Brain-machine interface using brain surface electrodes • real-time robotic control and a fully implantable wireless system

The brain-machine interface (BMI) enables us to control machines and to communicate with others, not with the use of input devices, but through the direct use of brain signals. This paper describes the integrative approach we used to develop a BMI system with brain surface electrodes for real-time robotic arm control in severely disabled people, such as amyotrophic lateral sclerosis patients. This integrative BMI approach includes effective brain signal recording, accurate neural decoding, robust robotic control, a wireless and fully implantable device, and a noninvasive evaluation of surgical indications. We have previously shown that power in the high gamma band (80-150 Hz) gave the highest decoding accuracy. We succeeded in generating voluntary control over the grasping and releasing of objects, using a successive decoding and control algorithm that achieves smooth robotic hand movements. Even in patients with severe motor disturbances, merely imagining hand movements was enough to induce clear, high gamma band responses that were similar to those induced by real movements. A fully-implantable wireless system is indispensable for the clinical application of invasive BMI in order to reduce the risk of infection. We have developed a prototype which is a 128-channel fully-implantable wireless system that includes many new technologies such as a 64-channel integrated analog amplifier chip, a Bluetooth wireless data transfer circuit, a wirelessly rechargeable battery, 3 dimensional tissue-fitting high density electrodes, a titanium head casing, and a fluorine polymer body casing. We are planning clinical trials and the introduction of our BMI system after the completion of a two-staged clinical research program using wired and then wireless systems.