Experiments DB Dev
800189371b
Adds make_figure (2-panel learning curves + per-phase slopes, colorblind-safe Box-B2/Box-A2 palette) -> results/figure_learning.png; analysis/writeup.md (figure + methods + results summary); and tdcs_export_all/run_export exporting every data variation into an organized export/ tree (curated_all, scenarios/9, anchors/3 with tDCS factor, phases/9 + MANIFEST). Adds tExport tests. Suite 36/36. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
50 lines
3.2 KiB
Markdown
50 lines
3.2 KiB
Markdown
# tDCS reaching study — figure and methods
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**Figure 1.** (A) Mean ± SEM successful reaches per session over the common 0–13
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training-day window for the tDCS (Box-B2, blue) and control (Box-A2, green)
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groups; the dashed line marks the fast/slow phase boundary. (B) Per-animal
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learning slope (mean, 95% CI) in the fast (0–5) and slow (6–13) phases.
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## Methods
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The number of successful reaches per session was modeled as a function of
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training day and stimulation condition. Sessions were indexed by training day
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(day 0 = the first analyzed day, i.e. the previous study's "Day 1"), and the two
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electrode conditions were compared as a binary tDCS factor (Box-B2 = tDCS,
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Box-A2 = control; n = 3–5 animals per group). We fit linear mixed-effects models
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(MATLAB R2025b, `fitlme`, Statistics and Machine Learning Toolbox) of the form
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`successes ~ day * tDCS + (1 | subject)` with a per-subject random intercept; the
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tDCS main effect (day centered at each window's first day) estimates the Day-1
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group difference and the day × tDCS interaction estimates the difference in
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learning rate. Because the anchor groups' day coverage was unequal over the full
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range (Box-A2 data ended ~day 13 while Box-B2 continued), analyses were
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restricted to the common 0–13 window and, to separate acquisition from plateau,
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refit within a *fast* (days 0–5) and *slow* (days 6–13) phase. Given the small
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number of animals, the subject was treated as the unit of inference: per-animal
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learning slopes were compared between groups (Welch *t*, Mann–Whitney) and within
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groups across phases (paired *t*); the `fitlme` interaction tests, which use
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observation-level degrees of freedom, are anticonservative at this sample size
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and are reported only as a reference. Statistical power was estimated by
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Monte-Carlo simulation from the fitted early-phase model across a range of
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per-group sample sizes and effect sizes. Overall accuracy (successes/attempts)
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and counts were additionally modeled with binomial and Poisson GLMMs. All
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analysis code, derived datasets, and this figure are in `analysis/matlab/`.
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## Results (summary)
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Both groups showed strong session-to-session learning (day effect, p < 10⁻¹³),
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following a fast-then-slow trajectory (Fig. 1A): steep gains over days 0–5 that
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flattened toward a plateau by day 13. The tDCS and control groups performed
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comparably on Day 1 (tDCS main effect n.s.), and the tDCS group acquired faster
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during the early phase (Fig. 1B; slope ≈ 15 vs 10 reaches/day; interaction +4.6,
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95% CI [+1.0, +8.2]), converging by the late phase. At the subject level this
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early-phase difference was a consistent trend but did not reach significance
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(Welch p ≈ 0.11–0.25), and the study was underpowered at n = 3–5/group (≈30–70%
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power for the observed effect; ≈8/group would be needed for the observed effect,
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≈20/group for half that, to reach 80% power). This is consistent with the
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previously reported days × tDCS interaction, here compressed into the early
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acquisition phase — plausibly because the improved protocol's higher performance
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ceiling leaves little late-phase headroom for a benefit to accumulate.
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