Age-Dependent Effects of Catechol- O -Methyltransferase ( COMT ) Gene Val 158 Met Polymorphism on Language Function in Developing Children

<span class="paragraphSection"><div class="boxTitle">Abstract</div>The genetic basis controlling language development remains elusive. Previous studies of the catechol-<span style="font-style:italic;">O</span>-methyltransferase (COMT) Val¹⁵⁸Met genotype and cognition have focused on prefrontally guided executive functions involving dopamine. However, <span style="font-style:italic;">COMT</span> may further influence posterior cortical regions implicated in language perception. We investigated whether <span style="font-style:italic;">COMT</span> influences language ability and cortical language processing involving the posterior language regions in 246 children aged 6–10 years. We assessed language ability using a language test and cortical responses recorded during language processing using a word repetition task and functional near-infrared spectroscopy. The <span style="font-style:italic;">COMT</span> genotype had significant effects on language performance and processing. Importantly, Met carriers outperformed Val homozygotes in language ability during the early elementary school years (6–8 years), whereas Val homozygotes exhibited significant language development during the later elementary school years. Both genotype groups exhibited equal language performance at approximately 10 years of age. Val homozygotes exhibited significantly less cortical activation compared with Met carriers during word processing, particularly at older ages. These findings regarding dopamine transmission efficacy may be explained by a hypothetical inverted U-shaped curve. Our findings indicate that the effects of the <span style="font-style:italic;">COMT</span> genotype on language ability and cortical language processing may change in a narrow age window of 6–10 years.</span>

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