POTENTIAL FLOW OF FRONTAL MIDLINE THETA-ACTIVITY DURING A MENTAL TASKIN THE HUMAN ELECTROENCEPHALOGRAM

The movement of potential field (potential flow) of frontal midline th eta activity (Fmtheta) as well as its potential distribution was exami ned in 7 subjects by using optical flow detection techniques in image processing. Electroencephalograms (EEGs) over the fronto-central regio n were recorded from 13 electrodes near the frontal midline (F(z)) whi le the subjects were performing a mental task. The potential flow of F mtheta was estimated on a frame consisting of a square grid with F(z) at its center. In regions anterior to F(z), the direction of potential flow was from lateral to medial, whereas it was from medial to latera l in regions posterior to F(z). The peak-to-trough amplitude distribut ion was round or oval with a maximum just anterior to F(z). The source density distribution showed the greatest potential along the midline in the frontal region and bilaterally symmetric smaller maximum areas mostly in the prefrontal regions. Our findings suggested the presence of 2 different source areas of opposite direction in each hemisphere i n spite of a round or oval amplitude distribution.