Functional hemispheric asymmetry assessment in a visual language task using MEG.
We used magnetoencephalography (MEG) to assess the degree of hemispheric activation in eleven normal, right-handed subjects with no history of neurological disorder or learning disability during performance of a word- and a face-recognition tasks. Neuromagnetic activity was recorded using a whole-head system, and the sources of the recorded magnetic fields were modeled as single equivalent current dipoles. Early (<200 msec) cerebral activation, defined by the number of dipoles identified by the data-fitting algorithm, was localized in the occipital cortex during both tasks, as expected. During the language task, the extent of the later (>200 msec) cerebral activation was approximately double in the left hemisphere in almost all subjects, involving temporal and temporoparietal areas. In contrast, during the face-recognition task, the corresponding activation was mostly symmetrical across the two occipital lobes, also involving the posterior-inferior aspect of the right temporal lobe. Our results suggest that the MEG is a suitable method of assessing noninvasively hemispheric specialization for language.
Zouridakis
G
G
Department of Neurosurgery, University of Texas-Houston Medical School, 77030, USA. zouridakis@uth.tmc.edu
Simos
P G
PG
Breier
J I
JI
Papanicolaou
A C
AC
D000328:Adult; D000465:Algorithms; D001931:Brain Mapping / Q000379:methods*; D005069:Evaluation Studies as Topic; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007802:Language; D015225:Magnetoencephalography; D008297:Male; D011939:Mental Recall / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*