The Proposal objectives are to design a wireless framework that can simultaneously record large scale neuronal ensembles over the entire brain area. The wireless framework will be based on an array of free-floating distributed implants and an external power transmitter and interrogator array of overlapping hexagonal planar spiral coils (hex-PSC). The proposed approach is different from the traditional paradigm in that a vast number of tiny implants (1 mm in diameter and 0.1 mm thick) in the form of pushpins will be distributed over the target brain surface, each recording single unit activities (SUA) from one to four thin microwires (35 um tetrodes including Teflon coating), while being directly powered and interrogated from a wearable head-cap.
In the United States, approximately 262,000 people suffer from spinal cord injuries and more than 800,000 strokes happen every year. People with severe neurological disorders become completely paralyzed and dependent on caregivers. Because the commands from their brain fail to reach the target limbs in the natural communication pathways (nerves). It would change the lives of these individuals if an engineered system would be safe, secure, and capable enough to recognize their intentions form brain electrical signals, and translate them to communication with others or control their paralyzed limbs or artificial prostheses, such as robotic arms. Brain structure is extremely complex and the mechanisms of understanding, memory, actions, and emotions as well as many brain disorders remain mysterious because they emerge from interactions among large populations of neurons in widespread networks across the brain. Therefore, to better understand the brain, neuroscientists need advanced tools capable of recording the activity of individual neurons over many different areas of the brain, as emphasized in the recent BRAIN initiative.
Traditional methods to record brain electrical signals have relied on a single centralized high density electrode array despite the aforementioned requirements of wide area and distributed network coverage. Another problem in prior work is the tissue damage due to large implant size and wiring, resulting in degradation of the signal quality over time. This can be remedied if the implant is small and free-floating on the brain surface. We propose to develop a distributed system of small wireless neural interfaces for recording of multi-channel signals over a large brain area. The distributed implants will be small enough to be floating on the brain surface without being wired to any other large centralized structure. We will find ways to deliver power to these small implants and communicate with them. We will also test them on human brain models and anesthetized animals.
The proposed work is an attempt to design a wireless framework that can simultaneously record large scale neuronal ensembles over the entire brain area. It will be based on an array of free-floating distributed implants and an external transmitter/interrogator array of overlapping coils. There is increasing realization that neural function in the brain arises from a large distributed network. Thus, neural recording and modulation of the future will require the ability to simultaneously interface with multiple neural sites distributed over a large area. The current neural interfaces clearly fall short of achieving this goal because of their limited area coverage. The proposed approach is different from the traditional paradigm in that a vast number of tiny implants in the form of pushpins will be distributed over the target brain surface, each recording single unit activities from thin microwires, while being directly powered and interrogated from a wearable head-cap.
By reducing foreign body reaction, the small free-floating implants are expected to minimize tissue damage and enable chronic wireless recording. We will investigate the tissue response, such as inflammation and cell death in rats to assess the longevity, reliability, and fidelity of the proposed free-floating implants. We will develop novel packaging structures with hermetic sealing, which require new process flows for sub-mm sized, wirelessly-powered, free-floating devices. Unlike previous wireless power transfer systems, which have been optimized for powering a single implant, the optimization paradigm in the proposed work will consider the entire brain area. We will optimize powering of multiple implants with arbitrary orientations and alignments. This will be achieved by a novel 120¢ª offset external array of planar coils with an entirely new drive mechanism, which offers unprecedented flexibility in wireless power delivery.
