Left Perisylvian Cortex Damage Selectively Impairs Pseudoword Spelling.
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1
Johns Hopkins University, United States
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2
University of North Carolina at Greensboro, United States
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 33 individuals with post-stroke, chronic dysgraphia (age range 36-80; 15 female). Word and pseudoword spelling data was entered into linear mixed effects models to obtain beta estimates for frequency effects, pseudoword spelling, and length effects in each participant. These served as estimates of damage severity to the orthographic lexical, sublexical, and working memory systems respectively. To account for any variability in phonological input processing, regressors included a minimal pair pseudoword discrimination (PALPA 1; Kay et al., 1992). For 7 of the 33 individuals a PALPA1 score was imputed using a nonparametric random forest procedure (Stekhoven & Bühlman, 2011).
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 selectively associated with PGC, 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: pseudoword spelling ability. We simultaneously accounted for other covariates such as frequency effect, length effect, lesion volume, spelling severity, age, digit span, 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 that extended from the anterior supramarginal gyrus, pre/post-central gyri, insula, and dorsal IFG.
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 impaired PGC in spelling were restricted to damage dorsal to the Sylvian fissure.
Acknowledgements
The multi-site, NIDCD-supported project examining the neurobiology of language recovery in aphasia (DC006740).
References
DeMarco, Andrew T., and Peter E. Turkeltaub. 2018. “A Multivariate Lesion Symptom Mapping Toolbox and Examination of Lesion-Volume Biases and Correction Methods in Lesion-Symptom Mapping.” Human Brain Mapping 39 (11): 4169–82.
Goodman, R A, and A Caramazza. 1985. “The Johns Hopkins University Dysgraphia Battery.” The Johns Hopkins University, Baltimore, MD.
Kay, J., Coltheart, M., & Lesser, R. (1992). Psychololinguistic Assessments of Language Processing in Aphasia (PALPA). Hove, East Sussex: Lawrence Erlbaum.
Henry, M L, P M Beeson, A J Stark, and S Z Rapcsak. 2007. “The Role of Left Perisylvian Cortical Regions in Spelling.” Brain Lang 100 (1): 44–52.
Nachev, Parashkev, Elizabeth Coulthard, H. Rolf Jäger, Christopher Kennard, and Masud Husain. 2008. “Enantiomorphic Normalization of Focally Lesioned Brains.” Neuroimage 39 (3–3): 1215–26.
Stekhoven, D. J., & Bühlmann, P. (2011). MissForest—non-parametric missing value imputation for mixed-type data. Bioinformatics, 28(1), 112-118.
Thomspon, C.K. & Weintraub, S. (2014) Northwestern Naming Battery, Northwestern University.
Keywords:
spelling,
Lesion overlap,
Phoneme-Grapheme conversion,
pseudoword spelling,
written language,
dysgraphia,
lesion symptom mapping,
SVR-LSM,
Perisylvian,
Post-stroke aphasia,
orthography,
Nonword spelling
Conference:
Academy of Aphasia 57th Annual Meeting, Macau, Macao, SAR China, 27 Oct - 29 Oct, 2019.
Presentation Type:
Poster presentation
Topic:
Not eligible for student award
Citation:
Rapp
B,
Shea
J,
Petrozzino
G,
Wiley
R and
Purcell
J
(2019). Left Perisylvian Cortex Damage Selectively Impairs Pseudoword Spelling..
Front. Hum. Neurosci.
Conference Abstract:
Academy of Aphasia 57th Annual Meeting.
doi: 10.3389/conf.fnhum.2019.01.00039
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Received:
06 May 2019;
Published Online:
09 Oct 2019.
*
Correspondence:
Dr. Brenda Rapp, Johns Hopkins University, Baltimore, Maryland, 21218, United States, brapp1@jhu.edu