Search Abstracts | Symposia | Slide Sessions | Poster Sessions
Transcranial photobiomodulation over the left prefrontal cortex facilitates orthography-phonology rule learning
Poster Session F, Friday, October 2, 2:45 - 4:45 pm, Wangari Maathai
Mingchuan Yang1, Rujun Duan1, Gangyi Feng1; 1The Chinese University of Hong Kong
Learning to read a new writing system requires learners to discover systematic mappings between visual forms and phonological units. This process is especially challenging when the mapping is rule-governed but not transparent, as in logographic systems where visual radicals and lexical tone jointly determine category membership. Such learning requires learners to identify relevant dimensions, maintain candidate rules, use feedback to revise hypotheses, and gradually form stable orthography-phonology associative representations. Because these operations depend strongly on prefrontal control mechanisms, enhancing prefrontal function may facilitate the acquisition of novel mapping rules. Transcranial photobiomodulation (tPBM), a non-invasive neuromodulation technique using near-infrared light, may support this process by improving prefrontal metabolic efficiency and strengthening the neural dynamics that enable rule-guided learning. Here, we tested whether left-prefrontal tPBM facilitates the formation of novel orthography-phonology representations. Thirty adults were randomly assigned to active or sham stimulation. Before learning, the active group received 16 min of 1064-nm tPBM over the left prefrontal cortex at 150 mW/cm², whereas the sham group received placebo stimulation. Participants then completed a feedback-guided orthography-phonology category-learning task while EEG signals were recorded. They learned artificial logographic characters paired with level or falling tones. Category membership was defined by a two-dimensional radical-by-tone rule, requiring learners to integrate visual and phonological cues using trial-by-trial feedback. We assessed emerging category representations using stimulus-locked EEG representational similarity analysis and examined early feedback processing using feedback-locked ERPs. Active tPBM strengthened neural category representations during late learning. In the active group, a significant category representation emerged between 816 and 949 ms after stimulus onset (p = 0.016, cluster-based permutation test), whereas no reliable category representation was observed in the sham group. A direct group comparison confirmed stronger late-learning category coding after active than after sham stimulation between 818 and 910 ms (p = 0.018, cluster-based permutation test). Critically, active tPBM also enhanced the feedback-locked posterior P1 during early learning [t(28) = 2.951, p = 0.006, Cohen’s d = 1.080], suggesting stronger attentional encoding of feedback signals. Across participants, larger early P1 responses predicted stronger category representations (r = 0.401, p = 0.028), linking early feedback processing to the subsequent formation of orthography-phonology category structure. These findings suggest that left-prefrontal tPBM facilitates orthography-phonology learning by enhancing the neural processes through which learners use feedback to build new mapping representations. Beyond acting only on category coding, tPBM appears to strengthen early feedback-guided attentional processing, which supports the later emergence of structured orthography-phonology representations. More broadly, this study provides preliminary neural evidence that non-invasive neuromodulation can scaffold a core component of language learning, namely the discovery and representation of new rules linking written forms to their phonological units.
Topic Areas: Language Development/Acquisition, Phonology