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no ecb messages

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ocrampal
2026-06-21 10:16:34 +02:00
parent 1c20c24961
commit 0df834108a
2 changed files with 89 additions and 8 deletions
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elements/neuron/appunti/2026-06-19-biological-reference-v10.md
+57
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@@ -274,3 +274,60 @@ The distinction matters biologically: a private reserve guarantees a component s
(the bouton can refill its RRP from its own vesicles even when lactate is scarce), while a
contested supply couples a component's fate to its neighbours' demands (operational budget
fails first where many active synapses compete for the same lactate).
---
## PRE ↔ POST interaction: local computation, message-only coupling
The presynapse and postsynapse never read each other's internal state. They interact only
by writing to and reading from shared cleft channels. Each side computes entirely locally on
what it has: its own variables plus whatever signals have arrived in the cleft. This is the
message-passing realization of the locality principle.
**Forward channel — glutamate (PRE → POST and ASTRO).** The presynapse writes glutamate via
NT_flux. The postsynapse reads it (AMPA, NMDA) and the astrosynapse reads it (clearance,
mGluR5). The astrosynapse clears it. PRE never knows whether POST responded — it only emits.
**Gate channel — astro_Dserine (ASTRO → POST).** The astrosynapse writes D-serine; the
postsynapse reads it as the obligatory NMDA co-agonist. POST cannot open NMDA without this
arrived signal, but it does not read the astrocyte's state — only the delivered D-serine.
**Backward channel + — retro_NO (POST → PRE).** When the postsynapse's NMDA opens (Mg²⁺
ejected, D-serine present, glutamate bound), nNOS — physically tethered to the NMDA receptor
through PSD-95 — synthesises nitric oxide (and, on a slower timescale, BDNF is released).
These diffuse retrogradely to the presynapse. Biologically this is the classic retrograde
messenger of LTP: it tells the bouton that its release landed on a postsynapse that genuinely
responded. In the model, POST emits `retro_NO` proportional to its own NMDA-driven calcium —
computed purely from POST's local state — and PRE reads it as `retro_NO_local`.
`retro_NO_local` is exactly the grounding of the presynaptic endurance signal. The
presynapse's local success proxy is "I was releasing strongly" (`pre_fast_trace` high). On
its own that only says the bouton was working hard, not that the work mattered. `retro_NO`
adds the missing confirmation — that the postsynapse responded — without PRE ever reading
POST's calcium. So PRE deposits endurance need as `pre_fast_trace × (1 + retro_NO_local)`:
strong release that was confirmed effective makes the strongest claim that fuel, not
futility, was what interrupted a forming success. retro_NO is short-lived (NO degrades and
diffuses within seconds), so the channel decays fast — confirmation must be recent to count.
**Backward channel − — retro_eCB (POST → PRE).** When the postsynapse is strongly
depolarised, it synthesises endocannabinoids (2-AG, anandamide) that diffuse retrogradely and
bind presynaptic CB1 receptors, suppressing release. This is depolarisation-induced
suppression of excitation (DSE) — a homeostatic negative feedback: an over-driven postsynapse
tells the presynapse to release less. In the model, POST emits `retro_eCB` from its own
membrane potential, and PRE reads it as `retro_eCB_local`, which reduces the release drive
`sat(...) × (1 - retro_eCB_local)`. Again POST computes from its own state; PRE adjusts from
the arrived signal; neither reads the other's interior.
The two backward channels are opposite-signed messages the postsynapse sends about its own
condition: retro_NO says "your input was effective — worth sustaining," retro_eCB says "I am
saturated — ease off." Together with the forward glutamate and the D-serine gate, they make
the synapse a fully message-coupled system of locally-computing components.
**Why RRP refill is in NOT_AP only.** During an AP the bouton releases — RRP depletes. Refill
(VATPase reloading vesicles from the reserve pool) is a recovery process that proceeds between
spikes. Placing `fill(RRP, ...)` only in the NOT_AP context makes the AP context pure
depletion and the NOT_AP context pure recovery. A consequence falls out for free: during
sustained high-frequency firing there are many AP steps and few NOT_AP steps, so RRP depletes
faster than it recovers — short-term depression deepens with frequency, with no explicit
depression rule. The release itself is throttled further when budget is low (VATPase refill
is energy-limited), coupling metabolic state to the depth of depression.
elements/neuron/appunti/2026-06-19-tripartite-synapse_v10.md
+31 -7
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@@ -30,6 +30,13 @@ NIGHT variables
LOCALITY RULE
every evaluation uses only local state + signals that have arrived.
no component reads another compartment's internal state.
CLEFT MESSAGE CHANNELS (the only PRE/POST/ASTRO interaction — each writes, others read)
glutamate PRE → POST, ASTRO (forward transmitter; cleared by ASTRO)
astro_Dserine ASTRO → POST (NMDA co-agonist gate)
retro_NO POST → PRE (+) (NO/BDNF: "release reached a responsive target")
retro_eCB POST → PRE (−) (endocannabinoid: "over-driven, suppress release" = DSE)
Each channel decays/clears; a component reads a channel into a local copy and computes locally.
```
---
@@ -46,7 +53,7 @@ sat(x, K) = x / (K + x)
```
K_release K_AMPA K_Dserine
Mg_eject Ca_STP Ca_TAG
Mg_eject Ca_STP Ca_TAG eCB_thr
elig dop_thr tag_thr tag_expiry
traj_thr endur_thr
spillover inactivation overload
@@ -96,24 +103,34 @@ that neighbours compete for.
## PRE
```
// Backward messages from POST (computed by POST from its own local state, read here):
// retro_NO (+) : POST responded — release reached a responsive target
// retro_eCB (−) : POST over-driven — suppress release (DSE)
// PRE reads these as arrived signals; it never reads POST's internal state.
DAY | AP:
if pre_budget < release_cost:
suppress(NT_flux)
if pre_fast_trace > traj_thr: // LOCAL success: I released strongly
pre_endurance_need += pre_fast_trace × (1 + retrograde_local)
// interrupted LOCAL success: I was releasing strongly (own fast_trace),
// confirmed by retro_NO that POST actually responded
if pre_fast_trace > traj_thr:
pre_endurance_need += pre_fast_trace × (1 + retro_NO_local)
exit
pre_fast_trace += spike_Ca(input_freq); pre_fast_trace *= decay(100ms)
drive = sat(pre_fast_trace, K_release)
drive = sat(pre_fast_trace, K_release) × (1 - retro_eCB_local) // DSE brake from POST
if RRP > 0:
NT_flux = RRP × drive
glutamate += NT_flux·Δt; RRP -= NT_flux·Δt; pre_budget -= NT_flux·fusion_cost
fill(RRP, pre_structure.slot_ceiling, pre_structure.refill_ceiling, vatpase_cost, pre_budget)
if glutamate > spillover: drive *= brake // output brake (not a fill)
if glutamate > spillover: drive *= brake // autoreceptor/astro brake (output)
// NO fill here — AP only depletes RRP; recovery happens in NOT_AP
// (sustained high-frequency firing therefore deepens short-term depression)
DAY | NOT_AP:
pre_fast_trace *= decay(100ms); pre_endurance_need *= decay(min)
retro_NO_local = retro_NO; retro_NO *= decay(s) // receive + channel clears (NO short-lived)
retro_eCB_local = retro_eCB; retro_eCB *= decay(s) // receive + channel clears
refill(pre from astro_lactate[syn] + axon_ship_pre) // contested: lactate + shipment
fill(RRP, pre_structure.slot_ceiling, pre_structure.refill_ceiling, vatpase_cost, pre_budget)
fill(RRP, pre_structure.slot_ceiling, pre_structure.refill_ceiling, vatpase_cost, pre_budget) // private reserve
if pre_fast_trace > elig: pre_possible_tag += pre_fast_trace
pre_possible_tag *= decay(s); dopamine *= decay(ms)
if dopamine > dop_thr and pre_possible_tag > tag_thr:
@@ -137,6 +154,13 @@ DAY | NOT_bAP:
// SOURCE 2 — NMDA: large Ca if local coincidence
if Vm > Mg_eject and astro_Dserine > thr and glutamate > 0:
post_fast_trace += NMDA_Ca(glutamate)·rise_speed(); post_budget -= NMDA_cost
retro_NO += NO_emit(post_fast_trace); post_budget -= NO_synth_cost
// POST → PRE (+): nNOS coupled to NMDA emits NO/BDNF — "your release was effective"
// backward brake to PRE (−): strong depolarization → endocannabinoid (DSE)
if Vm > eCB_thr:
retro_eCB += eCB_emit(Vm); post_budget -= eCB_synth_cost
// POST → PRE (−): "I am over-driven — reduce release"
post_fast_trace *= decay(ms)