Hypothesis to explain yawning, cortisol rise, brain cooling and motor cortex involvement of involuntary arm movement in neurologically impaired patients.

Association between the hormone cortisol and yawning has been found. The Thompson Cortisol Hypothesis proposed a link between yawning and rises in cortisol with further recent evidence from neuroscience showing communication between the motor cortex, brain-stem and hypothalamus. Hormonal and neuronal links form the proposed network that influences and also monitors cortisol and brain temperature regulation via the hypothalamus. Evidence supports the proposed connection between brain-stem, hypothalamus and motor cortex and further supports the Thompson Cortisol Hypothesis suggesting threshold levels of cortisol elicit yawning to cool the brain. Additionally, this may explain the well-known observed phenomenon known as parakinesia brachialis oscitans in brain-stem ischaemic stroke patients during involuntary yawning.