Clinicians have known for a long time that motivation can enhance a patient’s recovery from spinal cord injury or stroke, and that depressive symptoms resulting from brain injury can delay functional recovery.
To date, however, the mechanism has remained elusive and there has been no neuroscientific evidence as to how motivation affects recovery of motor function in rehabilitation.
A research team led by Yukio Nishimura and Hirotaka Onoe has found that the nucleus accumbens, which controls motivation in the brain, stimulates the activity of the motor cortex of the brain, and then promotes recovery of motor function during the early stage of recovery after spinal cord injury. This result was published in Science.
The research team focused on the relationship between the neuronal activity of the nucleus accumbens and that of the motor cortex, which controls motor function, in a monkey suffering from spinal cord injury. When the researchers temporally blocked the activity of the nucleus accumbens of the monkey one month after spinal cord injury, they observed that motor cortex activity was suppressed and a transient deficit of amelioration in finger dexterity was obtained by rehabilitation. In the intact monkey, and also in the fully recovered stage (three months after spinal cord injury), such deficit in hand movement by blocking the activity of the nucleus accumbens was not observed. This suggests that the nucleus accumbens makes a causal contribution to the functional reinstatement of hand control during early stage recovery, and the activity of the nucleus accumbens successfully promotes functional recovery.
“Our result suggests that in the early stage after brain injury including spinal cord injury, it is important to motivate the patients for promoting functional recovery in rehabilitation. Psychological support may also be important,” said Nishimura.
Reference: M. Sawada, K. Kato, T. Kunieda, N. Mikuni, S. Miyamoto, H. Onoe, T. Isa, Y. Nishimura. Function of the nucleus accumbens in motor control during recovery after spinal cord injury. Science, 2015; 350 (6256): 98 DOI: 10.1126/science.aab3825