We performed functional MRI (FMRI) in 22 consecutive epilepsy
patients undergoing intracarotid amobarbital (Wada) testing and
compared language lateralization measures obtained with the two
procedures. FMRI used a single-word semantic decision task previously
shown to activate lateralized language areas in normal
adults. Correlation between the two tests was highly significant (r =
0.96; 95% CIs 0.90 to 0.98; p < 0.0001). These results validate the
FMRI technique and suggest that "active" areas observed with this
semantic processing task correspond to those underlying hemispheric
dominance for language. This strong correlation observed supports the
view that language lateralization is a continuous rather than a
dichotomous variable. In addition to lateralization information, FMRI
consistently demonstrated focal regions of activity in lateral frontal
and temporo-parieto-occipital cortex. These functional maps may be
helpful in defining the boundaries of surgical excisions.