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This Defense Intelligence Reference Document from the Defense Intelligence Agency, dated 23 March 2010, was produced under the Advanced Aerospace Weapon System Applications (AAWSA) Program. It surveys invasive and noninvasive brain-machine interface technologies for controlling external devices without limb-operated interfaces. The technologies covered include EEG, MEG, fMRI, NIRS, and implanted electrode arrays. It concludes that noninvasive electrical monitoring is the most promising near-term approach. In the long term, it favors invasive single-neuron cortical connections that use optical stimulation or chip-based arrays.
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CHRONIC NEURAL IMPLANTS AND FMRI
While developing microelectric neural chips for functional studies appears revolutionary
on the surface, it only presents a piece to the greater puzzle of understanding the
feasibility between neuroprosthetic chips and BMI development. For a BMI system to
succeed, researchers must understand the brain, its regions of activity and how those
area correlate to real time stimulation and neural responses, and how the brain may
evolve with training on use of the BMI. This will require the employment of sensitive
neural mapping devices such as fMRI.
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Figure 6. Implant Location. Cartoon shows location and orientation of the different electrode sites in the various
layers of an animal's neocortical implant (layer thicknesses are approximately scaled). The gray band is the 200μm
separation region between the upper and lower layers of the neocortex.
To address this question, studies performed by Parikh et al., have targeted tissue-
specific layers within the motor cortex region, essentially a modified ECoG, where
penetrating microelectrodes exhibit the greatest functionality in cortical prosthetic
design (Reference 47). The interesting parameter of this experimental design is its
ability to successfully employ a behavioral task paradigm where electrodes could
accurately record brain activity and animal response based on audible and visual cues.
With this information the researchers discovered that the lower layers of the cortex are
more likely to encode directional information as compared to units in the upper layers.
This understanding has prompted the use of prosthetic neural implants as critical
instruments for developing accurate BMI models and the mapping all neurological
(brain triggered) responses.
For these experiments, accurate measurement of responses was placed solely into the
unique design of chronic implantable neural prosthetic devices. These devices enabled
investigation of activity in the upper or lower brain tissue layers, including whether
either had a preference for ipsilateral (same body side) versus contralateral (opposite
side of body) movement. In addition, chronic neural implants provided an innovative
method to target isolated brain regions. During this experiment a craniotomy was
performed over the target cortical area. In this procedure, a 2 mm diameter hole is
made into the skull to expose the dura mater. This dura matter is then removed to
reveal the cortical surface. An electrode scaffold array is inserted by hand with the use
of fine PTFE-coated forceps into the target cortical area. Typically, the electrode will be
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Report, from the dia 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.