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ref: -2019 tags: Kleinfeld Harris record every neuron date: 09-13-2019 01:51 gmt revision:0 [head]

PMID-31495645 Can One Concurrently Record Electrical Spikes from Every Neuron in a Mammalian Brain?

  • Argues for a concrete arrangement of 6um diamond (1.2TPa modulus) shanks, 2mm long, on 40um hexagonal grid. Each would be patterned with 5 layers of metal, 30nm x 30nm Au traces (what about surface roughness?), high dielectric insulation, 9um x 14um TiN contacts.
  • This will be mated to state of the art adaptive amplifiers, which would be biased to only burn necessary power needed to sort spikes.
  • The sharpened spikes should penetrate the brain; 4um diameter diamond shanks should also work...
  • Overall volume displacement ~ 2% (which still seems high).
  • Suggest that the shanks can push capillaries out of the way, or puncture them while making a seal. Clearly, that's possible ...
  • ... but realistically, unless these are inserted glacially slowly, it will cause possibly catastrophic / cascading inflammation. (Which can spread on the order of 100-150um).
  • Does not cite Marblestone 2013.

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ref: -0 tags: Kleinfeld vasculature cortex review ischemia perfusion date: 01-22-2017 19:40 gmt revision:3 [2] [1] [0] [head]

PMID-25705966 Robust and fragile aspects of cortical blood flow in relation to the underlying angioarchitecture.

  • "The penetrating arterioles that connect the pial network to the subsurface network are bottlenecks to flow; occlusion of even a single penetrating arteriole results in the death of a 500 μm diameter cylinder of cortical tissue despite the potential for collateral flow through microvessels."
  • The pioneering work of Fox and Raichle [7] suggest that there is simply not enough blood to go around if all areas of the cortex were activated at once.
  • There is strong if only partially understood coupling between neuronal and vascular dysfunction [15]. In particular, vascular disease leads to neurological decline and diminished cognition and memory [16].
  • A single microliter of cortex holds nearly one meter of total vasculature length wow! PMID-23749145
  • Subsurface micro vasculature (not arterioles or venules) is relatively robust to occlusion; figure 4.

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ref: -0 tags: David Kleinfeld penetrating arterioles perfusion cortex vasculature date: 10-17-2016 23:24 gmt revision:1 [0] [head]

PMID-17190804 Penetrating arterioles are a bottleneck in the perfusion of neocortex.

  • Focal photothrombosis was used to occlude single penetrating arterioles in rat parietal cortex, and the resultant changes in flow of red blood cells were measured with two-photon laser-scanning microscopy in individual subsurface microvessels that surround the occlusion.
  • We observed that the average flow of red blood cells nearly stalls adjacent to the occlusion and remains within 30% of its baseline value in vessels as far as 10 branch points downstream from the occlusion.
  • Preservation of average flow emerges 350 mum away; this length scale is consistent with the spatial distribution of penetrating arterioles
  • Rose bengal photosensitizer.
  • 2p laser scanning microscopy.
  • Downstream and connected arterioles show a dramatic reduction in blood flow, even 1-4 branches in; there is little reduncancy (figure 2)
  • Measured a good number of vessels (and look at their density!); results are satisfactorily quantitative.
  • Vessel leakiness extends up to 1.1mm away (!) (figure 5).

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ref: -0 tags: David Kleinfeld cortical vasculature laser surgery network occlusion flow date: 09-23-2016 06:35 gmt revision:1 [0] [head]

Heller Lecture - Prof. David Kleinfeld

  • Also mentions the use of LIBS + q-switched laser for precisely drilling holes in the scull. Seems to work!
    • Use 20ns delay .. seems like there is still spectral broadening.
    • "Turn neuroscience into an industrial process, not an art form" After doing many surgeries, agreed!
  • Vasodiliation & vasoconstriction is very highly regulated; there is not enough blood to go around.
    • Vessels distant from a energetic / stimulated site will (net) constrict.
  • Vascular network is most entirely closed-loop, and not tree-like at all -- you can occlude one artery, or one capillary, and the network will route around the occlusion.
    • The density of the angio-architecture in the brain is unique in this.
  • Tested micro-occlusions by injecting rose bengal, which releases free radicals on light exposure (532nm, 0.5mw), causing coagulation.
  • "Blood flow on the surface arteriole network is insensitive to single occlusions"
  • Penetrating arterioles and venules are largely stubs -- single unbranching vessels, which again renders some immunity to blockage.
  • However! Occlusion of a penetrating arteriole retards flow within a 400 - 600um cylinder (larger than a cortical column!)
  • Occulsion of many penetrating vessels, unsurprisingly, leads to large swaths of dead cortex, "UBOS" in MRI parlance (unidentified bright objects).
  • Death and depolarizing depression can be effectively prevented by excitotoxicity inhibitors -- MK801 in the slides (NMDA blocker, systemically)