Cortical reorganization following brain injury
is being investigated in our laboratories with three techniques:
multi-channel EEG recordings in conjunction with anatomical
MRI, Transcranial Magnetic Stimulation in conjunction with
anatomical MRI, functional MRI, and Diffusion Tensor Imaging. Through these investigations
we seek to illustrate the difference in somatotopic organization
between normal and injured brains. Significant differences
will support the premise that abnormal movement constraints
observed in the hemiparetic extremity of people post stroke
are due to reorganization of the brain following brain injury.
Investigation of possible roles of cortical reorganization
in the emergence of abnormal movement patterns after stroke
using EEG, fMRI, and Transcranial Magnetic Stimulation (TMS).
By using multiple techniques, we hope to overcome their individual
disadvantages. EEG and fMRI are used to understand brain organization
during voluntary movments. EEG allows us to investigate in
depth, any temporal changes in the movements and also has
the great advantage of allowing large isometric exertions
at the elbow and shoulder that are not possible in the MRI
environment. TMS activates the arm muscles by stimulation
of the brain while the subject is at rest, thereby allowing
the study of the cortical connections without any additional
input by other areas as would happen during voluntary movement.
Both EEG and TMS are used in coordination with a 6 degree
of freedom load cell and 12 channels of electromyographic
(EMG) recording to accurately measure arm movement and muscle
activity for a highly controlled experiment. We are currently
working on ways to quantitatively measure movements and/or
muscle activity in the MRI environment. |
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| Cortical activity Related
to Isometric Joint Torques Measured with EEG |
The objective of this grant is to demonstrate
quantifiable spatiotemporal differences in macroscopic electrical
activity of human sensorimotor cortices during voluntary isometric
torque generation in the upper limb.
RO3 HD39804-01A1 Agency: NIH
The objective of this grant is to elucidate the temporal
development of the brain activity from motor planning to the
execution. This AHA proposal will provide information on the
effect of motor planning on the performance of an isometric
torque generation.
Scientist development grant Agency: AHA
The objective of this grant is to elucidate the role of
sensorimotor cortices in the loss of independent joint control
when stroke subject generates an isometric torque. Linear
regression modeling will be used to identify the main factors
that lead to the discoordination. Results found by the modeling
work will be used to investigate the effect of a novel multi-degree
of freedom isometric training protocol on cortical activity
in stroke subjects.
5 R01 HD 047569-01 Agency: NIH
The general aim of this proposal is to elucidate the roles
of cortex and descending motor pathways in the expression
of abnormal muscle coactivation patterns following stroke.
R21 Agency: NIH
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| Functional Magnetic Resonance Imaging (fMRI) |
We are currently using functional magnetic resonance imaging (fMRI) to investigate the cortical activation areas that control elbow and shoulder contraction. Using a nonferrous six-degrees-of-freedom load cell, we collect joint torque information at the shoulder and elbow simultaneously with fMRI data. We hypothesize, based on EEG results, that there is a greater overlap in the shoulder and elbow representations in the motor cortices in chronic stroke patients than in non-impaired participants. Changes in somatotopic organization and laterality in individuals with chronic stroke are also being investigated. |
| Diffusion Tensor
Imaging (DTI) |
Diffusion tensor imaging is an MRI-derived technique that uses water motion as a probe to measure macroscopic axonal organization and thus infer the neuroanatomy of the brain. The diffusion tensor characterizes the magnitude, the degree of anisotropy, and the orientation of directional diffusion.
Our research focuses on using DTI to estimate the axonal organization of white matter and use anisotropy to quantify how this organization is affected after stroke or in cerebral palsy.
We also use DTI to reconstruct white matter tracts using probabilistic tractography in order to assess changes in structure and integrity of cortex afferents due to lesion. We aim to correlate integrity and structural metrics with behavioral metrics obtained experimentally.
    
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| Corticospinal tract excitability as measured by Transcranial Magnetic Stimulation |
TMS Details.... |
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Lab members involved:
Jules Dewald
Jun Yao
Carolina Carmona
Alexis Kuncel
Daniel Krainak
Natalia Sanchez
Rachel Hawe |
