2011 Volume 49 Issue 6 Pages 858-863
Motion-defined pattern perception is realized, when we watch an area composed of coherently moving dots surrounded by a “sand storm” zone of incoherently moving dots. In our preceding psychophysical experiments concerning this pattern perception with varied moving dot velocities, we found that at the velocity of 14.4deg/s, both perception of motion itself and of relevant pattern were carried out, whereas at the velocity of 43.2deg/s, perception of motion alone was performed. The measurements of magnetoencephalogram (MEG) to the same stimuli suggested that this pattern perception was processed in both ventral and dorsal portions of the occipital cortex with the latency at 250-290 ms. In order to achieve more precise identifications of activated areas and latency times by statistical treatments of MEG data, we employed the ERD/ERS (event related de-synchronization/synchronization) analyses in the present study and applied it to the grouped data of 8 participants, for the frequency band of 10-13Hz. The results of the analyses revealed that, under the condition of velocity 14.4deg/s, the significant ERD signals (p<1×10-6) were observed between 250-350 ms at the ventral portions in the primary visual cortex (BA17, BA18 and BA19, where BA:Brodmann area) and in the dorsal portion of the cortex (BA40). At the velocity of 43.2deg/s, the active areas with significantly enhanced ERD signals were found at BA37 and dorsal portion of BA19. No significant area was revealed for the ERS signals under condition of 14.4deg/s. These results suggest that the final processing of motion-defined pattern perception is performed at around 250-350 ms in early visual cortex including BA17, BA18 and BA19.
