Brain and Language 105 (2008) 185–198 www.elsevier.com/locate/b&l
Spoken-word processing in aphasia: Eﬀects of item overlap and item repetition
Utrecht Institute of Linguistics OTS, Utrecht University, Janskerkhof 13, 3512 BL Utrecht, The Netherlands Accepted 16 October 2007 Available online 19 November 2007
Abstract Two studieswere carried out to investigate the eﬀects of presentation of primes showing partial (word-initial) or full overlap on processing of spoken target words. The ﬁrst study investigated whether time compression would interfere with lexical processing so as to elicit aphasic-like performance in non-brain-damaged subjects. The second study was designed to compare eﬀects of item overlap and itemrepetition in aphasic patients of diﬀerent diagnostic types. Time compression did not interfere with lexical deactivation for the non-brain-damaged subjects. Furthermore, all aphasic patients showed immediate inhibition of co-activated candidates. These combined results show that deactivation is a fast process. Repetition eﬀects, however, seem to arise only at the longer term in aphasic patients.Importantly, poor performance on diagnostic verbal STM tasks was shown to be related to lexical decision performance in both overlap and repetition conditions, which suggests a common underlying deﬁcit. Ó 2007 Elsevier Inc. All rights reserved.
Keywords: Spoken-word processing; Aphasia; Inhibition; Lexical activation; Priming; Lexical deactivation; Repetition priming
1. Introduction During auditoryword recognition, lexical word candidates compete for recognition and inﬂuence each other’s activation levels. Evidence for lateral inhibition between competing word candidates comes from interference eﬀects found with high-similarity word-initial form-overlap between a prime (e.g., diﬃcult) and a following target (e.g., diﬃdent; cf. Monsell & Hirsh, 1998; Slowiaczek & Hamburger, 1992). When theprime is being processed, several word candidates compete. In the TRACE (McClelland & Elman, 1986) model of auditory word recognition, there are direct inhibitory connections between words. An increase in the level of activation of one candidate then automatically leads to a decrease in the activation level of others. McClelland and Elman (1986) claim that this ‘winner-takes-all’ principle makes therecognition process more
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eﬃcient. Once one of the candidates has been isolated and recognised, the other candidates are decreased in activation.When one of these once-activated candidates is subsequently presented as the next item, recognition of this item is inhibited, relative to unrelated (control) targets. Monsell and Hirsh (1998) describe the competitor interference eﬀect (i.e., slower lexical decision responses to diﬃdent if preceded by diﬃcult than if preceded by an unrelated control word) and the facilitatory eﬀect of repetition(faster lexical decision responses to diﬃdent if preceded by diﬃdent than if preceded by an unrelated control word) as two sides of the same coin: recognition of a word makes it easier to recognise on the next encounter, but at the cost of making similar words (i.e, onset-overlapping words) more diﬃcult to recognise. Whereas theories as TRACE describe the competition process as ‘‘lateral’’inhibition between several lexical candidates, others have argued for bottom-up inhibition: if there is a mismatch between the input form and the lexical entry’s form, activation of that candidate is lowered (Marslen-Wilson, Moss, & van Halen, 1996; Marslen-Wilson &
E. Janse / Brain and Language 105 (2008) 185–198
Warren, 1994). The extent to which activation is lowered may be gradient:...