Figure 1. End-tidal CO₂ percentage and activity of a respiratory neuron during spontaneous breathing in NREM and REM sleep and wakefulness.

Neuronal activity is shown as cumulative impulses from the beginning of the record. The dashed line is 8 impulses s⁻¹. In REM sleep the mean discharge rate increased to 14 impulses s⁻¹. The neuron was an augmenting inspiratory cell with an η² value of 0.9.