Journal Article

Semantic access dysphasia resulting from left temporal lobe tumours

Fabio Campanella, Massimo Mondani, Miran Skrap and Tim Shallice

in Brain

Published on behalf of The Guarantors of Brain

Volume 132, issue 1, pages 87-102
Published in print January 2009 | ISSN: 0006-8950
Published online December 2008 | e-ISSN: 1460-2156 | DOI: http://dx.doi.org/10.1093/brain/awn302

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Unlike semantic degradation disorders, the mechanisms and the anatomical underpinnings of semantic access disorders are still unclear. We report the results of a case series study on the effects of temporal lobe gliomas on semantic access abilities of a group of 20 patients. Patients were tested 1–2 days before and 4–6 days after the removal of the tumour. Their semantic access skills were assessed with two spoken word-to-picture matching tasks, which aimed to separately control for rate of presentation, consistency and serial position effects (Experiment 1) and for word frequency and semantic distance effects (Experiment 2). These variables have been held to be critical in characterizing access in contrast to degraded-store semantic deficits, with access deficits characterized by inconsistency of response, better performance with slower presentation rates and with semantically distant stimuli, in the absence of frequency effects. Degradation deficits show the opposite pattern. Our results showed that low-grade slowly growing tumours tend not to produce signs of access problems. However, high-grade tumours especially within the left hemisphere consistently produce strong semantic deficits of a clear access type: response inconsistency and strong semantic distance effects in the absence of word frequency effects were detected. However, effects of presentation rate and serial position were very weak, suggesting non-refractory behaviour in the tumour patients tested. This evidence, together with the results of lesion overlapping, suggests the presence of a type of non-refractory semantic access deficit. We suggest that this deficit could be caused by the disconnection of posterior temporal lexical input areas from semantic system.

Keywords: semantic access; brain tumours; refractoriness; dysphasia; temporal lobes

Journal Article.  11177 words.  Illustrated.

Subjects: Neurology ; Neuroscience

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