the brain doesn't like it hot

An adequate body temperature is essential for our survival. Strict control mechanisms make sure the temperature stays within a limited range. When the temperature within the body gets too high or too low normal biochemical processes are no longer possible and death follows. Minor changes can have a positive effect.

Humans have the ability to adapt to a great diversity of climates. Effective thermoregulation is reduced though in hot, humid environments. When the environmental temperature is above the core body temperature, sweating is the only physiological way for humans to lose heat. High temperatures pose serious stresses for the human body. Temperatures above 40ºC can be life threatening. The brain itself can’t tolerate temperatures above 40.5ºC.

Experimentally, hyperthermia is used to treat some kinds of cancer. Raising temperature causes apoptosis, programmed cell death. Hyperthermia therapy is applied locally to damage and kill cancer cells.

Brain cooling appears to have therapeutic potential for epilepsy, stroke, asphyxia, and other neurological diseases. It also prevents brain damage after heart attacks and can control intracranial pressure after an ischemic stroke as it reduces swelling. Cooling is an interesting technique for treatment of focal epilepsy. When applied very close to the epileptogenic focus, cooling terminates neocortical seizures.

Further research should give more insight into the contribution of brain temperature to emotion. There might exist a link with depression. The neurotransmitter serotonin plays a role in both depression and thermoregulation. Maybe brain temperature in individuals suffering from depression is higher than normal, which would add to negative feelings.