Magnetoencephalographic study on cerebral cortical activities related to speech

Human motor speech function has been investigated neuropsychologically [1]. Recently by using non-invasive techniques measuring regional cerebral blood flows such as the functional magnetic resonance imaging (fMRI) [3] and the positron emission tomography (PET) [5], it was demonstrated that several cortical areas not only in the dominant hemisphere but also in the non-dominant hemisphere were activated during speech tasks. As these methods, however, have poor time resolution, it is difficult to get temporal information of the cortical activities. The magnetoencephalography (MEG) is suitable for investigating the temporal sequence of the activation of cortical areas on speech, since MEG has good temporal and spatial resolution. The present study is a trial to identify functionally the motor speech center in the frontal lobe of human cerebral cortex by using multichannel SQUID gradiometers. Parts of the results have been reported shortly [8].