Implantable stimulator featuring multiple programs, adjustable stimulation amplitude and bi-directional communication for implantation in mice.

We describe an implantable stimulator with adjustable output amplitude and bi-directional communication at a size of approximately 1 cm(3). The user selects from preset patterns of stimulation and adjusts the stimulation amplitude by sending coded flashes of light, and receives active confirmation of the chosen settings via a powerful LED in the device. These characteristics allow selectivity of motor nerve stimulation and minimize unwanted excitation of adjacent structures. For example, stimulation of dorsiflexors can be achieved in mice without stimulation of plantarflexors. The device can deliver constant frequency stimulation as well as burst-like stimulation patterns with adjustable ON/OFF times. A lifetime of at least 4 weeks of stimulation at an average frequency of 40 Hz can be achieved. The device was built from standard surface mount components and encapsulated with biocompatible silicone rubber. The use of modern microelectronics allowed us to develop a versatile and highly customizable miniature stimulator.