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Director: Kristie Spencer, Ph.D.

We are interested in understanding the nature of neurogenic motor speech and cognitive disorders and how best to serve clients who experience these disorders.

Current projects include:
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**Feedback Schedules and Speech Motor Learning in Healthy Older Adults and Individuals with Parkinson’s Disease (PIs: Spencer, Weir)

Neurologic injury often has devastating consequences for a person’s ability to speak, a condition known as dysarthria. Therapeutic interventions for dysarthria often result in meager outcomes and, importantly, gains are not typically maintained over time (Spencer et al., 2003). Experts in the field of speech-language pathology have proposed that theories of “motor learning” may be the key to improving the efficiency and effectiveness of dysarthria treatment (Duffy, 2005; McNeil, 2009), yet little is known about how to apply these theories to speech rehabilitation. Evidence for the use of these principles of motor learning has emerged from decades of research on how to train healthy adults to perform novel upper limb movements (Schmidt & Lee, 2005). The evidence is overwhelmingly positive but, thus far, the application of these principles to individuals with neurologic injury has been limited. Even sparser are studies applying these principles to individuals with dysarthria and other neurologic speech impairments. This ongoing investigation will examine the effect of feedback frequency on the ability of 60 healthy older adults and 60 individuals with idiopathic Parkinson disease to learn a novel speech and manual task. The speech task entails producing a phrase 2x and 3x slower than the individual’s habitual speech rate, while the manual task involves tracing a visual target at a rate 2x and 3x slower than habitual rate. Findings will begin to fill a crucial gap in the speech rehabilitation literature and will provide an integrated, theoretical contribution to the motor learning literature.

**Perceptual Classification of Adults with Ataxic Dysarthria (PIs: France, Spencer)

**Relationship between Speech Severity and Communicative Participation in Adults with Parkinson’s Disease (PIs: Gomez, Baylor, Spencer)

**The Effect of Attention Process Training III on Cognitive-Linguistic Functioning in Individuals with Traumatic Brain Injury (PIs: Sears, Spencer)

Attention deficits are among the most common, persistent deficits following traumatic brain injury. This recently completed study was a case study investigating the effect of Sohlberg and Mateer’s (2011) Attention Process Training III on outcomes across levels of disablement in a man with chronic mild-moderate traumatic brain injury.

**Nature and Laterality of Motor Symptoms in Parkinson’s Disease and Relationship to Cognitive Profile (PIs: Hutchison, Spencer, Leverenz, Peter, et al.)

The purpose of this study was to determine the relationship between cognitive profile and the nature/laterality of initial motor symptoms in Parkinson’s disease (PD). Research suggests that initial onset of tremor is linked to better cognitive performance than initial onset of bradykinesia or rigidity, while studies of the laterality of symptom onset have been inconclusive. Very few investigations have considered the interaction of nature and laterality of symptoms in individuals with PD and the association with cognitive functioning.

Participants with PD (N=272) were divided into subgroups based on nature and laterality of symptom onset: left bradykinesia/rigidity onset (L-B/R), left tremor onset (L-Tr), right bradykinesia/rigidity onset (R-B/R), and right tremor onset (R-Tr). Participants completed a neuropsychological test battery assessing memory, attention, visuospatial function, executive functions, and language. Subgroups were equivalent with respect to sex, years of education, disease duration and disease severity. Multimodal, multivariate logistic regression was used to compare the right tremor onset group (R-Tr) to the three other subgroups.

Significant differences between the R-Tr subgroup and the other three subgroups emerged (overall p = .0069). Predictors for R-Tr membership were higher depression scores and later disease onset, compared to the R-B/R group; higher verbal learning scores, compared to the L-Tr group; and lower scores on a general measure of cognitive function, compared to the L-B/R group.

The results of the current study reinforced the findings of Katzen et al. (2006) that laterality and nature must be considered in combination to unveil the link between cognitive profile and initial motor symptoms. However, while Katzen and colleagues reported that the R-Tr subgroup performed better than other subgroups and similarly to healthy controls, the current study found that subgroup predictors varied by cognitive domain.