The Neural Basis of Laughter

Caruana and Scott (open source) distinguish ancient and more modern brain systems regulating our laughter:  

Highlights

Behavioral and clinical evidence distinguish two major forms of human laughter: spontaneous, emotionally driven vocalizations and volitional expressions used in social communication.

Progress in the neuroscience of laughter has been limited by the difficulty of capturing spontaneous, natural signals in laboratory settings. Invasive investigations in humans, such as direct electrical stimulation, have provided a unique causal window into its underlying circuitry.

Evidence supports a dual-system framework, in which an evolutionarily ancient cingulo-temporal network drives spontaneous laughter and its social bonding and analgesic functions, while a lateral motor-opercular system co-opts speech networks for volitional expression used in social negotiation and conversation.

Abstract

Laughter is a universal social signal and a defining clinical sign of various neurological disorders. Yet, its neural orchestration remains elusive, due in part to the challenge of reproducing its spontaneous nature in the laboratory. In this review, we showcase how recent invasive investigations—from direct electrical stimulation to intracranial recordings—unveil the underlying circuitry. We propose a dual-system framework: an evolutionarily ancient cingulo-temporal network that acts as the gateway for spontaneous, involuntary outbursts; and a lateral motor-opercular system that co-opts speech-production networks for volitional, conversational laughter. This neuroethological perspective reveals how parallel cortico-subcortical pathways drive laughter as both a primal affective signal and a sophisticated communicative tool, offering a new roadmap for understanding human social bonding and its clinical disruptions.