Dexterous finger movements depend largely on the corticospinal tract (CST) in higher primates. Following a partial spinal cord injury (SCI) including the CST at the mid-cervical segment in non-human primates, dexterous finger movements impaired immediately, but recover within 1-3 months by intensive rehabilitation. Plastic changes in activity of the primary motor cortex (M1), premotor cortex (PM), and spinal circuits associated with recovery of dexterous finger movements. However, the contribution of up-stream of the motor cortices to recovery after a partial SCI remains unclear. Recently, we demonstrated that the nucleus accumbens (NAcc), which is known as a key node for processing motivation and reward, facilitates activity of the M1 and is directly involved in the control of finger movements in the early recovery stage after a partial SCI. We further clarified that the NAcc is essential for recover of dexterous finger movements after a partial SCI. Although the NAcc is not thought to be involved directly in motor control, our findings demonstrated that the NAcc has a functional role for motor control after a partial SCI. Furthermore, neuroimaging study revealed that reorganization of the NAcc-motor networks occurs after a partial SCI. Our findings suggest that the NAcc is the key node of the cortical reorganization required for functional recovery of finger dexterity.

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A proprioceptive disorder in a leg can cause knee collapse and genu recurvatum during walking. However, there are few reports on rehabilitation of this walking disorder when it is due to sensory disturbance. Herein we describe a stroke patient in his 60s with severe sensory disturbance subsequent to a right putaminal hemorrhage who underwent walking exercise based on the inverted pendulum model. On day 15 post-onset, his left lower extremity had a Brunnstrom recovery stage of VI and the manual muscle test score for his left hip extensors was 3. His tactile sensation and proprioception in the left lower extremity were severely decreased. He could walk while grasping a parallel bar with his right hand but knee collapse and genu recurvatum occurred. We implemented walking exercises based on the inverted pendulum model for 40–60 minutes/day for about a month. On day 53 post-onset, his knee collapse and genu recurvatum resolved and he was able to walk independently indoors with a cane. Although there was no obvious improvement in his sensory disturbance, his manual muscle test for the left hip extensors increased to 4. The progress suggests that walking exercise based on the inverted pendulum model may have a positive effect on walking ability in a patient with severe sensory disturbance. The improvement in walking ability in this patient was attributed not to sensory improvement but to muscle strengthening and reacquisition of motor control using residual physical function.

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