Abstract
Children with ADHD have impairment in recognition of angry expression, although they recognizes happy expressions accurately (e.g., Pelc et al., 2006). Also, atypical pattern of brain activity to facial expressions have been reported in ADHD. ADHD children showed brain activation for happy expression but not for angry expression, whereas typical developing children showed brain activity for both expressions (Ichikawa et al., 2014). However, little is known about neural basis of impaired recognition of facial expressions in ADHD. Therefore, we further explored processing of facial expressions in ADHD children using near-infrared spectroscopy. We compared hemodynamic responses in ADHD children when observing happy and angry expressions before and after methylphenidate (MPH) administration. MPH increases synaptic transmission by inhibiting reuptake of dopamine, and consequently improves not only cerebral processing but also cognitive performance (e.g., Monden et al., 2012). Considering that MPH administration improved recognition of angry expression (Williams et al., 2008), we predicted that activation in brain areas involved in recognition of angry expressions increased after MPH administration. As a result, we found that compared to baseline, right inferior temporal cortex (IT) showed increased brain activity to angry expression after MPH administration but not before MPH administration, whereas showed brain activation to happy expression regardless of MPH administration. The left IT showed no significant activation to angry expression before and after MPH administration. However, we found significant difference in brain activity to angry expression between before and after MPH administration. In sum, we revealed increased hemodynamic responses in right IT to angry expression after MPH administration, suggesting that this region is involved in impaired recognition of angry expressions in ADHD children. Additionally, our finding that left IT showed significant difference in hemodynamic responses to angry expressions between before and after MPH administration implies that an alternative processing of angry expression may be driven.
Acknowledgement: This work was supported in part by JST-RISTEX to ID, and Grant-in-Aid for Scientific Research on Innovative Areas No. 17H06343