ACKNOWLEDGEMENTS 067. Heightened attention to proprioceptive feedback is not sufficient for long-latency reflex modulation during arm posture. E.H.E. Walker 1,4 R. Ruiz-Torres 2 L.E. Miller 1,2,3 E.J. Perreault 1,3,4 1 Biomedical Engineering, 2 Physiology, 3 Physical Medicine and Rehabilitation, Northwestern University, Evanston (Chicago), IL 4 Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL INTRODUCTION This work was done in conjunction with Northwestern University and the Sensory Motor Performance Program and was supported in part by the NSF grant 0932263 and NIH grant NS053813-08. The authors would like to thank Timothy Haswell for his help with the experimental setup. CONCLUSIONS METHODS 3 Attention Conditions: • Propriocep tive (bumps) • Visual (dots) • Control (none) 3 Measurements: • Stretch reflexes (20% perturbation trials) • H-reflexes (electrical stimulation of median nerve) • SEPs - Somatosensory Evoked Potentials (C3’ ref Fpz’) • Stretch reflexes are important for postural stability in the arm. • Long-latency stretch reflexes become more sensitive in unstable environments. • It is not clear what factors drive long-latency reflex modulation as seen in different environments. • Hypothesis: Heightened attention to proprioceptive feedback drives this type of reflex modulation. more stable less stable Perreault et al. 2008, J Neurophysiology: Adaptive stimulus intensities ensured selective attention Stretch reflexes were not significantly influenced by attention H-reflexes and SEPs were not significantly influenced by attention Post-hoc Power Analysis • The output of reflex loops, sensitivity of spinal circuitry, and the strength of ascending sensory information are not affected by attention in this task. • Attention alone is insufficient to accomplish long-latency reflex modulation during posture. • Engagement with novel environmental dynamics may be key to long-latency reflex modulation. BGA: F≤1.56 p≥0.24 SLR : F≤2.58 p≥0.11 LLR1: F≤0.46 p≥0.64 LLR2: F≤1.91 p≥0.20 • ANOVA with alpha = 0.05 and sample size = 9 • Estimated effect size = 1.5 to 4.0 • Based on Perreault et al. 2008, Shemmell et al. 2009, Krutky et al. 2010 • Statistical power ≥ 87%