Research Interests
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To understand movement deficits following neurological injury, I examine how electrical signals in the brain and spinal cord control the human arm. I use a robot to move the arms of healthy and brain-injured patients, invoking movement-related electrical responses in the spinal cord which we quantify and compare. I also use a magnetic stimulator to activate different parts of the brain that control the arm. I investigate how repetitive physical training changes arm movements evoked by the magnetic stimulator. Also, I use the stimulator to temporarily disrupt the neural circuits in the brain that control the arm. Examples of my research are described below:
My research may contribute to improvements in physical therapy interventions aimed at restoring movement following stroke, Parkinson’s disease, and cerebral palsy. Such diseases can make simple, daily tasks such as brushing your teeth nearly impossible, but improved treatments could help patients overcome their movement deficits to live less constrained lives.
Use-Dependent Neural Plasticity in Motor Cortex
The term “neural plasticity” describes the ability of the nervous system to endure experience-induced restructuring. Plasticity in the neural structures which control voluntary movement allows motor skill acquisition i.e. the ability to learn to play the piano or swing a golf club. More importantly, neuroplasticity also facilitates the recovery of motor function following stroke. Even though motor learning and long-term neuroplasticity may take place over weeks and months, we use laboratory techniques which are able to assess the neural correlates of a single 30-minute training session. Specifically, we assess use-dependent neuroplasticity by recording muscle responses (EMG) to transcranial magnetic stimulation (TMS), applied to the human motor cortex, before and after repetitive training. The size of these muscle responses increases in muscles used during training, due to use-dependent excitability increases in the neural pathways which controlled the muscles used in the training. According to the procedures we use to assess plasticity, repetitive single-joint training in the human upper-limb induces the most plasticity in corticomotor structures controlling the distal upper-limb. Corticomotor plasticity is graded and decreases in structures controlling more proximal joints in the upper-limb. This implies that when quickly learning whole-limb tasks, structures other than corticomotor pathways may be relied on more heavily than when quickly learning distal tasks. These results are in submission.
The Separate Neural Control of Force and Motion
When interacting with our environment we must simultaneously control our hand motion as well as the interaction forces that arise from contact with the environment. On the level of musculoskeletal biomechanics, motions and forces are coupled by intrinsic limb impedance. However, it has yet to be established if the control of motion and forces is coupled or independent at the neural level. We used a robotic manipulandum to characterize the neural control of motion and force, and single pulse transcranial magnetic stimulation (TMS) to posterior parietal cortex to disrupt neural control. Subjects made center-out movements with the HapticMaster 3D robotic manipulandum, in tasks which required varying degrees of endpoint and force control. The results are in, and they are in submission.
Spinal Reflex Contributions to Multi-joint Posture
I am beginning a project that focuses on postural control of the arm rather than movement control, using techniques that are well established in our laboratory. Specifically, we are interested in how the ability to successfully maintain arm posture is constrained by abnormal patterns of reflex excitability following stroke. Whole-limb posture is controlled by feedforward (corticomotor) and feedback (reflex) neural pathways which activate muscles of the arm to regulate whole-limb mechanics. When postural control is unimpaired, these pathways control the effortless coordination of movements of multiple joints within the arm. This allows the arm to function as a whole and serve as a scaffold for the hand, supporting its own weight while transporting the hand through space to execute fine motor tasks. Thus, nearly all purposeful whole limb movements, such as opening a door handle, twisting a screwdriver, brushing our teeth, and lifting a glass to our mouth to drink, are dependent on the ability to maintain stable whole-limb postures. However, the neural pathways controlling multijoint coordination become altered following stroke, leading to a characteristic inability to control the joints of the upper-limb independently. This constricts the workspace of the hemiparetic upper limb, decreases its function, and degrades the quality of life of the chronic stroke survivor. My work focuses on reflex control of whole-arm posture in healthy subjects.
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Selected Publications
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Krutky, Matthew A., and Eric J. Perreault. “Use-dependent Plasticity is Graded from Distal to Proximal in the Human Upper-Limb .” (Journal of Neurophysiology).
Chib, Vikram S., Krutky Matthew A., Lynch, Kevin M., and Ferdinando A. Mussa-Ivaldi. “The Separate Neural Control of Hand Movements and Contact Forces” (In Submission to Nature).
Krutky, Matthew A., Eric J. Perreault, Gwyn N. Lewis, and Colum D. MacKinnon. “Cortical Contributions to the Stretch Reflex Respons in Biceps Brachii.” Conference Proceedings from the IEEE Engineering in Medicine and Biology Society: 2004; 7: 4673-4676.
Krutky, Matthew A., Jillian L. Atherton, Spence Smith, Frederick A. Dodge, and Robert B. Barlow. “Do the Properties of Underwater Lighting Influence the Visually Guided Behavior of Limulus?” Biological Bulletin: Oct. 2000. Pp. 178-180.
Atherton, Jillian L., Matthew A. Krutky, James M. Hitt, Frederick A. Dodge, and Robert B. Barlow. “Optic Nerve Responses of Limulus in its Natural Habitat at Night.” Biological Bulletin: Oct. 2000. Pp. 176-178.
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Invited Talks
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Krutky, Matthew A. and Eric J. Perreault, “Use dependent plasticity in the pathways controlling proximal and distal human upper-limb joints.” Biomedical Engineering Society, Chicago, October 11 - October 14, 2006.
Krutky, Matthew A. and Eric J. Perreault, “Use dependent plasticity in the corticospinal pathways controlling human arm movement.” International Conference on Rehabilitation Robotics, Chicago, June 28 - July 1, 2005.
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Conference Proceedings
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Perreault, Eric J., Krutky, Matthew A., and Randy Trumbower. “Influence of environmental mechanics on multijoint reflex gain and coordination.” Society for Neuroscience, San Diego, November, 2007.
Chib, Vikram S., Krutky, Matthew A., Kevin M. Lynch, and Ferdinando A. Mussa-Ivaldi. “The nervous system independently controls motion and force.” International Society of Motor Control: Progress in Motor Control VI, Santos, Brazil, August 2007.
Chib, Vikram S., Krutky, Matthew A., Lynch, Kevin M., and Ferdinando A. Mussa-Ivaldi. “The nervous system independently controls motion and force.” Society for the Neural Control of Movement, Seville, Spain, March 2007.
Krutky, Matthew A., Vikram S. Chib, and Ferdinando A. Mussa-Ivaldi. “Differential interference of motion and force control in the central nervous system.” Society for Neuroscience, Atlanta, October 2006.
Chib, Vikram S., Matthew A. Krutky, Kevin M. Lynch, and Ferdinando A. Mussa-Ivaldi. “The nervous system independently controls motion and force.” Advances in Computational Motor Control V, Atlanta, October 13, 2006.
Krutky, Matthew A. and Eric J. Perreault. “Use dependent plasticity in the pathways controlling human wrist movements.” Society for Neuroscience, Washington DC, November 12-16, 2005.
Krutky, Matthew A. and Eric J. Perreault. “Use dependent plasticity in the pathways controlling proximal and distal arm muscles.” A poster presentation at the European Science Foundation – EMBO Symposia, Sant Feliu de Quixols, Spain, October 8-13, 2005.
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