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EMBC 2014, Chicago IL USA | Thursday, August 28 | Motor Learning and Neural Control II 1
Effect of Arm Dominance on Long-Latency Stabilizing Reflex Gain during Posture
Elise H. E. WalkerEric J. Perreault
Northwestern University &Rehabilitation Institute of Chicago
EMBC 2014, Chicago IL USA | Thursday, August 28 | Motor Learning and Neural Control II 2
Arm dominance as control specialization in the cortical hemispheres
__DOMINANT__ • Predictive
• Trajectory
• Limb dynamics
• Reach initiation
NONDOMINANT• Impedance
• Position
• Stabilizing
• Final position
Bagesteiro & Sainburg, J Neurophys 2002“Handedness: dominant arm advantages in control of limb dynamics”
Bagesteiro & Sainburg, J Neurophys 2003“Nondominant arm advantages in load compensation during rapid elbow joint movements”
Mani, Mutha, Przybyla, Haaland, Good, Sainburg, Brain 2013“Contralesional motor deficits after unilateral stroke reflect hemiphere-specific control mechanisms”
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EMBC 2014, Chicago IL USA | Thursday, August 28 | Motor Learning and Neural Control II 3
Modified from Shemmell et al. 2009 J Neurosci 29(42)
Time (ms)PTB
0.1 mV
-50 0 50 100 150
Bice
ps E
MG
Stiff DNICompliant DNI
Stabilizing stretch reflexes: task-appropriate feedback responses during posture
Hypothesis: Nondominant arm will display more effective stabilizing
stretch reflex
LLR
EMBC 2014, Chicago IL USA | Thursday, August 28 | Motor Learning and Neural Control II 4
Postural experiment in right-handed subjects
• Dominant (R) & nondominant (L) arm
• Stable & unstable environments• Elbow flexor & extensor
perturbations
EMBC 2014, Chicago IL USA | Thursday, August 28 | Motor Learning and Neural Control II 5
Perturbations of elbow posture elicit reflexes
EMBC 2014, Chicago IL USA | Thursday, August 28 | Motor Learning and Neural Control II 6
Perturbations of elbow posture elicit reflexes
Onset ofPerturbation
EMG trace
BackgroundActivity
BGA
Short Latency
Early LongLatency
Late LongLatency
SLR LLR1 LLR2
10%MVC
0 50 10025 75-100 milliseconds
No change
↑ sensitivity forunstable, nondominant
EMBC 2014, Chicago IL USA | Thursday, August 28 | Motor Learning and Neural Control II 7
Biceps
Some individual subjects display differences between arms
Brachioradialis
Feedforward mechanism
-50 ms 0 50 10025 75
R (dominant)L (nondominant)
25%MVC
Feedback mechanism
EMBC 2014, Chicago IL USA | Thursday, August 28 | Motor Learning and Neural Control II 8
Unmatched reflexes were slightly higher in some left-arm muscles
Tric
eps L
ater
alTr
icep
s Lon
g
LLLL RRRR
*** ***
**
* *
..
LL LL RR RR
*** ***
****
** **
**
.*
**
.
BGA SLR LLR1 LLR2
10%MVC
BGA SLR LLR1 LLR2
10%MVC
EMBC 2014, Chicago IL USA | Thursday, August 28 | Motor Learning and Neural Control II 9
Matched reflexes show no difference in sensitivity for the two arms
* *
* *
Tric
eps L
ater
al
L RL RL RL R
BGA SLR LLR1 LLR2
10%MVC
L RL R
Tric
eps L
ong
L RL R
BGA SLR LLR1 LLR2
10%MVC
Arm dominance does not influence reflex sensitivity
EMBC 2014, Chicago IL USA | Thursday, August 28 | Motor Learning and Neural Control II 10
Arm dominance affects feedforward strategy, but does not affect feedback gains
• Stabilizing reflexes in the nondominant arm do not display greater sensitivity.
• Differences in reflex amplitude stem from feedforward strategies of muscle activation.
• Our current understanding of postural reflexes in the upper limb is probably not affected by arm dominance.
EMBC 2014, Chicago IL USA | Thursday, August 28 | Motor Learning and Neural Control II 11
ACKNOWLEDGEMENTS
Support & Funding:
Northwestern
NSF 0932263
SMPP
Guidance:
Eric Perreault
Robert Sainburg
NMCL:Timothy Haswell
Daniel Ludvig
Claire Honeycutt
David Lipps
Hyunglae Lee
Rosalind Heckman
Emma Bailllargeon
John Spanias
Mariah Whitmore
Bing Wang
Andrea Beer
EMBC 2014, Chicago IL USA | Thursday, August 28 | Motor Learning and Neural Control II 12
EMBC 2014, Chicago IL USA | Thursday, August 28 | Motor Learning and Neural Control II
Arm strength and task difficulty not significantly different between arms
A1