Recent research at University of Washington has produced an implantable chip that can induce strengthened neuronal connections in the motor parts (movement control) of the brain in monkeys lasting more than a week.
Improving this way weak neuronal connections might rehabilitate people with brain injuries, stroke, or paralysis.
The awake brain continuously controls all the voluntary movements through the nerve cells (neurons) from the motor cortex of the brain, which send command signals to all the skeletal muscles. The scientists looked for a computer or mechanical device outside of the body that could be operated to send the same neuronal signals.
A miniature device with a tiny computer chip - called Neurochip - could create changes within motor neurons. Neurochips were placed on the heads of monkeys left to behave naturally (including to sleep). "The Neurochip records the activity of motor cortex cells", explained Dr. Eberhard Fetz, professor of physiology and biophysics. "It can convert this activity into a stimulus that can be sent back to the brain, spinal cord, or muscle, and thereby set up an artificial connection that operates continuously during normal behavior. This recurrent brain-computer interface creates an artificial motor pathway that the brain may learn to use to compensate for impaired pathways."
When the brain-computer interface continuously puts in contact close areas in the motor cortex, it produces long-lasting changes. The movements from the recording site changed to resemble those from the stimulation site. It is likely that pathways within the cortex from the recording to the stimulation site are strengthened by the continuous synchronization of activity at the two sites, due to the device. The strengthening effect appears only if the time between the recorded activity and the stimulation is short enough.
The strengthening effect appears in a day of continuous excitement with the recurrent brain-computer interface, but it may last more than a week after removing the device. "This unusually long-lasting plasticity may be related to the fact that the conditioning is associated with normal behavior," Fetz said.