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posted by martyb on Monday April 16, @10:22AM   Printer-friendly
from the Is-this-thing-on? dept.

Are we getting closer to a complete brain mapping? New devices explore more regions safely

Researchers at the University of Southern California Viterbi School of Engineering have developed thin, flexible polymer-based materials for use in microelectrode arrays that record activity more deeply in the brain and with more specific placement than ever before. What's more is that each microelectrode array is made up of eight "tines," each with eight microelectrodes which can record from a total 64 subregions of the brain at once.

In addition, the polymer-based material, called Parylene C, is less invasive and damaging to surrounding cells and tissue than previous microelectrode arrays comprised of silicon or microwires. However, the long and thin probes can easily buckle upon insertion, making it necessary to add a self-dissolving brace made up of polyethylene glycol (PEG) that shortens the array and prevents it from bending.

Professor Ellis Meng of the USC Viterbi Department of Biomedical Engineering and Michelson Center for Convergent Bioscience said that the performance of the new polymer-based material is on par with microwires in terms of recording fidelity and sensitivity. "The information that we can get out is equivalent, but the damage is much less," Meng said. "Polymers are gentler on the brain, and because of that, these devices get recordings of neuronal communication over long periods of time."

Acute in vivo testing of a conformal polymer microelectrode array for multi-region hippocampal recordings (DOI: 10.1088/1741-2552/aa9451) (DX)


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  • (Score: 0) by Anonymous Coward on Monday April 16, @10:49AM

    by Anonymous Coward on Monday April 16, @10:49AM (#667569)

    Closer? Yes.
    Close? Nowhere near.

  • (Score: 2, Funny) by Anonymous Coward on Monday April 16, @11:01AM (1 child)

    by Anonymous Coward on Monday April 16, @11:01AM (#667572)

    Say what? Insert plastic in my brain?
    If the alternative is acceptable, I'd rather buy Facebook stock, thank you.

  • (Score: 2) by c0lo on Monday April 16, @11:54AM (3 children)

    by c0lo (156) Subscriber Badge on Monday April 16, @11:54AM (#667588)

    Researchers at the University of Southern California Viterbi School of Engineering have developed thin, flexible polymer-based materials for use in microelectrode arrays that record activity more deeply in the brain and with more specific placement than ever before...

    In addition, the polymer-based material, called Parylene C,...

    Hang on, the Parylene name sounds somehow familiar.

    Parylene [wikipedia.org]

    Parylene is the trade name for a variety of chemical vapor deposited poly(p-xylylene) polymers used as moisture and dielectric barriers. Among them, Parylene C is the most popular due to its combination of barrier properties, cost, and other processing advantages.

    That's where I stumbled on it, it is used in conformal coating [wikipedia.org] - some call it green chemistry [pctconformalcoating.com] 'cause no initiator is required and the polymerization proceeds at room temperature.

    parylene properties [parylene.com]

    Dielectric strength:
    - parylene N - 7,000 V/mil
    - parylene C - 6,800 V/mil
    - parylene N - 5,500 V/mil

    Volumetric resistivity:
    - parylene N - 1e17 ohm x cm
    - parylene C - 6e16 ohm x cm
    - parylene N - 2e16 ohm x cm

    : parylenes are damn'd good insulators; unless your brain work at 100kV++, they aren't going to conduct.

    ---

    Anyone who can hint something to solve the mystery of brain electrodes derived from excellent insulators?

    • (Score: 1, Interesting) by Anonymous Coward on Monday April 16, @12:59PM (2 children)

      by Anonymous Coward on Monday April 16, @12:59PM (#667607)

      Speculation -- the parylene is used as very thin insulation around some kind of conductive core. Since it's not bio reactive, it does minimal damage to the brain material that it contacts. The core might even be parylene that is doped with something to make it conductive?

      • (Score: 2) by c0lo on Monday April 16, @01:54PM (1 child)

        by c0lo (156) Subscriber Badge on Monday April 16, @01:54PM (#667623)

        Speculation -- the parylene is used as very thin insulation around some kind of conductive core.

        That would be the only thing I can think of and it would make sense.

        The core might even be parylene that is doped with something to make it conductive?

        Since they managed to make carbon nanotubes with lengths over 0.5m, why bother doping the inside instead of coating?
        Besides, TFS mentions "tines" and multi-electrodes in arrays - that's easier with "coating a bunch of wires" than "doping the inside"

        • (Score: 0) by Anonymous Coward on Monday April 16, @02:33PM

          by Anonymous Coward on Monday April 16, @02:33PM (#667641)

          Would be interesting to know more about the "core" conductive part. From what little I know, matching any material to sense (but not interfere with) a nerve impulse is tricky.

          Jerry Lettvin talked about it a little when describing the experimental setup for "What the Frog's Eye Tells the Frog's Brain" (easy to find this neat old paper). Nerves are not wires, the signals are electro-chemical, not just electric. His results were not easily repeated, in part because other labs had a lot of trouble reproducing his electrode setup. Jerry was somewhat of an electrical engineer as well as a biologist.

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