| Case studies of primary progressive aphasia (PPA) provide a unique opportunity to learn about brain-behaviour relationships because of the slow and circumscribed nature of the disease process. This thesis is based on the case study of a patient (NL) with non-fluent PPA who presents with what is claimed to be a subtle variation of phonological dyslexia. A combined assessment approach utilizing standardized neuropsychological tests and cognitive neuropsychological experiments is presented. Experiments motivated by the dual-route model (Coltheart, Rastle, Perry, Langdon, & Zeigler, 2001) were designed to test NL's reading ability. Experiments motivated by the model of Baddeley and Hitch (1974) were designed to test NL's working memory ability. It is claimed that NL's phonological dyslexia is attributable to a reduction in attentional resources available from the central executive component of working memory. Converging evidence from healthy control participants is presented. Namely, a selective nonword reading deficit similar to NL was emulated in healthy controls by reducing attentional resources utilizing a dual-task paradigm. Based on NL's pattern of performance, and the performance of healthy controls reading aloud under conditions of full attention and reduced attention, it is concluded that a disruption to the central executive can result in phonological dyslexia. |
