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[0] Rousche PJ, Normann RA, Chronic recording capability of the Utah Intracortical Electrode Array in cat sensory cortex.J Neurosci Methods 82:1, 1-15 (1998 Jul 1)

[0] Mojarradi M, Binkley D, Blalock B, Andersen R, Ulshoefer N, Johnson T, Del Castillo L, A miniaturized neuroprosthesis suitable for implantation into the brain.IEEE Trans Neural Syst Rehabil Eng 11:1, 38-42 (2003 Mar)

{1163}
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ref: Schmidt-1993.11 tags: Normann utah array histology silicon electrode array cats date: 02-23-2017 22:03 gmt revision:4 [3] [2] [1] [0] [head]

PMID-8263001[0] Biocompatibility of silicon-based electrode arrays implanted in feline cortical tissue.

  • Tried two different times:
    • one day before euthanasia
    • 6 month implant.
  • Tried three different implants:
    • Uncoated silicon,
    • polymide coating
    • polymide coating with SiO2 adhesion layer / primer.
  • The last was the worst in terms of histopathological response.
  • Chronic implants showed relatively restrained immune response,
    • Gliosis was found around all tracks, 20-40um.
  • Encapsulation was less than 9um.
  • Edema and hemorrhage was minor but present on a subset of all implants.
  • Acute (24h) hemorrhage was more severe -- ~ 60%; edema ~ 20%.
  • Chronic histology revealed considerable macrophages w/ hemosiderin (a complex including ferritin)
  • See also [1]

____References____

[0] Schmidt S, Horch K, Normann R, Biocompatibility of silicon-based electrode arrays implanted in feline cortical tissue.J Biomed Mater Res 27:11, 1393-9 (1993 Nov)
[1] Jones KE, Campbell PK, Normann RA, A glass/silicon composite intracortical electrode array.Ann Biomed Eng 20:4, 423-37 (1992)

{1292}
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ref: -0 tags: intracortical utah array fabrication MEMS Normann date: 08-14-2014 01:35 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-1937509 A silicon-based, three-dimensional neural interface: manufacturing processes for an intracortical electrode array.

  • Campbell PK1, Jones KE, Huber RJ, Horch KW, Normann RA. (1991)
  • One of (but not the) first papers describing their methods / idea (I think).
  • First conf paper: {1294} (1988)
  • later adopted glass frit insulator --

{307}
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ref: Rousche-1998.07 tags: BMI Utah cat Normann recording electrode MEA histology date: 06-29-2012 01:12 gmt revision:9 [8] [7] [6] [5] [4] [3] [head]

PMID-10223510 Chronic recording capability of the Utah Intracortical Electrode Array in cat sensory cortex.

  • Focus on (surprisingly) chronic recording from the utah array: they want to demonstrate that it works.
  • Platinum coating.
  • insulated with 2-3um polymide.
  • 10 cats, 12 arrays: 2 in S1, 8 in auditory ctx, 2 V1.
  • 11 electrodes connected in each array.
  • After a 6-month implant period, 60% of implanted arrays could still record 'some type of activity'.
  • They were completely targeting neuroprostheses.
    • But acknowledge that 'the presence of fibrous encapsulation and chronic astrogliosis suggests that more research is necessary before the UIEA can be uses as a cornerstone of a neuroprosthetic device for human use.
      • And yet they went through with the human trials?
  • Electrode impedance gave no hint as to the ability of a given electrode to record neural units: many electrodes with average impedance could not record neural activity.
  • Impedances generally decreased , which is not unusual (Schmidt and Bak, 1976).
    • Likely that the polymide had become permeated with water vapor to and equilibrium point. (rather than pinhole leaks or water permeation).
  • Quiet amplifiers: 2uv pk-pk.
  • No significant trend in background activity was noted over the implant durations.
  • In nearly every cat, the dura above the electrode array adhered to the bone flap, and the electrode array adhered to the dura. Therefore, when the bone flap was removed, the UIEA was concurrently explanted from the cortex.
    • Similar to Hoogerwerf and Wise 1994 {1025}
    • The explanted UIEAs typically had become encapsulated, the encapsulation was the cause of the cortical depression.
    • Only 1 did not become encapsulated in dura.
    • This encapsulation explains the gradually varying recording properties -- the electrodes were moving out of the brain.
    • "The capsule which formed around the substrate of the UIEA was usually continuous with the dura, which was enmeshed directly to the overlying skull. The encapsulated array therefore had no freedom of movement with respect to the skull, and this may have caused local trauma which reduced the possibility of recording neural activity. This relative micromovement between the fixed array and the ‘floating’ cortical tissue may also be responsible for sustaining continued growth of the encapsulation as described above."
    • Have tried putting teflon on the top of the Utah array -- did this work?
  • Two UIEAs were not found near the cortical surface -- these two arrays were totally removed from the leptomeningeal space. although originally implanted into the cortex beneath the dura, at the time of sacrafice these arrays were found above the repaired dura, and the implanted cortex showed no evicence of cortical implant.
  • Some electrodes healthy; other showed chronic inflammation.
  • General and intense inflamation in the upper layers of cortex even on their best-performing array; no guarantee that this ctx was working properly, as it is heavily compressed with fibroblasts.
  • Regarding vascluature, see {1024}.
  • Say that the largest impediment is the formation of a capsule around the implant. (Do not mention issue of infection; I guess cats have strong immune systems as well?)
  • Rather good biological discussion and conclusion. worth a re-read. "We currently recommend that the UIEA be used for acute and short-term applications."
    • Not too many follow-ups re teflon or fixing the encapsulation problem: See {1026}
      • Indeed, {1027} doesn't even cite this! Too disastrous?

____References____

{1056}
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ref: Nordhausen-1996.07 tags: Normann Utah array recording date: 02-06-2012 21:37 gmt revision:3 [2] [1] [0] [head]

PMID-8836553[0] Single unit recording capabilities of a 100 microelectrode array. Nordhausen CT, Maynard EM, Normann RA.

  • Used the Utah array in visual stimulus-evoked response in cats.
  • 58.6% of electrodes in the array recorded neural activity.
  • The density of the electrodes in the UIEA makes it impossible to simply push the needles into the cortex with forceps. This only results in surface dimpling, incomplete insertion, and possible cortical damage.
    • We have instead designed a high speed pneumatic insertion tool which takes advantage of viscoelectric properties of the cortical tissue by advancing the electrodes into the tissue at very high velocity.

____References____

[0] Nordhausen CT, Maynard EM, Normann RA, Single unit recording capabilities of a 100 microelectrode array.Brain Res 726:1-2, 129-40 (1996 Jul 8)

{316}
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ref: Mojarradi-2003.03 tags: MEMS recording telemetry Normann Andersen wireless date: 01-15-2012 04:29 gmt revision:2 [1] [0] [head]

PMID-12797724[0] A miniaturized neuroprosthesis suitable for implantation into the brain.

  • Standard tricks: cascode configuration, deep-ohmic PMOS Devices for resistive feedback, wide PMOS weak-inversion input stage for good transconductance and low noise.
  • Varaible power for variable noise levels & bandwidths.
  • Wireless transceiver and power stage are in early concept stages.

____References____