Phase relationship between the low-frequency oscillatory components of cerebral [HbO] and [Hb] assessed by NIRS during sleep in human subjects

We measured the phase of low-frequency oscillations (LFOs) of [Hb] and [HbO] in the human brain during sleep. We found that, on average, the phase lead of [Hb] vs [HbO] LFOs is greater during slow-wave sleep than during REM sleep.