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[0] Kipke DR, Vetter RJ, Williams JC, Hetke JF, Silicon-substrate intracortical microelectrode arrays for long-term recording of neuronal spike activity in cerebral cortex.IEEE Trans Neural Syst Rehabil Eng 11:2, 151-5 (2003 Jun)

[0] Sodagar AM, Wise KD, Najafi K, A fully integrated mixed-signal neural processor for implantable multichannel cortical recording.IEEE Trans Biomed Eng 54:6 Pt 1, 1075-88 (2007 Jun)

[0] Csicsvari J, Henze DA, Jamieson B, Harris KD, Sirota A, Bartho P, Wise KD, Buzsaki G, Massively parallel recording of unit and local field potentials with silicon-based electrodes.J Neurophysiol 90:2, 1314-23 (2003 Aug)

[0] Williams JC, Rennaker RL, Kipke DR, Long-term neural recording characteristics of wire microelectrode arrays implanted in cerebral cortex.Brain Res Brain Res Protoc 4:3, 303-13 (1999 Dec)

{1388}
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ref: -0 tags: PEDOT PSS electroplate eletrodeposition neural recording michigan probe stimulation CSC date: 04-27-2017 01:36 gmt revision:1 [0] [head]

PMID-19543541 Poly(3,4-ethylenedioxythiophene) as a micro-neural interface material for electrostimulation

  • 23k on a 177um^2 site.
  • demonstrated in-vitro durable stimulation.
  • Electrodeposited with 6na for 900 seconds per electrode.
    • Which is high -- c.f. 100pA for 600 seconds {1356}
  • Greater CSC and lower impedance / phase than (comparable?) Ir or IrOx plating.

{1203}
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ref: Cheung-2007.03 tags: flexible electrode array Michigan probe histology Vancouver current source density EPFL polyimide date: 12-21-2013 21:07 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-17027251[0] Flexible polyimide microelectrode array for in vivo recordings and current source density analysis.

  • Polyimide -- PI-2611 precusor.
  • 50nm Ti adhesion, 200nm Pt, both sputtered.
  • Electrodes etched via RIE in Cl2.
    • Sputtered and photo-patterned SiO2 etch mask.
  • Used regular solder to connect to a Samtec.
  • 15um total thickness.
  • 25um electrode diameter.
  • They were inserted directly (no carrier nor guide) into the brain; can be re-used.
  • Tested to 8 weeks.
  • No figure comparing silicon and polyimide, though they claim minimal GFAP response to the electrodes.

____References____

[0] Cheung KC, Renaud P, Tanila H, Djupsund K, Flexible polyimide microelectrode array for in vivo recordings and current source density analysis.Biosens Bioelectron 22:8, 1783-90 (2007 Mar 15)

{1218}
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ref: -0 tags: silicon electrode histology Michigan tip shape shear force date: 04-24-2013 20:02 gmt revision:3 [2] [1] [0] [head]

PMID-1601445 Factors influencing the biocompatibility of insertable silicon microshafts in cerebral cortex.

  • Relatively early assessment of tissue reaction to silicon electrodes.
  • Noted 'severe' reaction at electrode tip; recommend recording along the shaft, Michigan style.
  • Noted microhematoma formation.
  • Recommend fast insertion.
  • Bending of the shafts (e.g. they exert lateral force) causes lateral tissue damage.
    • Problem with fast insertion is that it may cause the needle to bend a bit -- resulting in lateral 'kill zone'.
    • Ultimate speed must be a compromise.
  • Advocate shearing blade tip or chisel point to sever microtubules, rather than a conical tip pushing them to a annular ring that can grab to the sides of the needle.
  • Good paper, reviews the relevant cellular anatomy...

{781}
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ref: Polikov-2005.1 tags: neural response glia histology immune electrodes recording 2005 Tresco Michigan microglia date: 01-29-2013 00:34 gmt revision:10 [9] [8] [7] [6] [5] [4] [head]

PMID-16198003[0] Response of brain tissue to chronically implanted neural electrodes

  • Good review (the kind where figures are taken from other papers). Nothing terribly new (upon a very cursory inspection)
  • When CNS damage severs blood vessels, microglia are indistinguishable from the blood borne, monocyte-derived macrophages that are recruited by the degranulation of platelets and the cellular release of cytokines.
  • Furthermore, microglia are known to secrete, either constitutively, or in response to pathological stimuli, neurotrophic factors that aid in neuronal survival and growth.
    • Also release cytotoxic and neurotoxic factors that can lead to neuronal death in vitro.
    • It has been suggested that the presence of insoluble materials in the brain may lead to a state of 'frustrated phagocytosis' or inability of the macrophages to remove the foreign body, resulting in persistent release of neurotoxic substances.
  • When a 10x10 array of silicon probes was implanted in feline cortex, 60% of the needle tracks showed evidence of hemorrhage and 25% showed edema upon explantation of the probes after one day (Schmidt et al 1993) {1163}
    • Although a large number of the tracks were affected, only 3-5% of the area was actually covered by hemorrhages and edema, suggesting the actual damage to blood vessels may have been relatively minor. (!!)
  • Excess fluid and cellular debris diminishes 6-8 days due to the action of activated microglia and re-absorption.
  • As testament to the transitory nature of this mechanically induced wound healing response, electrode tracks could not be found in animals after several months when the electrode was inerted and quickly removed (Yuen and Agnew 1995, Rousche et al 2001; Csicsvari et al 2003, Biran et al 2005).
  • Biran et al 2005: observed persistent ED-1 immunoreactivity around silicon microelectrode arrays implanted in rat cortex at 2 and 4 weeks following implantation; not seen in microelectrode stab wound controls.
  • On the glial scar:
    • observed in the CNS of all vertebrates, presumably to isolate damaged parts of the nervous system and maintain the integrity of the blood-brain barrier.
    • mostly composed of reactive astrocytes.
    • presumably the glial scar insulates electrodes from nearby neurons, hindering diffusion and increasing impedance.
  • On the meninges:
    • Meningeal fibroblasts, which also stain for vimentin, but not for GFAP, may migrate down the electrode shaft from the brain surface and form the early basis for the glial scar.
  • On recording quality:
    • Histological examination upon explantation revealed that every electrode with stable unit recordings had at least one large neuron near the electrode tip, while every electrode that was not able to record resolvable action potentials was explanted from a site with no large neurons nearby.
  • Perhaps the clearest example of this variability was observed in the in vivo response to plastic “mock electrodes” implanted in rabbit brain by Stensaas and Stensaas (1976) {1210} and explanted over the course of 2 years. They separated the response into three types: Type 1 was characterized by little to no gliosis with neurons adjacent to the implant, Type 2 had a reactive astrocyte zone, and Type 3 exhibited a layer of connective tissue between the reactive astrocyte layer and the implant, with neurons pushed more than 100 um away. All three responses are well documented in the literature; however this study found that the model electrodes produced all three types of reactions simultaneously,depending on where along the electrode one looked.

____References____

[0] Polikov VS, Tresco PA, Reichert WM, Response of brain tissue to chronically implanted neural electrodes.J Neurosci Methods 148:1, 1-18 (2005 Oct 15)

{1028}
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ref: Szarowski-2003.09 tags: Michigan array silicon histology MEA cornell date: 01-28-2013 20:47 gmt revision:6 [5] [4] [3] [2] [1] [0] [head]

PMID-12914963[0] Brain responses to micro-machined silicon devices.

  • Used 2 different implants (rough & sharp corners, smooth), 2 different ways of inserting (slow, by hand).
    • Neither made much diff.
  • Measured GFAP = glial fibrillary acidic protein, a standard measure for assesing reactive gliosis [44,18,28,33,35].
    • Normally larger astrocytes were seen around larger blood vessels.
    • "At four weeks, a clear sheath of GFAP-positive astrocytes was observed"
    • GFAP labeled sheath seems to have plateaued at 6 weeks. (The sheath may be useful for our devices... )
  • Measured Vimentin, which is increased in reactive astrocytes and is not normally expressed in mature astrocytes [6,12,15,40].
    • In control animals vimentin only present in ependymal lining of the ventricles.
    • At 6 weeks, sites around both types of devices had a compact sheath of vimentin-positive astrocytes 50-100um.
    • Seemed to be a plateau as with GFAP .. though it seems to label a slightly distinct set of cells.
  • Also labeled reactive microglia with ED1 [4,19,27,36].
  • Quote: These data indicate that device insertion promotes two responses-an early response that is proportional to device size and a sustained response that is independent of device size, geometry, and surface roughness. The early response may be associated with the amount of damage generated during insertion. The sustained response is more likely due to tissue-device interactions.

____References____

[0] Szarowski DH, Andersen MD, Retterer S, Spence AJ, Isaacson M, Craighead HG, Turner JN, Shain W, Brain responses to micro-machined silicon devices.Brain Res 983:1-2, 23-35 (2003 Sep 5)

{1216}
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ref: Lee-2005.12 tags: micromotion silicon michigan array simulation strain date: 01-28-2013 03:13 gmt revision:1 [0] [head]

PMID-16317231[0] Biomechanical analysis of silicon microelectrode-induced strain in the brain.

  • Simulation.
  • Our analysis demonstrates that when physical coupling between the electrode and the brain increases, the micromotion-induced strain of tissue around the electrode decreases as does the relative slip between the electrode and the brain.
  • Argue that micromotion and shear cause lost recording sensitivity due to inflammation and astroglial scarring around the electrode.
    • This seems to be the scientific consensus ATM.

____References____

[0] Lee H, Bellamkonda RV, Sun W, Levenston ME, Biomechanical analysis of silicon microelectrode-induced strain in the brain.J Neural Eng 2:4, 81-9 (2005 Dec)

{1196}
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ref: Skousen-2011.01 tags: electrodes immune response Tresco Wise Michigan histology GFAP atrocyte surface area foreign body response date: 01-25-2013 01:44 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-21867802[0] Reducing surface area while maintaining implant penetrating profile lowers the brain foreign body response to chronically implanted planar silicon microelectrode arrays.

  • We studied the chronic brain foreign body response to planar solid silicon microelectrode arrays and planar lattice arrays with identical penetrating profiles but with reduced surface area in rats after an 8-week indwelling period.
  • Using quantitative immunohistochemistry, we found that presenting less surface area after equivalent iatrogenic injury is accompanied by significantly less
    • persistent macrophage activation,
    • decreased blood brain barrier leakiness,
    • and reduced neuronal cell loss.
  • Could be a factor of micromotion, too -- the lattice array has more anchoring points (?)
  • They propose it's a factor of TNF- α concentration around the implants. This, and other proinflammatory and cytoxic cytokines, is released by macrophages.
  • "Recent studies from our lab have described disruption of BBB integrity, indicated by the presence of autologous IgG in the brain parenchyma, surrounding both microwire and planar silicon recording devices ([1][2]. Under normal conditions, autologous IgG is excluded from the brain parenchyma (Azzi et al., 1990; Seitz et al., 1985) but has been observed following BBB disruption (Aihara et al., 1994).
    • E.g. the presence of IgG proves that the BBB was compromised.
      • Less so with the lattice implants.
  • Previous work from our lab using single microwires and single shaft, planar silicon microelectrode arrays indicated that the spatial distribution of GFAP does not increase with time over the indwelling period and did not support the “increase in astrogliosis over time hypothesis” as a dominant or general biologically related failure mechanism for this type of microelectrode recording device {1197}.

____References____

[0] Skousen JL, Merriam SM, Srivannavit O, Perlin G, Wise KD, Tresco PA, Reducing surface area while maintaining implant penetrating profile lowers the brain foreign body response to chronically implanted planar silicon microelectrode arrays.Prog Brain Res 194no Issue 167-80 (2011)
[1] Winslow BD, Christensen MB, Yang WK, Solzbacher F, Tresco PA, A comparison of the tissue response to chronically implanted Parylene-C-coated and uncoated planar silicon microelectrode arrays in rat cortex.Biomaterials 31:35, 9163-72 (2010 Dec)
[2] Winslow BD, Tresco PA, Quantitative analysis of the tissue response to chronically implanted microwire electrodes in rat cortex.Biomaterials 31:7, 1558-67 (2010 Mar)

{737}
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ref: Biran-2005.09 tags: microelectrode Michigan probe glia tissue response electrode immune histology MEA Biran date: 01-24-2013 20:49 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-16045910[0] Neuronal cell loss accompanies the brain tissue response to chronically implanted silicon microelectrode arrays.

  • See also {1190} (wow, I'm redundant!)
  • Important point: ED1 up-regulation and neuronal loss were not observed in microelectrode stab controls, indicating that the phenotype did not result from the initial mechanical trauma of electrode implantation, but was associated with the foreign body response.
    • CD68 = ED1 is a marker for microglia and other macrophages. (wikipedia article is informative).
    • GFAP = glial fibrillary acidic protein, marker for astrocytes.
  • Recording failure is caused by chronic inflammation (mostly activated microglia) at the microelectrode brain tissue interface.
  • Only tested response 2 and 4 weeks after implantation. Makes sense for stab wound, but didn't the want to see a longer term response? Or do their electrodes just not last that long?
  • What did they coat the silicon probes in?
  • Used silastic to shock-mount their floating electrodes, but this apparently made no difference compared to conventional dental cement and bone screw mounting.
  • Suggest that chronic inflammatory response may be related to the absorption of fibrogen and complement to the surface of the device (device should not be porous?), the subsequent release of pro-inflammatory and cytotoxic cytokines by activated microphages, and the persistence of activated macrophages around materials which cannot be broken down.
    • Well then, how do you make the electrodes biochemically / biologically 'invisible'?
    • Persistently activated microglia are found around insoluble plaques in AD (plaques that cannot be / are not removed from the brain via proteolysis. Microglia form 'glitter cells' when they engulf undigestible stubstances). This has been termed 'frustrated phagocytosis', which results in increased secretion of proinflamatory cytokines that directly or indirectly cause neuronal death.
  • Significant reductions in neurofiliament reactivity was seen up to 230um from the microelectrode interface; this was not seen for stab wounds. Maximum recording distance is about 130um; 100um more reasonable in normal conditions.
  • Accumulating evidence from postmortem analysis of patients implanted with DBS electrodes reveals that chronic neuroinflamation is part of the response to such (duller, larger) implants as well. They have seen cell loss up to 1mm fromt the electrode surface here.

____References____

[0] Biran R, Martin DC, Tresco PA, Neuronal cell loss accompanies the brain tissue response to chronically implanted silicon microelectrode arrays.Exp Neurol 195:1, 115-26 (2005 Sep)

{749}
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ref: Biran-2007.07 tags: tresco biocompatibility tether skull electrodes Michigan probe recording Tresco date: 01-24-2013 20:11 gmt revision:6 [5] [4] [3] [2] [1] [0] [head]

PMID-17266019[0] The brain tissue response to implanted silicon microelectrode arrays is increased when the device is tethered to the skull.

  • Good, convincing, figures.

____References____

[0] Biran R, Martin DC, Tresco PA, The brain tissue response to implanted silicon microelectrode arrays is increased when the device is tethered to the skull.J Biomed Mater Res A 82:1, 169-78 (2007 Jul)

{1061}
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ref: -0 tags: Najafi electrode spring dissolving Michigan date: 01-16-2012 17:55 gmt revision:1 [0] [head]

IEEE-5969351 (pdf) New class of chronic recording multichannel neural probes with post-implant self-deployed satellite recording sites

{1025}
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ref: Hoogerwerf-1994.12 tags: Wise Michigan array MEA recording 3D date: 01-15-2012 07:12 gmt revision:4 [3] [2] [1] [0] [head]

IEEE-335862 (pdf) A three-dimensional microelectrode array for chronic neural recording.

  • see {995} for reasonable photos (they don't show up in the black and white IEEE scan).
  • 16-channel, 4 shanks.
  • 3D : 16 shanks, 64 channels, includes a 16:1 MNOS mux on the attached micromachined silicon platform.
  • Nickel plated lead stransfers (90 deg) see figure 6 electroplating current.
    • This was a point of difficulty, it seems.

____References____

Hoogerwerf, A.C. and Wise, K.D. A three-dimensional microelectrode array for chronic neural recording Biomedical Engineering, IEEE Transactions on 41 12 1136 -1146 (1994)

{740}
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ref: BeMent-1986.02 tags: Najafi Michigan probe recording silicon MEA date: 01-15-2012 06:59 gmt revision:6 [5] [4] [3] [2] [1] [0] [head]

PMID-3957372[0] Solid-state electrodes for multichannel multiplexed intracortical neuronal recording.

  • 1986 (!!) - but same basic technology for manufacture of these devices. Modern Michigan probes are much smaller, though - this paper uses 6um feature sizes. It seems like the rate-limiting step for a lot of this is marketization/selling it & getting the money for further R&D.
  • Mention closed-loop neuroprotheses ... 26 years ago. Why do we not have this yet? This is a really important question!
  • 12 channel on-chip analog processing, G=100, bandwidth 100-6kHz.
  • Mention that they think most of the current has to flow around other cells (glia), which makes it possible to record considerably further from the soma (ref [1],); see also PMID-14490040 which through modeling claims much smaller spread of current.
  • Electrode sites are highly capacitive, phase angle 80 deg.
  • 8 um interconnect leads.
  • Enhancement-mode LOCOS NMOS process.

____References____

[0] BeMent SL, Wise KD, Anderson DJ, Najafi K, Drake KL, Solid-state electrodes for multichannel multiplexed intracortical neuronal recording.IEEE Trans Biomed Eng 33:2, 230-41 (1986 Feb)

{1042}
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ref: Ji-1992.03 tags: recording ASIC Michigan date: 01-15-2012 05:32 gmt revision:1 [0] [head]

IEEE-121568 (pdf) An implantable CMOS circuit interface for multiplexed microelectrode recording arrays

  • 15 uV RMS input-referred noise (high!), 8 channels, AC gain 300 15Hz - 7kHz, 2.5 mW, 3um feature size.
  • Self-test features.

____References____

Ji, J. and Wise, K.D. ''An implantable CMOS circuit interface for multiplexed microelectrode recording arrays'' Solid-State Circuits, IEEE Journal of 27 3 433 -443 (1992)

{308}
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ref: Kipke-2003.06 tags: Michigan rat Kipke recording electrode MEA date: 01-08-2012 03:34 gmt revision:5 [4] [3] [2] [1] [0] [head]

IEEE-1214707 (pdf) Silicon-substrate intracortical microelectrode arrays for long-term recording of neuronal spike activity in cerebral cortex.

  • 4 of the 6 implants (66%) remaining functional for more than 28 weeks (7 mo)
  • Recording sites separated by 100um; at this site separation, adjacent sites may sometimes record the same unit.
  • It is notable that in each case in this series was terminated due to reasons other than the microelectrode not recording unit activity. (SC LIn agrees, pc).
  • around 80% of sites recorded neural activity.

____References____

{997}
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ref: Najafi-1985.07 tags: Najafi original silicon michigan recording array 1985 MEA date: 01-06-2012 05:27 gmt revision:10 [9] [8] [7] [6] [5] [4] [head]

IEEE-1484848 (pdf) A high-yield IC-compatible multielectrode recording array.

  • Already talks about closed-loop control of a neuroprosthesis.
  • Started testing on-chip NMOS amplifiers.
  • tantalum and polysilicon conductors. some resistivity, but much less than the electrode interface.

____References____

Najafi, K. and Wise, K.D. and Mochizuki, T. A high-yield IC-compatible multichannel recording array Electron Devices, IEEE Transactions on 32 7 1206 - 1211 (1985)

{995}
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ref: QingBai and Wise-2001.08 tags: Bai Wise buffered MEA recording electrodes Michigan date: 01-05-2012 04:53 gmt revision:5 [4] [3] [2] [1] [0] [head]

IEEE-936367 (pdf) Single-unit neural recording with active microelectrode arrays

  • Design neural probes with on-chip unity-gain amplifiers. Proven to not degrade recordings (indeed, it should help!)
  • 200ohm output impedance
  • 11uV RMS noise, 100Hz-10kHz.
  • Multiplexer adds 8uV rms noise. noise from clock transitions 2ppm.
  • Also built amplifiers with 40db voltage gain (100x).

____References____

Qing Bai and Wise, K.D. Single-unit neural recording with active microelectrode arrays Biomedical Engineering, IEEE Transactions on 48 8 911 -920 (2001)

{996}
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ref: Najafi-1986.12 tags: Najafi implantable wired recording Michigan array multiplexing silicon boron MEA date: 01-05-2012 03:07 gmt revision:8 [7] [6] [5] [4] [3] [2] [head]

IEEE-1052646 (pdf) An implantable multielectrode array with on-chip signal processing

  • "The major reason for the slow progress in the understanding of neural circuits has been the lack of adequate instrumentation."
  • previous photolithographic: [4],[5]. Their first publication: [7].
  • Kensall Wise, not Stephen.
  • Single shank
  • 10 recording sites spaced at 100um
  • Amplifying 100x, b/w 15kHz., multiplexing.
  • width: 15um near tip, 160um at base.
  • 3 leads (!) power, ground, data.
  • 6um LOCOS enhancement and depletion NMOS technology -- not CMOS. (latter is prone to latch-up)
  • 5mW power.
  • boron dope silicon, etch back non doped portion with ethylenediamine-pyrocatechol (EDP) water solution.
  • must not have any substrate bias!

____References____

Najafi, K. and Wise, K.D. An implantable multielectrode array with on-chip signal processing Solid-State Circuits, IEEE Journal of 21 6 1035 - 1044 (1986)

{1022}
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ref: Kuperstein-1981.03 tags: MEA Michigan probe MIT 1981 date: 01-05-2012 02:27 gmt revision:3 [2] [1] [0] [head]

IEEE-4121195 (pdf) A Practical 24 Channel Microelectrode for Neural Recording in Vivo

  • Molybdenum substrate (??).
  • progenitor to the Michigan probe?

____References____

Kuperstein, Michael and Whittington, Douglas A. A Practical 24 Channel Microelectrode for Neural Recording in Vivo Biomedical Engineering, IEEE Transactions on BME-28 3 288 -293 (1981)

{393}
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ref: Sodagar-2007.06 tags: neural recording telemetry Wise Najafi mulitichannel electrophysiology Michigan ASIC date: 01-03-2012 23:07 gmt revision:4 [3] [2] [1] [0] [head]

PMID-17554826[0] A fully integrated mixed-signal neural processor for implantable multichannel cortical recording.

  • document is rich in details! looks pretty well designed, too.
  • Michigan 3-d electrodes
  • inductively powered, 2Mbps output
  • 64 channels
  • 18b/spike for 64 channels in scan mode, continuous waveforms on 2 channels in monitor mode
  • programmable analog spike detection. resolution: 5 bits.
  • no timestamps - send them out as they come in, with a clock rate fast enough so that this does not matter.
    • temporary storage in SRAM
    • time compression and buffering is somewhat complex (?)
  • only transmit threshold crossings, positive, negative, and both.
    • they do not detail how the signal is telemetered - perhaps this is for another publication.
  • fabricated chip occupies 3.5 x 2.7 mm. 0.5um process.
  • fabricated chip has a power of 200uw @ 1.8V. that's 6.4mW altogether! I need to get down to this figure! (well..)

____References____

{739}
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ref: Najafi-1990.05 tags: Najafi Michigan probe silicon strength electrodes recording MEA date: 01-03-2012 22:45 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-2345003[0] Strength characterization of silicon microprobes in neurophysiological tissues.

  • These active (with amplification/buffering circuitry) electrodes were around since 1990! It's been a while, and at least the devices are commercially available now.
  • Show that thin-film silicon is remarkably flexible and tough - about six times as strong as bulk silicon.
  • Have developed a silicon probe with an integrated phosphorous-doped polysilicon strain guague - nice.

____References____

[0] Najafi K, Hetke JF, Strength characterization of silicon microprobes in neurophysiological tissues.IEEE Trans Biomed Eng 37:5, 474-81 (1990 May)

{149}
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ref: WISE-2004.01 tags: wireless electrodes silicon Michigan Kipke Najafi recording MEA date: 01-03-2012 03:23 gmt revision:12 [11] [10] [9] [8] [7] [6] [head]

IEEE-01258173 (pdf) Wireless implantable microsystems: high-density electronic interfaces to the nervous system - January 2004.

  • very impressive!
  • based on the old / well established beam-lead technology (see the image of the paper at the bottom of that page).
    • required 20 years of development to create an etching process with sufficient yield, though. Microprobes have been in development since 1966.
    • Silicon is slowly attacked by saline; however, the use of a boron etch-stop to define the substrate virtually eliminates such erosion.
    • Silicon dioxide is known to slowly hydrate in water, but this can be mitigated by CVD of silicon nitride / silicon oxide stacks. Polysilicon can be used too, since it forms a tight bond with silicon oxide, keeping water out.
      • Why don't they just seal it with a known impermeable plastic/epoxy/whatever? (They do, later) Utah probe is sealed in parylene.
    • Shunt capacitance is negligible compared to site capacitance; heavy substrate doping minimizes electrical or optically induced noise & virtually eliminates crosstalk.
    • (Of course) Silicon allows amplifiers and circuitry to be formed at/near the electrode, eliminating the need for (some) interconnects.
    • Silicon ribbon connectors cannot be made much longer than a few centimeters. 4um thick silicon cables are 100x more flexible than a 25um gold wire (!!) - but that is out-of-plane; they are relatively weak for in-plane stress.
  • Gold has a maximum charge delivery of 20uC/cm^2 ; platinum, 75 uC/cm^2 ; iridium oxide, 3000 uC/cm^2.
  • Glass can be hermetically bonded to silicon if both flat clean surfaces are put in opposition with a high voltage (1500V) placed across the interface at an elevated temperature (400C). These packages have been shown to be stable and inert in guinea pigs.
    • Silicon nitride, thin metal films, and metal films over polymers are all attractive coatings for probes (with no mention of biocompatibility); they last decades in salt water, and eventually succumb to pinholes.
  • Silicon probes outperform microwire arrays by a factor of (up to) 50 in terms of volume of tissue displaced / recording site. Michigan probes are typically 15um thick x 60um in cross section.
  • they tend to use many more recording sites than recording channels, hence, have a low expected yield. e.g. they have a 1024 site electrode (see the cool figures!), and can record from the best 128 of those. good idea, reasonable strategy, I guess.
    • they demonstrate that it is not too hard to remove the artifact of multiplexing on their systems - the multiplexing noise is below electrode noise.
  • talk about spongifying their iridium electrodes using current pulses in a PBS solution to (apparently) lower electrode impedance.
  • talk about drug delivery too
  • describe the exact manufacturing procedures that the Michigan arrays are created, including the critical back-etch (which i don't exactly understand).
  • describe the circuits used to amplify low-level neural signals.
  • Their charge-redistribution ADC is okay - 250ksps, 9b resolution, 1.4mW from a 3v source. Commercial ADCS are better - AD7467 is 0.6mw, 200ksps, 10bits. (though it scales up to 1.3mW @ 3V, 200ksps ; 0.36mW @1.8V - so the devices are comparable.)
  • some of the (very tiny) electrodes have 'holes' (!)
  • also have wireless microstimulators.
  • demonstrate long-term recording: 383days post implant in a rat & there are still many cells (though the figure is not that great, it is easy to understand) (this might be an exemplar)
  • associated website?
  • (quote:) "For ranges of a few centimeters, the high attenuation of RF signals in biological tissue dictates carrier frequencies below 10Mhz." Their solution is to use FSK with octave jumps in freqency & modulation rates up to 60% that of the carrier frequency.

____References____

WISE, K.D. and ANDERSON, D.J. and HETKE, J.F. and KIPKE, D.R. and NAJAFI, K. Wireless implantable microsystems: high-density electronic interfaces to the nervous system Proceedings of the IEEE 92 1 76 - 97 (2004)

{312}
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ref: Csicsvari-2003.08 tags: recording michigan silicon electrodes Buzsaki MEA date: 01-03-2012 03:23 gmt revision:4 [3] [2] [1] [0] [head]

PMID-12904510[0] Csicsvari 2003 Massively parallel recording of unit and local field potentials with silicon-based electrodes

  • What's so massive? 64 or 96 channel Michigan probes.
  • Motivation: recording local connections and interactions requires precise knoledge of the location of your recording sites.
  • Some classic refs on cortical building blocks.
  • Optical recording: Mao et al 2001 PMID-11738033.
  • Wired recording:, Chicurel 2001; Deadwyler and Hampson 1995 PMID-7481817; Evarts 1968; {994}
  • Tetrodes: Drake 1988, Gray 1995, McNaughton et al 1983; Recce and O'Keefe 1989.
  • on-chip active circuitry (simple voltage feedback op-amp - without reference electrodes!) reduces microphone artifact. 6mm 'antenna'.
    • refs: Bai and Wise 2001 {995}; Olsson et al. 2002
    • also Najafi and Wise 1986 {996}; Wise and Najafi 1991 .
  • Stored wideband data; sorted via KlustaKwik.
  • Total recording area 1.6mm deep by 1.8mm wide. Shanks separated by 300um ; recordings sites separated by 100um; shanks 12um thick.
    • Made via double-sided deep reactive reactive ion etching (DRIE).
  • stimulated the entorhinal cortex & recorded in the hippocampus; used the precise spatial layout of the micromachined silicon electrodes to map out the evoked potentials.
  • figure 3 shows that they can record the 'same' neuron from multiple 100um-spaced sites on a given shank. Some of this is due to the physically large extent of the hippocampal cells which they recorded; spike propagate both down the axon and back into the soma, and by using Current Source Density maps, they could estimate some of spatio-temporal characterisics of the AP.
    • CSD is the second spatial derivtive of the local field potentials.
    • Could measure forward and back-propagation of APs to the dendrites (!)
  • quote: in contrast to wire tetrodes with blunt cute ends, it was possible to record from the same cell layer numerous times after moving the probe up and subsequently back to the previous recording location.
    • size of the electrode shanks: 62um wide x 12um thick at top of recording site of 12 site shank; 82um wide at top of 16 site shank.
    • Top 4 recording sites' recording quality deteriorated with multiple penetrations.
  • good place-cell map; cells were discriminated based on a PCA across both time and electrode.

____References____

{310}
hide / edit[2] / print
ref: Williams-1999.12 tags: recording microwire guinea kipke MEA Michigan date: 01-03-2012 03:18 gmt revision:2 [1] [0] [head]

PMID-10592339[0] Long term neural recording characteristics of wire microelectrode arrays implanted in cerebral cortex

  • details the williams microwire array assembly protocol - basically the same as what gary does here in the nicolelis lab, only written up nicely and for guinea pigs not rhesus macaques.
  • references miguel's book on multielectrode recordings

____References____

{741}
hide / edit[5] / print
ref: Sodagar-2006.31 tags: Najafi michigan probe silicon recording 2006 date: 01-03-2012 00:56 gmt revision:5 [4] [3] [2] [1] [0] [head]

IEEE-4463150 (pdf) A neural signal processor for an implantable multi-channel cortical recording microsystem

  • Full 64 ch NPU (neural processing unit). The 'competition'.
    • Scan mode: all 64 channels are searched for the occurence of neural spikes. Addresses with neural activity are sorted, packed, and sent to the outside world.
      • Each channel can be individually set to +, -, or +- spikes. (no templates).
    • monitor mode: 2 channels of broadband transmission.
  • ref [3] claims 100 channels integrated.
  • inductive bidirectional wireless link.
  • Hierarchical design: 64 channels = 2 32 channel master/slave NPUs, each 4 8-channel modules.
  • External 8-bit A/D converter.
  • One 32-ch NPU in 0.5um AMI N-well CMOS process, 3.5mm x 2.7mm.
  • channel scan rate 64ksample/sec; 64 kspikes/sec, typical 8:1 data compression.
  • 2mbps output rate.
  • see also {393} and {149} - they report the same results, perhaps in more detail.

____References____

Sodagar, A.M. and Wise, K.D. and Najafi, K. Engineering in Medicine and Biology Society, 2006. EMBS '06. 28th Annual International Conference of the IEEE 5900 -5903 (2006)