Design of a computer-controlled current stimulator for neree and muscle excitation

Abstract

Electrical stimulation of excitable tissues has been widely used for diagnosing and treating neurological and muscular disorders. Electrical stimulation is also used to analyze and understand inherent functions of nerves and muscles. This study includes the circuit design of a current stimulator and its custom LabVIEW interface. The device is based on a modi ed Howland current-source topology due to its e ciency for injecting precise current without being a ected by load resistance variations. Modi ed Howland current source converts voltage signals to desired current signals. The device is powered by an external power supply with high compliance 37 Vdc. Waveforms are produced by using a computer audio output which is controlled by LabVIEW. Therefore any user can create its own user interface with any programming environment. Sinusoidal, square and triangle waveforms, in di erent frequencies, amplitudes and pulse widths, can be generated within the range of the sound card speci cations. The device can generate both monopolar and bipolar current pulses with pulse duration of 0:05 {u100000} 10 ms. Reliable frequency range of the system is 10 {u100000} 10; 000 Hz and it can deliver 6:6 mApp at 10 k dummy load. This system can be easily constructed and is very inexpensive compared to commercial units. Both electrical and physiological tests are performed in order to prove that the device is running properly and it can be utilized in laboratory experiments of electrophysiology especially for somatosensory evoked potentials.|Keywords : Electrical stimulation, modi ed Howland current source, LabVIEW, audio output, electrophysiology.