Neurorobotics as a means for assessing brain function after spinal injury

Neurorobotics is suggested as a way to evaluate functional changes in brain neural circuits after spinal cord injury and repair. We suggest that the critical question when evaluating the effects of spinal lesion on brain circuits is not the extent to which these circuits can respond to passive stimulation but the ability of these circuits to code for motor plans. Arrays of microelectrodes (32 total) were chronically implanted into the sensorimotor region of the brain and used to monitor neuronal activity before and after a subtotal spinal hemisection. The response of neurons to stimulation of their receptive field was quantified and microstimulation was used to assess the motor output of the circuits. Neurons were recorded while the animal walked on a treadmill and a population function was generated to predict foot contact on the treadmill. The ability to predict foot contact was used as a measure of the ability of the neural circuits to code for motor output (i.e. foot contact prediction). Preliminary results suggest that while there was a significant decrease in the response of these neurons to stimulation of their receptive fields after spinal lesion and microstimulation was no longer able to generate coordinated muscle contraction, the population function was still able to predict foot contact on the treadmill more than 90% of the time, similar to prehemisection prediction rates.