2016 Seminar Series

January 26, 2016
Ambulatory Monitoring of Upper Limb Movement, Sedentary Behavior, and Physical Activity After Stroke
Ryan Bailey, PhD, MSCI, OTR/L - Atlanta Veterans Affairs Medical Center

February 25, 2016
Linking Impairments of Visual Search with Functional Outcomes Following Stroke
Troy Herter, PhD - University of South Carolina
Many stroke survivors experience poor functional outcomes even if they have little motor impairment. This suggests that functional outcomes are influenced by other factors. Visual search, defined as patterns of eye movements used to actively scan the environment for visual information, is an essential component of many functional activities, thus impairments of visual search may contribute to poor functional outcomes following stroke. Using a novel paradigm that couples upper-limb robotics with eye tracking, we are examining how visual search influences motor behavior and motor learning. In this talk I will show evidence that many stroke survivors exhibit impairments of visual search that are not related to visual field deficits, oculomotor deficits or spatial neglect. Furthermore, because visual search involves integration of visual, cognitive and oculomotor processes, I will discuss how various underlying factors may contribute to impairments visual search in a task-dependent manner. I will also show how impairments of visual search may influence functional outcomes by interfering with motor learning. Finally, I will present preliminary evidence that post-stroke changes in structural connectivity of frontoparietal networks may underlie impairments of visual search.

March 31, 2016
Stability of Posture and Action in Cortical and Subcortical Disorders
Mark L. Latash, PhD - The Pennsylvania State University
When people move, they organize large sets of elements (limbs, joints, digits, muscles, motor units, etc.) in a task–specific way to ensure action stability, which is crucial given the unpredictable external forces and varying intrinsic body states. We have quantified synergies stabilizing salient variables during posture and movement. Patients with Parkinson’s disease (PD), multi-system atrophy, and multiple sclerosis show lower synergy indices as well as smaller anticipatory synergy adjustments (ASAs – a drop in the synergy index in preparation to a quick action). These two aspects reflect poor stability and poor agility of actions. Such differences are seen in apparently uninvolved hands in stage-I PD and during tasks involving vertical posture in stage-II PD; they are sensitive to dopamine replacement therapy. Lower synergy indices are also seen in asymptomatic welders who are at high risk for PD. In contrast, mild-to-moderate stroke leads to major changes in actions by contralesional extremities without changes in associated synergies, while ASAs are reduced. These results emphasize the importance of subcortical loops for stability of steady-state actions. They suggest that changes in the synergic control can provide pre-symptomatic behavioral biomarkers.