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[0] Foster DJ, Wilson MA, Reverse replay of behavioural sequences in hippocampal place cells during the awake state.Nature 440:7084, 680-3 (2006 Mar 30)

[0] Soetedjo R, Fuchs AF, Complex spike activity of purkinje cells in the oculomotor vermis during behavioral adaptation of monkey saccades.J Neurosci 26:29, 7741-55 (2006 Jul 19)

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ref: -0 tags: iridium oxide nanotube intracellular recording electroplate MEA date: 02-22-2017 22:41 gmt revision:0 [head]

PMID-24487777 Iridium oxide nanotube electrodes for sensitive and prolonged intracellular measurement of action potentials.

  • Electrodeposition of IrOx "magically" forms 500nm tubes.
  • Holes in Si3N4 / SiO2 were formed via e-beam lithography; underlying Pt wires via liftoff.
  • Showed long (minutes) intracellular access, though it tended to dip with time.

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ref: -0 tags: nanoprobe transmembrane intracellular thiol gold AFM juxtacellular date: 02-06-2017 23:45 gmt revision:3 [2] [1] [0] [head]

PMID-20212151 Fusion of biomimetic stealth probes into lipid bilayer cores

  • Used e-beam evaporation of Cr/Au/Cr 10/10/10 or 10/5/10 onto a Si AFM tip.
    • Approx 200nm diameter; 1800 lipid interaction at the circumference.
  • Exposed the Au in the sandwich via FIB
  • Functionalized the Au with butanethiol or dodecanthiol; former is mobile on the surface, latter is polycrystaline.
    • Butanethiol showed higher adhesion to the synthetic membranes
  • Measured the penetration force & displacement through synthetic multi-layer lipid bilayers.
    • These were made via a custom protocol with 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine (SOPC) and cholesterol

PMID-21469728 '''Molecular Structure Influences the Stability of Membrane Penetrating Biointerfaces.

  • Surprisingly, hydrophobicity is found to be a secondary factor with monolayer crystallinity the major determinate of interface strength
  • Previous studies using ellipsometry and IR spectroscopy have shown that alkanethiol self-assembled monolayers display an abrupt transition from a fluid to a crystalline phase between hexanethiol and octanethiol.
    • This suggests the weakening of the membrane stealth probe interface is due to the crystallinity of the molecular surface with fluid, disordered monolayers promoting a high strength interface regime and rigid, crystalline SAMs forming weak interfaces.

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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: intracellular juxtacellular recording tungsten nanowire whole cell patch date: 02-06-2017 22:39 gmt revision:2 [1] [0] [head]

PMID-22905231 Neuronal recordings with solid-conductor intracellular nanoelectrodes (SCINEs).

  • <300 nm diameter W fibers, several um long, fabricated via FIB.
  • Functionalized with a hydrophobic silane on the oxide.
    • Quite complete & custom methods here.
  • Not quite whole cell recording, but excellent SNR; 4mv APs.
    • Slice, rat hippocampus organotypic.
    • Expected much larger recorded APs; suspect partial membrane penetration.
    • Only lasted a few seconds to minutes.
  • Needed custom recording setup for interfacing with 100Gohm electrodes; stray capacitance < 4 pf.
  • Intracellular electrodes must be designed to not shunt the membrane open upon insertion.
    • In a study where whole-cell recordings were established prior sharp microelectrode penetration, all neurons showed significant depolarization following impalement.
    • Here there was no change in membrane voltage in 10% of insertions of the silane-functionalized SCINEs. only in the functionalized electrodes).
    • Minor distortion of the AP was observed.
  • In whole-cell patch clamping, diffusion from the pipette to the cytosol interrupts biochemical processes necessary for normal cellular function (e.g. respiration!).
  • The hardness of the tungsten ensures that SCINEs can be repeatedly inserted millimeter-deep into brain tissue without noticeable damage to the tip.
    • E.g. 300 nm tungsten will not easily navigate vasculature...

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ref: -0 tags: nanotube tracking extracellular space fluorescent date: 02-02-2017 22:13 gmt revision:0 [head]

PMID-27870840 Single-nanotube tracking reveals the nanoscale organization of the extracellular space in the live brain

  • Extracellular space (ECS) takes up nearly a quarter the volume of the brain (!!!)
  • Used the intrinsic fluorescence of single-walled carbon nanotubes @ 1um, 845nm excitation, with super-resolution tracking of diffusion.
    • Were coated in phospholipid-polyethylene glycol (PL-PEG), which display low cytotoxicity compared to other encapsulants.
  • 5ul, 3ug/ml injected into the ventricles of young rats; allowed to diffuse for 30 minutes post-injection.
  • No apparent response of the microglia.
  • Diffusion tracking revealed substantial dead-space domains in the ECS.
    • As compared to patch-clamp loaded SWCNTs
  • Estimate from parallel and perpendicular diffusion rates that the characteristic scale of ECS dimension is 80 to 270nm, or 150 +- 40nm.
  • The ECS nanoscale dimensions as visualized by tracking similar in dimension and tortuosity to electron microscopy.
  • Viscosity of the extracellular matrix from 1 to 50 mPa S, up to two orders of magnitude higher than the CSF.
  • Positive control through hyalurinase + several hours to digest the hyaluronic acid.
    • But no observed changes in morphology of the neurons via confocal .. interesting.
    • Enzyme digestion normalized the spatial heterogenaity of diffusion.

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ref: -0 tags: Leiber nanoFET review silicon neural recording intracellular date: 02-01-2017 03:32 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-23451719 Synthetic Nanoelectronic Probes for Biological Cells and Tissue

  • Review of nanowireFETS for biological sensing
  • Silicon nanowires can be grown via vapor-liquid-solid or vapor-solid-solid, 1D catalyzed growth, usually with a Au nanoparticle.
  • Interestingly, kinks can be introduced via "iterative control over nucleation and growth", 'allowing the synthesis of complex 2D and 3D structures akin to organic chemistry"
    • Doping can similarly be introduced in highly localized areas.
    • This bottom-up synthesis is adaptable to flexible and organic substrates.
  • Initial tests used polylysine patterning to encourage axonal and dendritic growth across a nanoFET.
    • Positively charged amino group interacts with negative surface charge phospholipid
    • Lieber's group coats their SU-8 electrodes in poly-d-lysine as well {1352}
  • Have tested multiple configurations of the nanowire FET, including kinked, one with a SiO2 nanopipette channel for integration with the cell membrane, and one where the cell-attached fluid membrane functions as the semiconductor; see figure 4.
    • Were able to show recordings as one of the electrodes was endovascularized.
  • It's not entirely clear how stable and scalable these are; Si and SiO2 gradually dissolve in physiological fluid, and no mention was made of longevity.

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ref: -0 tags: juxtacellular recording gold mushroom cultured hippocampal neurons Spira date: 02-01-2017 02:44 gmt revision:7 [6] [5] [4] [3] [2] [1] [head]

Large-Scale Juxtacellular Recordings from Cultured Hippocampal Neurons by an Array of Gold-Mushroom Shaped Microelectrodes

  • Micrometer sized Au mushroom MEA electrodes.
  • Functionalized by poly-ethylene-imine (PEI, positively charged)/laminin (extracellular matrix protein) undergo a process to form juxtacellular junctions between the neurons and the gMµEs.
  • No figures, but:
    • Whereas substrate integrated planar MEA record FPs dominated by negative-peak or biphasic-signals with amplitudes typically ranging between 40-100 µV and a signal to noise ratio of ≤ 5,
    • The gMµE-MEA recordings were dominated by positive monophasic action potentials.
    • It is important to note that monophasic high peak amplitudes ≥ 100 µV are rarely obtained using planar electrodes arrays, whereas when using the gMµE-MEA, 34.48 % of the gMµEs recorded potentials ≥ 200 µV and 10.64 % recorded potentials in the range of 300-5,085 µV.
  • So, there is a distribution of coupling, approximately 10% "good".

PMID-27256971 Multisite electrophysiological recordings by self-assembled loose-patch-like junctions between cultured hippocampal neurons and mushroom-shaped microelectrodes.

  • Note 300uV - 1mV extracellular 'juxtacellular' action potentials from these mushroom recordings. This is 2 - 5x better than microwire extacellular in-vivo ephys; coupling is imperfect.
    • Sharp glass-insulated W electrodes, ~ 10Mohm, might achieve better SNR if driven carefully.
  • 2um mushroom cap Au electrodes, 1um diameter 1um long shaft
    • No coating, other than the rough one left by electroplating process.
    • Impedance 10 - 25 Mohm.
  • APs decline within a burst of up to 35% -- electrostatic reasons?
  • Most electrodes record more than one neuron, similar to in-vivo ephys, with less LFP coupling.

PMID-23380931 Multi-electrode array technologies for neuroscience and cardiology

  • The key to the multi-electrode-array ‘in-cell recording’ approach developed by us is the outcome of three converging cell biological principals:
    • (a) the activation of endocytotic-like mechanisms in which cultured Aplysia neurons are induced to actively engulf gold mushroom-shaped microelectrodes (gMμE) that protrude from a flat substrate,
    • (b) the generation of high Rseal between the cell’s membrane and the engulfed gMμE, and
    • (c) the increased junctional membrane conductance.
  • Functionalized the Au mushrooms with an RGD-based peptide
    • RGD is an extracellular matrix binding site on fibronectin, which mediates it's interaction with integrin, a cell surface receptor; it is thought that other elements of fibronectin regulate specificity with its receptor. PMID-2418980

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ref: -0 tags: vertical nanowire juxtacellular recording date: 02-01-2017 00:50 gmt revision:2 [1] [0] [head]

PMID-22231664 Vertical nanowire electrode arrays as a scalable platform for intracellular interfacing to neuronal circuits.

  • Note actual coupling is low, 0.002, compared to patch-clamp (400uV vs 200mV). Signal is rather noisy.
  • Dissociated cultures of rat cortical neurons
  • Stimulation current 200 pa enough to change membrane potential, but not initiate a spike.
    • This is 200e-12 / 20e-6 = 5 orders of magnitude lower current than typical ICMS.

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ref: -0 tags: L1 cell adhesion neural implants microglia DRG spinal cord dorsal root inflammation date: 11-19-2016 22:55 gmt revision:1 [0] [head]

PMID-22750248 In vivo effects of L1 coating on inflammation and neuronal health at the electrode-tissue interface in rat spinal cord and dorsal root ganglion.

  • Kolarcik CL1, Bourbeau D, Azemi E, Rost E, Zhang L, Lagenaur CF, Weber DJ, Cui XT.
  • Quote: With L1, neurofilament staining was significantly increased while neuronal cell death decreased.
  • These results indicate that L1-modified electrodes may result in an improved chronic neural interface and will be evaluated in recording and stimulation studies.
  • Ok, so this CAM seems to mitigate against microglia / inflammation, but how was it selected vs any of the other CAMs and surface proteins? (This domain is almost completely unknown by me..)
  • Ultimate strategy likely to be a broad combination of mechanical (size, flexibility), biochemical (inflammation, cell migration), electrochamical (surface coatings) and vasculature-avoiding approaches.

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ref: -0 tags: ice charles lieber silicon nanowire probes su-8 microwire extracellular date: 10-14-2016 23:28 gmt revision:2 [1] [0] [head]

PMID-26436341 Three-dimensional macroporous nanoelectronic networks as minimally invasive brain probes.

  • Xie C1, Liu J1, Fu TM1, Dai X1, Zhou W1, Lieber CM1,2.
  • Again, use silicon nanowire transistors as sensing elements. These seem rather good; can increase the signal, and do not suffer from shunt resistance / capacitance like wires.
    • They're getting a lot of mileage out of the technology; initial pub back in 2006.
  • Su-8, Cr/Pd/Cr (stress elements) and Cr/Au/Cr (conductor) spontaneously rolled into a ball, then the froze in LN2. Devices seemed robust to freezing in LN2.
  • 300-500nm Su-8 passivation layers, as with the syringe injectable electrodes.
  • 3um trace / 7um insulation (better than us!)
  • Used 100nm Ni release layer; thin / stiff enough Su-8 with rigid Si support chip permitted wirebonding a connector (!!)
    • Might want to use this as well for our electrodes -- of course, then we'd have to use the dicing saw, and free-etch away a Ni (or Al?) polyimide adhesion layer -- or use Su-8 like them. See figure S-4
  • See also {1352}

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ref: -0 tags: retinal ganglion cells neural encoding Farrow date: 07-31-2013 16:21 gmt revision:0 [head]

PMID-21273316 Physiological clustering of visual channels in the mouse retina

  • Anatomy predicts that mammalian retinas should have in excess of 12 physiological channels, each encoding a specific aspect of the visual scene.
  • Although several channels have been correlated with morphological cell types, the number of morphological types generally exceeds the known physiological types.
  • Here, we attempted to sort the ganglion cells of the mouse retina purely on a physiological basis.
  • Result: The optimal partition was the 12-cluster solution of the Fuzzy Gustafson-Kessel algorithm.
    • This might be useful elsewhere ...
  • Farrow Lab is responsible for the 11,011 electrode array.

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ref: -0 tags: DBS parkinsons stem cell therapy date: 02-21-2012 20:56 gmt revision:1 [0] [head]

PMID-21875864 Dopamine cell transplantation in Parkinson's disease: challenge and perspective.

  • Long-term strategy is to graft fetal mesencelphatic tissue into the striatum (putamen) of PD patients.
  • Requires one to four donors per side.
  • Requires immune suppression for graft survival.
  • PET offers a sensitive mechanism for assessing the success of the transplant
  • Earlier review [5].
  • Full double-blind study [2].
    • significant improvement in 39 patients, but only in the younger patients (<60 years).
    • No changes in cognitive function or personality traits.
    • Looks safe at least.
  • Second study [3]
    • Full immune suppressant action, 34 PD patients.
    • No overall clinical effect, even though there was significant FDOPA uptake.
    • significant improvement in less severely affected patients out to 2 years post-surgery.
  • Imaging results not so dramatic?
  • But off-state UPDRS significant
  • 5 of the 33 patients developed graft-induced dyskinesia in addition to therepeutic effects on akinesia -- possibly due to the lack of projecting axons?
    • FDOPA uptake was higher in the dyskinetic graft recipients with dyskinesias.
  • In second trial, 13 of the 23 implanted patients exhibited dyskinesias, but there was no difference in regional or global FDOPA uptake.
    • Might be caused by inflammatory response to the grafts, as per animal studies.
    • Another study showed the worsening if dyskinesias following withdrawal of immunosuppression.
    • Might also be related to DA exposure prior the surgery, or serotonin expression within the grafts (not controlled).
      • Suggest fluorescent cell sorting.
  • Possible solution to the donor problem: human retinal pigment endothelial cells, which produce L-DOPA naturally as an neuromelanin precursor (!!).
    • Open-label study worked, but placebo-controlled did not meet clinical significance.
  • Alternate strategy is to reprogram host somatic cells (e.g. fibroblasts), limiting the need for chronic immune suppressants.
    • Trial in one young patient with PD.

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ref: -0 tags: stem cell therapy parkinsons disease DBS date: 02-21-2012 19:04 gmt revision:1 [0] [head]

PMID-15272269 Stem cell therapy for human neurodegenerative disorders-how to make it work.

  • Before clinical trials are initiated, we need to know how to control stem cell proliferation and differentiation into specific phenotypes, induce integration into existing circuits and optimize functional recovery in animal models. (from abstract)
  • It may seem untralistic, though, to induce functional recovery by replacing cells lost through disease, considering the complexity of human brain structure and function.
    • Animal models have shown at least that it is possible.
  • Intrastriatal transplantation of human fetal mesencephatic tissue have provided a proof of principle that neuronal replacement can work in humans; neurons survive, even as the patients own SN neurons die, for up to 10 years [1,2]. Seems they can become functionally integrated into the brain, and releive symptoms of akinesia [3].
  • Sham-controlled surgieries showed modest benefit, showing that the transplantation techniques are suboptimal.
  • Dyskinesias are a common side-effect in 7-15% of patients, likely due to patchy reinervation or inflammatory response to the grafted cells.
  • Unlikely that this will be a common treatment, due to unavailabiltiy of the fetal tissue.
    • Better bet: culture the cells in vitro.
  • Requirements for graft:
    • Cells should release a regulated amount of DA
    • Cells must reverse PD in animal models
    • at least 1e5 cells must survive in humans
    • grafted cells should establish a dense terminal network throughout the striatum
    • and cells should become functionally integrated into the BG.
      • Debilitating symptoms in PD and related disorders are caused by pathological canges in non-dopaminergic systems (neuroplasticity hypothesis).
      • For more complete reversal of Parkinson's symptoms, it may be necessary to stimulate regrowth of axons from grafts in the SNpc to the striatum, which would require modification of host migration markers / growth inhibitory mechanisms [33].
  • Only embryonic stem cells have been shown to work; stem cells from the adult brain don't.
    • Human ESC may have chromosomal instability.
  • Only 5-10% of cells in fetal mesencelphatic grafts are dopaminergic neurons. It is not yet known whether it is favorable to implant pure DA cells or if the grant should contain other cells, like glia, specifically atrocytes, which control cell fate [18,19].
  • Many different pathways to dopmaninergic ESC.
    • FACS = fluorescence-assisted cell sorting.
  • To date, improvements after fetal grafts have not exceeded those found with deep brain stimulation [4,6,7], and there is no convincing evidence for the reversal of drug-resistant symptoms [4]
    • Even in animals with good reinnervation improvements are only partial [27].
  • Some evidence for the generation of striatal neurons in mice after a stroke -- figure 3.
  • Implantation of mouse ESCs into rat striatum caused teratomas in 20% of the animals [36].
    • ESCs are more likely to generate tumors when implanted in the same species that they were derived from.

Stroke:

  • No notable regeneration int eh cerebral cortex.
  • Targeted apoptosis of neurons in mice, leaving tissue intact, leads to reformation of cortical neurons which extend axons into the thalamus. Therefore restricted self-repair is probably due to lack of cues to trigger neurogenesis from SC.

ALS:

  • Several promising lines of research, but much more basic science needs to be done regarding differentiation and delivery before treatment can be attempted.
  • Protecting existing neurons from degeneration seems like a better strategy.

Synthesis:

  • Much more work is required, especially the basic science of differentiation / cell survival, but it's undoubtedly worth it.

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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: Thomas-1972.09 tags: MEA electrodes cell culture platinum black date: 01-04-2012 02:40 gmt revision:6 [5] [4] [3] [2] [1] [0] [head]

PMID-4672477[0] A miniature microelectrode array to monitor the bioelectric activity of cultured cells

  • Designed for heart cells.
  • 30-element muilt into the cluture chambers.
  • Utilizes PCB lithography technology. Indeed, the insulation is photoresist / 'photopolymer'.
  • platinum black

____References____

[0] Thomas CA Jr, Springer PA, Loeb GE, Berwald-Netter Y, Okun LM, A miniature microelectrode array to monitor the bioelectric activity of cultured cells.Exp Cell Res 74:1, 61-6 (1972 Sep)

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ref: Tian-2010.08 tags: nanowire nanoprobe silicon FET doping cis trans extracellular intracellular recording neuro MEA date: 01-03-2012 16:35 gmt revision:4 [3] [2] [1] [0] [head]

PMID-20705858[0] Three-Dimensional, Flexible Nanoscale Field-Effect Transistors as Localized Bioprobes

  • Made a silicon nanowire with 60 deg. kinks via trans/cis manipulation.
  • Doped one part of the N nanowire P to make a 200nm long FET whose gate is simply the surface of the nanowire (I think, have to check the refs)
  • Attached the nanoprobe / nanowire to flexible PMMA / SM-8 support which, due to interfacial stress, rose off the substrate (clever!)
  • Coated tip with phospholipid layers -> better cell attachment / penetration.
    • Possible to have the cell pull the nanoprobe in via endocytic pathways.
  • Were able to record intracellular and extracellular AP from rabbit cardiocytes. (!!!)

____References____

[0] Tian B, Cohen-Karni T, Qing Q, Duan X, Xie P, Lieber CM, Three-dimensional, flexible nanoscale field-effect transistors as localized bioprobes.Science 329:5993, 830-4 (2010 Aug 13)

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ref: notes-0 tags: programming excellence norvig 10 years date: 04-07-2009 20:26 gmt revision:0 [head]

Teach yourself programming in 10 years

  • points out that, in order to be excellent at any difficult skill/art, you must practice 10 years or 10,000 hours, and this practice must be focused and deliberate.
    • quote: "have shown it takes about ten years to develop expertise in any of a wide variety of areas, including chess playing, music composition, telegraph operation, painting, piano playing, swimming, tennis, and research in neuropsychology and topology"
    • possibly this is partially due to competition - most other people drop out after 10 years!
    • Or this is due to the fact that, for general purpose behaviors, we are really no better than the present gradient descent & reinforcement learning algorithms which require repeated presentation of patterns and behaviors. Where humans achieve sub-gradient/RL performance is where evolution has supplied us with hardware or 'prior assumptions' to bias for a correct solution / correct solution space. These prior assumptions are (part of) that which the make study brain interesting!
  • "Life is short, [the] craft long, opportunity fleeting, experiment treacherous, judgment difficult." -- Hippocrates.

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ref: Foster-2006.03 tags: hippocampus memory place cells reverse replay Wilson date: 03-06-2009 17:53 gmt revision:1 [0] [head]

PMID-16474382[0] Reverse replay of behavioral sequences in hippocampal place cells during the awake state.

  • wow: they show compressed reverse replay of firing sequences of hippocampal place cells during movement. While the rat is awake, too!
  • recorded up to 128 cells from the rat hippocampus; 4 animals.
  • the replay occurred while the rat was stopped, and lasted a few hundred milliseconds (~300).
  • phenomena appears to be very common, at least for the rats on the novel tracks.
  • replay events were coincident with ripples in the hippocampal EEG, which also occurs during sleep.
    • however, during slow-wave sleep, the replay was forward.
  • they offer a reasonable hypothesis for the reverse replay's function: it is used to propagate value information from the rewarded lcoation backwards along incoming (behavioral) trajectories.
    • quote "awake replay represents efficient use of hard-won experience."

____References____

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ref: Soetedjo-2006.07 tags: cerebellum purkinje cells complex spike saccade date: 12-09-2008 18:46 gmt revision:2 [1] [0] [head]

PMID-16855102[0] Complex spike activity of purkinje cells in the oculomotor vermis during behavioral adaptation of monkey saccades.

  • central conclusion: that change in complex spike rate correlates with the sign of scaccade error, but not the magnitude.
  • analysis is far more complicated than what this conclusion seems to require, though ... or maybe it is just too late for me.

____References____

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ref: bookmark-0 tags: open source cellphone public network date: 11-13-2007 21:28 gmt revision:2 [1] [0] [head]

http://dotpublic.istumbler.net/

  • kinda high-level, rather amorphous, but generally in the right direction. The drive is there, the time is coming, but we are not quite there yet..
  • have some designs for wireless repeaters, based on 802.11g mini-pci cards in a SBC, 3 repeaters. total cost about $1000
  • also interesting: http://www.opencellphone.org/index.php?title=Main_Page

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ref: bookmark-0 tags: phase converter gilbert cell analog multiplication RF bipolar transistors phase detector modulator date: 07-23-2007 20:48 gmt revision:0 [head]

http://www.electronics.dit.ie/staff/ypanarin/Lecture%20Notes/DT021-4/7AnalogMultipliers.pdf

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ref: notes-0 tags: VOR OKR climbing_fibers cerebellum purkinje cells date: 02-05-2007 23:45 gmt revision:1 [0] [head]

  • Motor Coding in Floccular Climbing fibers
  • On climbing fiber signals and their consequences 1996, review
  • The site of a motor memory shifts with consolidation
  • Learning in a simple motor system (February 2006)
    • in the abstract: "we propose that short-term motor memory is initially stored in the cerebellar cortex, and during consolodation the motor memory locus shifts to include a brainstem site"
      • ISO learning as a method of consolodation, reflex-adatpation and internalization? that would be cool.
    • a good diagram of the system for the lateral rectus
    • due to its pivotal nature, motor learning may have been one of the first forms of learning to be implemented by biology. "universal in freely-moving animals"
    • these authors define it as procedural - does not require conscious attention (but it can be influenced by it)
    • eye movements procedurally simpler than arm movements, which I've spent some time looking at.
      • lately, I've been having to do a lot of this, after my glasses lost one earpeice and have been moving about since :) slight changes in the angles of the lenses are very noticeable.
    • I thought that the theory for this system would be complete by now, and ready for the application to more complicated motor movements, but this is not so. The thoeries are still a bit controversial, and require a molecular understanding.
---- Description of the system: see figure. need to label this on the slides. (comment: I'm sure many of you know this better than i, but for review ...) need diagram of the direction that the eyes turn, including the lateral/medial rectus muscles. Note that the eyes are stabilized in the two other directions - pitch and roll. here we study yaw, but people have demonstrated the same effects in the other directions. { cat and human have gain < 1, monkey just about 1 (perfect) - humans require extra input, via OKR} - basic circuit known since 1967 (Eccles). - Maekawa and Simpson: the cerebelar purkinje cell recieves climbing fiber input from the inferior olivary nucleus that encodes visual information. - information about ongoing movements arrives at the lateral vestibulocerebellum via mossy fivers from the dorsolateral pontine nuclei. - some mossy fibers also carry visual information. - purkinje cells project directly back to the vestibular nuclei.