IntroductionContinuous theta-burst stimulation (cTBS) has been used as an effective tool in inducing inhibitory aftereffect within a short time periods in the motor cortex; this has been demonstrated in the language network to a limited degree with controversial effect. In this study, we aimed to delineate the offline effect of cTBS-induced changes to the left posterior inferior frontal gyrus (pIFG) in healthy subjects using functional magnetic resonance imaging (fMRI).MethodsTwenty healthy, normal subjects (mean age: 30.84 years) were recruited. They all were right-handed and had no contra-indications for fMRI or cTBS. They were randomly assigned into the treatment group or the sham control group.ResultsANOVA showed that cTBS had a significant main effect only when the sham treatment was subtracted from the real stimulation in left superior temporal, left inferior frontal gyrus, thalamus, and right insular cortex (uncorrected p < 0.002). The subjects' post-cTBS condition differed significantly from their pre-cTBS condition in the left pIFG (uncorrected p < 0.002). There were interactions in the pIFG, bilateral superior parietal lobules, left superior temporal, left supramarginal, and left cuneus areas. The application of cTBS induced increased BOLD signals in language-related networks by stimulating the left pIFG (BA 44). This implies that inhibiting the pIFG led to increased use of language network resources.ConclusionThis study demonstrated cTBS-induced changes in the language network caused by stimulation of the left pIFG. Based on these findings, future studies on the therapeutic effects of cTBS on the right Broca's homolog area are warranted.
The catechol-O-methyltransferase (COMT) gene has been noted to play an important role in individual variations in the aging process. We investigated whether COMT polymorphism could influence cognition related to white matter networks. More specifically, we examined whether methionine (Met) allele loading is associated with better individual cognitive performance. Thirtyfour healthy elderly participants were recruited; each participant's COMT genotype was determined, and Korean version of Montreal Cognitive Assessment scores and a diffusion tensor image were obtained for all participants. The Met carrier group showed significantly lower mean diffusivity, axial diffusivity, and radial diffusivity values for the right hippocampus, thalamus, uncinate fasciculus, and left caudate nucleus than the valine homozygote group. The Met carrier group also scored higher for executive function and attention on the Korean version of Montreal Cognitive Assessment. Based on these results, we can assume that the COMT Met allele has a protective effect on cognitive decline contributing to individual differences in cognitive function in late life period. Abbreviations: AD = axial diffusivity, CN = caudate nucleus, COMT = catechol-O-methyltransferase, DA = dopamine, DLPFC = dorsolateral prefrontal cortex, DNA = Deoxyribonucleic Acid, DTI = diffusion tensor image, FA = fractional anisotropy, FSL = FMRIB Software Library, HC = hippocampus, IFOF = inferior fronto-occipital fasciculus, MCI = mild cognitive impairment, MD = mean diffusivity, Met = methionine, MMSE = mini-mental status examination, MoCA-K = Korean version of Montreal Cognitive Assessment, MRI = magnetic resonance imaging, PFC = prefrontal cortex, RD = radial diffusivity, ROIs = region of interests, TE = echo time, TM = thalamus, TR = repetition time, UF = uncinate fasciculus, Val = valine, VLPFC = ventrolateral prefrontal cortex.
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