This is a 2D age-structured (mean-field) rendering of the same exercise-BDNF-neurogenesis model as the 3D cell-cloud version: instead of animating individual cell instances in a 3D hippocampal tube, it tracks the expected count of new granule neurons at every age-in-weeks as a continuously evolving age-cohort histogram, alongside the BDNF dose-response curve that drives it and a time-series of the resulting volume/memory read-outs.
intensity effect i = clamp((HR% − 40) / 55, 0, 1)
session effect s = clamp(duration / 30min, 0, 1.5)
weekly load L = i · s · sessions/week
BDNF(L) = 1 + 2.2 · (1 − e^(−L / 3.5)) [saturating, ~1×–3.2× baseline]
neurogenesis rate (Hill function, K=1.6, n=2):
births/week = 42 · BDNF² / (1.6² + BDNF²)
survival while immature (ages 0→1→2→3, critical window):
each step, fraction P(survive) = 0.5 + 0.4·clamp((BDNF−1)/2.2, 0, 1) carries forward
age 3→4: the whole surviving cohort matures (no further death check)
age ≥4: mature neurons persist and keep aging; those older than 8 weeks total
count as permanent survivors driving hippocampal volume/memory
Volume change and the spatial-memory score are the same linear read-outs used in the 3D version, calibrated to the roughly +2% hippocampal volume over a year of moderate training reported by Erickson et al. (2011, PNAS). Green bars are the immature critical-window cohort; violet bars are matured new neurons, aging left→right until the rightmost bar (a permanent accumulator of long-term survivors).
- Intensity / duration / sessions — set the weekly aerobic training load that drives BDNF release.
- Simulation speed — how fast simulated weeks pass; each tick runs one week of the age-cohort update.
- The top strip is the Hill-function dose-response curve with a live marker at the current BDNF level.