[Abstract Title]. - Society for Neuroscience

Abstract: Introduction: Chronic, hemiparetic stroke survivors usually have difficulty in
independently controlling adjacent joints in the paretic upper limb. The neural mechanisms
underlying the loss of independent joint control are largely unknown. Our recent results have
shown evidence for a significant association between abnormally increased overlap of cortical
joint representations and the loss of independent joint control following stroke. In this study, we
continued to investigate changes of cortical overlap from the preparation to execution phases of
isometric single joint motor tasks in stroke subjects.
Methods: Cortical activity during the generation of single joint isometric motor tasks was
recorded using high-resolution (160 channel) EEG in 8 severely impaired chronic hemiparetic
stroke and 8 able-bodied control subjects. The experimental setup also included the simultaneous
measurements of 15-channel surface EMG and 6 degree-of-freedom (DOF) force/moment
signals. Motor tasks performed by the subjects were isometric single DOF shoulder abduction
(SABD) or elbow flexion (EF), all normalized to 25% of the subject‟s maximum voluntary
torque generating ability. After EEG data processing and averaging, cortical current density
reconstructions were created with the CURRY software program and analyzed in MATLAB.
Results: Stroke subjects show significant abnormal coupling between SABD and EF during both
motor tasks as measured by the torque-coupling ratio. Comparing to the control subjects, in
stroke subjects the overlap of cortical shoulder/elbow joint representations significantly increases
starting at the motor preparation phase (about 400 ms before the onset of motor task).
Furthermore, the overlap increases over time from the motor preparation to the execution phases
in severely impaired stroke survivors (Fugl-Meyer score < 20). However, in able-bodied control
subjects the overlap decreases.
Conclusions: Our results present evidence that changes in the overlap of cortical joint
representations following stroke occur during the motor preparation phase and increases over
time contrary to what is observed in able-bodied subjects. These increases in cortical overlap
may explain the loss of independent joint control observed in severely impaired stroke survivors.
Disclosures: J. Yao , None; J.P.A. Dewald, None.
Poster
277. Voluntary Movement: Cortical Planning and Execution II
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 277.17/LL9
Topic: D.17.b. Cortical planning and execution
Support: Wellcome Trust
Title: Changes in corticospinal excitability during probabilistic sequence learning