To reach high temporal and spatial resolution, N3 will focus on two approaches: noninvasive (Technical Area 1 –TA1) and “minutely” invasive (Technical Area 2 – TA2) neural interfaces. Noninvasive interfaces will include the development of sensors and stimulators that do not breach the skin and will achieve neural ensemble resolution (<1mm3). Minutely invasive approaches will permit nonsurgical delivery of a nanotransducer: this could include a self- assembly approach, viral vectors, molecular, chemical and/or biomolecular technology delivered to neurons of interest to reach single neuron resolution (<50μm3). In this application, the developed technology will serve as an interface between targeted neurons and the sensor/stimulator. They should be sufficiently small to not cause tissue damage or impede the natural neuronal circuit. The sensors and stimulators developed under the minutely invasive approach will be external to the skull and will interact with the nanotransducers to enable high resolution neural recording and stimulation.
Both noninvasive and minutely invasive approaches will be required to overcome issues with signal scattering, attenuation, and signal-to-noise ratio typically seen with state of the art noninvasive neural interfaces. Systems that are larger or requiring a highly controlled environment – such as magnetoencephalography (MEG), or magnetic resonance imaging (MRI) – and proposals describing incremental improvements upon current technologies, such as electroencephalography (EEG), may not be considered responsive to this BAA and may not be evaluated.
Final N3 deliverables will include a complete integrated bidirectional brain-machine interface system. Non-invasive approaches will include sensor (read) and stimulator (write) subcomponents integrated into a device (or devices) external to the body (Figure 1B). Minutely invasive approaches will develop the nanotransducers for use inside the brain to facilitate read out and write in (Figure 1A). Minutely invasive approaches will also develop the external subcomponents and integrated devices that interact with the internal nanotransducers. N3 developed technologies may move beyond the traditional voltage recordings associated with action potentials, and include different types of signals, such as light, magnetic/electric fields, radiofrequency, and neurotransmitter/ion concentrations. These atypical signals may require the development of new algorithms to enable accurate decoding and encoding of neural activity. To that end, the N3 program will include a computational and processing unit that must provide task- relevant decoded neural signals for control in a DoD-relevant application. It must also provide the capability to encode signals from a DoD-relevant application and deliver sensory feedback to the brain. The processing unit must decode/encode in real time with minimal system latency (Figure 1C). A block diagram of the expected final prototype is shown in Figure 2.
To prove the capabilities of the N3 system, four major demonstrations will show progress from a benchtop proof-of-concept, to validation in animal models, to a final demonstration of a DoD- relevant application in human subjects. In order to transition the developed technology to clinical readiness, N3 performers will actively collaborate with the Food and Drug Administration (FDA) throughout the program.
ABC
Figure 1. Notional N3 prototype. 1A - Nanotransducers supporting read and write functions (for TA2 devices only). 1B right - Notional concept of at least two subcomponents integrated into one device. 1B left – notional diagram of multiple devices used to achieve multi-focal interaction with the brain. 1C - Processing unit for decoding and encoding computation between the N3 system and relevant DoD application.
   (minutely invasive devices only)
 Internal
Figure 2. Block diagram of N3 technology
External
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HR001118S0029, Next-Generation Non-Surgical Neurotechnology
1.2. TECHNICAL AREAS
The N3 program will provide up to four years of funding to deliver a nonsurgical neural interface system and is divided into three sequential Phases: Phase I (base effort)– 12 months, Phase II (option) – 18 months, and Phase III (option) – 18 months. N3 anticipates that each proposal will involve multiple integrated teams (from the same or different institutions) collectively developing the technological approaches for read out and write in. Teams must structure proposals as a single, unified effort with a system integrator that address all the program goals of the specified Technical Area (TA). Proposals that do not address all of the technical objectives may be considered non-responsive. Proposals must address a complete bidirectional neural interface system based on at least one of the following TAs:
Technical Area 1. Noninvasive neural interface
Technical Area 2. Minutely invasive neural interface
System Integration
Due to the complexity and performance objectives of the N3 system, proposals must identify a lead integrator with a proven track record of managing and integrating disparate technologies. Starting as early as Phase I, system integration should be a consideration throughout the program.
Security Measures
Proposers must use approaches that ensure confidentiality, integrity, and availability (also known as the CIA triad) to prevent spoofing, tampering, or denial of service. It will be necessary to adequately secure the connection between the integrated device, the processing unit, and the system user’s brain. Proposers must incorporate inherently safe techniques into any wireless and electronic portions of their system, and proposals must describe the specific protocols and techniques to be used.
Ethical, Legal, and Societal Implications (ELSI)
DARPA maintains its commitment to ensuring that efforts funded under this BAA adhere to ethical and legal regulations currently in place for federally and DoD-funded research. Program developments will be discussed with a panel of expert external advisors with expertise in bioethical issues that may emerge as a consequence of advances in neurotechnology. Proposers to this BAA must address potential ethical, legal, and societal implications of their proposed technology.