40 Hz sensory stimulation is a drug-free daily practice of flickering light, clicking sound or vibration meant to pull the brain's fast rhythms into step and protect the ageing brain. It is low-risk but time-demanding. Human studies are small, mostly company-linked, and show no clear gain in memory or thinking; ringing in the ears and headache are the main drawbacks. Benefit for brain health remains unproven. (Full Review)
| Marker | Target | Why |
|---|---|---|
| 40 Hz brain response on EEG during stimulation | No established target; track presence of a 40 Hz peak against own baseline | Confirms the brain follows the stimulus |
| Cognitive screen (Montreal Cognitive Assessment or Mini-Mental State Examination) | No established target; track change from own baseline | Main benefit target |
| Daily-function rating | No established target; track change from own baseline | Outcome that improved in OVERTURE |
| Plasma p-tau217 | No established target; track change from own baseline | Exploratory disease-activity marker |
| MRI brain volume (whole brain, hippocampus) | No established target; track annual change | Atrophy rate, the most consistent trial signal |
| Pure-tone audiometry | No established target; track threshold shift from own baseline | Safety check: new tinnitus or threshold shift prompts pausing use |
| EEG with photic stimulation (seizure history or flashing-light sensitivity only) | No established target; track presence or absence of a photoparoxysmal response | Safety check: an abnormal response rules out visual flicker |
Cadence: Baseline before starting; symptom check at 1 week and 4 weeks; cognitive and function testing at 3 and 6 months, then every 6–12 months; hearing at 6 months or immediately if tinnitus appears; MRI and blood markers yearly.