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This Defense Intelligence Reference Document was produced by the Defense Intelligence Agency's Defense Warning Office under the Advanced Aerospace Weapon System Applications program and dated 23 March 2010. It surveys noninvasive and invasive brain-machine interface technologies, including EEG, MEG, fMRI, NIRS and implanted electrode arrays, that could control external devices without limb-operated interfaces. It concludes that noninvasive electrical monitoring is the most promising near-term approach. For the long term it favors invasive single-neuron cortical connections.
From the source: Release of 2026-09-18 Incident: 3/23/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD surveys brain-machine interface technologies intended to allow users to control external devices without conventional manual controls, and it evaluates both noninvasive and invasive approaches for turning neural or related physiological signals into usable commands. The report reviews the underlying neural signals, distinguishes between open- and closed-loop control systems, and examines technologies including scalp-based electrical recording, magnetic and imaging-based methods, and implanted cortical interfaces, with particular attention to bandwidth, response time, signal quality, and practical usability. It concludes that, in the near term, the most practical systems are likely to be noninvasive electrical approaches that draw heavily on muscle and neural signals, while longer-term high-bandwidth control would likely require more advanced invasive interfaces capable of robust two-way communication with individual neurons. The document presents thought-based control of external devices as a research field with plausible assistive and specialized applications, while emphasizing that naturalistic, high-performance control remained constrained by major technical and physiological limits.
UNCLASSIFIED/ ;'FOR OFFl&I.t.k Wliliii &NL¥ The signal transmission down the axon of a neuron is an all-or-nothing process. When the cell body is stimulated above threshold, the axon transmits the same action potential at the same speed and in the same direction, regardless of the extent above threshold or duration of the input. Action potentials have durations of 1-10 milliseconds. Input signals can result in transmission of multiple action potentials, and thus the frequency and number of neuronal firings do vary with the input. Neurons require some t ime to reset between firings, nominally the duration of the pulse for that axon, yielding a typical maximum firing rate of between 100 hertz (Hz) and 1 kilohertz (kHz). It is instructional at this point to contrast this mechanism with propagation of signals through a physical electrical circuit, the planned external portion of our BMI. In a copper wire, electrons carry the signal. Electrons drift along the signal path, but the signal itself moves as a compression wave rather than a transverse wave as in the biologica l system. Going back to our garden hose example, consider the hose now filled with small marbles: inserting a marble at one end will move each marble in the hose just a little, but very rapidly the last marble in line will pop out of the far end of the hose. As with the biological system, the signal is propagated to the far end of the hose by local actors rather than physical motion of a single ion or electron moving the whole distance. The underlying physics governing the signal transmission makes metallic and semimetallic circuits about a million times faster than the biological system. This difference in the carriers and underlying mechanisms of signa l transmission between biological and physical circuits has so far prevented the invention of a direct connection between the two disparate systems. Instead, both noninvasive and invasive direct-detection technologies rely on placing physical sensors or transmitters in close proximity to the neurons of interest and utilizing classical electrodynamics to govern signal jump between the systems. Additionally, given the maximum typical firing rate for neurons of 1 kHz, sampling of action potentials at a few kHz will be fast enough to detect firing of any individual neuron, though super-sampling above 10 kHz can be used to reduce noise. Higher sampl ing frequencies also may be required if multiple neurons are monitored and quantitative information about their relative firing sequence is desired . Frequencies of a 1 kHz or below are sufficient to stimulate action potentials, and again, higher system frequency may be required for multiple neuron sequential stimulation. Finally, higher frequencies may be required if monitoring or stimulation of some aspect of signal transmission other than action potentials is sought, such as monitoring single ion channels. 1 There is currently no evidence that transduction frequencies above 100 kHz have any advantage in BMis, thus the main challenge is the connection dynamics, since even this ultra-maximum frequency is easily attainable with current electronic manufacturing technology. The human brain doesn't process information as a traditional computer does. Information is moved around through pathways and at certain neurons it is allowed or not allowed to pass based on excitory or inhibitory dendritic signals arriving before triggering of action potentials . Local groups of neurons can act nearly coherently, for example in volition of motor action like a hand movement. Detecting such coherent firing at nodes around the bra in is robust both noninvasively and invasively, though 1 Technologies that monitor single ion channels on a neuronal membrane are important for researc h on neural function and neurotransm itter action . However, these devices are ultra -sensitive to physical motion, and have so far not proven useful in large scale information transfer required in BMis . UNCLASSIFIED/ /fOll OFFl@IAl W&lii OPU..¥ 2
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Official release, from the pursue collection. The PDF is mirrored here; the original link is above. 36 pages are in the text index: search them above, or from the library's search.