Besharati, S. | Search bioRxiv

bioRxiv2025

Is cultural context the crucial touch? Neurophysiological and self-reported responses to affective touch in women in South Africa and the United Kingdom.

Affective touch, involving touch-sensitive C-tactile (CT-) afferent nerve fibres, is integral to human development and wellbeing. Despite presumed cultural differences, affective touch research typically includes Western, minority-world contexts, with findings extrapolated cross-culturally. We report the first cross-cultural study to experimentally investigate subjective and neurophysiological correlates of affective touch in women in South Africa (SA) and the United Kingdom (UK) using (1) subjective touch ratings, and (2) cortical oscillations for slow CT-optimal (vs. faster non-CT-optimal) touch on two body regions (arm, palm). Cultural context modulated affective touch experiences: SA (vs. UK) participants rated touch as more positive and less intense, with enhanced differentiation in sensorimotor beta band oscillations, especially during palm touch. UK participants differentiated between stroking speeds, with opposite directions of effects at arm and palm for frontal theta oscillations. Results highlight the importance of cultural context in subjective experience and neural processing of affective touch.

neuroscience↗

bioRxiv2019

Welcoming back my arm: Affective touch increases body ownership following right hemisphere stroke

Right hemisphere stroke can impair the ability to recognise ones contralesional body parts as belonging to ones self. The study of this so-called disturbed sense of limb ownership (DSO) can provide unique insights into the neurocognitive mechanisms of body ownership. Here, we address a hypothesis built upon experimental studies on body ownership in healthy volunteers. These studies have shown that affective (pleasant) touch, an interoceptive modality associated with unmyelinated, slow-conducting C tactile afferents, has a unique role in the sense of body ownership. Here we systematically investigated whether affective touch stimulation could increase body ownership in patients with DSO following right hemisphere stroke. An initial feasibility study in 16 adult, acute stroke patients enabled us to optimise and calibrate an affective touch protocol to be administered by the bedside. The main experiment, conducted with a different sample of 26 right hemisphere patients, assessed changes in limb ownership elicited following self-(patient) versus other-(experimenter) generated tactile stimulation, using a velocity known to optimally activate C-tactile fibres (i.e. 3cm/s), and a second velocity that is suboptimal for C-tactile activation (i.e. 18cm/s). We further examined the specificity and mechanism of observed changes in limb ownership in secondary analyses looking at (1) the influence of perceived intensity and pleasantness of touch, (2) touch laterality, and (3) level of DSO on ownership change, as well as (4) changes in unilateral neglect arising from touch. Findings indicated a significant increase in limb ownership following experimenter-administered, CT-optimal touch. Voxel-based Lesion-Symptom Mapping (VLSM) identified damage to the right insula and, more substantially, the right corpus callosum, associated with a failure to increase body ownership following experimenter-administered, affective touch. Our findings suggest that affective touch can increase the sense of body-part ownership following right hemisphere stroke, potentially due to its unique role in the multisensory integration processes that underlie the sense of body ownership.

neuroscience↗

bioRxiv2019

Damage to the Right Insula Disrupts the Perception of Affective Touch

Specific, peripheral C-tactile afferents contribute to the perception of tactile pleasure, but the brain areas involved in their processing remain debated. We report the first human lesion study on the perception of C-tactile touch (N = 59), revealing that posterior and anterior right insula lesions reduce tactile, contralateral and ipsilateral pleasantness sensitivity, respectively. These findings are consistent with a posterior-to-anterior pattern of integration of interoceptive information in the frontoinsular junction.

neuroscience↗