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ref: -2021 tags: hippocampal behavior scale plasticity Magee Romani Bittner date: 12-20-2021 22:39 gmt revision:0 [head]

Bidirectional synaptic plasticity rapidly modifies hippocampal representations

  • Normal Hebbian plasticity depends on pre and post synaptic activity & their time course.
  • Three-factor plasticity depends on pre, post, and neuromodulatory activity, typically formalized as an eligibility trace (ET) and instructive signal (IS).
  • Here they show that dendritic-plateau dependent hippocampal place field generation, in particular LTD, is not (quite so) dependent on post synaptic activity.
  • Instead, it appears to be a 'register update' operation, where a new pattern is remembered (through LTP) and an old pattern is forgotten (through LTD).
    • That is, the synapses are updating information, not accumulating information.
  • The eq for a single synapse: ΔW/δt=(W maxW)k +q +(ET*IS)Wk q (ET*IS)\Delta W / \delta t = (W_{max} - W) k^+ q^+(ET * IS) - W k^- q^-(ET * IS)
    • Where k are the learning rates, and q are the nonlinear functions regulating potentiation / depression based on eligibility trace and instructive signal.

I'm still not 100% sure that this excludes any influence on presynaptic activity ... they didn't control for that. But certainly LTD in their model does not require postsynaptic activity; indeed, it may only require net-synaptic homeostasis.

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ref: -0 tags: superresolution imaging scanning lens nanoscale date: 02-04-2019 20:34 gmt revision:1 [0] [head]

PMID-27934860 Scanning superlens microscopy for non-invasive large field-of-view visible light nanoscale imaging

  • Recently, the diffraction barrier has been surpassed by simply introducing dielectrics with a micro-scale spherical configuration when using conventional optical microscopes by transforming evanescent waves into propagating waves. 18,19,20,21,22,23,24,25,26,27,28,29,30
  • The resolution of this superlens-based microscopy has been decreased to ∼50 nm (ref. 26) from an initial resolution of ∼200 nm (ref. 21).
  • This method can be further enhanced to ∼25 nm when coupled with a scanning laser confocal microscope 31.
  • It has achieved fast development in biological applications, as the sub-diffraction-limited resolution of high-index liquid-immersed microspheres has now been demonstrated23,32, enabling its application in the aqueous environment required to maintain biological activity.
  • Microlens is a 57 um diameter BaTiO3 microsphere, resolution of lambda / 6.3 under partial and inclined illumination
  • Microshpere is in contact with the surface during imaging, by gluing it to the cantilever tip of an AFM.
  • Get an image with the microsphere-lens, which improves imaging performance by ~ 200x. (with a loss in quality, naturally).

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ref: -0 tags: brain mapping Deisseroth Donoghue widescale recording date: 04-10-2013 19:31 gmt revision:1 [0] [head]

PMID-23514423 Nanotools for Neuroscience and Brain Activity Mapping

  • human brain has roughly 85e9 neurons, 1e14 synapses, 100 neurotransmitters.
  • focus on novel nanoprobes.
  • Assuming a uniform connaction probability, the lielihood of finding synaptically coupled cells increases quadratically with N.
  • pretty high-level article.
  • Multiferroic antennas (?) -- must look this up!
  • Look up ref 146 -- microendoscope. Did they design the camera module?

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ref: bookmark-0 tags: embedded linux eCos ARM intellectualProperty IP MIPS Xscale MIT date: 10-08-2007 17:55 gmt revision:0 [head]