diff --git a/elements/neuron/appunti/2026-06-11-tripartite_synapse_v7.md b/elements/neuron/appunti/2026-06-11-tripartite_synapse_v7.md index 3efeaf6..8530f3f 100644 --- a/elements/neuron/appunti/2026-06-11-tripartite_synapse_v7.md +++ b/elements/neuron/appunti/2026-06-11-tripartite_synapse_v7.md @@ -1177,3 +1177,104 @@ Depotentiation is neglect — the alignment trace decays when mismatches stop, w The system finds equilibrium through the residual of its own imperfection — just enough mismatch persists to maintain just enough alignment. And critically, the soma achieves temporal prediction — firing in phase with its input rhythm — **without ever representing the rhythm**. The prediction is implicit in the structure of the recovery dynamics, built up from purely local, reactive, bottom-up trace deposits. This is the same way a potentiated synapse "predicts" that its input will be significant without representing the prediction: the prediction is the physical bias left by past experience, not a computed expectation. The soma's phase-coupling is the temporal version of the synapse's weight — both are implicit predictions encoded as physical bias, both built bottom-up from local coincidence, both maintained by reinforcement and lost by neglect. + +## Energy depletion in Presynapse + +how does the budget and energy influence the model. If for example a presynapse has no more energy variuos times during day, what happens? + +Good question. Let me trace through exactly what happens when energy is repeatedly depleted, following the mechanics already in the pseudocode. + +--- + +### The Immediate Effect — Behavior Suppression + +When `pre_budget < AP_release_cost`, the pseudocode does: + +``` +if pre_budget < AP_release_cost: + suppress(NT_flux) + exit context +``` + +So the immediate consequence of an energy-depleted bouton is **silence** — it does not release neurotransmitter for that AP, regardless of how strong the incoming spike was. The AP arrives, but nothing comes out the other side. This is biologically real: ATP-depleted boutons fail to release because the VATPase cannot refill vesicles and the calcium pumps cannot maintain the gradients that drive release. + +--- + +### The Cascade of Consequences Within DAY + +A single depletion is recoverable — the bouton refuels from astrocyte lactate in the next NOT_AP context and resumes. But **repeated depletion during DAY** sets off a cascade that runs through the entire trace and tagging machinery. + +**No release means no glutamate means no downstream trace.** When the bouton is silent, no glutamate reaches the cleft. The postsynapse receives no AMPA current, its NMDA channels do not open, and `post_fast_trace` does not rise. The astrosynapse detects no spillover, so `astro_fast_trace` does not rise and no D-serine pulse is released. The entire synaptic event simply does not happen. A bouton that is energy-depleted at the moment a significant pattern arrives causes that pattern to be invisible to the postsynapse — the synapse fails to participate in whatever the network is doing. + +**No participation means no eligibility.** Because the bouton did not release, `pre_fast_trace` is not elevated by a release event (it still rises from calcium influx, but without the reinforcing facilitation of successful release). More importantly, the postsynapse, having received no input, accumulates no `post_possible_tagging`. When dopamine arrives to validate the moment, there is nothing to validate at this synapse — the eligibility window is empty. The synapse misses the tagging opportunity entirely. + +**Missing the tag means missing the NIGHT commit.** Since no tag was set during DAY, the synapse has nothing to draw structural resources with during NIGHT. It does not potentiate. And because the system's depotentiation is by neglect, **a synapse that fails to potentiate is automatically on the path to depotentiation** — it receives only maintenance allocation, and if other synapses potentiated and drew down the shared pool, even maintenance may be insufficient. + +--- + +### The Deeper Consequence — Energy Depletion Becomes Structural Depression + +Here is the important emergent property: **repeated energy depletion at a bouton during DAY leads to its structural depression during NIGHT, even though no depression signal was ever sent.** + +The chain is entirely passive: + +``` +repeated pre_budget depletion in DAY + → bouton silent during significant events + → no glutamate release + → no post_fast_trace, no post_possible_tagging + → no tag set (pre or post) + → no NIGHT structural commit at this synapse + → only maintenance allocation received + → if pool depleted by other synapses' potentiation: + maintenance insufficient + → pre_structure and post_structure decay + → DEPOTENTIATION +``` + +The energy-starved synapse is outcompeted not because it was marked for depression but because it could not generate the activity needed to claim resources. Energy availability during DAY therefore directly determines which synapses can even enter the competition for NIGHT potentiation. + +--- + +### The Feedback Loop — Depression Reduces Future Energy Demand + +There is a stabilizing feedback here. A depotentiated synapse has smaller `pre_structure` — a smaller active zone, fewer docking slots, lower release probability. This means it costs **less energy to operate**. So a synapse that was energy-starved and consequently depotentiated now has lower energy demands, making it less likely to be energy-starved in the future. + +``` +energy depletion → depotentiation → smaller structure → lower energy demand + → less likely to deplete → stabilizes at a low-activity equilibrium +``` + +The synapse settles into a low-energy, low-structure, low-activity state. It is not dead — it still operates at baseline — but it has been demoted from the pool of synapses competing for potentiation. Energy scarcity has selected it out. + +--- + +### Why This Is Functionally Important + +This is not a bug — it is a resource-allocation mechanism with real computational value. + +**Energy availability acts as a second gate on plasticity, parallel to the neuromodulatory gate.** Dopamine asks "was this worth saving?" Energy asks "can this synapse afford to participate?" A synapse must pass both gates to be potentiated. This means the system preferentially potentiates synapses that are both behaviorally significant AND metabolically sustainable. A synapse that cannot sustain its own activity is not a good candidate for strengthening, because strengthening it would only increase its energy demand and make it fail more often. + +**Local energy competition implements a form of spatial sparsification.** Boutons on the same axon share `axon_budget` and ultimately the same astrocytic lactate supply. When many boutons are active simultaneously, the shared energy is divided among them, and the weakest — those with the least efficient structure or the least reliable input — deplete first and fall silent. This automatically sparsifies activity: under energy pressure, only the most robust synapses keep firing, and they are the ones that get potentiated. The system concentrates its limited resources on its strongest connections. + +**The astrocyte's energy delivery becomes a control signal.** Because the astrocyte controls lactate distribution across its territory, it has indirect control over which synapses can sustain activity and therefore which can be potentiated. A region of the astrocyte territory that is well-perfused and well-fueled supports vigorous plasticity. A region that is metabolically stressed — perhaps because of high overall demand or reduced vascular supply — suppresses plasticity in its synapses regardless of their activity. This couples the metabolic state of the tissue directly to its capacity to learn. + +--- + +### What Repeated Depletion Looks Like Over Days + +If a bouton is chronically energy-starved across multiple DAY cycles — perhaps because it is in a metabolically compromised region, or because it is competing with many highly active neighbors — the trajectory is: + +``` +Day 1: depletes occasionally → misses some events → weak tag → partial commit +Day 2: smaller structure → still depletes under load → weaker tag → less commit +Day 3: structure decaying → maintenance insufficient → depotentiation accelerates +... +Equilibrium: minimal structure, minimal energy demand, minimal participation + synapse survives but is functionally silent + resources it would have consumed now available to neighbors +``` + +This is a reasonable model of what happens to synapses in metabolically stressed tissue — they do not die immediately, but they are progressively silenced and depotentiated, freeing their resources for synapses in healthier regions. It is also a model of how chronic metabolic limitation — aging, vascular disease, mitochondrial dysfunction — would manifest as a gradual loss of plasticity capacity: not through any depression signal, but through the simple inability of energy-starved synapses to participate in the activity that would let them claim resources. + +The energy budget is therefore not just a constraint that occasionally blocks behavior — it is a continuous selective pressure that shapes which synapses thrive and which fade, operating silently in parallel with the explicit activity-and-reward-driven plasticity, and ultimately determining the metabolic sustainability of whatever the system chooses to remember.