Dataset Information

Dissociation between behavior and motor cortical excitability before and during ballistic wrist flexion and extension in young and old adults.

ABSTRACT:

Purpose

Aging is associated with slow reactive movement generation and poor termination.

Objective

We examined the hypothesis that the build-up of excitability in the primary motor cortex in the agonist muscle to generate ballistic wrist flexion and extension and in the antagonist to stop the movement, is lower and slower in old compared with young adults.

Methods

We measured the size of the motor potentials evoked (MEP) produced by transcranial magnetic stimulation (TMS), background integrated EMG (iEMG), and the MEP:iEMG ratio in healthy young (23 y, n = 14) and old adults' (73 y, n = 14) wrist flexors and extensors as they rapidly flexed or extended the wrist in response to an auditory cue. TMS was delivered at 80% of resting motor threshold randomly in 20 ms increments between 130 and 430 ms after the tone.

Results

Even though old compared to young adults executed the two wrist movements with ~23% longer movement duration and ~15% longer reaction time (both p < 0.05), the rise in MEP:iEMG ratio before the main similar in the two age groups.

Conclusion

These data suggest that an adjustment of current models might be needed to better understand how and if age affects the build-up excitability accompanying movement generation and termination.

SUBMITTER: Hortobagyi T

PROVIDER: S-EPMC5658056 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Publications

Dissociation between behavior and motor cortical excitability before and during ballistic wrist flexion and extension in young and old adults.

Hortobágyi Tibor T Mieras Adinda A Rothwell John J Del Olmo Miguel Fernandez MF

PloS one 20171026 10

<h4>Purpose</h4>Aging is associated with slow reactive movement generation and poor termination.<h4>Objective</h4>We examined the hypothesis that the build-up of excitability in the primary motor cortex in the agonist muscle to generate ballistic wrist flexion and extension and in the antagonist to stop the movement, is lower and slower in old compared with young adults.<h4>Methods</h4>We measured the size of the motor potentials evoked (MEP) produced by transcranial magnetic stimulation (TMS), ...[more]

PMID: 29073175

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Project description:ObjectiveIn stroke survivors, a treatment-resistant problem is inability to volitionally differentiate upper limb wrist extension versus flexion. When one intends to extend the wrist, the opposite occurs, wrist flexion, rendering the limb non-functional. Conventional therapeutic approaches have had limited success in achieving functional recovery of patients with chronic and severe upper extremity impairments. Functional magnetic resonance imaging (fMRI) neurofeedback is an emerging strategy that has shown potential for stroke rehabilitation. There is a lack of information regarding unique blood-oxygenation-level dependent (BOLD) cortical activations uniquely controlling execution of wrist extension versus uniquely controlling wrist flexion. Therefore, a first step in providing accurate neural feedback and training to the stroke survivor is to determine the feasibility of classifying (or differentiating) brain activity uniquely associated with wrist extension from that of wrist flexion, first in healthy adults.ApproachWe studied brain signal of 10 healthy adults, who performed wrist extension and wrist flexion during fMRI data acquisition. We selected four types of analyses to study the feasibility of differentiating brain signal driving wrist extension versus wrist flexion, as follows: 1) general linear model (GLM) analysis; 2) support vector machine (SVM) classification; 3) 'Winner Take All'; and 4) Relative Dominance.ResultsWith these four methods and our data, we found that few voxels were uniquely active during either wrist extension or wrist flexion. SVM resulted in only minimal classification accuracies. There was no significant difference in activation magnitude between wrist extension versus flexion; however, clusters of voxels showed extension signal > flexion signal and other clusters vice versa. Spatial patterns of activation differed among subjects.SignificanceWe encountered a number of obstacles to obtaining clear group results in healthy adults. These obstacles included the following: high variability across healthy adults in all measures studied; close proximity of uniquely active voxels to voxels that were common to both the extension and flexion movements; in general, higher magnitude of signal for the voxels common to both movements versus the magnitude of any given uniquely active voxel for one type of movement. Our results indicate that greater precision in imaging will be required to develop a truly effective method for differentiating wrist extension versus wrist flexion from fMRI data.

Dataset Information

Dissociation between behavior and motor cortical excitability before and during ballistic wrist flexion and extension in young and old adults.

Purpose

Objective

Methods

Results

Conclusion

Publications

Dissociation between behavior and motor cortical excitability before and during ballistic wrist flexion and extension in young and old adults.

Similar Datasets

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