STUDIES ON INTEGRATIVE FUNCTIONS OF THE HUMAN FRONTAL ASSOCIATION CORTEX WITH MEG

Our MEG studies on the human frontal association cortex are briefly re viewed. (1) The no-go potential was first found at go/no-go reaction-t ime hand movement task with discrimination between different colour li ght stimuli in the prefrontal cortex of monkeys. The potential was rec orded in human subjects with EEG over the scalp, but its current dipol es could be localized only by use of MEG, in the dorsolateral part of the frontal association cortex in both cerebral hemispheres. The funct ion for no-go decision and subsequent suppressor action was thus subst antiated in the human frontal cortex. (2) Utterance of a short noun in Japanese was found to be initially preceded by an activity in the low er lateral part of the frontal lobe and then by that around the centra l sulcus. The area of the former, often in both hemispheres, appears t o correspond to Broca's motor speech centre and that of the latter, al ways in both hemispheres, to correspond to the motor-somatosensory cor tices. (3) Intensive and continuous concentration on mental calculatio n and some 'abstract' thinking for a few minutes were often associated with magnetic theta (5-7 Hz) wave bursts in the frontal part of the s calp. Dipole fitting suggested that the electrical current dipoles occ ur successively and scattered in wide areas of the frontal lobe on bot h sides. They are to be called ''frontal mental theta wave'', revealin g dynamic and active participation of the frontal lobe in mental funct ions.