nightbrain
The signal atlas

One night, nine signals.

Your wearable hears all of these while you sleep. Nightbrain's job is narrower and harder: finding which of them, if any, actually move how rested you feel.

The descent

Falling asleep is a sequence.

From lights out to deep sleep, the brain's rhythm slows — quick alpha ripples stretch into the long swells of delta. Temperature leads the way down. Each wave below scrolls at its own tempo.

Temperature

before sleep

Skin temperature — the overnight drop is what triggers and holds sleep.

Warm shower before bed, cool bedroom after: engineer the drop.

Alpha waves

lights out

8–12 Hz — relaxed wakefulness as you settle toward sleep.

Screens off and slow breathing before lights out.

Theta waves

the drift

4–8 Hz — light sleep and the drift into it.

Wind down in dim light; keep a consistent pre-bed routine.

Sleep spindles

stage 2

12–15 Hz bursts in stage 2 — tied to memory consolidation.

Keep a regular schedule; caffeine after noon blunts them.

Delta waves

deepest hours

0.5–4 Hz — the slow waves of deep sleep, where physical recovery happens.

More of it: a cool room, a steady bedtime, and no alcohol close to sleep.

The return

Dreams do their own work.

REM concentrates in the final hours of the night — cut the night short and it's the first thing to go.

REM activity

toward morning

Fast mixed waves — dreaming, emotional processing, learning.

Protect the final hours: a consistent wake time, no early-alarm creep.

All night

The body keeps time.

Three vitals run continuously from lights out to alarm. Their overnight shape — the dip, the variability, the rhythm — is what your model reads.

Heart rate

all night

Beats per minute — should dip to its lowest in the middle of the night.

Late meals, alcohol and hard evening workouts keep it elevated.

HRV

all night

Beat-to-beat variability — a window on recovery and nervous-system balance.

Steady bedtimes and less evening alcohol raise it; breathwork helps.

Respiration

all night

Breaths per minute — a steady rhythm is the mark of untroubled sleep.

Nasal breathing and treating congestion smooth it out.

In the app

One of these is tonight's signal.

Each night the app features one signal with the explainer you see here. What none of this tells you is which signals matter for you — that claim your model has to earn from your own mornings.

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