Independent Component Analysis of the Effect of L-dopa on fMRI of Language Processing

Department of Statistics, The Ohio State University, Columbus, Ohio, United States of America.
PLoS ONE (Impact Factor: 3.23). 08/2010; 5(8):e11933. DOI: 10.1371/journal.pone.0011933
Source: PubMed


L-dopa, which is a precursor for dopamine, acts to amplify strong signals, and dampen weak signals as suggested by previous studies. The effect of L-dopa has been demonstrated in language studies, suggesting restriction of the semantic network. In this study, we aimed to examine the effect of L-dopa on language processing with fMRI using Independent Component Analysis (ICA). Two types of language tasks (phonological and semantic categorization tasks) were tested under two drug conditions (placebo and L-dopa) in 16 healthy subjects. Probabilistic ICA (PICA), part of FSL, was implemented to generate Independent Components (IC) for each subject for the four conditions and the ICs were classified into task-relevant source groups by a correlation threshold criterion. Our key findings include: (i) The highly task-relevant brain regions including the Left Inferior Frontal Gyrus (LIFG), Left Fusiform Gyrus (LFUS), Left Parietal lobe (LPAR) and Superior Temporal Gyrus (STG) were activated with both L-dopa and placebo for both tasks, and (ii) as compared to placebo, L-dopa was associated with increased activity in posterior regions, including the superior temporal area (BA 22), and decreased activity in the thalamus (pulvinar) and inferior frontal gyrus (BA 11/47) for both tasks. These results raise the possibility that L-dopa may exert an indirect effect on posterior regions mediated by the thalamus (pulvinar).

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    • "By using a data driven analysis method the temporal influence of the pharmaceutical agent on different brain regions can be observed and in this manner the functional connectivity between these regions can be deduced. This method has been applied in studies investigating, among others, the effects of the DA agonist L-dopa on a language task (Kim et al., 2010) and of the DA D 2 antagonist olanzapine on the resting-state BOLD signal (Sambataro et al., 2010). However, ICA has to our knowledge not been used before to analyze ASL data. "
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