Figure 3.

Inactivation experiments. Performance on the horizontal ladder is measured before (−) and during (+) inactivation. For experimental schema, see Figure 1A. A, Inactivation of the motor cortex in naive rats produces a strong and selective impairment in the contralateral (Contra) forelimb (paired t test, p = 0.02); the ipsilateral (Ipsi) forelimb is not affected. B, Loss of behavioral recovery with ipsilateral motor cortex inactivation. A subset of rats from the study of brain stimulation for motor recovery (n = 3 per group) was subjected to motor cortex inactivation (n = 6 inactivations per group). In the rats with injury only, inactivation did not change the error rate in the impaired forelimb. However, in rats with injury and stimulation, inactivation of the stimulated motor cortex reinstated their initial deficit in the ipsilateral forelimb (paired t test, p = 0.01). There was no difference between the two groups in the effect of inactivation on the contralateral forelimb. This demonstrates that improved motor performance with electrical stimulation was attributable to control from the ipsilateral and stimulated motor cortex. *p < 0.05.