Exercise-Induced Hippocampal Neurogenesis

Aerobic Training Load

Intensity (% max heart rate) 70%

Session duration 30 min

Sessions per week 3

Simulation speed 0.30 wk/s

Dentate Gyrus, Live

Week 0 of training

BDNF level

1.00×

New neurons / wk

Hippocampal volume Δ

+0.0%

Spatial memory score

How it works

Aerobic exercise above the fat-burning threshold triggers a surge of circulating brain-derived neurotrophic factor (BDNF), which promotes survival and integration of new granule neurons born in the dentate gyrus of the hippocampus (Cotman & Berchtold, 2002; van Praag et al., 1999).

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 of immature neurons (critical window ≈ 4 weeks):
  P(survive this week) = 0.5 + 0.4 · clamp((BDNF − 1)/2.2, 0, 1)

Only neurons that survive the ~4-week critical period and get recruited into active circuits (activity-dependent survival) count toward lasting hippocampal volume; the rest undergo apoptosis, matching the "use it or lose it" pattern seen for adult-born granule cells. Volume change and the spatial-memory score are simple linear read-outs of surviving new-neuron count, calibrated to the roughly +2% hippocampal volume over a year of moderate training reported by Erickson et al. (2011, PNAS).

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 neurogenesis and survival.
Green glowing cells are immature (< 4 simulated weeks old, still at risk of apoptosis); they fade to steady blue once matured.

Mature granule neurons Immature (critical window)

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