fNIRS detects temporal lobe response to affective touch

Abstract

Touch plays a crucial role in social-emotional development. Slow, gentle touch applied to hairy skin is processed by C-tactile (CT) nerve fibers. Furthermore, 'social brain' regions, such as the posterior superior temporal sulcus (pSTS) have been shown to process CT-targeted touch. Research on the development of these neural mechanisms is scant, yet such knowledge may inform our understanding of the critical role of touch in development and its dysfunction in disorders involving sensory issues, such as autism. The aim of this study was to validate the ability of functional near-infrared spectroscopy (fNIRS), an imaging technique well-suited for use with infants, to measure temporal lobe responses to CT-targeted touch. Healthy adults received brushing to the right forearm (CT) and palm (non-CT) separately, in a block design procedure. We found significant activation in right pSTS and dorsolateral prefrontal cortex to arm > palm touch. In addition, individual differences in autistic traits were related to the magnitude of peak activation within pSTS. These findings demonstrate that fNIRS can detect brain responses to CT-targeted touch and lay the foundation for future work with infant populations that will characterize the development of brain mechanisms for processing CT-targeted touch in typical and atypical populations.

Affective and non-affective touch evoke differential brain responses in 2-month-old infants

“…The largest statistical difference between slow and fast stroking is located in the insula. The activated regions found in the present study coincide with areas that are activated by affective stroking touch in adults, such as S2, posterior insula and STS (Olausson et al, 2002;Gordon et al, 2013;Voos et al, 2013;Bennett et al, 2014;Kaiser et al, 2015). Interestingly, the cortical activation cluster found in the current study further overlaps with areas that process emotional speech in naturally sleeping 3-7 month old infants as shown in an fMRI study and with areas shown, using fNIRS, to process socially relevant visual stimuli at 5 months of age (Lloyd-Fox et al, 2009).…”

“…Brain regions involved in processing affective, slow stroking, touch in adults include the secondary somatosensory cortex (S2), insular cortex, insular operculum, temporoparietal junction, superior temporal sulcus (STS), amygdala, striatum, orbitofrontal cortex and pregenual anterior cingulate cortex (Olausson et al, 2002;Lindgren et al, 2012;Gordon et al, 2013;Voos et al, 2013;Bennett et al, 2014;Kaiser et al, 2015;Perini et al, 2015;Case et al, 2016). A recent meta-analysis further revealed that affective touch differs from discriminative touch processing with a higher likelihood of activation of the posterior insula and S2 (Morrison, 2016).…”

The present and future use of functional near‐infrared spectroscopy (fNIRS) for cognitive neuroscience

“… showed that both infants and mothers have a positive fNIRS response in the PFC when seeing videos of the other smiling. Others take advantage of the flexibility of fNIRS to examine neural response to affective touch or to imitation behavior . For example, in the latter paper, participants completed an interactive task in which they saw a demonstrator make typical straight actions or abnormal curved actions and then had the opportunity to imitate them; right inferior parietal cortex showed a stronger activation signal when viewing the curved actions, which replicates previous fMRI studies.…”

Emotion Perception from Face, Voice, and Touch: Comparisons and Convergence

“…A recent meta-analysis identified the right posterior insula as a structure that is more frequently activated by pleasurable as compared to neutral touch [60, Figure 2]. Studies focusing specifically on the CT system additionally highlight the right posterior STS [61–63] and somewhat less consistently the right orbito-frontal [64–66] and pre-motor/motor areas [62,65,67]. There is some evidence that primary somatosensory cortex contributes to the pleasure from touch: a caress activates this region differentially depending on whether participants believe it to come from a person of the same or the opposite sex [68].…”