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[0] Schmidt EM, McIntosh JS, Durelli L, Bak MJ, Fine control of operantly conditioned firing patterns of cortical neurons.Exp Neurol 61:2, 349-69 (1978 Sep 1)[1] Serruya MD, Hatsopoulos NG, Paninski L, Fellows MR, Donoghue JP, Instant neural control of a movement signal.Nature 416:6877, 141-2 (2002 Mar 14)[2] Fetz EE, Operant conditioning of cortical unit activity.Science 163:870, 955-8 (1969 Feb 28)[3] Fetz EE, Finocchio DV, Operant conditioning of specific patterns of neural and muscular activity.Science 174:7, 431-5 (1971 Oct 22)[4] Fetz EE, Finocchio DV, Operant conditioning of isolated activity in specific muscles and precentral cells.Brain Res 40:1, 19-23 (1972 May 12)[5] Fetz EE, Baker MA, Operantly conditioned patterns on precentral unit activity and correlated responses in adjacent cells and contralateral muscles.J Neurophysiol 36:2, 179-204 (1973 Mar)

[0] Schmidt EM, Single neuron recording from motor cortex as a possible source of signals for control of external devices.Ann Biomed Eng 8:4-6, 339-49 (1980)[1] Schmidt EM, McIntosh JS, Durelli L, Bak MJ, Fine control of operantly conditioned firing patterns of cortical neurons.Exp Neurol 61:2, 349-69 (1978 Sep 1)[2] Salcman M, Bak MJ, A new chronic recording intracortical microelectrode.Med Biol Eng 14:1, 42-50 (1976 Jan)

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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)

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ref: Schmidt-1978.09 tags: Schmidt BMI original operant conditioning cortex HOT pyramidal information antidromic date: 04-22-2013 18:21 gmt revision:10 [9] [8] [7] [6] [5] [4] [head]

PMID-101388[0] Fine control of operantly conditioned firing patterns of cortical neurons.

  • hand-arm area of M1, 11 or 12 chronic recording electrodes, 3 monkeys.
    • but, they only used one unit at a time in the conditioning task (i think)
  • conditioning in 77% of single units and 65% of combined units (multiunits?).
  • trained to move a handle to a position indicated by 8 annular cursor lights.
    • cursor was updated at 50hz -- this was just a series of lights! talk about simple feedback...
    • Investigated different smoothing: too fast, FR does not stay in target; too slow, cursor acquires target too slowly.
    • My gamma function is very similar to their lowpass filter used for smoothing the firing rates.
    • 4 or 8 target random tracking task
    • time out of 8 seconds
    • run of 40 trials
      • the conditioning reached a significant level of performance after 2.2 runs of 40 trials (in well-trained monkeys); typically, they did 18 runs/day.
  • recordings:
    • scalar mapping of unit firing rate to cursor position.
    • filtered 600-6kHz
    • each accepted spike triggered a generator that produced a pulse of of constant amplitude and width -> this was fed into a lowpass filter (1.5 to 2.5 & 3.5Hz cutoff), and a gain stage, then a ADC, then (presumably) the PDP.
      • can determine if these units were in the pyramidal tract by measuring antidromic delay (stimulate muscles??)
    • recorded one neuron for 108 days!!
      • neuronal activity is still being recorded from one monkey 24 months after chronic implantation of the microelectrodes.
    • average period in which conditioning was attempted was 3.12 days.
  • successful conditioning was always associated with specific repeatable limb movements
    • "However, what appears to be conditioned in these experiments is a movement, and the neuron under study is correlated with that movement." YES.
    • the monkeys clearly learned to make (increasingly refined) movement to modulate the firing activity of the recorded units.
    • the monkey learned to turn off certain units with specific limb positions; the monkey used exaggerated movements for these purposes.
      • e.g. finger and shoulder movements, isometric contraction in one case.
  • Trained some monkeys or > 15 months; animals got better at the task over time.
  • PDP-12 computer!
  • Information measure: 0 bits for missed targets, 2 for a 4 target task, 3 for 8 target task; information rate = total number of bits / time to acquire targets.
    • 3.85 bits/sec peak with 4 targets, 500ms hold time
    • with this, monkeys were able to exert fine control of firing rate.
    • damn! compare to Paninski! [1]
  • 4.29 bits/sec when the same task was performed with a manipulandum & wrist movement
  • they were able to condition 77% of individual neurons and 65% of combined units.
  • Implanted a pyramidal tract electrode in one monkey; both cells recorded at that time were pyramidal tract neurons, antidromic latencies of 1.2 - 1.3ms.
    • failures had no relation to over movements of the monkey.
  • Fetz and Baker [2,3,4,5] found that 65% of precentral neurons could be conditioned for increased or decreased firing rates.
    • and it only took 6.5 minutes, on average, for the units to change firing rates!
  • Summarized in [1].

____References____

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ref: Schmidt-1984.11 tags: spike sorting Schmidt date: 01-15-2012 05:45 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-6392757[0] Instruments for sorting neuroelectric data: a review

  • Seems like it would be useful for me :-)
  • Amplifier bandwidth should be between 5 and 7.5kHz
  • High-pass between 100 and 600Hz, to reduce the 'baseline hash produced by the firing of distant neurons.
  • Electrodes generate Johnson noise (same as thermal noise): E=0.1219R×BμVrms , where B = bandwidth in Hz and R = resistance in MOhm.
  • Modern low-noise FET amplifiers produce noise equivalent to a source resistance of 15K
  • Describe a number of nonlinear spike detection filters using switched amplifiers; these do not seem to have survived.
  • Analog window comparators described have been largely replaced with digital filtering techniques.
    • That said, the use of photo-detectors taped to an oscilloscope is an ingenious method for spike discrimination!
  • Note that audio output is useful, too. Ear is a good discriminator.

____References____

[0] Schmidt EM, Instruments for sorting neuroelectric data: a review.J Neurosci Methods 12:1, 1-24 (1984 Nov)

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ref: Schmidt-1980.01 tags: BMI 1980 SUA M1 prosthetics Schmidt MEA date: 01-04-2012 22:59 gmt revision:14 [13] [12] [11] [10] [9] [8] [head]

PMID-6794389[0] Single neuron recording from motor cortex as a possible source of signals for control of external devices

  • also [1]
  • I guess this was the first published article claiming that motorneurons could be used to drive a prosthesis, and first clear attempt at long-term array recording (?)
  • recorded via arrays for up to 37 months!
    • only 2 of the 11 eelctrodes were recording at the time of sacrifice.
  • trained the monkey to perform an 8 target tracking task
    • with cortical neurons: 2.45 bits/second
    • with wrist flexion/extension: 4.48 bits/second
  • electrodes: {946} A new chronic recording intracortical microelectrode (1976!)
    • 25um iridium wires electropolished to a 1um tip; 1.5mm long.
    • electrodes float on the cortex; signals transmitted through 25um gold wire, which is in turn connected to a head-mounted connector.
    • iridium and gold are insulated with vapor-deposited parylene-C
    • electrode tips are exposed with a HV arc. (does this dull them? from the electromicrograph, it seems that it just makes them rougher.)
    • arrays of 12.
    • 1M impedance (average)
  • interesting: neural activity was recorded from at least 8 different neurons with this electrode during the course of the implant, indicating that it was migrating through cortical tissue.
    • the average recording time from the same electrode was 8 days; max 23 days.
  • second implant was more successful: maximium time recording from the same neuron was 108 days.
  • failure is associated with cracks in the parylene insulation (which apparently occurred on the grain boundaries of the iridium). "still only marginally reliable" (and still.. and still..)
  • they have operantly trained cortical units in another, earlier study.
  • have, effectively, 8 levels of activity, with feedback monkey has to match the proscribed firing rate.
  • > 50% rewarded trials = success for them; 26/28 of the neurons tested were eventually conditioned successfully.
  • looks like the monkey can track the target firing rate rather accurately. "the output of cortical cells can provide information output rates moderately less precise than the intact motor system. "
  • Monkey can also activated sequences of neurons: A, then AB, then B.
  • people have also tried conditioning individual EMG units; it is sometimes possible to control 2 different motor units in the same muscle independently, but in general only a single channel of information can be obtained from one muscle, and gross EMGs are fine for this.
    • Thus surface EMG is preferred.
    • you can get ~ 2.73 bits/sec with gross EMG on a human; 2.99 bits/sec (max) with a monkey.
  • they remind us, of course, that an enormous amount of work remains to be done.

____References____

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ref: Schmidt-1984.12 tags: Schmidt spike sorting PCA date: 12-20-2011 23:34 gmt revision:1 [0] [head]

PMID-6396456[0] Computer separation of multi-unit neuroelectric data: a review

  • goes through the standard, by then well-established ideas: template matching, PCA, spike amplitude, peak-to-peak amplitude, Fourier analysis, curve fitting, spike area, rms value.
  • These are all useful features, though template matching seems the standard now..
  • Gerstein and Clark 1964 -- stored spikes on tape, then sampled the tape until a threshold was exceeded. 32 samples of the waveform around threshold crossing were stored for analysis on the computer; up to 7000 points could be saved.
  • also looked at cross-correlation of a spike with a template -- back in 1968 on a LINC-8!
  • Reviews a good number of other very clever spike sorting techniques for using the lmiited hardware available.
  • Talk about template realignment and resampling Mambrito and De Luca 1983

____References____

[0] Schmidt EM, Computer separation of multi-unit neuroelectric data: a review.J Neurosci Methods 12:2, 95-111 (1984 Dec)