ORIGIN OF HUMAN MOTOR READINESS FIELD LINKED TO LEFT MIDDLE FRONTAL GYRUS BY MEG AND PET

Combined magnetoencephalography and positron emission tomography ident ified a prior source of activity in the left middle frontal gyrus dupi ng uncued movements of the right index finger Voluntary movements gave rise to a change in the cortical electrical potential known as the Be reitschaftspotential or Readiness Potential, recorded as early as 1500 ms before the onset of movement. The Readiness Field is the magnetic field counterpart to the Bereitschaftspotential. In the present study, magnetoencephalography identified four successively active sources of fluctuation in the Readiness Field in the period from 900 ms before, to 100 ms after; the onset of the movement. The first source to be act ive was registered between 900 and 200 ms prior to the onset of the mo vement. This source of initial activity was mapped by positron emissio n tomography to the middle frontal gyrus, Brodmann area 9. The three s ources subsequently to be active were mapped to the supplementary moto r area, premotor cortex, and motor cortex (M1), all in the left hemisp here. (C) 1998 Academic Press.