Poster A41, Saturday, March 24, 1:30–3:30 pm, Exhibit Hall C
Phase synchronization in the brain’s functional reading network during letter processing supports the development of word reading in elementary school children
Erin White1,2, Candace Nayman1, Benjamin Dunkley1,3,4, Zahra Emami1, Anne Keller1,2, Taufik Valiante2,4,5, Elizabeth Pang1,2,3,4; 1Sick Kids Research Institute, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, 686 Bay Street, Toronto, Ontario, Canada, M5G 0A4, 2Epilespy Research Program of the Ontario Brain Institute, 438 University Ave., #1618, Toronto, Ontario, Canada, M5G 2K8, 3The Hospital for Sick Children, 555 University Ave., Toronto, Ontario, Canada, M5G 1X8, 4University of Toronto, Toronto, Ontario, Canada, M5T 1W7, 5Krembil Research Institute, University Health Network and Toronto Western Hospital, 399 Bathurst St., Toronto, Ontario, Canada, M5T 2S8
Learning to read builds networks in the brain. Here we show developmental changes in functional connectivity (phase synchrony of EEG oscillations) during one aspect of reading: letter recognition. Nineteen adults (21-36 years; 10 female) and 24 children (4-14 years; 10 female) viewed consonant and unfamiliar symbol strings in a 1-back memory task, while wearing a 64-channel EEG cap. Global connectivity strength (mean phase lag index over all EEG sensors) measured network-processing costs, over time and for different canonical frequency bands. Adults showed increased connectivity for symbols 100-230 ms from stimulus onset in gamma band (30-80 Hz; p<0.05), due to connections among right occipital, left frontal/central sensors (i.e., right homologue of the visual word-form area and left frontal aspects of the reading network). This effect was not significant for children. Instead, children showed increased connectivity for letters in theta (3-7 Hz) band between 750-1000 ms (p<0.05). This was due to left occipital-frontal connections for experienced readers (grade 4-8; n=12), but right occipital-vertex connections for novice readers (grades JK-3; n=12), suggesting a developmental increase in reliance on the left visual word-form area during letter processing. Additionally, novice readers exhibited less connectivity for letters in beta (15-30 Hz) band between 650-935 ms (p<0.05), again due to right occipital vertex connections. This effect was not significant in experienced readers. Across all children, beta connectivity strength was negatively correlated with reading skill (r = -0.65). Functional connectivity may provide a new metric to quantify developmental changes, and letter competency, in the brain’s reading network.
Topic Area: LANGUAGE: Development & aging