Repetition conduction aphasia: cognitive or linguistic disorder?

1. Repetition conduction aphasia: cognitive or linguistic disorder? • Anon Great Student, 2010 • The University of Texas at Dallas

2. Project summary Conduction aphasia is an acquired neurogenic disorder which can be classified into subtypes, including reproduction and repetition. While the reproduction subtype is posited to be caused by a deficit in phonological planning, as evidenced by phonemic paraphasias during repetition, the repetition subtype is believed to be largely the result of a deficit in auditory-verbal working memory. The overwhelmingly cognitive bias of the second claim suggests the possibility that repetition conduction aphasia may actually result from a cognitive, not linguistic, deficit. This study proposes to investigate the involvement of the visual and auditory working memory systems, both verbally and nonverbally, in subjects with conduction aphasia by comparing them with normal controls. Criteria for subject selection will include a single lesion to the temporal lobe for the repetition conduction aphasia group and no previous history of brain damage or neurological disorder for the control group. In addition, subjects with aphasia must meet previously established criteria for repetition conduction aphasia. A between-subjects, single-blind group design will compare the two groups of 10 subjects each on the four tasks (auditory-verbal, auditory-nonverbal, visual-verbal, and visual-nonverbal). The pattern of deficits observed in this study will provide additional information on the nature of the deficits observed in repetition conduction aphasia so that appropriate treatments can be more easily explored.

3. Background and significance • Wernicke/Lichtheim/Geschwind model • Reproduction vs. Repetition subtypes • Differences in deficit pattern for pts with supra- and infrasylvian lesions (Axer et al., 2001) • Reproduction type appears to be language deficit • phonological planning deficit (Saito et al., 2003; Laganaro et al., 2008; Sidiropoulos et al., 2008) • Repetition subtype posited to be working memory deficit • remember gist, not verbatim (Baldo et al., 2008) • limitation in working memory leading to deficits in phonological reactivation (Friedmann & Gvion, 2003; 2007) • unstable phonological representation (Saito et al., 2003)

4. Background and significance • Memory deficits associated with temporal lobe lesions • herpes encephalitis- medial temporal lobe (Naude & Pretorius, 2003) • CBD- L superior temporal gyrus (Kimura et al., 2008) • crossed conduction aphasia- involvement of portions of R temporal lobe (Bartha et al., 2003) • dysgraphia in conduction aphasia- L temporoparietal area (Balasubramanian, 2004) • All working memory? Or just auditory-verbal? • visual working memory involvement with affected R MTL (Naude & Pretorius, 2003) • different types of working memory (Friedmann & Gvion, 2003) • different repetition abilities in pts with temporal vs. supramarginal or angular gyrus lesions and either conduction aphasia or working memory deficit (Sakurai et al., 1998) • Cognitive therapy for pts with aphasia? • memory (Koenig-Bruhim & Eichenberger, 2007) • attention (Murray et al., 2006)

5. Contemplated method of approach to the problem • Between-subjects, single blind group design • 2 groups (repetition conduction aphasia, controls) of 10 subjects each • Aphasia pt criteria: • single lesion in temporal lobe (results of acute MRI) • meet qualifications of conduction aphasia per BDAE • 2-5 years post acute CVA • Other subject criteria: • no (other) past history of neurological injuries/disorders • right handed • not color-blind, visual function WFL • must be competent in computer usage 5

6. Contemplated method of approach to the problem • 4 repetition tasks presented via computer • auditory-verbal (auditorily presented word, verbal repetition) • auditory-nonverbal (auditorily presented melody, vocal repetition) • visual-verbal (visually presented word, verbal repetition) • visual-nonverbal (visually presented light pattern, motoric response required for repetition of pattern) • Presentation of tasks randomized to control for ordering effects • Response correctness recorded for each subject • each subject’s file saved by research assistant and coded with a number, for blinding

7. Main questions to be investigated • Do the repetition deficits observed in repetition conduction aphasia result from a deficit in working memory related to language, or from a deficit in auditory working memory?

8. Specific predictions • Subjects with conduction aphasia will perform better with visually presented material, verbal or nonverbal, when compared with auditorily presented material • Controls will exhibit similar performance across all four tasks

9. Experimental problems • Influence of R MTL on auditory working memory • use masking for L ear during presentation of stimuli • Rehearsal of written material may still occur in auditory modality • use masking in both ears during presentation of written words • Subjects who are tone deaf • but, should be balanced between experimental and control groups • Subjects in this age group may have higher education than average if able to use computer, so results may not be generalizable to all pts

10. Ethical aspects • Minimal risk posed to pts • No treatment involved- no question about morality of withholding treatment • Payment for participation in study will be low enough to prevent perception of compulsory participation