Selective Muscle Activation in Primates

The purpose of the study is to assess the selectivity of intradural peripheral nerve activation in primates using a multiple contact cuff electrode. The cuff electrode consisted of four platinum contacts and was implanted around ventral nerve root L5 in the cauda equina. A constant current stimulator delivered single biphasic stimulation pulses. Four monopolar (using a surface indifferent anode) and bipolar electrode configurations (using two opposite contacts within the electrode) were tested. Electromyography (EMG) of four lower limb muscle groups was recorded. Current intensity was increased until saturation of all muscle responses was achieved. Rectified integrated EMG was normalised and plotted against current intensity to construct recruitment curves. Preliminary results show poor selectivity using monopolar as well as bipolar electrode configurations. It is concluded that no selectivity could be shown in this preliminary trial.