Related Experiment Video
Updated: Jun 25, 2026
06:31
Force and Position Control in Humans - The Role of Augmented Feedback
Published on: June 19, 2016
Cortical and subcortical mechanisms for precisely controlled force generation and force relaxation.
Matthew B Spraker1, Daniel M Corcos, David E Vaillancourt
1Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60612, USA.
Cerebral Cortex (New York, N.Y. : 1991)
|March 4, 2009
Summary
This study reveals distinct brain activity patterns for muscle relaxation versus contraction during precise force control. The right dorsolateral prefrontal cortex (DLPFC) shows greater involvement in muscle relaxation, challenging previous assumptions.
Area of Science:
- Neuroscience
- Motor Control
- Human Physiology
Background:
- Everyday tasks require coordinated muscle contraction and relaxation.
- Most research has focused on muscle contractions, leaving relaxation mechanisms less understood.
- While motor cortex roles in relaxation are known, other brain areas remain unclear.
Purpose of the Study:
- To compare neural activity during slow, controlled force generation and relaxation using functional magnetic resonance imaging (fMRI).
- To investigate brain regions beyond the motor cortex involved in muscle relaxation.
- To elucidate the neural circuits underlying precise force relaxation.
Main Methods:
- Functional magnetic resonance imaging (fMRI) was employed in human participants.
- Participants performed slow and precisely controlled force generation and relaxation tasks.
- Brain activity was analyzed and compared between generation and relaxation phases.
Main Results:
- Primary motor cortex and bilateral caudate nucleus showed higher activity during force generation.
- Right dorsolateral prefrontal cortex (DLPFC) exhibited greater activity during force relaxation.
- Anterior cingulate cortex showed greater deactivation during force relaxation.
- Force output parameters did not influence these brain imaging findings.
Conclusions:
- Neural mechanisms for force relaxation differ from force generation, involving distinct prefrontal-striatal and motor cortical-striatal circuits.
- The DLPFC plays a significant role in regulating slow and precisely controlled muscle relaxation, in addition to force generation.
- This study highlights the importance of exploring brain areas beyond the motor cortex for understanding muscle relaxation.
Related Concept Videos
01:20Motor Unit Stimulation
When the neuron of a motor unit fires an action potential, it triggers a series of events, leading to a twitch contraction in the muscle fibers. The process of excitation-contraction coupling is crucial in relaying the action potential to the muscle fibers.
The latent period of contraction marks the onset of excitation-contraction coupling, when the action potential propagates across the sarcolemma, preparing the muscle fibers for contraction. As the fibers enter the contraction phase, the...
The latent period of contraction marks the onset of excitation-contraction coupling, when the action potential propagates across the sarcolemma, preparing the muscle fibers for contraction. As the fibers enter the contraction phase, the...
01:22Muscle Stimulation Frequency
The contraction strength of muscles is regulated by motor neurons, which modulate the frequency of action potentials dispatched to the motor units based on the body's requirements. This process of varying the muscle stimulation frequency allows muscles to contract with a force that is precisely tailored to the needs of the moment, whether lifting a feather or a heavy box.
Wave summation
At low firing rates, motor neurons induce individual twitch contractions in muscle fibers. These twitches...
Wave summation
At low firing rates, motor neurons induce individual twitch contractions in muscle fibers. These twitches...
01:29Relaxation of Skeletal Muscles
The period of muscle contraction primarily influences the duration of stimulation at the neuromuscular junction (NMJ), the presence of free calcium ions in the sarcoplasm, and the availability of energy or ATP to support contractions.
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open.
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open.
01:25Smooth Muscle Contraction
Smooth muscle contraction is a complex process vital for various bodily functions, from maintaining blood vessel tension to facilitating the movement of food through the digestive tract. Unlike striated muscles, smooth muscle contraction begins more slowly and lasts longer.
The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...
The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...
01:20Excitation-Contraction Coupling in Skeletal Muscles
Excitation-contraction coupling is a series of events that occur between generating an action potential and initiating a muscle contraction. It occurs at the triad, a structure found in skeletal muscle fibers that comprise a T-tubule and terminal cisternae of the sarcoplasmic reticulum on each side. These triads are visible in longitudinally sectioned muscle fibers. They are typically located at the A-I junction — the junction between the A and I bands of the sarcomere.
When an action potential...
When an action potential...
01:24Generation of Action Potential in Skeletal Muscles
Every cell in the body maintains a membrane potential due to an uneven distribution of positive and negative charges across its plasma membrane. The membrane potential is measured in millivolts and quantifies the difference in charge across the membrane.
Like neurons, muscle cells are also regarded as excitable due to their capacity to change in response to stimuli, primarily due to voltage-gated ion channels embedded in their plasma membranes, which get activated by alterations in the cell's...
Like neurons, muscle cells are also regarded as excitable due to their capacity to change in response to stimuli, primarily due to voltage-gated ion channels embedded in their plasma membranes, which get activated by alterations in the cell's...