Magnetoencephalographic mapping of the language-specific cortex

Object. In this paper the authors introduce a novel use of magnetoencephalo graphy (MEG) for noninvasive mapping of language-specific cortex in individ ual patients and in healthy volunteers. Methods. The authors describe a ser ies of six experiments in which normative MEG data were collected and the r eliability, validity, and topographical accuracy of the data were assessed in patients who had also undergone the Wada procedure or language mapping t hrough intraoperative cortical stimulation. Conclusions. Findings include: 1) receptive language-specific areas can be reliably activated by simple language tasks and this activation can be read ily recorded in short MEG sessions; 2) MEG-derived maps of each individual are reliable because they remain stable over time and are independent of wh ether auditory or visual stimuli are used to activate the brain; and 3) the se maps are also valid because they concur with results of the Wada procedu re in assessing hemispheric dominance for language and with the results of cortical stimulation in identifying the precise topography of receptive lan guage regions within the dominant hemisphere. Although the MEG mapping technique should be further refined it has been sh own to be efficacious by correctly identifying the language-dominant hemisp here and specific language-related regions within this hemisphere. Further development of the technique may render it a valuable adjunct for routine p resurgical planning in many patients who harbor tumors or have epilepsy.