Increased neuronal activity results in increased local brain metabolism which in turn is associated with a proportional increase in cerebral blood flow (CBF). This mechanism, referred to as flow-metabolism coupling, is regulated by metabolic, glial, neural, and vascular factors.
Hypothermia decreases cerebral metabolic rate (CMR) by 6% to 7% per degree Celsius, with a proportional decrease in CBF. Hypothermia can even cause complete burst suppression (at about 18-20 C). However, in contrast to anesthetic drugs, hypothermia beyond the burst supression temperature will continue to produce a further decrease in CMR.
Hyperthermia, on the other hand, increases CMR and therefore CBF. However, above 42 C, a reduction in CMRO2 occurs, indicating a toxic threshold likely a result of protein denaturation.