 A separate protocol will be used to test the reticulospinal connectivity. We will record the audiospinal startle reaction ASR 30 msec tone of 90 dB based on EMG of multiple leg muscles. In addition, we will test the H-reflex facilitation of both the tibialis anterior and Soleus started 50 ms after the sound to peak after 75-125 ms and returned to baseline values after 250 ms. We will also record evoked responses in leg muscles in response to epidural stimulation after conditioning with sound stimulation . The delay between sound stimulation and epidural stimulation will range from 10 - 100 ms. 