C-tactile fiber (CT fiber)

C-tactile (CT) fibers are a specialized class of unmyelinated, low-threshold mechanoreceptive afferents found predominantly in the hairy skin of mammals (Löken et al., 2009). Unlike myelinated A-beta fibers that convey discriminative tactile information like texture and shape, CT fibers are specifically tuned to slow, gentle stroking velocities associated with pleasant or 'affective' social touch (Olausson et al., 2002). These fibers project primarily to the posterior insular cortex, bypassing the traditional somatosensory pathways to influence emotional processing and social bonding (McGlone et al., 2014). In clinical contexts, CT fibers play a crucial role in pain modulation through the gate control theory, where their activation can suppress nociceptive signaling and provide analgesic effects (Liljencrantz & Olausson, 2014). Dysregulation of this system is implicated in sensory processing disorders, autism spectrum disorder (ASD), and the development of tactile allodynia in chronic pain conditions (Cascio et al., 2019). Although CT fibers themselves are a cellular structure, the molecular targets they express, such as PIEZO2 and MRGPRB4, are increasingly investigated for the development of drugs to treat social-sensory deficits and neuropathic pain.

Other names

CT afferentUnmyelinated low-threshold mechanoreceptorCLTMRC-low threshold mechanoreceptor

Activation of low-threshold mechanoreceptive pathways via slow mechanical stimulation (1-10 cm/s), triggering PIEZO2-mediated depolarization and signaling to the insular cortex to modulate affective state and inhibit nociception (Chesler et al., 2016; Marshall et al., 2016).