An Arbitrary Waveform Wearable Neuro‑stimulator System for Neurophysiology Research on Freely Behaving Animals

Abstract

Portable wireless neuro‑stimulators have been developed to facilitate long‑term cognitive and behavioral studies on the central
nervous system in freely moving animals. These stimulators can provide precisely controllable input(s) to the nervous system, without
distracting the animal attention with cables connected to its body. In this study, a low power backpack neuro‑stimulator was developed
for animal brain researches that can provides arbitrary stimulus waveforms for the stimulation, while it is small and light weight to be
used for small animals including rats. The system consists of a controller that uses an RF link to program and activate a small and
light microprocessor‑based stimulator. A Howland current source was implemented to produce precise current controlled arbitrary
waveform stimulations. The system was optimized for ultra‑low power consumption and small size. The stimulator was first tested for
its electrical specifications. Then its performance was evaluated in a rat experiment when electrical stimulation of medial longitudinal
fasciculus induced circling behavior. The stimulator is capable of delivering programmed stimulations up to ± 2 mA with adjusting steps
of 1 µA, accuracy of 0.7% and compliance of 6 V. The stimulator is 15 mm × 20 mm × 40 mm in size, weights 13.5 g without battery
and consumes a total power of only 5.l mW. In the experiment, the rat could easily carry the stimulator and demonstrated the circling
behavior for 0.1 ms current pulses of above 400 µA. The developed system has a competitive size and weight, whereas providing
a wide range of operation and the flexibility of generating arbitrary stimulation patterns ideal for long‑term experiments in the field of
cognitive and neuroscience research.