Practice and retention of nonwords in adults who stutter.

PURPOSE: We investigated short-term practice and retention of nonwords in 10 adults who stutter (Mean age=30.7 years, SD=15.1) and age and sex-matched 10 control participants (Mean age=30.8 years, SD=14.9). METHODS: Participants were required to repeat nonwords varying in length (3, 4, and 6 syllables), phonotactic constraint (PC vs. NPC, on 3-syllable nonwords only), and complexity (simple, complex). They were tested twice with 1h gap between sessions. RESULTS: Logistic mixed model of speech accuracy revealed that the AWS showed a significantly lower probability of correct responses with increasing length and complexity. Analysis of speech kinematics revealed practice effects within Session 1 in AWS seen as a reduction in movement variability for the 3-syllable nonwords; the control group was performing at ceiling at this length. For the 4-syllable nonwords, the control group showed a significant reduction in movement variability with practice, and retained this reduction in Session 2, while the AWS group did not show practice or retention. Group differences were not evident at the 6-syllable level. CONCLUSIONS: Group differences in speech accuracy suggest differences in phonemic encoding and/or speech motor processes. Group differences in changes in movement variability within and between sessions suggest reduced practice and retention in AWS. Relevance of the combined use of both behavioral and kinematic measures to interpret the nature of the skill acquisition deficit in persons who stutter is discussed. EDUCATIONAL OBJECTIVES: At the end of this activity the reader will be able to: (a) summarize the process of skill acquisition; (b) discuss the literature on skill acquisition deficits in adults who stutter, (c) summarize the differences between AWS and control participants in speech accuracy and speech kinematics with short-term practice and retention of nonwords, (d) discuss potential research directions in the area of skill acquisition in AWS.

The effects of cognitive: linguistic variables and language experience on behavioural and kinematic performances in nonword learning.

The aim of the present study was to investigate the effects of cognitive-linguistic variables and language experience on behavioral and kinematic measures of nonword learning in young adults. Group 1 consisted of thirteen participants who spoke American English as the first and only language. Group 2 consisted of seven participants with varying levels of proficiency in a second language. Logistic regression of the percent of correct productions revealed short-term memory to be a significant contributor. The bilingual group showed better performance compared to the monolinguals. Linear regression of the kinematic data revealed that the short-term memory variable contributed significantly to movement coordination. Differences were not observed between the bilingual and the monolingual speakers in kinematic performance. Nonword properties including syllable length and complexity influenced both behavioral and kinematic performance. The findings supported the observation that nonword repetition is multiply determined in adults.

Natural variation in RPS2-mediated resistance among Arabidopsis accessions: correlation between gene expression profiles and phenotypic responses.

Natural variation in gene expression (expression traits or e-traits) is increasingly used for the discovery of genes controlling traits. An important question is whether a particular e-trait is correlated with a phenotypic trait. Here, we examined the correlations between phenotypic traits and e-traits among 10 Arabidopsis thaliana accessions. We studied defense against Pseudomonas syringae pv tomato DC3000 (Pst), with a focus on resistance gene-mediated resistance triggered by the type III effector protein AvrRpt2. As phenotypic traits, we measured growth of the bacteria and extent of the hypersensitive response (HR) as measured by electrolyte leakage. Genetic variation among accessions affected growth of Pst both with (Pst avrRpt2) and without (Pst) the AvrRpt2 effector. Variation in HR was not correlated with variation in bacterial growth. We also collected gene expression profiles 6 h after mock and Pst avrRpt2 inoculation using a custom microarray. Clusters of genes whose expression levels are correlated with bacterial growth or electrolyte leakage were identified. Thus, we demonstrated that variation in gene expression profiles of Arabidopsis accessions collected at one time point under one experimental condition has the power to explain variation in phenotypic responses to pathogen attack.