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Abstract

This study investigates the spoken word and non-word production of two individuals, RS and TK, who both presented with neologistic jargon aphasia (a form of fluent aphasia characterised by the presence of non-words). Trials of naming, reading and repetition of sets of nouns and verbs were carried out over a year, and different features of their production were investigated in further detail.

For both participants, naming was severely impaired, while reading and repetition appeared to benefit from non-semantic sources of activation. Evidence was found that word errors were genuine lexical retrievals and that there was a continuum of target relatedness in word and non-word errors. In both cases, a relationship was found between perseverative responses within individual trials and over-represented phonemes across different trials and tasks. These are argued to be default phonemes, readily available as gap-fills in the event of reduced activation at the phonemic level. The constant availability of a limited pool of phonemic material to help form the basis of an error phoneme string could explain lengthy intervals between perseverative responses. The perseveration of whole words or non-words is argued to arise from the phonemic level, with strings of phonemes which happen to correspond to words being reinforced by feedback to the lexical level and therefore more likely to recur than non-word strings.

TK demonstrated an inverse frequency effect in repetition. This is hypothesised to arise from the use of relatively unimpaired sub-lexical processing for low frequency words. A similar explanation is invoked for his superior performance on verbs over nouns in repetition.

RS also demonstrated interesting word class effects, with a superior performance on verbs over nouns in naming, argued to be due to additional syntactic activation. Meanwhile, he demonstrated an inferior performance on verbs in reading and repetition, argued to be due to a difficulty with processing the inflectional affix on the verb stimuli.

Finally, a longitudinal study of TK revealed an improved performance in terms of correct responses, as well as changes in the error patterns.

It is argued that these features can be accommodated within a model with feedback from the phonemic to the lexical level. Future investigations are also discussed.

Publication Type:	Thesis (Doctoral)
Subjects:	R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
Departments:	School of Health & Psychological Sciences > Language & Communication Science School of Health & Psychological Sciences > School of Health & Psychological Sciences Doctoral Theses Doctoral Theses

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