The effect of lexical deficits on narrative disturbances in fluent aphasia

Abstract

Background: The label “fluent aphasia” applies to different aphasic syndromes characterised by fluent speech with difficulties in lexical retrieval and/or grammatical processing.Aims: This study aims at investigating microlinguistic and macrolinguistic skills in persons with fluent aphasia. We hypothesised that their lexical and syntactic (i.e., microlinguistic) difficulties would affect also their narrative (i.e., macrolinguistic) skills.Methods & Procedures: Growing evidence shows that traditional tests may not be sensitive enough to capture the patterns of the linguistic impairments observed in these persons. Therefore, we used a narrative task to elicit linguistic samples. Spontaneous speech was elicited through a picture description task. The narrative samples were analysed with a multilevel approach that allows clinicians to quantify their productivity levels as well as their lexical, grammatical, and narrative skills. The spontaneous speech produced by a group of 20 persons with fluent aphasia was compared to that of a group of 20 healthy participants. All participants with aphasia were in the phase of neurological stability. The two groups were matched for age and level of formal education.Outcomes & Results: Results showed that the lexical impairment observed in the group of participants with fluent aphasia hampered the ability to produce well-formed sentences that, in turn, lowered the levels of cohesion of their narrative samples. Furthermore, the reduced levels of lexical informativeness were found correlated also to the production of errors of global coherence.Conclusions: These findings support the hypothesis that in these patients, microlinguistic difficulties might affect macrolinguistic processing. Furthermore, these results stress the importance of a multilevel approach to assess linguistic skills in patients with fluent aphasia, as it assesses both microlinguistic and macrolinguistic dimensions in parallel. Therefore, it allows linguists, psychologists, and clinicians to observe how the linguistic levels interact during natural language processing.