AAWSAP DIRD, Technological Approaches to Controlling External Devices, March 2010

Text

This text came with the file. It may have mistakes. When the text and the image disagree, the image is right.

UNCLASSIFIED/ fFOlil OFFI&I.t.k WIiii 8Plklf
NONINVASIVE MAGNETIC DEVICES
Detection of magnetic fields arising from neural activity using MEG or a future
technology have the same inherent limitations as EEG-only noninvasive sensors.
Resolving these signals from background in any naturalistic environment will not occur
without the development of a disruptive technology in shielding that is portable and
lightweight enough to be worn comfortably on the head, and will attenuate background
amplitude nearly 10 orders of magnitude across the entire range of neural signal
frequencies, and the entire range of frequencies where the detection electronics may be
sensitive. Body-temperature superconducting materials may accomplish the shielding if
engineering development continues, and these could be combined with atomic
magnetometer technology to produce a portable system, though the inherent
limitations of the method will still be present.
INVASIVE TECHNOLOGIES - GENERAL, OPTICAL, AND EX-VIVO
ENGINEERING
All invasive technologies will have to undergo substantial rigorous testing to determine
the long-term side-effects of implantation and operation, as well as drift in the
operational performance with extended use. Several pre-clinical devices detailed above
and discussed below show promise, but the handful of human trials show that direct
interface technologies based on proximal action potential stimulation and detection are
still a long way off from practical application since the trials themselves in duplex
operation show functional failure after only a matter of weeks. The mammalian auditory
system is well studied, and the cochlear implant has been in use and continued
development for more than 30 years, and there is yet to be any practical application for
implanting a cochlear device into a normal healthy individual. Proximal electrode
interfaces do not appear to be the answer for high bandwidth BMI, and further
development in the machine-biology contact is required. If the 30-year advancement of
cochlear is a realistic guide of innovation, the proximal electrical technology path to
success is 30-40 years off save for a disruptive advance in the development of
penetrating electrodes.
Two invasive research paths that are promising are optical stimulation and gating, and
ex-vivo growth of neural cells on physical circuits.
The advantage of optical stimulation and gating is that one could theoretically design an
optical link to act as a connected input dendrite on a single neuron. Theoretically, one
should also be able to use spectroscopic sampling to determine if an action potential is
progressing down an axon, thus providing a single neuron output (read or monitor)
capability as well. This invasive but noncontact full-duplex information channel would
effectively hook-up the physical computer seamlessly to the network structure of the
brain. Proof of principle studies in this technology could emerge at any time, and given
the demonstrated plasticity of neural networks in both closed-loop visual feedback and
lamprey experiments, could provide a disruptive path for advancement of BMI.
The ex-vivo growth of neural tissue on electrode arrays provides a controlled platform
for:
•
Testing long-term effects of electrode use on proximal neural tissue.
UNCLASSIFIED/ /FOlil OFFI€llAL 1:181! 8Htl"
26