Interleaved transcranial magnetic stimulation and fMRI suggests that lamotrigine and valproic acid have different effects on corticolimbic activity.
BACKGROUND
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.


OBJECTIVE
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.


CONCLUSIONS
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.
Li
Xingbao
X
Brain Stimulation Laboratory, Department of Psychiatry, Medical University of South Carolina, 502N, 67 President St, Charleston, SC 29425, USA. lixi@musc.edu
Ricci
Raffaella
R
Large
Charles H
CH
Anderson
Berry
B
Nahas
Ziad
Z
Bohning
Daryl E
DE
George
Mark S
MS
D000293:Adolescent; D000328:Adult; D000927:Anticonvulsants / Q000494:pharmacology*; D001931:Brain Mapping / Q000379:methods; D002540:Cerebral Cortex / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D000077213:Lamotrigine; D008032:Limbic System / Q000187:drug effects* / Q000502:physiology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D014227:Triazines / Q000494:pharmacology*; D014635:Valproic Acid / Q000494:pharmacology*
D000927:Anticonvulsants; D014227:Triazines; D014635:Valproic Acid; D000077213:Lamotrigine