Posts tagged corticospinal tract
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)
Irreversible tissue loss seen within 40 days of spinal cord injury
The rate and extent of damage to the spinal cord and brain following spinal cord injury have long been a mystery. Now, a joint research effort between the University of Zurich, University Hospital Balgrist and colleagues from University College London have found evidence that patients already have irreversible tissue loss in the spinal cord within 40 days of injury. Using a new imaging measurement technique the impact of therapeutic treatments and rehabilitative interventions can be now determined more quickly and directly than before.
A spinal cord injury changes the functional state and structure of the spinal cord and the brain. For example, the patients’ ability to walk or move their hands can become restricted. How quickly such degenerative changes develop, however, has remained a mystery until now. The assumption was that it took years for patients with a spinal cord injury to also display anatomical changes in the spinal cord and brain above the injury site. For the first time, researchers from the University of Zurich and the Uniklinik Balgrist, along with English colleagues from University College London (UCL), now demonstrate that these changes already occur within 40 days of acute spinal cord injury.
Spinal cord depletes rapidly
The scientists studied 13 patients with acute spinal cord injuries every three months for a year using novel MRI (magnetic resonance imaging) protocols. They discovered that the diameter of the spinal cord had rapidly decreased and was already seven percent smaller after twelve months. A lesser volume decline was also evident in the corticospinal tract, a tract indispensable for motor control, and nerve cells in the sensorimotor cortex. The extent of the degenerative changes coincided with the clinical outcome. “Patients with a greater tissue loss above the injury site recovered less effectively than those with less changes,” explains Patrick Freund, the investigator responsible for the study at the Paraplegic Center Balgrist.
Gaining insights into effect of therapies
Treatments targeting the injured spinal cord have entered clinical trials. Gaining insights into mechanisms of repair and recovery within the first year are crucial. Thanks to the use of the new neuroimaging protocols, Freund says, we now have the possibility of displaying the effect of therapeutic treatments on the central nervous system and of rehabilitative measures more quickly. Consequently, the effect of new therapies can also be recorded more rapidly.
“This study is an excellent example of the value of combining the complementary expertise of the two universities,” says UCL’s Dean of Brain Sciences, Professor Alan Thompson, who is one of the senior authors of the study. “It provides exciting new insights into the complications of spinal cord trauma and gives us the possibility of identifying both imaging biomarkers and therapeutic targets.”
The findings are the result of a new three-year neuroscience partnership between the Neuroscience Centre Zurich (ZNZ) and UCL.
Literature:
Patrick Freund, Nikolaus Weiskopf, John Ashburner, Katharina Wolf, Reto Sutter, Daniel R Altmann, Karl Friston, Alan Thompson, Armin Curt. MRI investigation of the sensorimotor cortex and corticospinal tract after acute spinal cord injury: a prospective longitudinal study. The Lancet Neurology. July 2, 2013.