Based on the neurophysiological observations accumulated in a decade of research, the BMI technology will incorporate a series of key design features. First, a new generation of high density microelectrode arrays will be utilized to record the type of brain-derived signals required to drive this new neuroprosthetic device. Such multi-electrode arrays will be chronically implanted throughout the upper and lower limb representations of at least five cortical regions in each cerebral hemisphere of the subject: the dorsal and ventral premotor cortices, the primary motor cortex, the primary somatosensory cortex, and the posterior parietal cortex.

Both single unit and multi-unit data, as well as local field potentials derived from the same large set of microwires, will provide the “voluntary motor signals” needed to drive this neuroprosthesis. Our expectation is that the neuroprosthetic device developed by the WAP™ will allow the simultaneous recording of the electrical activity generated by up to a couple of thousand individual brain cells. To maintain its performance and be of clinical use for patients, such large-scale brain activity recordings will have to remain stable for up to a decade without any further surgical repair. New material designs will be implemented that enable long term utility of these implanted devices.

Custom-designed microchips (also known as neurochips), chronically implanted in the skull, will be utilized for all signal processing conditioning required for making brain electrical signals capable of driving a neuroprosthetic device. To significantly reduce the risk of infection and damage to the cortex, these neurochips will also have to incorporate low-power, multi-channel wireless technology, capable of transmitting the collective information generated by thousands of individual brain cells to a small wearable processing unit. Such a unit, worn on the patient’s belt, will be the size of a modern cell phone. It will be responsible for running multiple and independent real-time computational models designed to optimize the real-time extraction of motor parameters from brain-derived signals. This unit will also control all training paradigms employed to allow paralyzed patients to learn how to operate the neuroprosthetic device.

Once extracted from the raw electrical brain activity, time-varying, kinematic and dynamic digital motor signals will then be employed to continuously control the actuators distributed across the joints of a wearable, whole-body, robotic suit. Such a suit is formally known as a full-body exoskeleton. We will employ derivatives of existing exoskeletons which are currently being tested in both rehabilitation settings and in studies on enhancing human performance. According to the current state-of-the-art techniques available for controlling such a device, high order brain-derived motor commands will interact with local electromechanical circuits, distributed across the exoskeleton, in order to mimic spinal-cord arc reflexes. Thus, higher-order motor instructions, such as initiation of the step cycle, changes of gait speed, or triggering of postural and gait adjustments in response to an unexpected change in terrain would be controlled directly by the patient’s voluntary motor activity. Meanwhile, low-level motor adjustments would be handled directly by the exoskeleton’s electromechanical circuits. Such interplay between brain-derived control signals and robotic reflexes, known as shared brain-machine control, would be responsible for controlling the autonomous locomotion of an upright patient who would literally be carried away by the exoskeleton, using his/her own voluntary will.

We also envision that force and stretch sensors, distributed throughout the exoskeleton would generate a continuous stream of artificial “touch and proprioceptive” feedback signals to inform the patient’s brain of the neuroprosthetic performance. Such signals would be delivered, via multi-channel cortical microstimulation, directly into the patient’s primary somatosensory cortices. Our prediction is that, after a few weeks, such a continuous stream of somatosensory feedback signals combined with vision, would allow patients to incorporate, via a process of experience-dependent cortical plasticity, the whole exoskeleton as a true extension of their body, and use this apparatus to once again move freely and autonomously around the world.