Knismesis: the aversive facet of tickle

There are two different kinds of tickle, knismesis (feather-light tickle) and gargalesis (more intense tickle eliciting involuntary laughter). In this article we review earlier and recent advances in tickle psychophysics and in neurophysiology of touch afferents and hypothesize that knismesis is signaled by populations of rapidly adapted hair follicle afferents, can stimulate itch neurons via dorsal horn projections, and is heavily moderated by afferent inputs from other touch neurons. Finally, we suggest that pathological light touch intolerance observed in autism spectrum disorder may reflect knismesis hyper-responsiveness and attenuated knismesis inhibition stemming from impaired integration of sensory inputs from other touch submodalities.