ANATOMICAL CONGRUENCE OF METABOLIC AND ELECTROMAGNETIC ACTIVATION SIGNALS DURING A SELF-PACED MOTOR TASK - A COMBINED PET-MEG STUDY

We have investigated the degree of spatial correlation between the cer ebral blood flow variations measured by positron emission tomography ( PET) and the electromagnetic sources as measured by magnetoencephalogr aphy (MEG) in five subjects while performing a self-paced right index finger tapping task. Data were processed independently for each techni que using both single-case and intersubject analysis. PET and MEG were coregistered with anatomical magnetic resonance images for each subje ct. Both extension and flexion motor-related fields were extracted fro m the MEG signal. Using the single dipole model we identified the moto r evoked field 1 (MEF1) in all subjects and the motor field (MF) in th ree subjects. Individual and intersubject averaged PET data showed con sistent contralateral primary sensorimotor (PSM) hand area and bilater al supplementary motor area activation. MEG individual and intersubjec t averaged results demonstrated that both MEF1 and MF dipoles were loc alized within the PSM PET activated area. Individual PSM mass center t o dipole distance was 12 and 15.3 mm on average for the MEF1 and the M F component, respectively. For the same components, the intersubject a veraged analysis shows distances between the PET Z-score maximum and t he dipole locations of 6.3 and 15.0 mm, respectively. These results sh ow that PET and MEG MEF1 activation signals spatially coincide within instrumental, registration, and modeling errors, (C) 1998 Academic Pre ss.