Seven-electrode EER stimulator-monitor for ambulatory monkeys.

An electrical evoked response (EER) stimulator-monitor for ambulatory monkeys is described. Seven time-multiplexed electrodes are used. The unit switches between stimulus and monitor modes at a 100-Hz rate. In the stimulus mode, 3.5 V peak, 0.45-ms pulses are applied at a 100-Hz rate to any electrode selected by means of toggle switches on a remote control panel. In the monitor mode, low-frequency -3 dB cutoff occurs at 0.2 Hz. A 20-MHz carrier is used as a local superheterodyne oscillator during the stimulus period, and as an FM transmitter during the monitor period. Three mercury cells supply 4 V at 10 mA. The unit weighs 80 g. It is 5.7 x 5 x 2.5 cm in size.