NON-INVASIVE STUDY OF HUMAN BRAIN FUNCTION USING PHYSIOLOGICAL METHODS,MAGNETOENCEPHALOGRAPHY AND ELECTROENCEPHALOGRAPHY

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We studied magnetic evoked fields (EF) following somatosensory (SEF) and visual (VEF) stimulation to investigate the mechanisms of sensory perception in terms of temporal and spatial information in the human brain.SEFWe recorded SEF following electrical or mechanical stimulation applied to the scalp, lip, upper limb and lower limb, and reconfirmed "homunculus" in the primary sensory area (SI) reported by Dr. Penfield. In general, receptive fields are consistent with "homunculus", but a large inter-individual difference was found, particularly in the lower limb area in SI.We also found the intra-individual (left-right) difference. We made a new device to produce "passive movement" to investigate cortical activities to the signals ascending through muscle afferent. Both waveforms and activated areas following passive movement of fingers were significantly different from those following electrical or mechanical stimulation applied to the fingers. Probably the difference was due to the fac … More ts that are 3a in SI was activated follwoing a passive movement, but area 3b in SI was activated following electrical or mechanical stimulation.VEFWe used pattern-reversal black and white checker board stimulation to record VEF,mainly to investigate the activated areas in the primary visual cortex (VI) to various visual fields stimulation. At first, we used a half and quadrant field stimulation and confirmed that the retinotopy corresponded to the separation of activated areas in VI.This finding was consistent with a so-called "cruciform model". Next, we recorded VEF following central and peripheral field stimulation. VEF to the central field stimulation was mainly located in the crown of the occipital lobe. It is difficult for VEF to record activities in such areas. In contrast, VEF to the peripheral field stimulation was clearly recorded with a large amplitude. We recorded VEF to the aparent motion, and found activities around the crossing point of the ascending branch of the inferior temporal sulcul and lateral occipital sulcus, being considered to be V5/MT area. This was the first reort to identify V5/MT in humans. Less