Posts tagged voluntary movement
Articles and news from the latest research reports.
Isolating the Circuits that Control Voluntary Movement
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.
(Source: www1.cuny.edu)
Spinal Stimulation Helps Four Patients with Paraplegia Regain Voluntary Movement
Four people with paraplegia are able to voluntarily move previously paralyzed muscles as a result of a novel therapy that involves electrical stimulation of the spinal cord, according to a study funded in part by the National Institutes of Health and the Christopher & Dana Reeve Foundation. The participants, each of whom had been paralyzed for more than two years, were able to voluntarily flex their toes, ankles, and knees while the stimulator was active, and the movements were enhanced over time when combined with physical rehabilitation. Researchers involved in the study say the therapy has the potential to change the prognosis of people with paralysis even years after injury.
“When we first learned that a patient had regained voluntary control as a result of spinal stimulation, we were cautiously optimistic,” said Roderic Pettigrew, Ph.D., M.D., director of the National Institute of Biomedical Imaging and Bioengineering (NIBIB) at NIH, which provided support for the study. “Now that spinal stimulation has been successful in 4 out of 4 patients, there is evidence to suggest that a large cohort of individuals, previously with little realistic hope of any meaningful recovery from spinal cord injury, may benefit from this intervention.”
One of the most impressive and unexpected findings of the study is that two of the patients who benefited from the spinal stimulation had complete motor and sensory paralysis. In these patients, the pathway that sends information about sensation from the legs to the brain is disrupted, in addition to the pathway that sends information from the brain to the legs in order to control movement. The researchers were surprised by the outcome; they had assumed that at least some of the sensory pathway needed to be intact for the therapy to be effective.