Slide Slam I12
Sulcal morphology in ventral temporal cortex and the development of reading skills
Florence Bouhali1, Jessica Dubois2,3, Kevin S. Weiner4, Fumiko Hoeft1,5,6; 1University of California San Francisco, 2University of Paris, NeuroDiderot, INSERM, Paris, France, 3UNIACT, NeuroSpin, CEA; Paris-Saclay University, France, 4University of California Berkeley, 5University of Connecticut, 6Haskins Laboratories
Literacy learning builds onto neural and cognitive architectures that are partially in place by the age children start literacy instruction. Many cognitive factors have been reported to predispose a child to acquire adequate reading skills, such as phonological awareness and rapid naming abilities. At the neural level, previous research shows that nearby anatomical locations in left ventral temporal cortex (VTC) are associated with reading. The occipito-temporal sulcus (OTS) notably hosts a cortical region that processes visual words, and its morphology predicts reading skills in 10-year-old children and adults (Borst et al., 2016; Cachia et al., 2018). A functional region in the mid-fusiform gyrus on the other hand, seems to process graphemes, critical for phonological decoding (Bouhali et al., 2019). However, none of these studies considered the morphological role of the mid-fusiform sulcus (MFS), recently shown to be a critical microstructural and functional landmark in VTC (Grill-Spector and Weiner, 2014). Here, we tested the direct hypotheses that (i) the structure of the left OTS would be prospectively associated with reading skills at early stages of literacy acquisition, and (ii) left MFS and OTS morphology would show a double dissociation consistent with their respective functional roles in orthographic processing; the MFS would be more related with phonemic decoding skills, while the OTS would better predict lexical reading skills. In order to test these hypotheses, we studied the associations between OTS and MFS morphology and the development of reading skills in a cohort of 50 children followed longitudinally from age 5, at the onset of literacy instruction, to age 8, when children are expected to have become fluent readers. Specifically, we identified the OTS and MFS at both ages in each child. We then investigated the relationship between reading (timed pseudo-word and real word reading), and several morphological features of bilateral OTS and MFS (number of sulcal interruptions, sulcal length, mean sulcal depth and cortical thickness). Consistent with our first hypothesis, we found that overall reading skills at age 8 were reliably associated with cortical thickness of the left OTS measured both at ages 5 and 8, when controlling for reading-related cognitive skills and standard control variables. Other sulcal properties did not show such reliable associations. With regard to our second hypothesis, we observed that pseudo-word reading scores at 8 were indeed associated with lower mean sulcal depth of the left MFS both at ages 5 and 8, over and above word reading and other cognitive precursors of reading. However, we did not observe a stronger association of OTS morphology with real word reading than with pseudo-word reading, maybe owing to the limited reliance on lexical reading strategies in 8-year-old readers. This work furthers our understanding of the interactions between early- and late-developing features of sulcal morphology of the VTC and the early development of reading skills during childhood.