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[0] 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)

[0] Hatsopoulos NG, Encoding in the motor cortex: was evarts right after all? Focus on "motor cortex neural correlates of output kinematics and kinetics during isometric-force and arm-reaching tasks".J Neurophysiol 94:4, 2261-2 (2005 Oct)

[0] Georgopoulos AP, Ashe J, Smyrnis N, Taira M, The motor cortex and the coding of force.Science 256:5064, 1692-5 (1992 Jun 19)

[0] Taira M, Boline J, Smyrnis N, Georgopoulos AP, Ashe J, On the relations between single cell activity in the motor cortex and the direction and magnitude of three-dimensional static isometric force.Exp Brain Res 109:3, 367-76 (1996 Jun)

[0] Kettner RE, Schwartz AB, Georgopoulos AP, Primate motor cortex and free arm movements to visual targets in three-dimensional space. III. Positional gradients and population coding of movement direction from various movement origins.J Neurosci 8:8, 2938-47 (1988 Aug)[1] Georgopoulos AP, Kettner RE, Schwartz AB, Primate motor cortex and free arm movements to visual targets in three-dimensional space. II. Coding of the direction of movement by a neuronal population.J Neurosci 8:8, 2928-37 (1988 Aug)[2] Schwartz AB, Kettner RE, Georgopoulos AP, Primate motor cortex and free arm movements to visual targets in three-dimensional space. I. Relations between single cell discharge and direction of movement.J Neurosci 8:8, 2913-27 (1988 Aug)[3] Georgopoulos AP, Kalaska JF, Caminiti R, Massey JT, On the relations between the direction of two-dimensional arm movements and cell discharge in primate motor cortex.J Neurosci 2:11, 1527-37 (1982 Nov)

[0] Georgopoulos AP, Kalaska JF, Caminiti R, Massey JT, On the relations between the direction of two-dimensional arm movements and cell discharge in primate motor cortex.J Neurosci 2:11, 1527-37 (1982 Nov)

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ref: -2019 tags: non degenerate two photon excitation fluorophores fluorescence OPO optical parametric oscillator date: 10-31-2019 20:53 gmt revision:0 [head]

Efficient non-degenerate two-photon excitation for fluorescence microscopy

  • Used an OPO + delay line to show that non-degenerate (e.g. photons of two different energies) can induce greater fluorescence, normalized to input energy, than normal same-energy excitation.

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ref: -0 tags: Hinton google tech talk dropout deep neural networks Boltzmann date: 02-12-2019 08:03 gmt revision:2 [1] [0] [head]

Brains, sex, and machine learning -- Hinton google tech talk.

  • Hinton believes in the the power of crowds -- he thinks that the brain fits many, many different models to the data, then selects afterward.
    • Random forests, as used in predator, is an example of this: they average many simple to fit and simple to run decision trees. (is apparently what Kinect does)
  • Talk focuses on dropout, a clever new form of model averaging where only half of the units in the hidden layers are trained for a given example.
    • He is inspired by biological evolution, where sexual reproduction often spontaneously adds or removes genes, hence individual genes or small linked genes must be self-sufficient. This equates to a 'rugged individualism' of units.
    • Likewise, dropout forces neurons to be robust to the loss of co-workers.
    • This is also great for parallelization: each unit or sub-network can be trained independently, on it's own core, with little need for communication! Later, the units can be combined via genetic algorithms then re-trained.
  • Hinton then observes that sending a real value p (output of logistic function) with probability 0.5 is the same as sending 0.5 with probability p. Hence, it makes sense to try pure binary neurons, like biological neurons in the brain.
    • Indeed, if you replace the backpropagation with single bit propagation, the resulting neural network is trained more slowly and needs to be bigger, but it generalizes better.
    • Neurons (allegedly) do something very similar to this by poisson spiking. Hinton claims this is the right thing to do (rather than sending real numbers via precise spike timing) if you want to robustly fit models to data.
      • Sending stochastic spikes is a very good way to average over the large number of models fit to incoming data.
      • Yes but this really explains little in neuroscience...
  • Paper referred to in intro: Livnat, Papadimitriou and Feldman, PMID-19073912 and later by the same authors PMID-20080594
    • A mixability theory for the role of sex in evolution. -- "We define a measure that represents the ability of alleles to perform well across different combinations and, using numerical iterations within a classical population-genetic framework, show that selection in the presence of sex favors this ability in a highly robust manner"
    • Plus David MacKay's concise illustration of why you need sex, pg 269, __Information theory, inference, and learning algorithms__
      • With rather simple assumptions, asexual reproduction yields 1 bit per generation,
      • Whereas sexual reproduction yields G\sqrt G , where G is the genome size.

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ref: -0 tags: tungsten eletropolishing hydroxide cleaning bath tartarate date: 03-28-2017 16:34 gmt revision:0 [head]

Method of electropolishing tungsten wire US 3287238 A

  • The bath is formed of 15% by weight sodium hydroxide, 30% by weight sodium potassium tartrate, and 55% by weight distilled water, with the bath temperature being between 70 and 100 F.
    • If the concentration of either the hydroxide or the tartrate is below the indicated minimum, the wire is electrocleaned rather than electropolished, and a matte finish is obtained rather than a specular surface.
    • If the concentration of either the hydroxide or the tartrate is greater than the indicated maximum, the electropolishing process is quite slow.
  • The voltage which is applied between the two electrodes 18 and 20 is from 16 to 18.5 volts, the current through the bath is 20 to 24 amperes, and the current density is 3,000 to 4,000 amperes per square foot of surface of wire in the bath.

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ref: -0 tags: nanopore membrane nanostraws melosh surface adhesion intracellular date: 02-06-2017 23:34 gmt revision:0 [head]

PMID-22166016 Nanostraws for Direct Fluidic Intracellular Access

  1. Used track-etched polycarbonate membranes, which have controlled pore density & ID.
  2. Deposited alumina on the pores & external surfaces using ALD
  3. Then etched away the top alumina
  4. and finally used O2 RIE to etch away the polycarbonate.
  • Show that these nanopores have cytosolic access (via Fluor 488 - hydrazide membrane impermeant dye
  • Also used nanostraws to deliver Co+2 to quench GFP fluorescence.

PMID-24710350, Quantification of nanowire penetration into living cells.

  • We discover that penetration is a rare event: 7.1±2.7% of the nanostraws penetrate the cell to provide cytosolic access for an extended period for an average of 10.7±5.8 penetrations per cell.
  • Using time-resolved delivery, the kinetics of the first penetration event are shown to be adhesion dependent and coincident with recruitment of focal adhesion-associated proteins.
    • Hours for unmodified, 5 minutes for adhesion-promoting surface.
  • Chinese hamster oviary cells expressing GFP, Co+2 quenching, EDTA chelation.
  • To modulate cell adhesion, nanostraw substrates were incubated in 10 μg ml−1 fibronectin, a well-characterized cell adhesion molecule, in addition to the standard polyornithine coating.

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ref: -0 tags: review neural recording penn state extensive biopolymers date: 02-06-2017 23:09 gmt revision:0 [head]

PMID-24677434 A Review of Organic and Inorganic Biomaterials for Neural Interfaces

  • Not necessarily insightful, but certainly exhaustive review of all the various problems and strategies for neural interfacing.
  • Some emphasis on graphene, conductive polymers, and biological surface treatments for reducing FBR.
  • Cites 467 articles!

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ref: -0 tags: PEDOT electropolymerization electroplating gold TFB borate counterion acetonitrile date: 10-18-2016 07:49 gmt revision:3 [2] [1] [0] [head]

Electrochemical and Optical Properties of the Poly(3,4-ethylenedioxythiophene) Film Electropolymerized in an Aqueous Sodium Dodecyl Sulfate and Lithium Tetrafluoroborate Medium

  • EDOT has a higher oxidation potential than water, which makes polymers electropolymerized from water "poorly defined".
  • Addition of SDS lowers the oxidation potential to 0.76V, below that of EDOT in acetonitrile at 1.1V.
  • " The potential was first switched from open circuit potential to 0.5 V for 100 s before polarizing the electrode to the desired potential. This initial step was to allow double-layer charging of the Au electrode|solution interface, which minimizes the distortion of the polymerization current transient by double-layer capacitance charging.17,18 "
    • Huh, interesting.
  • Plated at 0.82 - 0.84V, 0.03M EDOT conc.
  • 0.1M LiBF4 anion / electrolyte; 0.07M SDS sufactant.
    • This SDS is incorporated into the film, and affects redox reactions as shown in the cyclic voltammagram (fig 4)
      • Doping level 0.36
    • BF4-, in comparison, can be driven out of the film.

Improvement of the Electrosynthesis and Physicochemical Properties of Poly(3,4-ethylenedioxythiophene) Using a Sodium Dodecyl Sulfate Micellar Aqueous Medium

  • "The oxidation potential of thiopene = 1.8V; water = 1.23V.
  • Claim: "The polymer films prepared in micellar medium [SDS] are more stable than those obtained in organic solution as demonstrated by the fact that, when submitted to a great number of redox cycles (n ≈ 50), there is no significant loss of their electroactivity (<10%). These electrochemical properties are accompanied by color changes of the film which turns from blue-black to red-purple upon reduction."
  • Estimate that there is about 21% DS- anions in the PEDOT - SDS films.
    • Cl - was at ~ 7%.
  • I'm still not sure about incorporating soap into the electroplating solution.. !

Electrochemical Synthesis of Poly(3,4-ethylenedioxythiophene) on Steel Electrodes: Properties and Characterization

  • 0.01M EDOT and 0.1M LiClO4 in acetonitrile.
  • Claim excellent adhesion & film properties to 316 SS.
  • Oxidation / electrodeposition at 1.20V; voltages higher than 1.7V resulted in flaky films.

PMID-20715789 Investigation of near ohmic behavior for poly(3,4-ethylenedioxythiophene): a model consistent with systematic variations in polymerization conditions.

  • Again use acetonitrile.
  • 1.3V vs Ag/AgCl electrode.
  • Perchlorate and tetraflouroborate both seemed the best counterions (figure 4).
  • Figure 5: Film was difficult to remove from surface.
    • They did use a polycrystaline Au layer:
    • "The plating process was allowed to run for 1 min (until approximately 100 mC had passed) at a constant potential of 0.3 V versus Ag/AgCl in 50 mM HAuCl4 prepared in 0.1 M NaCl."
  • Claim that the counterions are trapped; not in agreement with the SDS study above.
  • "Conditions for the consistent production of conducting polymer films employing potentiostatic deposition at 1.3 V for 60-90 s have been determined. The optimal concentration of the monomer is 0.0125 M, and that of the counterion is 0.05 M. "

PMID-24576579 '''Improving the performance of poly(3,4-ethylenedioxythiophene) for brain–machine interface applications"

  • Show that TFB (BF4-) is a suitable counterion for EDOT electropolymerization.
  • Comparison is between PEDOT:TFB deposited in an anhydrous acetronitrile solution, and PEDOT:PSS deposited in an aqueous solution.
    • Presumably the PSS brings the EDOT into solution (??).
  • figure 3 is compelling, but long-term, electrodes are not that much better than Au!
    • Maybe we should just palate with that.

PEDOT-modified integrated microelectrodes for the detection of ascorbic acid, dopamine and uric acid

  • Direct comparison of acetonitrile and water solvents for electropolymerization of EDOT.
  • "PEDOT adhesion is best on gold surface due to the strong interactions between gold and sulphur atoms.
  • images/1353_2.pdf
    • Au plating is essential!

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ref: -0 tags: neural recording topologies circuits operational transconductance amplifiers date: 01-02-2013 20:00 gmt revision:0 [head]

PMID-22163863 Recent advances in neural recording microsystems.

  • Decent review. Has some depth on the critical first step of amplification.

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ref: DeLong-1985.02 tags: globus pallidus subthalamic STN electrophysiology Georgopoulos DeLong DBS date: 02-24-2012 21:50 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-3981228[0] Primate globus pallidus and subthalamic nucleus: functional organization

  • cells respond to arm, leg, and orofacial movements (mostly in the arm tho)
  • ~25% of these responded to passive joint movement - the latency is in accord with proprioceptive driving.
  • arm-related neurons were found throughout the rostrocaudal extent of both globus pallidus segments
  • look @ the articles that cite this!

____References____

[0] DeLong MR, Crutcher MD, Georgopoulos AP, Primate globus pallidus and subthalamic nucleus: functional organization.J Neurophysiol 53:2, 530-43 (1985 Feb)

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ref: Georgopoulos-1983.08 tags: STN monkeys primate Georgopoulos globus pallidus date: 02-10-2012 18:57 gmt revision:2 [1] [0] [head]

PMID-6875658[0] Relations between parameters of step-tracking movements and single cell discharge in the globus pallidus and subthalamic nucleus of the behaving monkey.

  • Step tracking task in monkeys; wrist flexion and extension.
    • first one in monkeys, apparently.
    • 87 neurons in GP, 36 in GPi, 29 in STN.
  • Linear tuning to direction and distance, same as in motor cortex by Georgopoulos.
    • More likely to see frequency increase.
  • Earlier firing rate change in STN than GPe than GPi.
  • Two patterns of firing in the globus pallidus external:
    • more frequent: high discharge rate interrupted with pauses of varying duration
    • less frequent: low average discharge rate with very high frequency bursts.
  • GPi: high frequency with frequent bursts.
  • GPi/e generally high firing rate - 80-100 Hz, with frequent bursts.
    • But not as deep movement tuning as M1.
  • Only primates have projections from the motor cortex to the STN.
    • This seems like an evolutionarily recent development -- apparently the cortex needs the extra level of control?

See also citing articles: http://scholar.google.com/scholar?cites=16339220378239936453&as_sdt=5,34&sciodt=0,34&hl=en

____References____

[0] Georgopoulos AP, DeLong MR, Crutcher MD, Relations between parameters of step-tracking movements and single cell discharge in the globus pallidus and subthalamic nucleus of the behaving monkey.J Neurosci 3:8, 1586-98 (1983 Aug)

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ref: Fagg-2007.1 tags: BMI kinarm Hatsopoulos Moxon Miller FES date: 01-06-2012 00:17 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-17978021[0] Biomimetic Brain Machine Interfaces for the Control of Movement.

  • images/482_1.pdf
  • describe structured models that include arm information & 'plant' dynamics.
    • current methods ignore the dynamics of the musculoskeletal system. Want to mimic natural arm movement.
    • To this end used a kinarm with a paralyzed monkey.
  • obtained real-time prediction of joint force, torque, and EMG
    • Concerning quality of prediction: they use fraction of movement variance that can be accounted for (FVAF) which, though google does not seem to know much about it, is probably the same as R^2. but it does not look that great:
      • 0.61 - 0.65 for torque prediction
      • 0.70 - 0.75 for EMG prediction once again, the limitation is the recording technology.
  • tested coupling predictions to the freehand FES system - see this crazy news brief
  • want to incorporate somatosensory feedback into the BMI.
  • they reference a paper from 2008 - huh? The document claims to be written/published in 2007.

____References____

[0] Fagg AH, Hatsopoulos NG, de Lafuente V, Moxon KA, Nemati S, Rebesco JM, Romo R, Solla SA, Reimer J, Tkach D, Pohlmeyer EA, Miller LE, Biomimetic brain machine interfaces for the control of movement.J Neurosci 27:44, 11842-6 (2007 Oct 31)

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ref: Hatsopoulos-2005.01 tags: BMI Hatsopoulos Donoghue cortex date: 01-03-2012 22:49 gmt revision:4 [3] [2] [1] [0] [head]

PMID-17282055[0][] Cortically controlled brain-machine interface

  • conference proceedings. describe the 6month teraplegic trial.
  • (above, monkey)
    • lets them record from 40% of electrodes.
    • 100-200uv units, 20uv noise.
    • one year to three years post implantation.
  • advocate hybrid multimodal control.
    • M1 = continuous control
    • PMd = discrete control
      • used a probabilistic model for this (poisson firing rate, individual neurons are independent)

____References____

[0] Hatsopoulos N, Mukand J, Polykoff G, Friehs G, Donoghue J, Cortically controlled brain-machine interface.Conf Proc IEEE Eng Med Biol Soc 7:1, 7660-7663 (2005)

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ref: Mohseni-2004.05 tags: recording amplifier biopotential Mohseni Najafi date: 01-03-2012 01:09 gmt revision:2 [1] [0] [head]

PMID-15132510[0] A fully Integrated Neural Recording Amplifier with DC Input Stabilization

  • The DC stabilization is the interesting part - use subthreshold PMOS transistors.
  • NEF not so good on this one - about 10. {729} much better.

____References____

[0] Mohseni P, Najafi K, A fully integrated neural recording amplifier with DC input stabilization.IEEE Trans Biomed Eng 51:5, 832-7 (2004 May)

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ref: -0 tags: Georgopoulos population vector arm motor control date: 12-20-2011 22:26 gmt revision:1 [0] [head]

PMID-3139485 Neural integration of movement: role of motor cortex in reaching.

  • Reviews his 2D and 3D population vector / cosine tuning results.
  • Isometric task in [13] varied as a sinusoidal function of load.
    • [1]3 Kalaska 1985 Area 4 and area 5: differences between the load direction-dependent discharge variability of cells during active postural fixation.
  • [14] suggests that separate motor cortical populations are concerned with the control of joint stiffness.
    • [14] Humphrey 1983 Seperate cortical systems for control of joint movement and joint stiffness: reciprocal activation and coactivation of antagonist muscles.
  • proximal muscles are controlled through C3-C4 propriospinal neurons, which receive input from corticospinal, rubrospinal, reticulospinal, and tectospinal tracts, and distribute axons to proximal motorneuron pools [25]
    • The propriospinal system seems to be selectively engaged during reaching movements [28].
    • There is corticspinal input on key inhibitory interneuron that mediates inhibition from afferent fibers to propriospinal neurons [29].
    • References in this from the cat.
  • This is similar to 'the sophisticated integration seen in the locomotor system' locomotive system.
  • From this, Georgopoulos supposes that the motor cortex is concerned with the specification of the direction of reaching in space.
  • He further supposes that this is enacted by individual motor cortical cells influence motoneuronal pools in a weighted fashion.
  • Looking back, I'm surprised at how clean his PV tuning plots are -- the neurons stop fiting when the monkey moves his arm in certain directions.

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ref: -0 tags: Georgopoulos 1988 population vector tuning date: 12-20-2011 01:13 gmt revision:1 [0] [head]

PMID-3411362[0] Primate motor cortex and free arm movements to visual targets in three-dimensional space. II. Coding of the direction of movement by a neuronal population.

  • This is the paper where they do predictions, and show that they can offline 'decode' 3D reaching movements.
    • Pretty spiffy 3D graphics, too.
  • Used three analyses to estimate variability of the population vector.
    • 1. Random sampling of the experimentally observed population (N= 475), using the mean discharge rate of each cell to each direction.
    • 2. Same cell population, but variability of discharge was drawn from a normal distro estimated from the mean and variance of the trial-to-trial recordings.
    • 3. Random sampling + trial-to-trial variability.
  • Plot 95% confidence interval over population size for the estimated direction; asymtopes at about 15%. Why not measured in steradians?
  • Figure 4 looks to have good SNR, and they look to be dataheads.
  • Use a bunch of different weighting functions to calculate the population vector; no numerical optimization?
    • best one basically looks like normalized, mean-removed firing rate.

____References____

[0] Georgopoulos AP, Kettner RE, Schwartz AB, Primate motor cortex and free arm movements to visual targets in three-dimensional space. II. Coding of the direction of movement by a neuronal population.J Neurosci 8:8, 2928-37 (1988 Aug)

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ref: -0 tags: Georgopoulos 1988 M1 population vector tuning 3D single unit date: 12-20-2011 00:58 gmt revision:2 [1] [0] [head]

PMID-3411363[0] Primate motor cortex and free arm movements to visual targets in three-dimensional space. III. Positional gradients and population coding of movement direction from various movement origins.

  • In comparison to the first experiment, where they showed that movement direction was encoded by single units within M1, here they varied the starting position of the movements.
  • tonic discharge of many cells varied in and orderly fashion with the position at which the hand was actively maintained in space.
  • however, cell activity changes were the same independent of movement onset and dependent on movement direction.
    • similar but not that similar -- vary based on tonic firing rate. See figure 9.

____References____

[0] Kettner RE, Schwartz AB, Georgopoulos AP, Primate motor cortex and free arm movements to visual targets in three-dimensional space. III. Positional gradients and population coding of movement direction from various movement origins.J Neurosci 8:8, 2938-47 (1988 Aug)

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ref: Schwartz-1988.08 tags: Georgopoulos 1988 motor coding cortex population vector date: 12-20-2011 00:49 gmt revision:3 [2] [1] [0] [head]

PMID-3411361[0] Primate motor cortex and free arm movements to visual targets in three-dimensional space. I. Relations between single cell discharge and direction of movement.

  • 475/568 (83%) of cells varied in an orderly fashion with movement -- tuned to a movement direction.
    • As before, binned the firing based on movement direction.
  • generalize 2-D results [1][2]
  • Totally awesome tracking system: a spark gap was attached to the monkey's wrist and was discharged every 20ms. The sonic signal was picked up by at least 3 of the 8 ultrasonic recievers placed at the corners of the workspace and the xyz coordinates were calculated from the sonic delays using a microprocessor-based system.
  • monkey(s) had to press lighted buttons (arcade buttons) within this workspace.
  • otherwise same materials / methods as before.
  • every effort was made to isolate initially negative-going action potentials, and indication that the neuron was less likely to be damaged.
    • fiber spikes are initially positive. Cite Mountcastle et al 1969.
  • EMG signals gained 3000 and bandpassed 100-500Hz. rather narrow, but normal I guess.
  • Neural data recorded as interspike intervals.
  • vectoral dot-product tuning of cells, with the coeficients set by multiple linear regression.
    • This is equivalent to cosine tuning.
  • rather complicated CUSUM for determining onset of activity - including inhibition.
  • as in the earlier study, 60% of cells were tuned in the reaction time, and 85% within the movement time.
  • EMG activity looks like it can be described with cosine tuning as well.
  • 3D tuning directed over the whole space.
  • Residuals of firing rates measured with respect to the tuning functions; residuals were mean zero and approximately the same spread, and were distributed equally over the 3D space.
  • movement latency about 300ms. pretty quick reaction time?
  • Got some pretty awesome graphics for 1986 :)
  • The discharge rate of motor cortical cells varies with the magnitude of force and that cells with higher thresholds are recruited at progressively higher forces (Hepp-Reymond et al 1978).
  • Murphy et al 1982 found that ICMS to M1 caused rotation about single joints, which is inconsistent with cosine tuning (would require complex tuning, or tuning to joints).
  • They argue that cosine tuning refects transformatino by the propriospinal system, which engages patterns of muscle activity.
    • Most PTNs can influence several motoneuron pools in the spinal cord. (Fetz and Finocchio 1975, Fetz and Cheney 1978, 1980 ... Lemon 1986, Cheney and Fetz 1985)
    • Suggest that PTNs related to the weighted combinations of muscles.

____References____

[0] Schwartz AB, Kettner RE, Georgopoulos AP, Primate motor cortex and free arm movements to visual targets in three-dimensional space. I. Relations between single cell discharge and direction of movement.J Neurosci 8:8, 2913-27 (1988 Aug)
[1] Georgopoulos AP, Kalaska JF, Caminiti R, Massey JT, On the relations between the direction of two-dimensional arm movements and cell discharge in primate motor cortex.J Neurosci 2:11, 1527-37 (1982 Nov)
[2] Thach WT, Correlation of neural discharge with pattern and force of muscular activity, joint position, and direction of intended next movement in motor cortex and cerebellum.J Neurophysiol 41:3, 654-76 (1978 May)

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ref: Georgopoulos-1982.11 tags: Georgopoulos 1982 motor tuning cortex M1 population vector date: 12-19-2011 23:52 gmt revision:1 [0] [head]

PMID-7143039 On the relations between the direction of two-dimensional arm movements and cell discharge in primate motor cortex.

  • eight directions 45deg intervals, 2D joystick, frictionless, LED tarkets in a blocked randomized experimental design.
    • MK made simultaneous saccades; saccade latency 150-170ms.
      • some motor cells responded to visual movement.
    • EMG activity began ~80ms before movement.
    • monkeys used both arms.
  • bell-shaped or cosine tuning in 75% of the cells.
    • This has also been described in the saccade system in the paramedian pontine reticular formation (Henn and Cohen 1976), the mesencelphatic reticular formation (Buttner eta la 1977) and the internal medullary lamina of the thalamus (Schlag and Schlag-Ney 1977)
  • cells tended to cluster by tuning in depth.
  • cells tended to respond to movement & small corrections to movement, but did not necessarily respond to non-task related movement. "Yet these same cells were frequently silent during other movements which also involved contraction of the same muscles [as used in the task]"
  • cell discharge was much stronger during active movements than during passive manipulations.
  • 64% of cells were activated before the earliest EMG changes; 87% before the onset of movement.
  • The famous one, where the population vector was formalized / conceived / validated.
  • most neurons begin firing ~ 100ms before movement begins.
  • useda PDP11/20 minicomputer to control the LEDs & data recording.
  • Thach 1978 -- approxmately equal proportions of motor cortical cells were related to muscle activity, hans position, and direction of intended movement Thach 1978) PMID-96223
  • single electrode Pt/Ir recording 2-3Mohm; recordings made for 6-7 hours.
  • cite georgopoulos 1983 -- they propose distributed population coding.
  • point out that the central problem -- upon which some progress has been made - is the translation between visual and motor coordinate frames.

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ref: -0 tags: xmos microcontroller microporcessor threading date: 08-11-2009 16:15 gmt revision:0 [head]

http://www.xmos.com/

  • Looks nice! They even publish their board designs and schematics - makes sense given they want their chips to be incorporated into products.
  • Their processors are 'event-driven', which seems to mean that they have 8 sets of registers, one set per thread, with presumably rapid switching between the threads. I did not investigate how excatly their processor works, whether this means they don't need DMA, etc.
  • -- an example with dual LAN8700 ethernet interfaces.

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ref: -0 tags: recroding biopotential MOS-bipolar pseudoresistor date: 04-15-2009 22:03 gmt revision:0 [head]

Linear transconductor with rail-to-rail input swing for very large time constanct applications

  • Outlines the structure, theory, and use of MOS-bipolar pseudoresistors.
  • These devices can operate up to 330 GOhm!
  • Concise article.

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ref: Serruya-2002.03 tags: BMI Donoghue 2002 Hatsopoulos Utah array Serruya date: 09-07-2008 19:08 gmt revision:1 [0] [head]

PMID-11894084[0] Instant neural control of a movement signal.

  • used only a few (7-30) motor cortex neurons
  • this let the monkey immediately manipulate a computer cursor, without extensive training (according to them).

____References____

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ref: Hatsopoulos-2005.1 tags: motor control M1 Hatsopoulos date: 04-09-2007 22:26 gmt revision:1 [0] [head]

PMID-16160087[] Encoding in the Motor Cortex: Was Evarts Right After All? Focus on "Motor Cortex Neural Correlates of Output Kinematics and Kinetics During Isometric-Force and Arm-Reaching Tasks"

  • this is a discussion of the isometric vs. pendulum movement task. (and editorial focus)
    • in the isometric task, neurons are tuned to the direction of force, and fire anticipatorily.
    • in the movement task, they show a characteristic triphasic activity profile, very similar to what the muscles need.
  • neurons in the rostral bank of the CS seem to (almost) control muscle activation directly.
  • One possibility mentioned by the authors is that motor cortex may need to compensate for nonlinearities at the spinal motoneuron level as well as the low-pass filter characteristics of the muscles resulting in a nonlinear mapping between these neurons and the resulting forces at the hand.

____References____

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ref: Georgopoulos-1992.06 tags: motor control force Georgopoulos date: 04-09-2007 19:56 gmt revision:1 [0] [head]

PMID-1609282[0] The motor cortex and the coding of force.

  • 2D isometric force, which dissociated force & changed in force.
  • cells are not tuned to the direction of the absolute force, but rather to the direction of both the visual cue and change in force (dF/dt) as measured using linear regressions in an isometric force task.

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ref: Taira-1996.06 tags: 3D Georgopoulos SUA M1 force motor control direction tuning date: 04-09-2007 15:16 gmt revision:1 [0] [head]

PMID-8817266[0] On the relations between single cell activity in the motor cortex and the direction and magnitude of three-dimensional static isometric force.

  • 3D isometric joystick.
  • stepwise multiple linear regression.
  • direction of force is a signal especially prominent in the motor cortex.
    • the pure directional effect was 1.8 times more prevalent in the cells than in the muscles studied (!)

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ref: Kettner-1988.08 tags: 3D motor control population_vector Schwartz Georgopoulos date: 04-05-2007 17:09 gmt revision:1 [0] [head]

A triptych of papers (good job increasing your publication count, guys!):

  • PMID-3411363[0] Primate motor cortex and free arm movements to visual targets in three-dimensional space. III. Positional gradients and population coding of movement direction from various movement origins.
    • propose multilinear model to predict firing rate of nneuron (a regression that is the same direction as the kalman filter)
    • i don't see how this is that much different from below (?)
  • PMID-3411362[1] Primate motor cortex and free arm movements to visual targets in three-dimensional space. II. Coding of the direction of movement by a neuronal population.
    • they show, basically, that they can predict movement direction (note this is different from actual movement!) using the poulation vector scheme.
  • PMID-3411361[2] Primate motor cortex and free arm movements to visual targets in three-dimensional space. I. Relations between single cell discharge and direction of movement.
    • 568 cells!!
    • 8 directional targets, again -- not sure how they were aranged; they say 'in approximately equal angular intervals'
    • these findings generalize the previous 2D results [3] (tuning to external space) to 3D

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ref: Georgopoulos-1982.11 tags: georgopoulos kalaska caminiti M1 motor control tuning population_vector date: 04-05-2007 16:27 gmt revision:0 [head]

PMID-7143039[0] On the relations between the direction of two-dimensional arm movements and cell discharge in primate motor cortex

  • famous 8-target center out task
  • dot-product tuning
  • 75% of cells were found to be tuned.
  • posits the population code for directional movements - statistical summation & averaging, i presume.

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ref: engineering notes-0 tags: homopolar generator motor superconducting magnet date: 03-09-2007 14:39 gmt revision:0 [head]

http://hardm.ath.cx:88/pdf/homopolar.pdf

  • the magnets are energized in 'opposite directions - forcing the field lines to go normal to the rotar.
  • still need brushes - perhaps there is no way to avoid them in a homopolar generator.

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ref: GarciaRill-1991.01 tags: PPN pedunculopontine nucleus brainstem sleep locomotion consciousness 1991 date: 0-0-2007 0:0 revision:0 [head]

PMID-1887068 The Pedunculopontine nucleus

  • extensive review!