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q-bio.NC · Neurons and Cognition

In awake mouse visual cortex (58 mice), spike transmission facilitated onto optotagged SST units and depressed onto PV and fast-spiking units after 6–60 ms intervals, as slice release models predict

Question: In brain slices, excitatory synapses onto SST interneurons facilitate, and those onto PV interneurons and pyramidal cells depress. We tested if this target-class rule controls spike transmission in the awake cortex. Approach: In Allen Visual Coding Neuropixels data (58 mice, six visual areas), we found monosynaptic couplings from regular-spiking (RS) units in spike cross-correlograms. We selected each coupling in one half of the session and measured it in the other half, as a function of the preceding presynaptic interval (ISI). The facilitation index (FI) is the transmission after a given ISI divided by the transmission after ISIs of 120 ms or more. We compared FI with Allen Synaptic Physiology release models of 400 slice synapses, driven by the same in vivo spike trains. We repeated the test in 59 Sst-Cre sessions of Visual Behavior Neuropixels (VBN). Results: RS-to-SST transmission (78 pairs) facilitated: FI 1.83 [1.17, 2.53] after 6-20 ms and 1.30 [1.06, 1.70] after 20-60 ms. At 20-60 ms, transmission onto PV-tagged (232 pairs), fast-spiking (FS, 4,895) and RS (618) targets depressed (FI 0.75, 0.92, 0.88). The slice models gave 1.29 for SST and 0.74 for PV at 20-60 ms (in vivo 1.30 and 0.75). Below 20 ms, in vivo transmission was higher than the models for all classes. Targets fired 1.1-1.5 times faster after short presynaptic ISIs, so we also used a rate-normalized estimator. SST facilitation (FI 1.61 at 6-20 ms) and PV and FS depression held under both estimators. In the same mice, the ratio of SST FI to FS FI was 1.76 at 6-20 ms (p = 0.013). Synthetic couplings showed that the estimates of facilitation are conservative. In VBN, the pooled test over all SST tags failed (FI 1.19 absolute, 0.87 rate-normalized at 6-20 ms). 73% of these couplings went to narrow-spike tagged units that depressed like FS cells, and five strong narrow units carried 21% of the pooled weight. This is consistent with known off-target labeling in Sst-IRES-Cre mice. In post hoc tests, broad-spike SST tags facilitated (FI 2.03 at 6-20 ms). In a planned test, the same presynaptic units facilitated onto SST units and depressed onto FS units (1.53 against 0.79). Limitations: optotags had no second marker; below 20 ms, synaptic and postsynaptic effects mix; slice and in vivo data come from different animals.

short-term plasticity · spike transmission · synaptic facilitation · somatostatin interneurons · parvalbumin interneurons · cross-correlogram · Neuropixels · optotagging · mouse visual cortex · Allen Synaptic Physiology · release model · structure-function · Visual Behavior Neuropixels · Sst-IRES-Cre off-target

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References

10
  1. usesNeuropixels spike couplings in visual cortex of 58 mice followed slice wiring in class order, latency and reciprocity, but couplings onto fast-spiking cells needed 2.9 times the slice-based gain sci:sha256:2d55cc85331e053f3cafcba0591169317b9c56fa0b15161b2495278987a90235

    We reuse its spike-time cache, unit and pair tables, optotag rule and coupling detection rule, and we extend its class-order test to short-term dynamics.

  2. usesAll 14,313 numeric pulse amplitude arrays in Allen Synaptic Physiology r2.1 were flat, and a shared list reproduced the loss of pulse order sci:sha256:989c63646cdf418f9663cb5767fc90245c7cf15182f746f5bef2e1e419d97342

    Its audit shows that the synphys r2.1 pulse-amplitude arrays are flat; we use only scalar fields and fitted release-model parameters.

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    Allen Visual Coding Neuropixels data set (spike times, optotagging).

  4. usesdoi:10.1126/science.abj5861

    Allen Synaptic Physiology data set: slice synapse release models, paired-pulse changes and membrane time constants.

  5. doi:10.1038/1092

    Target-cell-specific facilitation and depression in neocortical slices.

  6. doi:10.1073/pnas.95.9.5323

    Differential short-term dynamics of one pyramidal axon onto different targets.

  7. doi:10.1016/j.neuron.2007.02.012

    Facilitating pyramidal-to-Martinotti synapses and burst-dependent disynaptic inhibition.

  8. supportsdoi:10.1016/j.neuron.2014.11.025

    In vivo whole-cell pairs in barrel cortex found facilitating excitation onto SST cells; our population result agrees.

  9. doi:10.1016/j.neuron.2017.09.033

    In vivo spike-transmission dynamics from CCGs in hippocampus; methods precedent.

  10. doi:10.3389/fncir.2013.00195

    Off-target recombination in Sst-IRES-Cre mice labels fast-spiking interneurons; this may explain the narrow-spike tags in VBN.

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