Interleaved transcranial magnetic stimulation and fMRI suggests that lamotrigine and valproic acid have different effects on corticolimbic activity.
Author(s): Li X, Ricci R, Large CH, Anderson B, Nahas Z, Bohning DE, George MS
Affiliation(s): Brain Stimulation Laboratory, Department of Psychiatry, Medical University of South Carolina, 502N, 67 President St, Charleston, SC 29425, USA. lixi@musc.edu
Publication date & source: 2010-04, Psychopharmacology (Berl)., 209(3):233-44. Epub 2010 Mar 2.
Publication type: Comparative Study; Randomized Controlled Trial; Research Support, Non-U.S. Gov't
RATIONALE: Combined transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) can be used to study anticonvulsant drugs. A previous study showed that lamotrigine (LTG) inhibited brain activation induced when TMS was applied over motor cortex, whereas it increased activation induced by TMS applied over prefrontal cortex. OBJECTIVES: The present double-blind, placebo-controlled, crossover study in 30 healthy subjects again combined TMS and fMRI to test whether the effects seen previously with LTG would be confirmed and to compare these with a second anticonvulsant drug, valproic acid (VPA). RESULTS: Statistical parametric mapping analysis showed that both LTG and VPA, compared to placebo, inhibited TMS-induced activation of the motor cortex. In contrast, when TMS was applied over prefrontal cortex, LTG increased the activation of limbic regions, confirming previous results; VPA had no effect. CONCLUSION: We conclude that LTG and VPA have similar inhibitory effects on motor circuits, but differing effects on the prefrontal corticolimbic system. The study demonstrates that a combination of TMS and fMRI techniques may be useful in the study of the effects of neuroactive drugs on specific brain circuits.
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