Wendy L. Arnott

Semantic priming in Parkinson's disease : Evidence for delayed spreading activation

Nineteen persons with Parkinsons disease (PD) and 19 matched control participants completed a battery of online lexical decision tasks designed to isolate the automatic and attentional aspects of semantic activation within the semantic priming paradigm. Results highlighted key processing abnormalities in PD. Specifically, persons with PD exhibited a delayed time course of semantic activation. In addition, results suggest that experimental participants were unable to implicitly process prime information and, therefore, failed to engage strategic processing mechanisms in response to manipulations of the relatedness proportion. Results are discussed in terms of the Gain/Decay hypothesis (Milberg, McGlinchey-Berroth, Duncan, Higgins, 1999) and the dopaminergic modulation of signal to noise ratios in semantic networks.

Dopamine and semantic activation: An investigation of masked direct and indirect priming

To investigate the effects of dopamine on the dynamics of semantic activation, 39 healthy volunteers were randomly assigned to ingest either a placebo (n = 24) or a levodopa (n = 16) capsule. Participants then performed a lexical decision task that implemented a masked priming paradigm. Direct and indirect semantic priming was measured across stimulus onset asynchronies (SOAs) of 250, 500 and 1200 ms. The results revealed significant direct and indirect semantic priming effects for the placebo group at SOAs of 250 ms and 500 ms, but no significant direct or indirect priming effects at the 1200 ms SOA. In contrast, the levodopa group showed significant direct and indirect semantic priming effects at the 250 ms SOA, while no significant direct or indirect priming effects were evident at the SOAs of 500 ms or 1200 ms. These results suggest that dopamine has a role in modulating both automatic and attentional aspects of semantic activation according to a specific time course. The implications of these results for current theories of dopaminergic modulation of semantic activation are discussed.

Semantic activation in Parkinson's disease patients on and off levodopa.

Research suggests that dopamine may exert a neuromodulatory influence on automatic spreading activation within semantic networks. In order to investigate the influence of dopamine depletion on semantic activation in Parkinsons disease (PD), nine patients with PD performed a lexical decision task when on and off levodopa medication. Eleven healthy controls matched to the PD patients in terms of sex, age and education also participated in the study. Both directly related word pairs (e.g., tiger - stripe) and indirectly related word pairs (word pairs related via a mediating word, e.g., chalk - black) were used to measure semantic activation across stimulus onset asynchronies (SOAs) of 270msec, 520msec and 1020msec. Analysis of variance statistics revealed that the activation of directly related and indirectly related targets was slower for the PD group relative to the control group. Within group comparisons revealed further changes to semantic activation in PD patients off medication, with no activation of directly or indirectly related target words evident in PD patients off medication. These results further clarify the nature of dopamines neuromodulatory influence on semantic activation, and suggest that the nature of altered semantic activation in PD may depend on the magnitude of dopamine depletion.

Impaired reading comprehension in schizophrenia: Evidence for underlying phonological processing deficits

The present study examined reading ability in high functioning people with schizophrenia. To this end, 16 people with schizophrenia who were living in the community and 12 matched controls completed tests of passage reading (comprehension, accuracy, and rate), word recognition, and phonological processing (phonological awareness, phonological memory and rapid naming) and ratings of reading self-concept and practices. Performance of the participants with schizophrenia was impaired relative to control participants on reading comprehension and rapid naming and relative to the population norms on phonological awareness, and rapid naming. In addition, self-rating data revealed that participants with schizophrenia had poorer perceptions of their reading ability and engaged in reading activities less frequently than their control counterparts. Consistent with earlier research, significant correlations were found between phonological awareness and reading comprehension. These findings expand on previous research in the area to suggest that community-based individuals with schizophrenia experience problems with reading comprehension that may have a phonological basis.

An Investigation of Working Memory Influences on Lexical Ambiguity Resolution

The present study employed a combined semantic judgment and lexical decision priming paradigm to examine the impact of working memory on the inhibitory processes of lexical ambiguity resolution. The results indicated that overall, participants activated one meaning of a presented homograph while not priming the alternative meaning. As hypothesized, participants with high working-memory spans exhibited a pattern of priming for congruent conditions and a lack of positive priming for incongruent conditions. In contrast, participants with low working-memory capacity showed priming for both congruent and incongruent conditions, but only for conditions in which the context was related to the dominant meaning of the homograph. The results suggest that people with low working-memory capacity have difficulty inhibiting inappropriate homograph meanings and further demonstrate that these difficulties may vary as a function of context-meaning dominance.

The Autism Diagnostic Observation Schedule and narrative assessment: Evidence for specific narrative impairments in autism spectrum disorders

Abstract Purpose: The Autism Diagnostic Observation Schedule (ADOS) contains a narrative generation task in which clients tell a story from a wordless picture book; however, the resulting narrative is not usually examined for its linguistic properties. This study aimed to examine narrative generation in autism spectrum disorder (ASD) by comparing narratives elicited from children with ASD during the ADOS to those produced by language-matched typically-developing (TD) peers. Method: Participants were children with ASD (n = 11) and TD controls (n = 17). Both groups were aged 9–15 years and were matched for expressive and receptive language skills and non-verbal intelligence. Narratives were analysed for local structure elements (length, fluency, errors, semantics and syntax), cohesion and global elements (story grammar and internal state language). Result: Results indicated that the narratives of the children with ASD were syntactically less complex, contained more ambiguous pronouns and included fewer story grammar elements than their control counterparts; with further analysis showing differences between younger and older children. Conclusion: The present findings provide evidence that children with ASD exhibit subtle story generation impairments and provide preliminary support for the inclusion of narratives elicited as part of the ADOS in the assessment of specific language skills in this population.

A systematic review of electrophysiological outcomes following auditory training in school-age children with auditory processing deficits

Abstract Objective: To systematically review the peer-reviewed literature on electrophysiological outcomes following auditory training (AT) in school-age children with (central) auditory processing disorder ([C]APD). Design: A systematic review. Study sample: Searches of 16 electronic databases yielded four studies involving school-aged children whose auditory processing deficits had been confirmed in a manner consistent with 5 and 1 and compared to a treated and/or an untreated control group before and after AT. A further three studies were identified with one lacking a control group and two measuring auditory processing in a manner not consistent with 5 and 1. Results: There is limited evidence that AT leads to measurable electrophysiological changes in children with auditory processing deficits. Conclusion: The evidence base is too small and weak to provide clear guidance on the use of electrophysiological outcomes as a measure of AT outcomes in children with auditory processing problems. The currently limited data can only be used to suggest that click-evoked AMLR and tone-burst evoked auditory P300 might be more likely to detect such outcomes in children diagnosed with (C)APD, and that speech-evoked ALLR might be more likely to detect phonological processing changes in children without a specific diagnosis of (C)APD.

Phonological awareness and language intervention in preschoolers from low socio-economic backgrounds: A longitudinal investigation

This study examines the literacy outcomes for children from socially disadvantaged backgrounds who had received specific whole-class phonological awareness (PA) and language intervention in preschool. The participants were 57 children who had been involved in the original intervention study. Their PA skills, letter-sound knowledge, real word and non-word spelling and reading comprehension were assessed in Grade 2. The results indicated that children who had received intervention in preschool performed similarly to the children who had not received intervention. The gains made in PA and language skills post intervention had failed to augment further literacy development. A post hoc examination of individual student profiles, however, revealed that a subgroup of children who had received intervention had maintained their enhanced performance and that the intervention cohort had similar scores on tests of PA ability to their age-matched peers in the population. It was concluded that whole-class, teacher-delivered, PA and language intervention, while effective in the short term, does not lead to a generalized improvement in literacy skills in Grade 2. Possible reasons for the failure of the program to produce medium term gains are discussed.

The Influence of Dopamine on Automatic and Controlled Semantic Activation in Parkinson's Disease

Two semantic priming tasks, designed to isolate automatic and controlled semantic activation, were utilized to investigate the impact of dopamine depletion on semantic processing in Parkinsons disease (PD). Seven people with PD (tested whilst on and off levodopa medication) and seven healthy adults participated in the study. The healthy adult participants demonstrated intact automatic and controlled semantic activation. Aberrant controlled semantic activation was observed in the PD group on levodopa; however, automatic semantic activation was still evident. In contrast, automatic semantic activation was not evident in the PD group off levodopa. These results further clarify the impact of PD on semantic processing, demonstrating that dopamine depletion can cause disturbances in both automatic and controlled semantic activation.

Decreased semantic competitive inhibition in Parkinson's disease: Evidence from an investigation of word search performance

Aberrant semantic competitive inhibition has been reported in Parkinsons disease (PD). Whether PD-related alterations cause an increase or a decrease in lateral inhibition, however, remains unclear. Accordingly, the present study aimed to examine semantic inhibition during lexical-semantic processing in non-demented people with PD. Twenty-two people with PD and 18 matched controls completed a computerized word search task in which both the relationship between the background items and the target (related or unrelated) and the search type (open e.g., any dog or closed e.g., collie) were manipulated. It was hypothesized that decreased semantic inhibition would be evidenced by abnormally short response times for open searches among words related to the target, while increased inhibition would lead to abnormally long response times. Analysis of the results revealed that control participants performed open searches faster for unrelated vs related word lists. In contrast, the PD group recorded similar response times regardless of background items. Hence, the present findings are consistent with the notion of decreased semantic competitive inhibition in PD and suggest that an impaired ability to inhibit unwanted information during lexical retrieval may underlie observed deficits on semantic tasks such as verbal fluency.