TC: retune g_Na, g_K, g_KL for in-band M&H92 tonic AP shape (#307)#345
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The THALAMIC_RELAY preset previously inherited NeuronConfig's HH52 defaults (g_Na=120, g_K=36; the preset already overrode g_K to 18 for LTS-burst support). This drove the mean tonic AP peak to ~+49 mV and AHP to ~−77 mV, both outside the McCormick & Huguenard (1992) bands (peak +10 to +40 mV; AHP −75 to −55 mV). Same kinetic pattern as the cortical pyramidal (#298), Purkinje (#299), FSI (#301), DA (#304), and STN (#305) fixes. Set g_Na=45, g_K=10 as explicit somatic densities for the single- compartment reduction. Pospischil 2008 Table 2 specifies (90, 7) for TC, but at those values the MH92 Traub-Miles kinetics still overshoot peak (~+45 mV); (45, 10) is the smallest reduction that lands every M&H92 AP-shape metric comfortably inside its band. Bump g_KL from 0.18 → 0.19 to compensate for the lowered delayed- rectifier damping at rest. Without the bump, numerical noise grows into a slow LTS-coupled mini-burst over the 1-second quiescence test window because the reduced g_K's near-zero contribution to baseline outward damping is no longer enough to suppress sub-threshold perturbations. R_in stays at 5.26 kΩ·cm² (band 5–9). Recompute the coupled equilibrium under the new conductances: v_rest=−69.2550 mV (was −68.8121); ca_init=6.9107e-4 mM (was 7.4123e-4). Update the ACTION_POTENTIAL adjustment override from 20 µA/cm² × 2.5 ms to 8 µA/cm² × 0.5 ms. Excitability rose with the lower g_K, so the old stimulus now triggers an LTS-coupled rebound after the primary AP; the shorter 0.5 ms pulse keeps ICaT mostly inactivated and yields exactly one AP under the test_action_potential_preset assertion. Refs: - McCormick, D.A. & Huguenard, J.R. (1992) J. Neurophysiol. 68:1384 - Pospischil et al. (2008) Biol. Cybern. 99:427, Table 2 (TC)
The biological retune in the prior commit places the mean tonic peak at ~+39 mV (band +10 to +40) and AHP at ~−66 mV (band −75 to −55), both inside the McCormick & Huguenard (1992) bands these tests pin. strict=True would otherwise XPASS-fail the suite.
PR #345 review: two comment paragraphs in the THALAMIC_RELAY preset still cited the pre-retune values. Update the leak-block comment (g_KL ≈ 0.18 → 0.19; τ_m, R_in ≈ 5.6 → 5.26) and the SUBTHRESHOLD_RESPONSE adjustment comment (g_K = 18 → 10). Also note that g_KL cannot be raised to 0.20 without putting τ_m on the test_preset_passive_properties boundary.
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Summary
g_Na=45,g_K=10mS/cm² on theTHALAMIC_RELAYpreset (was silently inheriting HH52 defaults g_Na=120; g_K=18 was already overridden). Lower densities bring the mean tonic peak from ~+49 mV to ~+39 mV and the AHP from ~−77 mV to ~−66 mV — both inside the McCormick & Huguenard (1992) bands.g_KL0.18 → 0.19 to compensate for the reduced delayed-rectifier damping at rest. Without the bump, the cell exhibits a slow LTS-coupled mini-burst over the 1-secondtest_tc_quiescent_at_restwindow because the lowered g_K is no longer enough to suppress sub-threshold drift.v_rest=−69.2550 mV,ca_init=6.9107e-4 mM.ACTION_POTENTIALadjustment override (20 µA/cm² × 2.5 ms → 8 µA/cm² × 0.5 ms). Excitability rose with the lower g_K, so the old stimulus now triggers an LTS-coupled rebound after the primary AP; the shorter pulse keeps ICaT mostly inactivated and yields exactly one AP.xfail(strict=True)markers intests/integration/test_thalamic_relay.py(test_tc_ap_peak_voltage_in_tc_tonic_range,test_tc_ap_ahp_depth_in_tc_tonic_range).Same kinetic pattern and fix as the cortical pyramidal (#298), Purkinje (#299), FSI (#301), DA (#304), and STN (#305) presets.
Closes #307.
Test plan
tests/integration/test_thalamic_relay.pypasses (no xfails, no xpasses).test_thalamic_relay_step_release_produces_multi_spike_lts_burststill passes (LTS burst preserved).uv run --frozen -m pytest) passes (1518 passed, 2 xfailed locally).