Bottom-up gamma and stages of waking.
Medical Hypotheses July 1, 2017 E Garcia-Rill
The pedunculopontine nucleus (PPN), part of the brain's reticular activating system, generates gamma band (∼40 Hz) oscillations through intrinsic membrane properties and electrical coupling. If not all PPN neurons fire at every oscillation peak, the net firing frequency drops: firing at every second peak yields ∼20 Hz, every fourth peak ∼10 Hz. Below 10 Hz the system is essentially asleep. This implies that waking occurs in discrete steps—from ∼10 Hz to ∼20 Hz to ∼30 Hz to ∼40 Hz—as more neurons are recruited to fire at oscillation peaks, rather than as a gradual linear increase. Falling asleep would follow a similar stepwise pattern.