The lexical or sub-lexical locus of facilitation by phonemic cueing in aphasic speakers: the effect of onset cohort size

Abstract

ABSTRACTBackground: While the facilitation of word production by phonological cueing is used in clinical practice to evaluate the integrity of the lexical representations in anomia, the mechanisms by which phonological cueing facilitates oral production remain poorly understood. Most interpretations in psycholinguistic studies favor the phonological (sub-lexical) hypothesis, whereas results from studies on aphasia report evidence suggesting a lexical locus.Aims: This study aims to directly test the impact of phonological cues on lexical retrieval in participants with aphasia by manipulating the size of the cohort of nouns sharing the onset provided by the cue.Methods & Procedure: Fourteen aphasic participants presenting either a lexico-semantic or a phonological anomic profile performed a noun/object picture-naming task preceded by congruent or incongruent phonological cues. We manipulated the size of the lexical cohort of the words starting with the cue, reasoning that if phonological cues facilitate at the lexical level, a cue corresponding to a small number of words should be more effective than a cue compatible with a larger cohort.Outcomes & Results: The cue only improved accuracy in participants with lexico-semantic impairment, with a reduction of errors as a function of the cohort size (facilitation restricted to cues associated with a small onset cohort). In contrast, the cue onset cohort size only affects production latencies in participants with phonological impairment (shorter latencies for cues related to a small noun-onset cohort size).Conclusions: The observed effect of the cohort size associated with the cue favors a lexical locus of facilitation by phonological cueing. The fact that this effect is observed in different groups corresponding to different underlying impairments in error and in latencies suggests that the analyses of latencies reflect spared processes, whereas the analyses of errors tap into the impaired process.