the gamma range (35-45 Hz) was substantially higher at the f irst second of operation as compared with the second one testifying th at EEG changes in this range are more related with the processes of pe rception and recognition than with mental operations with images.