Tickle contagion in the somatosensory cortex

Abstract

The cellular mechanisms of emotional contagion are unknown. We investigated tickle contagion and the underlying neuronal representations in rats. We recorded trunk somatosensory cortex activity of observer rats while they received tickling, audio-visual playback of tickling footage, and while they witnessed tickling of demonstrator rats. Observers vocalized, and showed "Freudenspruenge" ("joy jumps") during witnessing live tickling, while they showed little behavioral responses to playbacks. A fraction of trunk somatosensory neurons responded to both direct and witnessed tickling in action-specific manner. The correlation between direct and witnessed tickling responses increased towards deeper cortical layers. Tickle-mirror neurons but not non-mirror neurons discharged prior to and during vocalizations and hence might drive contagious 'laughter'. We conclude that trunk somatosensory cortex represents mirrored ticklishness.

Unsupervised discovery of behaviorally relevant brain states in rats playing hide-and-seek

“…We think our brain-state-driven approach could in the future be implemented in more controlled tickling experiments where there is evidence of behavioral contagion and neural mirroring in the somatosensory cortex. 40 The combination of reverse physiology with neural state analyses will also undoubtedly play a future role in the neuroscience of naturalistic behavior. Specifically, recent advances in recording technologies 41 applied to freely living animals would help to clarify the role of PFC in action selection and execution of an animal’s complete ethogram.…”