Audit fixed D18 credit and conditional MBON transfer (Phase 4AL)

models/male-cns-lif/mb-credit-transfer-audit-v1/EVIDENCE.md

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+# Phase 4AL — credit specificity and conditional KC→MBON transfer
+
+## Purpose and frozen boundary
+
+This is a diagnostic audit of the already sealed Phase 4AK D18 branch, not
+conditioning, training, or a new learning candidate. Phase 4AK established its
+predeclared 100 ms KC representation gate; it did not establish appropriate
+credit assignment, functional associative memory, or biological fidelity of
+every omitted mechanism.
+
+Use all 120 Phase 4AK primary trials and all 24 exact-repeat trials. Keep the
+two cohorts and their two input modes separate. Repeats check reproducibility;
+they are not extra independent observations in the five-seed statistics. Do
+not replace seeds, select favorable odors, choose a best pair or compartment,
+or inspect old held-out dynamic outcomes to change this design.
+The inherited matched-energy mode matches expected input, not necessarily the
+realized event count of every stochastic trial; do not relabel it exact
+realized-count matching.
+
+All earlier raw, processed, frozen/reference, model and experiment artifacts
+remain read-only. Preserve the base CSR, anatomical counts, transmitter signs,
+LIF parameters, D18 operator, APL settings, eligibility-v2, and existing 14,232
+plastic-edge mask. All new records belong only to this new audit. No DAN
+stimulus is injected; no reinforcement is delivered to a brain; no learned
+`plastic_delta` is written. No decoder, action selection, game, RL, or visual
+interface is introduced.
+
+## Three distinct evidence levels
+
+1. **Exact baseline reconstruction.** Reconstruct target MBONs from the actual
+   frozen full-network events using real edges, original arithmetic/order,
+   initial states, arrivals, refractory acceptance, resets, and applicable APL
+   handling. Require bitwise identity of events, per-neuron counts, and final
+   V/g/ref against Phase 4AK D18. A failed or incomplete reconstruction blocks
+   scientific interpretation of that replay; it is never rescued by plausible
+   plots or by agreement of aggregate firing rates. Complete-audit integrity
+   requires all 144 baseline replays; do not silently drop failed cases and
+   report the remaining subset as the complete predeclared audit.
+2. **Virtual credit audit.** Replay the unchanged, existing float32 eligibility
+   operator and inspect its state at the fixed tick-900 virtual gate, after
+   that tick's original `mul → add → clamp` sequence. Tick-900 spikes are
+   included. This is shadow accounting only, not dopamine delivery or weight
+   updating; a before/after-update change is a different experiment. Do not
+   treat virtual gate amplitude as measured dopamine concentration.
+3. **One fixed conditional sensitivity test.** Compare the exact baseline with
+   one temporary replay applying uniform 25% depression to the whole existing
+   plastic-edge mask. This uses the pre-existing maximum allowed fractional
+   depression as a single declared diagnostic intervention. It is not a
+   fraction scan, an eligibility-trained delta, a selected successful memory,
+   or permission to enlarge the mask. The base weights remain unchanged; only
+   the diagnostic effective amplitudes change, preserving edge identity and
+   transmitter sign. On an independent incoming-weight copy, apply
+   `weights[plastic] *= 0.75` throughout the full 100 ms replay, not only after
+   tick 900. All presynaptic spike trains, including those of other MBONs and
+   DANs, remain the original recorded trains. Do not save the overlay as a
+   learned or official model.
+
+The 25% intervention is **not an upper bound on functional response**. LIF
+threshold, reset, refractory gating, and recurrent influences make responses
+nonlinear; the largest permitted fractional depression does not establish the
+largest attainable change in spikes, latency, or downstream activity.
+
+## Incoming-drive and overlap accounting
+
+Decompose actual MBON incoming drive into six mutually exclusive groups:
+
+- plastic KC→MBON;
+- non-plastic KC→MBON;
+- DAN;
+- MBON;
+- APL;
+- other.
+
+Use the frozen canonical IDs, mask membership and audited metadata, not guessed
+names or transmitter-to-cell-role substitutions. Preserve unknown role
+provenance inside the residual `other` group. Establish each edge's group once;
+do not reclassify it to improve the result. Report accepted/rejected arrivals,
+signed contributions, and roundoff/reset effects as the implementation makes
+available. The model's variable `g` is a model state; do not rename it a measured
+biophysical conductance or dopamine signal. A source's share of accepted drive
+is not its necessity, sufficiency, or unique causal contribution to a spike.
+Any ratio with a zero/undefined denominator must remain explicitly undefined.
+The sole set-similarity convention is empty/empty Jaccard = 1 with an explicit
+`empty_union` flag. Such pairs are counted separately and excluded from block
+overlap aggregates; this convention is never evidence of useful credit.
+
+For each cohort × mode, retain all 15 unordered pairs of its six odors: 60
+pair records in total. Report two separate three-of-five-seeds memberships for
+each odor: (1) a strictly positive frozen eligibility trace sampled after the
+tick-900 update, including tick-900 spikes, and (2) a strictly positive spike
+count anywhere in the full 100 ms trial. The primary virtual-credit grouping
+uses the first definition. The whole-window activity grouping is auxiliary;
+it cannot replace the primary grouping to rescue a result. These are
+descriptive reliability rules, not biological thresholds, top-K filters, or
+ways to delete cells/edges from replay. Preserve per-trial activity and
+eligibility alongside both aggregate memberships.
+
+Compute overlap on the actual A-active and B-active sets. In particular,
+`Jaccard(A_active, B_active)` must use their real intersection and union; never
+substitute the already disjoint sets `A_only` and `B_only`, whose zero
+intersection is true by construction. Shared, A-only, B-only, and inactive
+strata are useful descriptive partitions, not proof of stimulus-specific
+causation. Shared representations can support biological generalization;
+nonzero B effects are not automatically a defect, nor are they automatically
+evidence of valid generalization.
+
+Keep arithmetic/integrity checks separate from scientific results. Report all
+pairwise and trial-level outcomes without inventing an overall 120-trial
+biological PASS fraction, post hoc effect threshold, or pooled rescue gate.
+An absence of MBON spike change may coexist with a subthreshold change and
+does not mean the entire biological pathway is incapable of plasticity.
+
+## What a conditional replay can and cannot establish
+
+The baseline can establish that the saved events and the frozen operator
+reconstruct the saved MBON trajectory exactly. Virtual eligibility can reveal
+which real candidate edges would receive credit under that declared rule.
+The single depression replay can measure how the selected MBONs respond to
+that fixed intervention **with the external network event history held fixed**.
+
+It cannot establish closed-loop whole-brain necessity/sufficiency or learned
+behavior. If an MBON's replayed spikes change while its outgoing effects and
+the other neurons' events remain clamped to the old trial, MBON→DAN, MBON→MBON,
+and other feedback are not recomputed self-consistently. Their fixed incoming
+traces must not be described as counterfactual feedback responses. If the
+replay instead also clamps the target MBON's original reset/refractory gates,
+its result is narrower still: conditional drive/state accounting, not an
+independently recomputed functional spike response. State these scopes
+explicitly for each reported quantity.
+
+The anatomical D18 arrival delay is 18 × 0.1 ms = 1.8 ms. It is not the
+eligibility lifetime, a measured dopamine latency, or the CS–reinforcer
+association window. A 100 ms observation does not test memory retention,
+consolidation, extinction, reversal, or behavioral recall. Do not promote any
+successful replay to a dopamine-plasticity or learning candidate.
+
+## Primary evidence and non-measured assumptions
+
+- **Hige et al., Neuron (2015), DOI 10.1016/j.neuron.2015.11.003.** Pairing an
+  odor with selected DAN activation produced odor-specific, compartment-local
+  KC→MBON depression with order dependence. The reported induction did not
+  require postsynaptic MBON spiking; overlapping KC representations predicted
+  reduced specificity/generalization. This supports auditing the correct
+  presynaptic and compartment credit, not requiring MBON spikes to define all
+  plasticity. It does not specify MaleCNS per-edge learning parameters.
+  [Author publication and paper](https://www.janelia.org/publication/heterosynaptic-plasticity-underlies-aversive-olfactory-learning-drosophila).
+- **Handler et al., Cell (2019), DOI 10.1016/j.cell.2019.05.040.** DopR1/DopR2
+  pathways support opposing plasticity associated with different cue–DAN
+  timing. This establishes why time ordering matters, not that the frozen
+  float32 trace is a measured biochemical state or that one rule applies to
+  every compartment. [Primary paper](https://www.sciencedirect.com/science/article/pii/S0092867419306117).
+- **Aso and Rubin, eLife (2016), DOI 10.7554/eLife.16135.** DAN cell types differ
+  in memory formation, updating and persistence. PAM/PPL1 labels alone are
+  not a license to assign a universal valence or a common temporal rule.
+  [Primary paper](https://elifesciences.org/articles/16135).
+- **Aso et al., eLife (2014), DOI 10.7554/eLife.04580.** Different MBON types
+  bias approach/avoidance, with combined activation supporting population
+  integration. Assessing a population response is more appropriate than
+  equating greater weight or total firing with positive memory. The current
+  audit nevertheless has no behavioral decoder or demonstrated behavior.
+  [Primary paper](https://elifesciences.org/articles/04580.pdf).
+- **Huang et al., Nature (2024), DOI 10.1038/s41586-024-07819-w.** Physiological
+  measurements and a constrained model show heterogeneous, bidirectional
+  PPL1 signaling and feedback interactions among memory units. This motivates
+  explicit closed-loop limitations. Its fitted model weights and plasticity
+  parameters are not MaleCNS anatomical counts or measurements to import into
+  this frozen branch. [Primary paper](https://www.nature.com/articles/s41586-024-07819-w).
+- **Manoim et al., Current Biology (2022), DOI 10.1016/j.cub.2022.09.007, and
+  Manoim Wolkovitz et al. (2026), DOI 10.1016/j.cub.2026.01.014.** KC lateral
+  axonal mAChR-B modulation contributes to stimulus specificity; subsequent
+  work identifies voltage-dependent modulation relevant to active versus
+  inactive KCs. Sparse coding plus a timed reinforcer is therefore not, by
+  itself, proof of appropriate credit. These studies do not prove that an
+  omitted receptor mechanism caused any result in this fixed model, and do
+  not authorize a sign, gain, threshold, or receptor-parameter change.
+  [2022 paper](https://www.sciencedirect.com/science/article/pii/S0960982222014518);
+  [2026 paper](https://www.sciencedirect.com/science/article/pii/S096098222600014X).
+
+The frozen eligibility operator, tick-900 virtual gate, three-of-five activity
+summary, 25% uniform diagnostic depression, clamped event history, and chosen
+observation window are engineering/model assumptions. None is relabelled as a
+MaleCNS single-cell or synaptic measurement by citing the papers above.
+
+## Deferred functional-memory controls — not executed here
+
+A later explicitly authorized learning experiment would need pre/post CS+
+and CS− responses, reciprocal cue assignment, independent evaluation seeds,
+and reinforcement-free probes with updates disabled. CS-only, DAN-only,
+unpaired/yoked, D(t)=0, and frozen/delta=0 conditions distinguish associative
+effects from exposure, transient state, adaptation and unrelated modulation.
+Real DAN-only stimulation is not universally expected to have zero effect;
+that prediction depends on the declared model and compartment. Retention
+requires its own observation interval, and any model-specific output effect
+must remain distinct from a behavioral-memory claim. No such controls are
+silently replaced by virtual credit or the 25% sensitivity test.
+
+Google/DeepMind's [FlyBody work](https://www.nature.com/articles/s41586-025-09029-4)
+provides body physics and artificial RL controllers, not evidence for this
+KC→MBON credit rule. Google's [MaleCNS author resource](https://research.google/blog/a-connectomics-milestone-mapping-the-complete-male-fruit-fly-brain/)
+supports the anatomical resource, not measured dopamine kinetics or successful
+learning in this model. Neither permits bypassing the present mechanism audit.