S7-2. Facilitation effect on language function by transcranial direct current stimulation (tDCS)

Abstract

Our previous neuroimaging studies suggested that the left inferior frontal cortex (LIFC) is involved in the comprehension of ambiguous and vague language (Ihara et al., 2007). On the basis on the studies, we conducted two tDCS experiments to test a hypothesis that language comprehension is facilitated when the excitability of the LIFC is enhanced. In Experiment 1, we investigated the tDCS effect on behavioral indices obtained when the subjects performed a semantic judgment task in a semantic priming paradigm (Ihara et al., 2016). The stimuli were word pairs in which the targets were either ambiguous or unambiguous words, and these were either semantically related or unrelated to the primes. The reaction time was shorter in the anodal tDCS session than in the sham session for ambiguous words. In the Experiment 2, we investigated the tDCS effect on behavioral indices obtained when the subjects recognize visually degraded words. The recognition rates for the words with degradation levels of 55% were increased by the anodal tDCS. The results of the two experiments support our hypothesis that processing of language comprehension is improved when the excitability of the LIFC is enhanced.