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[0] Kennedy PR, Bakay RA, Moore MM, Adams K, Goldwaithe J, Direct control of a computer from the human central nervous system.IEEE Trans Rehabil Eng 8:2, 198-202 (2000 Jun)[1] Kennedy PR, Mirra SS, Bakay RA, The cone electrode: ultrastructural studies following long-term recording in rat and monkey cortex.Neurosci Lett 142:1, 89-94 (1992 Aug 3)

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ref: Salcman-1973.07 tags: Salcman MEA microelectrodes chronic recording glass cyanocrylate date: 12-29-2017 04:33 gmt revision:7 [6] [5] [4] [3] [2] [1] [head]

PMID-4708761 Design, Fabrication, and In Vivo Behavior of Chronic Recording Intracortical Microelectrodes

  • Teflon-coated 25um Pt-Ir (90/10)
  • Heat fuse this with a glass micropipette & backfill with cyanoacrylate. {1011}
    • Isobutyl acrylate is hydrolysed more slowly and hence is less toxic to the surronding tissue
    • cyanoacrylate is apparently biodegradable.
  • Durable, stable: one electrode displayed a single cortical spike (though not necessarily the same one) for more than 90 consecutive days.
  • unacceptably low impedance = 100K or less
  • Unit activity was present only 10-24H after surgery.
  • formal review of even older microelectrode studies.
  • 10nA should be 100x too small to have any effect on a platinum tip [17]
  • A seperable cell with a SNR of 3:1 would become lost if the electrode tip moved 15um away from a 20um soma.
    • "It becomes clear that the problem of holding single units for prolonged periods in the unrestrained animal is not achieved without considerable difficulty". Yet they think they have solved it.

____References____

Salcman, Michael and Bak, Martin J. Design, Fabrication, and In Vivo Behavior of Chronic Recording Intracortical Microelectrodes Biomedical Engineering, IEEE Transactions on BME-20 4 253 -260 (1973)

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ref: -0 tags: lieber mesh electronics SU-8 recording electrodes flexible polymer glass capillary date: 12-22-2017 00:14 gmt revision:0 [head]

PMID-29109247 Highly scalable multichannel mesh electronics for stable chronic brain electrophysiology

  • Key change was the addition of multiple conductor traces per longitudinal mesh line; this allows them to get 64 or 128 channels per mesh without a dramatic increase in modulus.
  • The latitudinal / diagonal lines still displace tissue ...
  • And the injection mechanism, glass pipette, 650um OD, 400um ID, is pretty large, even for 128 channels.
  • Use carbon nanotube ink, custom CNC printer, to connect to FPC.
    • Pretty impressive that they can manipulate ~800nm thick Su-8 film intraop and have it work well!

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ref: -0 tags: glassy carbon SU-8 pyrolysis CEC microelectrode stimulation stability platinum PEDOT date: 02-17-2017 00:05 gmt revision:2 [1] [0] [head]

A novel pattern transfer technique for mounting glassy carbon microelectrodes on polymeric flexible substrates

  • Use inert-atmosphere pyrolysis @ 900 - 1000 C of 20um SU-8 (which is aromatic) on a thermal oxide wafer.
  • Followed by spin & cure of PI.
  • Demonstrate strong carbonyl bonding of the glassy carbon with mechanical and FTIR testing.
  • Use of photosensitive PI allows through-vias to connect Cr/Au conductive traces.

PMID-28084398 Highly Stable Glassy Carbon Interfaces for Long-Term Neural Stimulation and Low-Noise Recording of Brain Activity

  • Use EIS to show superior charge-injection properties + stability of glassy carbon electrodes vs. Pt electrodes.
    • GC lasted > 5e6 pulses; Pt electrodes delaminated after 1e6 pulses.
    • Hydrogen bonding (above) clearly superior than neat PI-Pt interface
  • GC electrodes were, true to their name, glassy and much smoother than the platinum electrodes.
  • Further reduced impedance with PEDOT-PSS coating.
    • PEDOT-PSS coating on glassy carbon was, in their hands, far more stable than PEDOT-PSS on platinum.
  • All devices, GC, PEDOT:PSS, and Pt, had similar biocompatibility in their assay (figure 7)

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ref: -0 tags: palladium metal glass tought strong caltech date: 02-25-2014 19:02 gmt revision:1 [0] [head]

A damage-tolerant glass

  • Perhaps useful for the inserter needle?
  • WC-Co Tungesten carbide-cobalt cermet is another alternative.

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ref: -0 tags: parylene microchannel micromolding glass transition temperature microfluidics date: 06-28-2013 17:34 gmt revision:3 [2] [1] [0] [head]

Parylene micromolding, a rapid low-cost fabrication method for parylene microchannel

  • doi:10.1016/j.snb.2003.09.038
  • Hong-Seok Noha∗ , Yong Huangb, Peter J. Hesketha Clemson
  • Parylene properties:
    • Glass transition temperature <90C; c.f. {1247}
    • Melting point 290C
    • Oxidation in air at 120C
    • Thermal bonding here at 200C in a vacuum oven @ 24MPa.

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ref: -0 tags: microelectrodes original metal pipette glass recording MEA date: 01-31-2013 19:46 gmt revision:6 [5] [4] [3] [2] [1] [0] [head]

IEEE-4065599 (pdf) Comments on Microelectrodes

  • The amplifiers themselves, even back in 1950's, posed no problems -- low bandwidth. All that is required is low noise and high input impedance.
  • KCl Glass electrodes are LPF (10M resistive + 10pf parasitic capacitance); metal HPF (capacitive).
    • The fluid tip will not see external triphasic spikes of vertebrate axons above the noise level.
  • Metal probe the most useful.
  • Pt electrode in CSF behaves like a capacitor at low voltage across a broad frequency range. CSF has compounds that retard oxidation; impedance is more resistive with physiological saline.
  • Noise voltage generated by a metal electrode best specified by equivalent noise resistance at room temperature, E rmsnoise=4kTR nδF R_n should equal the real part of the electrode impedance at the same frequency.
  • Much of electrochemistry: solid AgCl diffuses away from an electrode tip with great speed and can hardly be continuously formed with an imposed current. Silver forms extremely stable complexes with organic molecules having attached amino and sulfhydril groups which occur in plenty where the electrode damages the tissue. Finally, the reduction-oxidation potential of axoplasm is low enough to reduce methylene blue, which places it below hydrogen. AgCl and HgCl are reduced.
  • The external current of nerve fibers is the second derivative of the traveling spike, the familiar triphasic (??) transient.
  • Svaetichin [1] and Dowben and Rose [3] plated with Platinum black. This increases the surface area.
    • Very quickly it burns onto itself a shell of very adherent stuff. It is kept from intimate contact with the tissue around it by a shell.
    • We found that if we add gelatin to the chloroplatinic acid bath from which we plate the Pt, the ball is not only made adherent to the tip but is, in a sense, prepoisoned and does not burn a shell into itself.
  • glass insulation using woods metal (which melts at a very low temperature). Platinum ball was plated onto 2-3um pipette tip. 3um gelatinized platinum black ball, impedance 100kOhm at 1kHz.
    • Highly capacitive probe: can be biased to 1 volt by a polarizing current of 1e-10 amp. (0.1nA).
  • Getting KCl solution into 1um pipettes is quite hard! They advise vacuum boiling to remove the air bubbles.
  • Humble authors, informative paper.

____References____

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ref: Vibert-1979.08 tags: spike sorting recording depth extracellular glass electrodes active feedback original date: 01-15-2012 06:46 gmt revision:3 [2] [1] [0] [head]

PMID-95711[0] Spike separation in multiunit records: A multivariate analysis of spike descriptive parameters

  • Glass coated tungsten microeletrodes have high capacitance; they compensate for this by spraying colloidal silver over the outside sheath of the glass, insulating that with varnish, and driving the shield in a positive-feedback way (stabillized in some way?) This negates the capacitance. 'low impedance capacitance compensated'.
    • Capacitance compensation really matters!!
  • Were able to record from single units for 40-100um range (average: 50um) with SNRs 2:1 to 7:1.
    • Some units had SNRs that could reach 15:1 (!!!), these could be recorded for 600 um of descent.
    • more than 3 units could usually be recognized at each recording point by visual inspection of the oscilloscope, and in some cases up to 6 units could be distinguished
    • Is there some clever RF way of neutralizing the capacitance of everything but the electrode tip? Hmm. Might as well try to minimize it.
  • Bandpass 300 Hz - 10 kHz.
  • When the signal crossed the threshold level, it was retained and assumed to be a spike if the duration of the first component was between 70 and 1000 us.
    • This 70 us lower limit was determined on a preliminary study as a fairly good rise time threshold for separation of fiber spikes from somatic or dendritic spikes.
    • I really need to do some single electrode recordings. Platt?
  • Would it be possible to implement this algorithm in realtime on the DSP?
  • Describe clustering based on PCA.
  • Programming this computer (PDP-12) must have been crazy!
  • They analyzed 20k spikes. Mango gives billions.
  • First principal component (F1) represented 60-65% of total information was based mostly on amplitude
  • Second principal component, 15-20% of total information represented mainly time parameters.
  • Suggested 3 parameters: Vmax, Vmin, and T3 (time from max to min).
  • Maybe they don't know what they are talking about:

____References____

[0] Vibert JF, Costa J, Spike separation in multiunit records: a multivariate analysis of spike descriptive parameters.Electroencephalogr Clin Neurophysiol 47:2, 172-82 (1979 Aug)

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ref: Kennedy-2000.06 tags: BMI Kennedy IEEE 1999 Bakay neurotrophic glass electrode date: 01-08-2012 00:30 gmt revision:7 [6] [5] [4] [3] [2] [1] [head]

PMID-10896186[] Direct control of a computer from the human central nervous system

  • 1999 - eight years ago!
  • Se also {1020}
  • 3 patients, one success. (one died of ALS :-( JR had a brainstem stroke.
    • Has disconjugate eye movements with nystagmus.
    • These patients are sick - ulcers, peripheral neuropathy.
  • invasive alternative to externally applied BCI.
  • one glass electrode
  • patient can type & produce synthesized speech.
  • cursor wraps off the right of the screen; only positive deflections matter. another signal or dwell used to select letters.
  • Used surface EMG to dissociate neural activity from muscle contraction, as in previous works.
  • electrode used in this study: [1] "The cone electrode: ultrastructural studies following long-term recording in rat and monkey cortex."

____References____

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ref: Lilly-1950 tags: Lilly original MEA glass pipette date: 01-04-2012 01:52 gmt revision:4 [3] [2] [1] [0] [head]

bibtex:Lilly-1950 A Method of Recording the Moving Electrical Potential Gradients in the Brain. The 25-Channel Bavatron and Electro-Iconograms.

  • images/1017_2.pdf
  • Every cell in the cortex is within 25 um of a capillary (!). Really?
  • You can already see him wanting to record from whales / dolphins.
  • Used electrode arrays and photocathode tubes to record from cat.
  • 8x8mm array, 2mm spacing, 100um tip opening in the glass pipettes.
    • Pipettes could slide up & down to rest gently on the pia.
    • Were filled via capilary action
    • Both acute and chronic recording.
  • 1mm spacing of electrodes would still record on the order of 5,000 neurons; good thing there is exponential space dependence.
    • Resistance 50k, low so that thermal noise has little effect.
  • recorded 3,500 feet of film (!!); 1,200 feet of film accumulates in two minutes; this takes 48 minutes to see once.
  • Results in preparation ... were they ever published? where? Must have been nearly impossible to analyze without a computer!