Mechanisms of change in the evolution of jargon aphasia

Abstract

Background: The evolution of jargon aphasia may reflect recovery in the speech production processes. Alternatively or additionally there may be improved self-monitoring, enabling the person to suppress jargon errors. Previous case reports offer evidence for both mechanisms of change, and suggest that they can co-occur. Aims: This longitudinal study aimed to uncover mechanisms of change in an individual with jargon aphasia. Four predictions of production processing recovery were examined against test data. The study also looked for evidence of improved error awareness, in both test and connected speech data, and explored the relationship between this improvement and the production gains. Methods & Procedures: The participant (TK) undertook tests of single word naming, reading and repetition eight times over a 21-month period, with matched sets of nouns and verbs. Analyses of correct responses and errors were conducted, in order to test predictions of processing recovery. Changes in self-monitoring behaviours were also investigated, to uncover evidence of increased error awareness. Finally, longitudinal changes in samples of connected speech were explored. Outcomes & Results: Two predictions of production processing recovery were upheld: there was a significant increase in the number of correct responses over time, and a significant decrease in the proportion of nonword errors. The error analysis also revealed a trend towards increased target-relatedness and decreased perseveration, but neither was significant. There was an increase in self-monitoring behaviours during testing, in that there were more null responses and attempted self-corrections. This increase correlated very strongly with the production gains. Connected speech showed little evidence of improved production, since the range of vocabulary employed by TK reduced as time progressed. However, self-monitoring behaviours were increasingly evident in this context. Conclusions: The origin of the production and monitoring gains experienced by TK are discussed. Implications are drawn out for further research.