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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/ /EOR OlifilEIAk W&li (UtLY The brain activity mentioned above is a complex chain of ionic motion within the central nervous system. Ionic production, release, and movement within and between cells all consume energy. This energy is supplied by the conversion of blood-borne oxyhemoglobin to deoxyhemoglobin. The rate of oxygen consumption in a localized volume varies based on local neural activity. The circulatory system compensates for changes in energy demand by increasing or decreasing both the flow rate and volume of blood, regionally and locally. Local energy demand, expressed in the capillary beds, will alter the rate at which oxygen is metabolized, called the cerebral rate of oxygen metabolism, abbreviated CMRO2. When brai n activity increases in a region, the circulatory response, called the hemodynamic response, will be increases in flow and volume, while the local areas increase CMRO2. The hemodynamic response consistently provides an excess of oxygen over what is required, and this results in some oxyhemoglobin traveling through the capillary bed and local venous structure without being converted into deoxyhemoglobin. Oxy- and deoxyhemoglobin have different magnetic susceptibilities, and different infrared spectra. The hemodynamic response, by changing the net ratio of oxy- to deoxyhemoglobin in the local venous structure, thus changes the local magnetic susceptibility and local infrared resonance spectra around focused brain activity. This complex chain reaction is called the Blood Oxygen Level Dependent, or BOLD effect (Reference 8). The BOLD effect leads to a method to indirectly measure the local brain activity by monitoring the hemodynamic response using Magnetic Resonance Imaging (MRI) or Near Infrared Spectroscopy (NIRS). The BOLD response to any event peaks about 4-6 seconds a~er the event occurs, limiti ng the applications for which monitoring these signals and their associated delay may be useful, given the BMI operating parameters defined above Furthermore, person to person variation in distributed signals show significant differences in regions activated (Reference 9), though there is evidence that these inter-subject variations are stable intra-subject over time (Reference 10). Control of External Devices In general, t here are two types of BMI design called open-loop and closed-loop. Open loop designs, those either detecting activity or providing stimulation, are important for BMI research and application other than the practical control of an external device. Closed-loop systems include both output signals from the brain to effect a change in the state of a device, and a stimulation channel, which can be used as feedback. In some system designs, the feedback can be via visual cues such as watching a display (Reference 11). Open- loop systems are important for BMI research and have application in sense replacement such as artificial hearing, or when extensive output signal processing is combined with external device state feedback (see remote robot operation below). For learning and fine, efficient control of external devices without significant external processin g, closed-loop systems are typically needed . Several components constitute a general BMI system for control of an external device (Figure 2). As mentioned in the previous section, the interfaces where the information signal makes the jump between biological and physical pathways are the most challenging part of the system. These connections can be placed to stimulate or read peripheral or cerebral neurons . The processing step could be as simple as amplification UNCLASSIFIED/ /FOR OFFl@IAL Y!H! 8HL1/ 4
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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.