Although the availability of MEG is still limited across epilepsy surgery centers, this study method may be substituted for the Wada procedure in assessing hemispheric dominance for language in select cases.

Intervention-related changes in spatiotemporal profiles of regional brain activation were examined by whole-head magnetoencephalography in 15 children with severe reading difficulties who had failed to show adequate progress to quality reading instruction during Grade 1. Intensive intervention initially focused on phonological decoding skills (for 8 weeks) and, during the subsequent 8 weeks, on rapid word recognition ability. Clinically significant improvement in reading skills was noted in 8 children who showed "normalizing" changes in their spatiotemporal profiles of regional brain activity (increased duration of activity in the left temporoparietal region and a shift in the relative timing of activity in temporoparietal and inferior frontal regions). Seven children who demonstrated "compensatory" changes in brain activity (increased duration of activity in the right temporoparietal region and frontal areas, bilaterally) did not show adequate response to intervention. Nonimpaired readers did not show systematic changes in brain activity across visits.

No abstract

Phonological and semantic aspects of language were examined in patients with unilateral temporal lobe epilepsy (TLE) and healthy controls using functional MRI. We expected to replicate previous findings in healthy individuals showing relatively greater activation in frontal regions for phonological compared with semantic processing, and greater activation in temporal regions for semantic compared with phonological processing. We hypothesized that differences between patients with left TLE and healthy controls would be found in the pattern of left temporal cortical activation associated specifically with semantic processing. Patients with right TLE were included as a seizure control group. All TLE patients previously showed left hemisphere language dominance on intracarotid sodium amytal studies. Greater blood oxygen level dependent activation was found during phonological processing compared with semantic processing in frontal regions for healthy participants but, contrary to expectation, semantic processing did not lead to increased temporal lobe activity relative to phonological processing. Furthermore, no differences between left temporal patients and controls were found specifically in left temporal cortex. Rather, patients with left temporal seizure foci showed significantly greater left dorsolateral prefrontal activity compared with controls, as well as increased signal change in left inferior frontal and right middle temporal gyrus. Surprisingly, patients with right, but not left, TLE showed poorer performance on the linguistic tasks compared with controls, as well as a decrease in right superior temporal activation. The results converge with studies of dyslexic patients showing increased left frontal activity in the presence of left temporal dysfunction and are suggestive of both inter- and intra-hemispheric functional reorganization of language representation in left TLE.

This longitudinal study examined the development of the brain mechanism involved in phonological decoding in beginning readers using magnetic source imaging. Kindergarten students were assigned to 2 groups: those who showed mastery of skills that are important predictors of proficient reading (low-risk group) and those who initially did not show mastery but later benefited from systematic reading instruction and developed average-range reading skills at the end of Grade 1 (high-risk responders). Spatiotemporal profiles of brain activity were obtained during performance of letter-sound and pseudoword naming tasks before and after Grade 1 instruction. With few exceptions, low-risk children showed early development of brain activation profiles that are typical of older skilled readers. Provided that temporoparietal and visual association areas were recruited into the brain mechanism that supported reading, the majority of high-risk responder children benefited from systematic reading instruction and developed adequate reading abilities.