Walker EHE, Ruiz-Torres R, Miller LE, Perreault EJ. Heightened attention to proprioceptive feedback is not sufficient for long-latency reflex modulation during arm posture. Society for Neuroscience Conference, Chicago IL, October 17 2015. (poster)

1. 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
1Biomedical Engineering, 2Physiology, 3Physical Medicine and Rehabilitation, Northwestern University, Evanston (Chicago), IL
4Sensory 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:
• Proprioceptive
(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%
1
0.98
0.96
0.94
0.92
0.90
0.88
Power(1–βerrprob)
1.5 2 2.5 3.53 4
Effect size
In each trial, the subject attends to a stimulus as directed on the screen.
Dots move more/less randomly. Bump force gets smaller/larger. Direction discrimination maintained at 70-80%
No significant differences at a level of α=0.05 in any time window or any muscle.Stretch reflexes were evoked by perturbations.
Equal BGA and M-wave ensures matched stimulations.
No signif. difference in sensitivity of spinal circuits (p=0.32).
No signif. difference in ascending sensory signals (p=0.85).
H-reflexes and SEPs were evoked by median nerve stimulation.
ms
ms