Functional Neuroimaging Studies in Humans

National Institute On Deafness And Other Communication Disorders

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Abstract

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, EEG, MEG and other brain mapping techniques are used to characterize phenotypic presentation, pathophysiology and treatment of communication disorders. PET scans are performed on the GE Advance and Scanditronix PC2048-15B tomographs using the H215O and C-11 Raclopride methods. Data are analyzed using Statistical Parametric Mapping software and newer covariance techniques developed in the section. Structural and functional MRI studies are performed on GE 1.5 and 3.0 Tesla instruments. Functional images are acquired using spiral, echoplanar imaging and arterial spin-tagging methods. Data are analyzed using MEDx, AFNI, and SPM software and newer covariance techniques developed in the Section. High density EEG studies are conducted using a Neuroscan 64 channel system and analyzed using BESA, Neuroscan and Brain Voyager packages. MEG data are collected on a 275 channel CTF instrument. A series of combined hemodynamic and electrophysiological studies of language in normal volunteers demonstrated unique task related patterns of brain activity for reading, naming, and semantic processing that will serve as a baseline when these paradigms are used to study language recovery in post-stroke aphasia. An arterial spin tagging fMRI study demonstrated the feasibility of studying continuous speech with this method (not possible with standard fMRI techniques because of artifact production) that will be useful in studying recovery of syntactic abilities in aphasics as well. Structural MRI studies evaluating relationships between aphasic symptoms and lesion location have been completed, with over 40 patients studied thus far. Functional MRI studies of confrontational naming in 20 aphasic patients have demonstrated unique patterns of activity in perilesional and contralesional cortical regions associated with correct and incorrect (paraphasic) responses and dissociable patterns of activity associated with production of nouns and verbs. MEG studies of syntactic comprehension in control subject have demonstrated differential activation associated with comprehension of simple and complex syntactic constructions. These methods will now be applied in clinical studies evaluating recovery of agrammatic aphasic patients. PET studies in deaf subjects using American Sign Language demonstrated modality independent features of language processing, strongly lateralized to the left hemisphere regardless of the hand used in signing. Other PET studies demonstrated unique patterns of brain activity for production of voice in humans. PET studies also demonstrated differences in the processing of language, melody and rhythm by deaf cochlear implant recipients. fMRI studies have demonstrated unique patterns of brain activity in trained musicians processing rhythmic stimuli. A number of additional studies in which fMRI and electrophysiological methods are combined to study language processing in controls and aphasic are being prepared for publication.