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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/ /FOA OFFIEill.tL l::181: 8HLY EMG Instead of measuring nerve impulses and amplifying them, one can design a system that monitors muscle movement in a hands-free approach to a mechanical interface, essentially using the muscles as a biological amplifier of neural signals. One may close the feedback loop using a heads-up display, monocle, or other visual device, or another traditional sensory feedback. The advantage of such a design is that controls may be actuated through a lightweight wireless system, effectively providing control stations anywhere such a wireless system would work. Such a system could be used to untie a pilot from the cockpit. Recent work has shown that performance of 1-2 bits/s is possible with minimal training, about four times the current performance of a comparison EEG forehead sensor (Reference 14). MRI AND FMRI Magnetic Resonance Imaging (MRI) works by a simple excitation and relaxation of spin states. When molecules containing hydrogen are placed in a strong static magnetic field, a small but detectable number of hydrogen protons align their intrinsic spins along the direction of the external field. An applied radiofrequency (RF) pulse near the proton resonant frequency, 42.6 MHz/Tesla or 128 MHz at 3 Tesla, knocks the spins perpend icular to the field and the relaxation back to ground state releases RF energy in patterns that can be reconstructed to show both composition and distribution of any hydrogen-rich materiel. The resonant frequency is a direct function of the local magnetic field defined by the Larmor relation: c.o = y B; where c.o is the frequency of precession, B is the local magnetic field, and y is a constant of the material, 42.6 MHz/Tesla for bare protons as mentioned above. Small perturbations to the static field will change the resonant frequency. By applying a small gradient to the static field, for example 100 milliTesla/meter along the z-axis, and limiting the bandwidth of the RF excitation signal to 8ro, one may select a slice of the brain perpendicular to the z-axis for excitation to 82. A change in the gradient field will change the position of the excited slice for the next excitation. Similar gradients in the x and y directions can limit the excitation to a single small volume of brain tissue. In current MRis, these gradient fields are produced with electromagnets, and the series of time-dependent imaging gradient manipulations is called the scan sequence. Free hydrogen (H) would produce a resonant signal slightly different than the bare proton due to the local field changes induced by its valance electron. Hydrogen gas (H 2) would produce a still different frequency since the local field around each proton is altered by the two shared electrons. Water molecules (H 2O) contain two hydrogen atoms and an entirely different "electron shield" than either H or H2 and thus shows still another slightly different resonant frequency. Fat and other lipid molecules, important cell structure building blocks, have long chains of hydrocarbons, and the resulting ensemble of electron screening produces a wide peak that is substantially shifted 10 from that of water. Brain gray matter and white matter have different macroscopic lipid content and are thus able to be differentiated in an MRI scan. Different signals also arise in bone, 1° Frequency detection sensitivities in MRI are very good, and "su bstantial " here means about 3 parts per million. The frequency shifts caused by imaging gradients ranges in the parts per thousand. UNCLASSIFIED/ f FOA OFFIEiIAL l::ISE 8PtLY 9
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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.