Figure 2. Average data recorded during the control period in quiet wakefulness (QW), active sleep (AS) and quiet sleep (QS).

Although carotid artery pressure and intracranial pressure were lower in AS than in QW and QS, cerebral perfusion pressure did not differ between the three behavioural states. Nevertheless, cerebral blood flow was greater in AS than in either QS or QW, and greater in QW than in QS. Also, cerebral vascular resistance was lower in AS than in either QS or QW and lower in QW than in QS. Values = mean ± s.d., n = 9. Bars indicate significant differences: *P < 0.05; **P < 0.01; ***P < 0.001.