Search Abstracts | Symposia | Slide Sessions | Poster Sessions
Fixation-related N400s reveal distinct mechanisms of lexical access and contextual integration across ADHD subtypes during natural reading
Poster Session B, Wednesday, September 30, 4:30 - 6:30 pm, Wangari Maathai
Pei-Chun Chao1, Jou-An Chung1,2, Jie-Li Tsai3, Chia-Ying Lee1,2,3,4; 1Academia Sinica, Taipei, Taiwan, 2National Central University, Taoyuan, Taiwan, 3Chengchi University, Taipei, Taiwan, 4Kaohsiung Medical University, Kaohsiung, Taiwan
Reading comprehension relies on both bottom-up word recognition and top-down prediction. These processes are supported by executive functions, including working memory, inhibition, and attentional shifting, which enable readers to maintain and update textual information, suppress irrelevant input, and allocate attention flexibly during reading. Executive dysfunction is a core feature of Attention-Deficit/Hyperactivity Disorder (ADHD). Consequently, individuals with ADHD often experience persistent difficulties with reading comprehension, recall, and reading efficiency throughout adulthood. Previous research has shown that word frequency and predictability modulate the N400, reflecting lexical access and contextual integration during reading comprehension. This study aims to examine how adults with ADHD engage these mechanisms during natural reading using simultaneous eye movement and fixation-related potential (EMFRP) recordings. Participants included 47 adults in the control group, 29 adults with combined-type ADHD (ADHD-C), and 20 adults with inattentive-type ADHD (ADHD-I). Participants completed a Digit Span task, recalling auditorily presented digit sequences in ascending order. Both ADHD groups performed worse on these assessments than controls, with no subtype differences, suggesting executive dysfunction in ADHD. EMFRP data were collected as participants read 2,504 words across 22 traditional Chinese articles. Word frequency (WF) was indexed as log-transformed occurrences per million from the Academia Sinica Corpus of Contemporary Taiwan Mandarin, and word predictability (WP) was obtained via a cloze task completed by 32 readers. Linear mixed-effects models (LMMs) were applied to eye movement measures and single-trial FRPs to examine the effects of WF and WP on lexical retrieval and contextual integration during reading. Compared with controls, the ADHD-C group showed lower accuracy and faster response times on comprehension questions following each passage, suggesting shallower processing during reading. Eye movement data showed that the control group had longer first-fixation and gaze durations for low-frequency or low-predictability words, whereas both ADHD groups showed only WF effects, not WP effects. Regarding the FRP data, the control group revealed the WP main effect and its interaction with WF (WF*WP) on centroparietal N400 amplitudes (375–475 ms), with reduced N400 amplitudes for low-frequency words in highly predictable contexts. In contrast, the ADHD-C group showed only a WF effect over frontal regions, whereas the ADHD-I group exhibited minimal effects of WF, WP, and their interaction. Furthermore, the WF*WP effect in the control group was negatively correlated with digit span performance, whereas in the ADHD-I group it was positively correlated. These findings suggest distinct cognitive mechanisms underlying reading comprehension across groups. Control readers relied more on contextual cues to facilitate word processing, indicating more automatic and efficient semantic integration during reading. In contrast, ADHD-C readers had difficulty integrating contextual cues despite relatively intact word decoding abilities. For the ADHD-I group, successful contextual integration may depend on preserved executive function. Overall, group differences in the interaction between frequency and predictability on the N400 may serve as neurocognitive markers for distinguishing ADHD-related reading difficulties.
Topic Areas: Reading, Disorders: Developmental