Functional imaging techniques are being used to characterize brain activation patterns in normal subjects and individuals with neurological disorders affecting human communication. Brain activation patterns characterized using PET, fMRI or other brain mapping techniques may be used to characterize phenotypic presentation and neurological consequences of communication disorders. PET scans are performed on the GE Advance and Scanditronix PC2048-15B tomographs using the H215O method. Data are analyzed using Statistical Parametric Mapping software and newer covariance techniques developed in the section. fMRI studies are performed on 1.5 and 3.0 Tesla instruments. Functional images are acquired using spiral, echoplanar imaging and spin-tagging methods. Data are analyzed using MEDx, IDL, and SPM software and newer covariance techniques developed in the Section. PET studies of narrative production in subjects fluent in English and ASL revealed common activations in a widespread array of regions and suggest a novel model for lateralization of cerebral activity during the generation of discourse. This pattern is not predicted by the standard Wernicke-Geschwind model, and may become apparent when language is produced in an ecologically valid contex (Brain, 124: 2028-44, 2001). Additonal studies in a bilingual individual with childhood brain damage showed evidence of increased right hemisphere activity compared to normal controls during spontaneous generation of narrative in both English and ASL, suggesting the possibility that plasticity, unmasking of neural pathways, and or other adaptations of language function in the right hemisphere may have occurred (Neuropsychologia 39:114-121, 2001). A functional MRI study of cross-categorical picture and word processing provided data suggesting that the left occipitotemporal and right temporal cortices are part of a neural network mediating picture-word conversions, whereas the frontal cortex functions as a central executive coordinating these transformations (Human Brain Mapping, In Press). Previous functional MRI studies in deaf and hearing individuals demonstrated similar left hemisphere, but distinct right hemisphere, recruitment for English and American Sign Language (PNAS, 95: 922-929, 1998; Neuroreport 9:1537-42, 1998). A morphometric analysis of the non-human primate brain revealed the presence of a similar morphology and pattern of left hemisphere predominance of the planum temporale in the temporal lobe of chimpanzees. Planum temporale cortical surface area was 20% larger on the left hemisphere in 10 of 11 chimpanzee brains. In humans, the left planum temporale is a key component of Wernicke's cortical language area, suggesting that chimpanzees may use this asymmetric cortical region for species-specific inter-individual communicatio (Science, 279: 220-222, 1998). PET studies in individuals with developmental stuttering demonstrated hemispheric lateralization patterns that differed from those observed in control subjects, providing a model for the pathophysiology of this disorder (Brain, 120: 761-784, 1997). A number of studies are being prepared for publication: PET studies in patients with spasmodic dysphonia demonstrate altered patterns of activity in motor and premotor cortices and basal ganglia that suggest a pathyophysiological model for motor dysfunction in this disorder. Functional MRI studies at 1.5 Tesla have revealed unique patterns of cerebral activity associated with text comprehension, discrete phases of verbal working memory and modification of central auditory processing by attention. PET studies of language processing reveal unique lateralization patterns in familial and non-familial left handers. Studies of CNS plasticity using PET and fMRI methods are underway in deaf subjects following cochlear implantation, in Parkinson's Disease patients undergoing deep brain stimulation, and in patients with post-stroke aphasia during recovery of language function.
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