Why are yawns contagious, and how does contagion relate to autism and epilepsy?

New research from the University Of Nottingham, U.K., sheds light on the brain's "neural basis" for why yawns are contagious while uncovering the basis for "potential non-drug, personalized treatments" of conditions linked to cortical excitability and physiological inhibition, like epilepsy, Tourette syndrome, dementia and autism.

Conditions linked to excitability and inhibition

Epilepsy, Tourette syndrome, dementia and autism are among a "wide range of clinical conditions" that are linked to "increased cortical excitability and/or decreased physiological inhibition" in the primary motor cortex of the human brain, according to the study. Cortical excitability refers to increased neuron network excitement in the cerebral cortex.

The primary motor cortex is a complex of "highly interconnected areas" of motor neurons in the cerebral cortex of the frontal lobe. It is responsible for "complex temporal sequences of voluntary movements," according to the National Center for Biotechnological Information (NCBI).

Researchers in the multi-discipline study, led by Professor of Cognitive Neuroscience Stephen Jackson, University of Nottingham School of Psychology, hope to find personalized treatments to modulate "imbalances in [these] brain networks."

Volunteers filmed while viewing videos of yawning people

Thirty-six adult volunteers were filmed while viewing videos of people yawning. They were given two sets of instructions relevant to "separate blocks" of video viewing. In one block, they were instructed to inhibit their yawns, whereas in the other block they were instructed to yield to their yawns. Their various yawns and yawn inhibitions were counted, and their cortical excitability and inhibition were quantified through precise measurement using transcranial magnetic stimulation (TMS), which uses a magnetic field generator to stimulate targeted areas of the brain.

The research study showed that Contagious Yawns cannot be stopped during inhibition — their intensity can only be modified. It also showed that each person's "propensity for contagious yawning" is individual and is determined by each individual's "cortical excitability and physiological inhibition" related to the primary motor cortex.

Contagious yawning: humans, dogs, chimps and monkeys

Contagious yawning is an automatic imitation of another's action and is an echophenomena called echopraxia. The other form of echophenomena is the automatic imitation of another's words and is called echolalia, according to the study's explanation.

Humans are not the only ones who are affected by automatic imitation of contagious yawns.

Dogs, chimpanzees and a species of monkey also display yawn echopraxia triggered by the sound or sight of another yawning. The brain's neural basis for these irrepressible echophenomena was unknown, but now this study links the neural basis to "disinhibition" and "hyper-excitability of cortical motor areas," as was stated in "A Neural Basis for Contagious Yawning" published in the academic journal Current Biology.