Do C-tactile afferents go to sleep? A potential role for somatosensory stimulation in sleep regulation

Co-sleeping facilitates physiological regulation and interpersonal trust between partners. Here we discuss the possibility that this effect depends on C-tactile (CT) afferents—a class of unmyelinated mechanosensory cutaneous skin nerves that underlie both parasympathetic regulation and the rewarding neurochemistry of endogenous opioids and oxytocin. The literature reports that insomnia-related problems result from an overall difficulty to de-arouse. Moreover, sleep loss is prevalent in somatosensory-poor contexts such as in Isolated, Confined and Extreme (ICE) contexts (e.g. Antarctica, Covid-19 pandemic). On this backdrop, we propose two mechanisms by which CT-afferents may moderate a touch-sleep association, that is, a long-term mechanism-dependent on epigenetic programming in the course of child development and a short-term mechanism-dependent on a CT-modulation of autonomic and endocrine processes.