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Poster C36, Thursday, November 9, 10:00 – 11:15 am, Harborview and Loch Raven Ballrooms

Selective involvement of posterior perisylvian regions in sublexical processing: Evidence from brain tumor patients

Fleur van Ierschot1,2,3, Wencke Veenstra3,4, Barbara Santini5, Michiel Wagemakers4, Hanne-Rinck Jeltema4, Giampietro Pinna5, Roelien Bastiaanse1,3, Gabriele Miceli1,2;1International Doctorate for Experimental Approached to Language and Brain (IDEALAB), 2University of Trento, 3University of Groningen, 4University Medical Center of Groningen, 5University of Verona

Introduction: Sublexical phoneme-grapheme conversion processes have been associated with left perisylvian regions. Functional neuroimaging studies have shown increased BOLD activity in the posterior superior temporal gyrus during non-word spelling in healthy controls (Ludersdorfer, Kronbichler, & Wimmer, 2015). In lesion studies, isolated damage to anterior (inferior frontal gyrus, precentral gyrus and insula) and posterior perisylvian regions (superior temporal gyrus and supramarginal gyrus) resulted in the inability to write novel words and non-words (e.g., Henry, Beeson, Stark, & Rapcsak, 2007; Mariën, Pickut, Engelborghs, Martin, & De Deyn, 2001). In addition, studies pointed at a distributed perisylvian network including both anterior and posterior regions as a critical neural substrate for sublexical processing (Rapcsak et al., 2009). However, most lesion studies are based on stroke patients with extensive brain damage. We investigate the functional roles of anterior and posterior perisylvian regions in brain tumor patients. Methods: Seven patients with a glioma in anterior or posterior perisylvian regions were included; 3 had an anterior glioma and 4 a posterior glioma. All patients were assessed in their native language with an extensive written language test battery specifically designed for neurocognitive assessment in gliomas, including word writing (controlled for length, frequency, grammatical class, morphology, orthography and imageability) and non-word writing (controlled for length and similarity to words). For each version (Italian and Dutch), normative data were obtained from 50 non brain-damaged individuals to calculate cut-off scores at 95%. Individual performance on writing tasks was evaluated as being above or below cut-off. Results on word vs non-word writing were contrasted using Fisher’s Exact Test. Results: None of the patients with anterior perisylvian gliomas (0/3) scored below cut-off on non-word writing. Performance accuracy on word and non-word writing was comparable in all cases (p= 1, p= 1, p= 1, two-tailed Fisher’s Exact Test). In posterior perisylvian glioma patients, non-word writing was below cut-off in 3/4 cases (75.0%). Non-word writing was significantly worse than word writing in 2/4 patients (50.0%) and marginally worse in 1/4 cases (25.0%) with posterior gliomas (p=.022, p=.039, p=.055, p=.564, two-tailed Fisher’s Exact Test). Conclusion: A clear difference between patients with gliomas in posterior and anterior regions was observed. Data are relevant to the ongoing debate on the involvement of specific perisylvian regions in sublexical processing. Selective impairments in phoneme-grapheme conversion processes were frequently found following posterior perisylvian damage, while non-word writing was preserved in anterior gliomas. The results, albeit from a small sample, support the hypothesis that posterior perisylvian regions are crucial for phoneme-grapheme conversion. Anterior regions may play a more indirect role, via their subcortical connections with posterior regions. Damage to the arcuate fasciculus and/or to the superficial layer of the inferior fronto-occipital fasciculus may disrupt interactions between posterior and anterior perisylvian areas. In patients with anterior lesions, impaired non-word writing may result from subcortical damage that prevents interaction within an anterior-posterior perisylvian network, rather than from isolated damage to anterior perisylvian structures.

Topic Area: Writing and Spelling

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