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Yagmur Idil Ozdemir, October 30 2020

Touch makes us happy

CT-fiber and its implications in our well-being

The 4 groups of low-threshold mechanoreceptors that we covered in our previous blog are highly studied, but they are not the only types of mechanoreceptors worth exploring. 

The discrete C-afferent tactile fibers, or CT-fibers for short, innervate a heterogeneous group of mechanoreceptors that are found on both hairy and non-hairy (glabrous) skin, and they are essential for our sense of well-being (McGlone et al., 2014; Vallbo et al., 1999).

Research shows that CT-fibers are crucial for the pleasantness we often associate with touch. These unmyelinated fibers have slower conduction speed and lower temporal discrimination, but have a higher sensitivity to pressure, which make them respond well to brushing/stroking of the skin (Ackerley et al., 2014)

Research shows that CT-fibers have the highest firing rates for a stimuli moving at velocities 1 to 10 cm/s, a stimuli conduction trend that closely matches brushing and gentle stroking. What’s more, the higher firing rates elicited by these brushes correlate to increased feelings of  pleasantness on the skin (Ackerley et al., 2014;Huisman et al., 2016,Löken et al., 2009,Vallbo et al., 1999).

Pawling and colleagues show that this type of touch is not only a pleasant somatosensory experience, but also makes us encode neutral stimuli such as blank faces as more positively appealing (Pawling et al., 2017).

The 4 groups of low-threshold mechanoreceptors that we covered in our previous blog are highly studied, but they are not the only types of mechanoreceptors worth exploring. The discrete C-afferent tactile fibers, or CT-fibers for short, innervate a heterogeneous group of mechanoreceptors that are found on both hairy and non-hairy (glabrous) skin, and they are essential for our sense of well-being (McGlone et al., 2014; Vallbo et al., 1999).



Mean pleasantness ratings are the highest between 1 to 10 cm/s strokes at different locations in the body. This speed range feels like a gentle stroke.











CT-fibers communicate with various regions in the central nervous system that are involved in sympathetic regulation of our emotions and well-being. In cerebral cortex, CT-fibers innervate both the left anterior insular cortex, which is a region implicated in positive emotional feelings and interoceptive (self-)regulation; along with the  posterior insular and orbitofrontal cortex that analyse other affective properties of touch and are linked to reward systems (Ackerley et al., 2012; Francis et al. 1999; Gordon et al., 2013; Löken et al., 2009; McGlone et al. 2012; McGlone et al., 2014;Morrison et al., 2010; Trotter et al., 2016)

One interesting study demonstrating this relationship was conducted by Morrison and colleagues (2011), showing that people who are born without CT-fibers, show a loss of modulatory activity in the insular cortex and as a result do not derive pleasure from touch that normally elicits such feelings(Morrison et al., 2010). Additionally, another study showed that CT-fiber activity resulting from stroke leads to more activation of  the muscle responsible for smiling (Pawling et al., 2017).




Zygomaticus muscle is the main muscle responsible for smiling. It gets activated most when a 3 cm/s stroke is applied to the arm. 

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Yagmur Idil Ozdemir

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