Poster B44, Tuesday, August 20, 2019, 3:15 – 5:00 pm, Restaurant Hall
Morphological sensitivity is associated with ventral white matter pathways across orthographies
Maya Yablonski1, Michal Ben-Shachar1;1Bar Ilan University
Morphological information is an important factor in lexical access, a process which is hypothesized to rely on the ventral stream (Rastle, 2018). In line with this view, we recently showed that sensitivity to morphological information in adult English readers is associated with the ventral reading pathways, bilaterally (Yablonski et al., 2018). It remains unclear, however, whether this association generalizes across languages with different orthographies and morphological systems. To investigate this question, we assessed neurocognitive correlations between white matter properties and morphological sensitivity in Hebrew, a Semitic language where morphemes are interleaved, not concatenated. Morphological sensitivity was operationalized using the Morpheme Interference Effect (MIE, e.g., Crepaldi et al., 2010), a robust measure that may be quantified reliably at the single subject level. In the Hebrew version of the MIE (Yablonski & Ben-Shachar, 2016), participants perform a lexical decision task on pseudowords that contain either real or invented root morphemes. Participants with enhanced sensitivity to morphological information may slow down or respond erroneously in response to real-root pseudowords. Morphological sensitivity is therefore defined for each participant as the difference in performance on real root vs. invented root pseudowords, divided by their overall performance. Based on our prior findings in English, we hypothesized that morphological sensitivity in Hebrew relies primarily on the ventral reading pathways, bilaterally. Accordingly, we targeted the inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF) and uncinate fasciculus (UF). As a control, we further analyzed two dorsal pathways: the long and anterior segments of the arcuate fasciculus. Forty-five adult native Hebrew-speakers (29 females, 20-35y) completed the morpheme interference paradigm as part of an extensive behavioral battery, and underwent a diffusion MRI scan (Siemens 3T scanner, 64 diffusion directions at b=1000 s/mm2 and 3 volumes at b=0; isotropic voxel size: 1.7*1.7*1.7mm3). Tracts of interest were identified bilaterally in each participant’s native space, using deterministic tractography and automatic tract segmentation (Yeatman et al., 2012). Fractional anisotropy (FA) and mean diffusivity (MD) profiles were calculated along each tract, and Spearman’s correlations were calculated between these profiles and morphological sensitivity. Our results show significant correlations between morphological sensitivity (accuracy) and FA of the left IFOF, as well as MD of the left ILF (r = -0.376 and r = 0.382, respectively). In addition, morphological sensitivity (RT) correlated with FA of the right UF (r = 0.463). These correlations are significant after correcting for multiple comparisons within a tract by controlling the familywise error at p<0.05, and controlling the false discovery rate (FDR) across tracts at a level of q< 0.05. We followed-up on these effects by calculating partial correlations that controlled for timed measures of word and nonword reading. These partial correlations remained significant, suggesting some level of cognitive specificity. In sum, implicit morphological sensitivity for Hebrew written words is associated with structural properties of the bilateral ventral tracts, in striking similarity to our findings in English. Our results support the view that morphological information contributes to lexical access along the bilateral ventral pathways, across orthographies and morphological systems.
Themes: Morphology, Reading
Method: White Matter Imaging (dMRI, DSI, DKI)