Poster D78, Wednesday, August 21, 2019, 5:15 – 7:00 pm, Restaurant Hall
Left Perisylvian Cortex Damage Selectively Impairs Pseudoword Spelling.
Brenda Rapp1, Jennifer Shea1, Gianni Petrozzino1, Robert Wiley1, Jeremy J. Purcell1;1Johns Hopkins University
Introduction. Spelling involves retrieving orthographic knowledge from orthographic long-term memory (OLTM) or computing phoneme-to-grapheme correspondences (PGC), and then processing the letter information via orthographic working memory (OWM) prior to producing a written or oral spelling response. Although recent work has used lesion symptom mapping to identify regions associated with OLTM in the inferior frontal gyrus and ventral occipitotemporal cortex and with OWM in the left parietal cortex (Rapp et al., 2015), this work did not test for regions uniquely associated with PGC. In this study, we address this knowledge gap by using a recently refined multivariate lesion-symptom mapping technique (DeMarco and Turkeltaub 2018) to examine the brain basis of PGC, while simultaneously accounting for impairments in either OLTM or OWM (or both). Methods. Participants were 19 individuals with post-stroke, chronic dysgraphia (age range 45-80; 8 female). The JHU Dysgraphia battery (Goodman and Caramazza, 1985) was used to measure pseudoword spelling, length effects (i.e. worse spelling for long vs short words) and frequency effects (i.e. worse spelling for low vs high frequency words). Linear mixed effects models were used to obtain beta estimates for the severity of impairment in pseudoword spelling, frequency effects, and length effects in each participant. These served as estimates of damage severity to the PGC, OWM, and OLTM systems respectively. Although no participant had abnormal auditory word comprehension, to account for any variability in phonological input processing, we also included measures of auditory comprehension (NNB; Thompson & Weintraub, 2014) and minimal pair pseudoword discrimination (PALPA1; Kay et al., 1992). Each participant had a T1-weighted MRI scan and MRIcron was used to draw each lesion. Enantiomorphic normalization to standard MNI space was carried out using SPM12 (Nachev et al. 2008). To identify brain regions associated with PGC while accounting for OLTM and OWM deficits, we used support vector regression lesion-symptom mapping (SVR-LSM; DeMarco and Turkeltaub, 2018). This approach estimated the relationship between the lesion status of all voxels simultaneously and the independent variable of pseudoword spelling ability. Further, the analysis accounted for other variables such as frequency effect, length effect, lesion volume, spelling severity, age, NNB and PALPA1. Label scrambling permutation testing was used to evaluate chance (corrected threshold of 0.05). Results. Severity of impairment in PGC was associated with damage to left perisylvian regions including the pre/post central gyri, insula, and anterior superior temporal gyrus. Discussion. Using a multivariate lesion symptom mapping technique, we determined that portions of the left perisylvian cortex are associated with the severity of PGC impairment. These findings fit with previous literature reporting that impairments in PGC in spelling - along with phonological input deficits - were associated with damage to left perisylvian cortex (Henry et al. 2007). We extend this work by demonstrating that damage to the left perisylvian cortex selectively impaired PGC in spelling independent of auditory comprehension deficits.
Themes: Writing and Spelling, Disorders: Acquired
Method: Other