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[0] Gandolfo F, Mussa-Ivaldi FA, Bizzi E, Motor learning by field approximation.Proc Natl Acad Sci U S A 93:9, 3843-6 (1996 Apr 30)[1] Mussa-Ivaldi FA, Giszter SF, Vector field approximation: a computational paradigm for motor control and learning.Biol Cybern 67:6, 491-500 (1992)

[0] Li CS, Padoa-Schioppa C, Bizzi E, Neuronal correlates of motor performance and motor learning in the primary motor cortex of monkeys adapting to an external force field.Neuron 30:2, 593-607 (2001 May)[1] Caminiti R, Johnson PB, Urbano A, Making arm movements within different parts of space: dynamic aspects in the primate motor cortex.J Neurosci 10:7, 2039-58 (1990 Jul)

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ref: -0 tags: swept field confocal date: 09-12-2019 20:01 gmt revision:1 [0] [head]

PMID-22831554 Swept field laser confocal microscopy for enhanced spatial and temporal resolution in live-cell imaging.

  • Invented by Marvin Minsky back in 1955 memoir!
  • Idea is not unlike light-sheet imaging -- sweep a confocal slit and laser line across a sample, rather than a pinhole and point, respectively.
  • This results in lower phototoxicity, but still reasonable rejection of out-of-focus light compared to widefield imaging.

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ref: -0 tags: sparse coding reference list olshausen field date: 03-11-2019 21:59 gmt revision:3 [2] [1] [0] [head]

This was compiled from searching papers which referenced Olhausen and Field 1996 PMID-8637596 Emergence of simple-cell receptive field properties by learning a sparse code for natural images.

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ref: -2017 tags: calcium imaging seeded iterative demixing light field microscopy mouse cortex hippocampus date: 02-13-2019 22:44 gmt revision:1 [0] [head]

PMID-28650477 Video rate volumetric Ca2+ imaging across cortex using seeded iterative demixing (SID) microscopy

  • Tobias Nöbauer, Oliver Skocek, Alejandro J Pernía-Andrade, Lukas Weilguny, Francisca Martínez Traub, Maxim I Molodtsov & Alipasha Vaziri
  • Cell-scale imaging at video rates of hundreds of GCaMP6 labeled neurons with light-field imaging followed by computationally-efficient deconvolution and iterative demixing based on non-negative factorization in space and time.
  • Utilized a hybrid light-field and 2p microscope, but didn't use the latter to inform the SID algorithm.
  • Algorithm:
    • Remove motion artifacts
    • Time iteration:
      • Compute the standard deviation versus time (subtract mean over time, measure standard deviance)
      • Deconvolve standard deviation image using Richardson-Lucy algo, with non-negativity, sparsity constraints, and a simulated PSF.
      • Yields hotspots of activity, putative neurons.
      • These neuron lcoations are convolved with the PSF, thereby estimating its ballistic image on the LFM.
      • This is converted to a binary mask of pixels which contribute information to the activity of a given neuron, a 'footprint'
        • Form a matrix of these footprints, p * n, S 0S_0 (p pixels, n neurons)
      • Also get the corresponding image data YY , p * t, (t time)
      • Solve: minimize over T ||YST|| 2|| Y - ST||_2 subject to T0T \geq 0
        • That is, find a non-negative matrix of temporal components TT which predicts data YY from masks SS .
    • Space iteration:
      • Start with the masks again, SS , find all sets O kO^k of spatially overlapping components s is_i (e.g. where footprints overlap)
      • Extract the corresponding data columns t it_i of T (from temporal step above) from O kO^k to yield T kT^k . Each column corresponds to temporal data corresponding to the spatial overlap sets. (additively?)
      • Also get the data matrix Y kY^k that is image data in the overlapping regions in the same way.
      • Minimize over S kS^k ||Y kS kT k|| 2|| Y^k - S^k T^k||_2
      • Subject to S k>=0S^k >= 0
        • That is, solve over the footprints S kS^k to best predict the data from the corresponding temporal components T kT^k .
        • They also impose spatial constraints on this non-negative least squares problem (not explained).
    • This process repeats.
    • allegedly 1000x better than existing deconvolution / blind source segmentation algorithms, such as those used in CaImAn

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ref: -0 tags: ACF chip bonding parylene field's metal polyimide date: 07-10-2013 18:34 gmt revision:10 [9] [8] [7] [6] [5] [4] [head]

We're making parylene electrodes for neural recording, and one critical step is connecting them to recording electronics.

Currently Berkeley uses ACF (anisotropic conductive film) for connection, which is widely used for connecting flex tape to LCD panels, or for connecting driver chips to LCD glass. According to the internet, pitches can be as low as 20um, with pad areas as low as 800um^2. source

However, this does not seem to be a very reliable nor compact process with platinum films on parylene, possibly because ACF bonding relies on raised areas between mated conductors (current design has the Pt recessed into the parylene), and on rigid substrates. ACF consists of springy polymer balls coated in Ni and Au and embedded in a thermoset epoxy resin. The ACF film is put under moderate temperature (180C) and pressure (3mpa, 430psi), which causes the epoxy to cure in a state that leaves the gold/nickel/polymer balls to be compressed between the two conductors. Hence, even if the conductors move slightly due to thermal cycling, the small balls maintain good mechanical and electrical contact. The balls are dispersed sufficiently in the epoxy matrix that there is little to no chance of conduction between adjacent pads.

(Or so I have learned from the internet.) Now, as mentioned, this is an imperfect method for joining Pt on parylene films, possibly because the parylene is so flexible, and the platinum foil is very thin (200-300 nm). Indeed, platinum does not bond very strongly to parylene, hence care must be taken to allow sufficient overlap to prevent water ingress. My proposed solution -- to be tested shortly -- is to use a low-melting temperature metal with strong wetting ability -- such as Field's metal (bismuth, tin, indium, melting point 149F, see http://www.gizmology.net/fusiblemetals.htm) to low-temperature solder the platinum to a carrier board (initially) or to a custom amplifier ASIC (later!). Parylene is stable to 200C (392F), so this should be safe. One worry is that the indium/bismuth will wet the parylene or polyimide, too; however I consider this unlikely due to the difficulty in attaching parylene to any metal.

That said, there must be good reason why ACF is so popular, so perhaps a better ultimate solution is to stiffen the parylene (or ultimately polyimide) substrate so that it can support both the temperature/pressure of ACF bonding and the stress of a continued electrical/mechanical bond to polyimide fan-out board or ASIC. It may also be possible to gold or nickel electroplate the connector pads to be slightly raised instead of recessed.


Update: ACF bond to rigid 1/2 oz copper, 4mil trace / space connector (3mil trace/space board):

Note that the copper traces are raised, and the parylene is stretched over the uneven surface (this is much easier to see with the stereo microscope). To the left of the image, the ACF paste has been sqeezed out from between the FR4 and parylene. Also note that the platinum can make potential contact with vias in the PCB.


Update 7/2: Fields metal (mentioned above) does stick to platinum reasonably well, but it also sticks to parylene (somewhat), and glass (exceptionally well!). In fact, I had a difficult time removing traces of field's metal from the Pyrex beakers that I was melting the metal with. These beakers were filled with boiling water, which may have been the problem.

When I added flux (Kester flux-pen 951 No-clean MSDS), the metal became noticeably more shiny, and the contact angle increased on the borosilicate glass (e.g. looked more like mercury); this leads me to believe that it is not the metal itself that attaches to glass, but rather oxides of indium and bismuth. Kester 951 flux consists of:

  • 2-propanol 15% (as a denaturing agent) boiling point 82.6C
  • Ethanol 73% (solvent) boiling point 78.3C
  • Butyl Acetate 7% boiling point 127C, flash point 27C
  • Methanol <3% b.p. 64.7C
  • Carboxylic acids < 3% -- proton donors? formic or oxalic acid?
  • Surfacants < 1% -- ?
Total boiling point is 173F.

After coating the parylene/platinum sample with flux, I raised the field's metal to the flux activation point, which released some smoke and left brown organic residues on the bottom of the glass dish. Then I dipped the parylene probe into the molten metal, causing the flux again to be activated, and partially wetting the platinum contacts. The figure below shows the result:

Note the incomplete wetting, all the white solids left from the process, and how the field's metal caused the platinum to delaminate from the parylene when the cable was (accidentally) flexed. Tests with platinum foil revealed that the metal bond was not actually that strong, significantly weaker than that made with a flux-core SnPb solder. also, I'm not sure of the activation temperature of this flux, and think I may have overheated the parylene.


Update 7/10:

Am considering electrodeless Ni / Pt / Au deposition, which occurs in aqueous solution, hence at much lower temperatures than e-beam evaporation Electrodeless Ni ref. On polyimide substrates, there is extensive literature describing how to activate the surface for plating: Polyimides and Other High Temperature Polymers: Synthesis ..., Volume 4. Parylene would likely need a different possibly more aggressive treatment, as it does not have imide bonds to open.

Furthermore, if the parylene / polyimide surface is *not* activated, the electrodeless plating could be specific to the exposed electrode and contact sites, which could help to solve the connector issue by strengthening & thickening the contact areas. The second fairly obvious solution is to planarize the contact site on the PCB, too, as seen above. ACF bonds can be quite reliable; last night I took apart (and successfully re-assembled) my 32" Samsung LCD monitor, and none of the flex-on-glass or chip-on-flex binds failed (despite my clumsy hands!).

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ref: -0 tags: springfield downtown library health society date: 05-27-2012 00:44 gmt revision:0 [head]

Just to my left, a woman in a walker rolled into the library, and promptly complained to the police officer on duty about chest pains. The library faces a square in the middle of Springfield where teenagers, shirtless hippies, skateboarders, and other non-mainstream people kill time in the warm afternoon. The library as such is a cool haven to read and access the internet -- several teenagers were playing WoW on the library computers, and I too am tapping into the resource. A possibly adrift artsy-type man of about my age similarly came to conduct his wayward business, having 'just ended up in Springfield', saying it as both and excuse and a badge of pride evincing his free spirit.

The woman is one of the classic types of hypochondriac, and though I'm only listening to them the EMT and police men know this, but they also know that on the off chance of being wrong, not taking the situation seriously could be a disaster. And so they administered simple blood pressure and pulse rate tests, both which seemed normal, then went about convincing her that she needed to be taken to the hospital to be completely checked out, thereby shifting the burden of liability to a place better protected by the standard operating procedure of a battery of tests.

The woman immediately protested, worried about the heavy cost of a ambulance ride, coupled with a paranoia that she would lose her walker. To this the EMT -- a short woman with her practical ponytail shoved through a baseball cap, as often they do -- let glints of irritation show through, asking her repeatedly to decide which hospital she wished to go to, and then asking her to arrange another means to the hospital. The woman protested, but the EMT could scarecly be blamed -- she is stuck in a system not of her design -- and somehow the smooth-souled librarian, who before had been placating library customers by putting holds on books, convinced both parties to go to the nearest hopsital. How exactly this was done I'll forever remain in ignorance, for another ambulance spun through the downtown circle at that instant, scattering sports cars, stopping sedans, and causing the skaters to pause their idling and look.

The incident vaguely reminds me when I had similar issues in Brooklyn, when i was sufficiently pained to drive my ass through the dirty orange-lit streets to a hospital in Williamsburg. They proceeded to do drug tests on me, despite my insistences, but everything checked out fine. In retrospect, the pain was likely heartburn antagonized by psychological isolation; this was before I really learned to listen to myself, and take care of the social and more basic physiological needs. The walker woman fell through these same cracks in a likely preventable but now very expensive way.

Meanwhile, a large black transsexual and a wrinkly white guy walk hurriedly past the plate glass windows of the library, talking animatedly. They may be in a fissure of sorts, but i doubt they consider it a fall...

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ref: Penfield-1937 tags: Penfield 1937 motor cortex stimulation ICMS human neurosurgery electrodes date: 01-03-2012 22:08 gmt revision:3 [2] [1] [0] [head]

No PMID / bibtex penfield-1937. Somatic motor and sensory representation in the cerebral cortex of man as studied by electrical stimulation

  • Fritsch and Hitzig (1870) [0] cited as the first paper in electrical excitation of the CNS.
  • Good review of the scientific experiments thereafter, including stimulation to S1 by Ferrier, work with apes etc.
  • Central sulcus called the 'Rolandic fissure'.
  • Interesting! quote:

The account of Bartholow (1874) is interesting to say the least and may be cited. His patient was a 30-year old-domestic. As an infant this unfortunate had chanced to fall into the fire, burning her scalp so badly that " hair was never reproduced." A piece of whale bone in the wig she was forced to wear irritated the scarred scalp and, by her statement, three months before she was admitted, an ulcer appeared. When she presented herself for relief, this had eroded the skull over a space 2 in. in diameter " where the pulsations of the brain are plainly seen." Although " rather feeble-minded " Bartholow observed that Mary returned replies to all questions and no sensory or motor loss could be made out in spite of the fact that brain substance apparently had been injured in the process of evacuation of pus from the infected area. The doctor believed, therefore, that fine insulated needles could be introduced without further damage.

While the electrodes were in the right side Bartholow decided to try the effect of more current. ' Her countenance exhibited great distress and she began to cry. Very soon the left hand was extended as if in the act of taking hold of some object in front of her; the arm presently was agitated with clonic spasms ; her eyes became fixed with pupils widely dilated ; the lips were blue and she frothed at the mouth ; her breathing became stertorous, she lost conscious-ness and was violently convulsed on the left side. This convulsion lasted for five minutes and was succeeded by coma. She returned to consciousness in twenty minutes from the beginning of the attack and complained of some weakness and vertigo." Three days after this stimulation, following a series of right-sided seizures, the patient died.

  • Relatively modern neurosurgical procedures.
  • They observe changes to blood circulation prior epileptic procedures. wow!
  • Very careful hand-drawn maps of what they have observed. Important, as you'll probably never get this trough an IRB. It pays to be meticulous.

____References____

[0] Fritsch G, Hitzig E, Electric excitability of the cerebrum (Uber die elektrische Erregbarkeit des Grosshirns).Epilepsy Behav 15:2, 123-30 (2009 Jun)

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ref: PENFIELD-1963.12 tags: Penfield memory stimulation music epilepsy awesome date: 12-29-2011 22:21 gmt revision:4 [3] [2] [1] [0] [head]

PMID-14090522[0] The Brains record of auditory and visual experience -- A final summary and discussion

  • 102 pages. basically, this is a book.
  • Electrical stimulation causes 'hallucinations of things previously seen or heard or experienced.'
    • 'Both the experience and the interpretation are produced by discharge in the temporal cortex and not in other areas'
    • Experiential responses only followed stimulation in the temporal lobe.
  • These tests were done in an effort to locate the source of a seizure.
  • Damn, references the Caliph at Cordova as the first to document epileptic hallucinations (1519!)
    • And Hughlings Jackson (1888)!
  • Extirpation of memories elicited by ustim to an area persist after removal of that area.
  • Performed 1,288 surgeries, 520 of them for seizures in the temporal lobes, 40 of these with experiential responses, and 24 of those with experiential epileptic hallucinations.
    • Many of the patients' epilepsy was caused by ischemia, perhaps developmental; others by glioma..
  • Stimulation of the white matter has never produced an experiential response. Deep stimulation in the amygdala or hippocampus (??) also failed to elicit experiential responses.
  • Talks about 'difficult birth' -- was/is this the cause of some epilepsy? Or has that been discounted?
  • Buncha stuff on human cortical anatomy / topology, which is not so interesting to me.
  • Walker on the chimpanzee (1938) showed that the temporal cortex has no direct connections to the thalamus except posteriorly, where projections are received from nucleus lateralis posterior and pulvinar (visual attention), and within the transverse temporal gyri which receive auditory afferent projections from the medial geniculate body.
    • Also receives large fiber projections from the hippocampus.
  • This is absolutely fascinating. Memories, art, songs (music, so much music -- temporal lobe!), childbirth, counting, childhood molestation, a whole host of experiences were brought forth by electrical stimulation.
    • Case 9. E. Le. This 44-year old woman began to have seizures at age 22 during a pregnancy. The attack pattern was: (1) flushing of face and neck (2) automatism; (3) occasional generalized seizure. During and automatism she was apt to say, "I am alright". Then she would walk about the room and show marked affection toward anyone who happened to be present.
    • Repeated without warning: She said, "Yes, another experience, a different experience." Then she added, "A true experience. This man, Mr. Meerburger, he, oh well, he drinks. Twice his boy has run away. I went to the store once for an ice cream cone and I saw that he was back, and I said 'Hmm, he is back,' and the lady asked me 'What is the matter,' and I didn't know how to explain so I said, 'Well you know Mr. Meerburger drinks.' I thought that was the easiest way but later mother told me, no, and it made it a lot worse."
    • What surprises me is the relative lack of breadth in these --many of the responses to stimulation are quite similar, over a wide range of cortex, many of them very dream-like in features and recall.
      • Their impression: It is often evident that ''each stimulation leaves behind a facilitating influence so that the same response follows each stimulation and this facilitation may cause a given response to follow stimulation at one to three centimeters distance. Illustrated by the case 5, D.F
      • This deserves far more experimentation! E.g. ask the patient to think about something, and see if the same stimulation elicits different memories.
    • Another patient had a series of experiential hallucinations which all involved some aspect of 'grabbing' -- a man grabbing a rifle from a cadet during a parade, a man snatching his hat from the hat-check girl, grabbing a stick from a dog's mouth. In this epileptic, an instance of 'grabbing' was the ictal focus. Amazing.
  • Points out that stimulation must activate a great number of neural circuits, only one specific memory is recalled -- indicating that there is strong inhibition for mutual-exclusion.
  • Non-dominant, non-speech temporal cortex is almost always involved in interpretation: stimulation produces visual experiences, or visual interpretive illusions (change in distance or speed).
    • Stimluation also produces changes in the state-of-mind.
  • Certain sorts of experiences seem absent:
    • The times of making up ones mind
    • Times of carrying out skilled acts, writing messages or adding figures,
    • Eating food
    • Sexual excitement and experience (unless the patients may have self-censored this?)
    • Intense pain or suffering.
    • These things do not involve interpretation, and the focus of attention is not on the way that things are heard or seen.
  • They would remove quite large sections of the temporal lobe!
    • Still, the excision of these areas does not abolish memory: it does not contain a record of the past.
    • Yet stimulation in the temporal lobe recalls memories as nowhere else does.
  • There is a sharp frontier / boundary between auditory and visual temporal cortices and interpretive -- millimeters movement may change phosphenes into recall of a familiar person.
  • Note the comparison between speech cortex (dominant) and interpretive -- stimulation of speech cortex produces no speech, only aphasia, whereas stimulation of non-dominant termporal cortex forces recall.
  • "He who is faithfully analysing many cases of epilepsy is doing far more than studying epilepsy"

____References____

[0] PENFIELD W, PEROT P, THE BRAIN'S RECORD OF AUDITORY AND VISUAL EXPERIENCE. A FINAL SUMMARY AND DISCUSSION.Brain 86no Issue 595-696 (1963 Dec)

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ref: Gandolfo-1996.04 tags: learning approximation kernel field Bizzi Gandolfo date: 12-07-2011 03:40 gmt revision:1 [0] [head]

Motor learning by field approximation.

  • PMID-8632977[0]
    • studied the generalization properties of force compensation in humans.
    • learning to compensate only occurs in regions of space where the subject actually experianced the force.
    • they posit that the CNS builds an internal model of the external world in order to predict and compensate for it. what a friggn surprise! eh well.
  • PMID-1472573[1] Vector field approximation: a computational paradigm for motor control and learning
    • Recent experiments in the spinalized frog (Bizzi et al. 1991) have shown that focal microstimulation of a site in the premotor layers in the lumbar grey matter of the spinal cord results in a field of forces acting on the frog's ankle and converging to a single equilibrium position
    • they propose that the process of generating movements is the process of combining basis functions/fields. these feilds may be optimized based on making it easy to achieve goals/move in reasonable ways.
  • alternatly, these basis functions could make movements invariant under a number of output transformations. yes...

____References____

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ref: Gandolfo-2000.02 tags: Gandolfo Bizzi dynamic environment force fields learning motor control MIT M1 date: 12-02-2011 00:10 gmt revision:1 [0] [head]

PMID-10681435 Cortical correlates of learning in monkey adapting to a new dynamical environment.

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ref: Brown-2007.09 tags: motor force field learning vision date: 02-20-2009 00:28 gmt revision:1 [0] [head]

PMID-17855611 Motor Force Field Learning Influences Visual Processing of Target Motion

  • as you can see from the title - this is an interesting result.
  • learning to compensate for forces applied to the hand influenced how participants predicted target motion for interception.
  • subjects were trained on a robotic manipulandum that applied different force fields; they had to use the manipulandum to hit a accelerating target.
  • There were 3 force feilds: rightward, leftward, and null. Target accelerated left to right. Subjects with the rightward force field hit more targets than the null, and these more targets than the leftward force field. Hence motor knowledge of the environment (associated accelerations, as if there were wind or water current...) influenced how motion was perceived and acted upon.
    • perhaps there is a simple explanation for this (rather than their evolutionary information-sharing hypothesis): there exists a network that serves to convert visual-spatial coordinates into motor plans, and later muscle activations. The presence of a force field initially only affects the motor/muscle control parts of the ctx, but as training continues, the changes are propagated earlier into the system - to the visual system (or at least the visual-planning system). But this is a complicated system, and it's hard to predict how and where adaptation occurs.

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ref: Li-2001.05 tags: Bizzi motor learning force field MIT M1 plasticity memory direction tuning transform date: 09-24-2008 22:49 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-11395017[0] Neuronal correlates of motor performance and motor learning in the primary motor cortex of monkeys adapting to an external force field

  • this is concerned with memory cells, cells that 'remember' or remain permanently changed after learning the force-field.
  • In the above figure, the blue lines (or rather vertices of the blue lines) indicate the firing rate during the movement period (and 200ms before); angular position indicates the target of the movement. The force-field in this case was a curl field where force was proportional to velocity.
  • Preferred direction of the motor cortical units changed when the preferred driection of the EMGs changed
  • evidence of encoding of an internal model in the changes in tuning properties of the cells.
    • this can suppor both online performance and motor learning.
    • but what mechanisms allow the motor cortex to change in this way???
  • also see [1]

____References____