The neural correlates of laughter show two distinctive pathways: voluntary and involuntary laughter.

Laughter may have evolved from release of tension, signalling averted danger, promoting social safety.

Laughter is important in child development, shaping emotional regulation, resilience, and social competence.

Laughter reduces cortisone, a stress hormone and stimulate neurotransmitters associated with well-being.

After reading a New York Times article reporting that some patients find AI chatbots more helpful and compassionate than physicians, I asked an AI:

“Are you going to replace us doctors?”

We’ll still need someone to restart the Wi-Fi.”

Humans have been telling jokes for thousands of years. The oldest surviving collection of jokes, Philogelos (Greek for “Love of Laughter”) was compiled around the fourth century AD. One joke aimed at physicians (a favorite target even then) goes like this:

A patient says to the doctor,

“Doctor, when I wake up for half an hour I feel dizzy.”

“Wake up half an hour later.”

Although humor and laughter are elemental to human experience, the neuroscience has only recently begun to reveal how laughter works and why it may be so important for our health.

Two Pathways to Laughter

I still remember a patient I saw during my neurology residency. She had suffered a stroke 6 months earleir which left her paralyzed on the left side, including her face. She could not smile symmetrically when I ask her to, as part of the routine neurological examination.

Yet later in the visit, a natural smile would appear while we were talking.

The answer lies in the fact that the brain contains two partially separate pathways for smiling and laughter.

The voluntary pathway allows us to smile or laugh on command. It originates at the motor cortex of the frontal lobe that control facial and vocal muscles.

The involuntary pathway originates in emotional centers such as the amygdala, hypothalamus, and anterior cingulate........

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