Distributed source modeling of language with magnetoencephalography: application to patients with intractable epilepsy.
OBJECTIVE
To examine distributed patterns of language processing in healthy controls and patients with epilepsy using magnetoencephalography (MEG), and to evaluate the concordance between laterality of distributed MEG sources and language laterality as determined by the intracarotid amobarbital procedure (IAP).


METHODS
MEG was performed in 10 healthy controls using an anatomically constrained, noise-normalized distributed source solution (dynamic statistical parametric map, dSPM). Distributed source modeling of language was then applied to eight patients with intractable epilepsy. Average source strengths within temporoparietal and frontal lobe regions of interest (ROIs) were calculated, and the laterality of activity within ROIs during discrete time windows was compared to results from the IAP.


RESULTS
In healthy controls, dSPM revealed activity in visual cortex bilaterally from approximately 80 to 120 ms in response to novel words and sensory control stimuli (i.e., false fonts). Activity then spread to fusiform cortex approximately 160-200 ms, and was dominated by left hemisphere activity in response to novel words. From approximately 240 to 450 ms, novel words produced activity that was left-lateralized in frontal and temporal lobe regions, including anterior and inferior temporal, temporal pole, and pars opercularis, as well as bilaterally in posterior superior temporal cortex. Analysis of patient data with dSPM demonstrated that from 350 to 450 ms, laterality of temporoparietal sources agreed with the IAP 75% of the time, whereas laterality of frontal MEG sources agreed with the IAP in all eight patients.


CONCLUSIONS
Our results reveal that dSPM can unveil the timing and spatial extent of language processes in patients with epilepsy and may enhance knowledge of language lateralization and localization for use in preoperative planning.
McDonald
Carrie R
CR
Department of Psychiatry, University of California, San Diego, California, USA. camcdonald@ucsd.edu
Thesen
Thomas
T
Hagler
Donald J
DJ
Carlson
Chad
C
Devinksy
Orrin
O
Kuzniecky
Rubin
R
Barr
William
W
Gharapetian
Lusineh
L
Trongnetrpunya
Amy
A
Dale
Anders M
AM
Halgren
Eric
E
D000328:Adult; D000654:Amobarbital / Q000008:administration & dosage / Q000494:pharmacology; D001931:Brain Mapping / Q000379:methods; D002540:Cerebral Cortex / Q000502:physiology / Q000503:physiopathology* / Q000601:surgery; D004827:Epilepsy / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D005625:Frontal Lobe; D007839:Functional Laterality / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007600:Judgment / Q000187:drug effects / Q000502:physiology; D007802:Language; D007807:Language Tests; D015225:Magnetoencephalography / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D010296:Parietal Lobe / Q000502:physiology / Q000503:physiopathology / Q000601:surgery; D011300:Preoperative Care; D011597:Psychomotor Performance / Q000187:drug effects / Q000502:physiology; D012660:Semantics; D013702:Temporal Lobe / Q000502:physiology / Q000503:physiopathology; D014705:Verbal Behavior / Q000187:drug effects / Q000502:physiology
D000654:Amobarbital