Isolating the circuits that control voluntary movement

May 7, 2014 by Sophie Davis
brain

(Medical Xpress)—Extraordinarily complex networks of circuits that transmit signals from the brain to the spinal cord control voluntary movements. Researchers have been challenged to identify the controlling circuits, but they lacked the tools needed to dissect, at the neural level, the way the brain produces voluntary movements.

Recently, Dr. John Martin, medical professor in City College's Sophie Davis School of Biomedical Education, postdoctoral fellow Dr. Najet Serradi and other colleagues employed a sensitive genetic technique that eliminated a particular gene in the cerebral cortex and, in the process, changed the circuitry.

The team hypothesized that the corticospinal tract, which stretches from cerebral cortex to the spinal cord, is important for voluntary reaching movements, but not for more routine and stereotypic walking movements. "We reasoned that if we genetically altered the corticospinal tract we would affect voluntary reaching movements, but not walking." Professor Martin said.

In genetically intact mice, corticospinal tract signals are transmitted from one side of the cerebral cortex to the opposite side of the spinal cord. Such mice reach with one arm, or the other – but not both arms together.

Professor Martin and colleagues used specially bred mice, i.e. knockout mice, with the gene EphA4 removed from the cerebral cortex. These mice reached with both forelimbs together, rather than with one. This happened because the genetic manipulation changed the circuit; it caused the signal to move to be transmitted from one side of the cerebral cortex to both sides of the spinal cord.

However, their stereotypic walking was unaffected. Professor Martin said this shows that while voluntary movements depend on the corticospinal tract walking depends on circuits in other parts of the brain and spinal cord, which are not affected by the gene manipulation.

The findings, he added, "etch away at the vexing problem of achieving a deeper understanding of how the brain functions in voluntary movement." In addition greater knowledge of how voluntary circuits function could lead to new understanding of cerebral palsy, a condition in which the corticospinal tract is injured around the time of birth and people often make "mirror movements" of both arms when they intend to move only one, he said.

The research, which is funded by the National Institute of Neurological Diseases and Stroke, aims to understand the brain and spinal cord circuits for voluntary movement. Using similar genetic tools, his team hopes to further dissect the connections and functions of the corticospinal tract movement circuits in ways to restore movements after brain or spinal cord injury.

The findings were published April 9 in the Journal of Neuroscience.

Explore further: Brainstem discovered as important relay site after stroke

More information: Paper: www.jneurosci.org/content/34/15/i.short

Related Stories

Brainstem discovered as important relay site after stroke

February 25, 2014
Around 16,000 people in Switzerland suffer a stroke every year. Often the result of a sudden occlusion of a vessel supplying the brain, it is the most frequent live-threatening neurological disorder. In most cases, it has ...

Scientists reveal circuitry of fundamental motor circuit

May 2, 2014
Scientists at the Salk Institute have discovered the developmental source for a key type of neuron that allows animals to walk, a finding that could help pave the way for new therapies for spinal cord injuries or other motor ...

Regenerating spinal cord fibers may be treatment for stroke-related disabilities

May 23, 2013
A study by researchers at Henry Ford Hospital found "substantial evidence" that a regenerative process involving damaged nerve fibers in the spinal cord could hold the key to better functional recovery by most stroke victims.

Hand use improved after spinal cord injury with noninvasive stimulation

November 29, 2012
By using noninvasive stimulation, researchers were able to temporarily improve the ability of people with spinal cord injuries to use their hands. The findings, reported on November 29th in Current Biology, a Cell Press publication, ...

Restoring paretic hand function via an artificial neural connection bridging spinal cord injury

April 11, 2013
Functional loss of limb control in individuals with spinal cord injury or stroke can be caused by interruption of the neural pathways between brain and spinal cord, although the neural circuits located above and below the ...

Recommended for you

Firing of neurons changes the cells that insulate them

August 22, 2017
Through their pattern of firing, neurons influence the behavior of the cells that upon maturation will provide insulation of neuronal axons, according to a new study publishing 22 August in the open access journal PLOS Biology ...

Activating brain region creates intense desire to use cocaine

August 22, 2017
Researchers have identified a portion of the brain that intensifies one's desire for certain rewards—in this case, mimicking addiction to cocaine.

Study suggests serotonin may worsen tinnitus

August 22, 2017
Millions of people suffer from the constant sensation of ringing or buzzing in the ears known as tinnitus, creating constant irritation for some and severe anxiety for others. Research by scientists at OHSU shows why a common ...

Brain region mediates pleasure of eating

August 22, 2017
Providing the body with food is essential for survival. But even when full, we can still take pleasure in eating. Researchers at the Max Planck Institute of Neurobiology in Martinsried and the Friedrich Miescher Institute ...

Chronic stress induces fatal organ dysfunctions via a new neural circuit

August 22, 2017
Hokkaido University researchers revealed that fatal gut failure in a multiple sclerosis (MS) mouse model under chronic stress is caused by a newly discovered nerve pathway. The findings could provide a new therapeutic strategy ...

Contact in sports may lead to differences in the brains of young, healthy athletes

August 22, 2017
People who play contact sports show changes to their brain structure and function, with sports that have greater risk of body contact showing greater effects on the brain, a new study has found.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.