[Insights into brain function though magnetic source imaging: A review of research and clinical applications]

The paper presents a brief outline of the rationale behind the use of non invasive functional imaging and of the features that any imaging technique should display in order to make a substantial contribution to the search of the brain mechanisms responsible for cognitive functions. One such technique, magnetic source imaging (MSI), that meets these specifications, is described in more detail. Advantages of MSI include the capacity to provide direct measures of regional neurophysiological activity, a millisecond range temporal resolution, and the capacity to provide images of brain activity on an individual basis. We then describe applications of MSI to the study of brain mechanisms involved in various language functions such as oral comprehension and reading. Among these applications, the accuracy of MSI protocols in determining hemispheric dominance for language functions and in identifying the precise location and extent language specific cortex (Wernicke s area) has been verified through comparison with standard invasive techniques (Wada procedure and electrocortical stimulation mapping) in over 60 consecutive cases. In another series of studies we combined data from MSI and direct cortical stimulation to determine the role of temporoparietal areas in phonological analysis of spoken language and in phonological decoding of print. Finally, we have used MSI to gain unique insights into the brain mechanisms that support reading in developmental reading disability.

Results from over 21 children diagnosed with this disorder suggest that impaired reading is associated with aberrant functional connections between temporal and temporoparietal areas of the left hemisphere that are normally engaged in reading.