| This study examined lexical access in adolescents and adults with cerebral palsy and severe speech and physical impairment (CP/SSPI) who have limited language production due to severe dysarthria or anarthria. Deficits in language comprehension and in phonological knowledge have been well documented (Beukelman & Mirenda, 2005; Binger & Light, 2008). Although many individuals with CP/SSPI perceive segmental differences, investigations of whether impaired speech production interferes with sound awareness and language development have led to contradictory findings (Card & Dodd, 2006; Dahlgren Sandberg & Hjelmquist, 1997; Foley & Pollatsek, 1999; Vandervelden & Siegel, 1999).;The motor theory of speech perception (Liberman & Mattingly, 1985) postulated that articulatory gestures are the basis for speech perception. Similarly, subvocal rehearsal (Bishop, Byers Brown, & Robson, 1990), assumed to underlie phonological working memory and aspects lexical development, requires articulatory coding. To date, however, the impact of a severe speech production deficit on lexical activation and the organization of the mental lexicon has not been investigated. Such an investigation may reveal limitations in lexical access that also play a role in language deficits that support or refute these views of an articulatory basis of speech perception and lexical development and access.;Investigations of spoken word recognition in children and adults using the visual world eye tracking paradigm have characterized this process as a cascading flow of information, whereby partial phonological representations activate semantic representations, This suggests a reciprocal influence between impoverished semantic and phonological representations that may explain the language impairment observed in CP/SSPI (Smith, 2001), where less efficient phonological processing might impact the ability to activate semantic associates. Thus, a weakness at one level of processing can influence another.;Moreover, children are less efficient than adults at eliminating competitors and resolving ambiguity (Huang & Snedeker, 2010; Sekerina & Brooks, 2007). If spoken word recognition is also less efficient for individuals with CP/SSPI, this may be attributed either to their speech production limitations or, more generally, to their delayed language development. The hypothesis of this study is that spoken word recognition will be severely reduced or absent in this population although individual differences in speech production and vocabulary comprehension may result in variations. The visual world eye tracking paradigm has been widely used to study activation in spoken word recognition, but has not been used with this population.;Method. Sixteen 15 to 50-year-olds with CP/SSPI participated. The experiment examined how these listeners resolve phonological or semantic competition among referents for a spoken word as it unfolds over time. In each trial, they saw four images, while listening to a spoken word as their eye movements were monitored. Each trial consisted of an auditory target word (e.g., tire), and four pictures including a picture corresponding to the target word, a phonological competitor (e.g., TIRE), or a semantic competitor (TIE/SHIRT) and two images that were phonologically and semantically unrelated to the target. In the phonological condition, listeners typically fixate more on pictures that are phonologically related than on unrelated images. In the semantic condition, listeners typically fixate on pictures that are semantically related more than unrelated images. Fixations to the target should be greater than to the three other images. An additional semantic onset competitor condition included a picture that was semantically related to an absent phonological competitor of the target (e.g., the target is TIRE and the competitor is a picture of a SHIRT related to absent TIE).;Because there was no single appropriate control group for the subjects, eye gaze patterns were compared to published data as well as to a group of eight age-matched adults with no neurological impairment (NNI). The participants were also compared to children with typical development (6;8 to 12;4 years-of-age, M = 8;9, SD = 1.97) from a previous study using the same stimuli and experimental design.;Results. Participants with CP/SSPI revealed significant fixations to targets and to phonological onset competitors but not to semantic relatives beyond those directed to unrelated pictures. In contrast, the adults with NNI rapidly fixated on the target picture, did not demonstrate significant fixations to phonological competitors and demonstrated marginally significant proportion of fixations to semantic relatives. Children with TD demonstrated significant phonological and semantic competition effects. None of the three groups demonstrated activation of semantic onset competitors. The time plots of gaze behavior revealed that adults did quickly fixate on phonological and semantic competitors, but then veryquickly fixated on the target, while the participants with CP/SSPI and higher PPVT-4 scores exhibited eye gaze patterns more similar to adults while those with lower scores were less efficient at resolving this competition. (Abstract shortened by ProQuest.). |
