Topical heterogeneity in affective touch: Does it impact body image?

Recent evidence suggests that altered responses to affective touch - a pleasant interoceptive stimulus associated with activation of the C-Tactile (CT) system, may contribute to the aetiology and maintenance of mental conditions characterised by body image disturbances (e.g., Anorexia Nervosa). Here, we investigated whether tactile pleasantness and intensity differ across body sites, and if individual differences in dysmorphic appearance concerns and body awareness might be associated to touch perceptions across body sites. To this end, we measured perceived pleasantness and intensity of gentle, dynamic stroking touches applied to the palm, forearm, face, abdomen and back of 30 female participants (mean age: 25.87±1.17yrs) using CT-optimal (3 cm/s) and non-CT optimal (0.3 and 30 cm/s) stroking touch. As expected, participants rated CT-targeted touch as more pleasant compared to the two non-CT optimal stroking touch at all body sites. Nevertheless, CT-targeted touch applied to the abdomen elicited the lowest pleasantness ratings compared to all other body sites and to the two non-CT optimal stroking touch. Individual differences in body awareness and dysmorphic concerns significantly predicted preference for CT-optimal over non-CT optimal stroking touch applied to the forearm and the back. These findings begin to elucidate the link between CT sensitivity, dysmorphic appearance concerns and body awareness, which may have implications for future research looking to inform early interventions. Addressing impaired processing of affective interoceptive stimuli, such as CT-targeted touch, may be the key to current treatment approaches available for those populations at risk of disorders characterised by body image disturbance.


Introduction
Touch is a crucial means of receiving information from the outside world by mediating 47 our interactions with objects, and other individuals. The touch experience is a combination of 48 the discriminative aspects of tactile perception (i.e. characterising and localising external 49 stimuli), and the affective and social qualities encoded therein [1,2]. Previous investigations 50 have demonstrated that slow, caress-like touch is usually experienced as highly pleasant [3-   [36]. Therefore, we collected participants' ratings of touch intensity, to account for potential 167 individual differences in the two aspects of touch (discriminative vs. affective).

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Overall, we expected that differences in touch velocities and application sites would 169 inform the degree to which responses to predominantly discriminatory (touch to the palm and 170 non-CT optimal touch) compared to affective/CT-activating (e.g., CT targeted 3 cm/s touch    Ascetism and Maturity Fear). Examples of items of this scale include items such as "I think 217 my hips are too big", "I am preoccupied with the desire to be thinner" "I feel alone in the 218 world" and "I stuff myself with food". Participants are instructed to rate each item on a 219 6-point Likert scale ranging from 'never' to 'always'. The EDI-3 allows the calculation of 12 220 scales and 6 composites describing different aspects of the ED symptomatology.

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In the current study, we were specifically interested in assessing whether participants' participants' concern about their physical appearance. The scale has been validated as a brief, associated with changes in the activity of the autonomic nervous system, such as "muscle 250 tension", "goose bumps", "stomach and gut pains", breathing and heart-beat rates. Items are 251 rated on a 5-point Likert scale ranging from 1 ("Never") to 5 ("Always"), and total scores 252 ranging between 12 and 60. In the current study, we focussed on the Body Awareness   After each trial participants rated, on a paper, the pleasantness and intensity of the 293 stimulation on 15 cm horizontal Visual Analogue Scales (VAS) ranging respectively from 294 "unpleasant" to "pleasant", and from "least intense" to "most intense" (see Fig 1). 295 At the end of the experiment, participants were weighted on the digital scale and 296 completed the self-report questionnaires.

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Demographics and self-report scales 328 Participants' demographics and self-report questionnaire scores are reported in Table 1.

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The mean EDRC score was 18.53 (±1.41, range: 1-29) which is deemed to be at low risk for    emerging as the only significant predictor (see Table 2). Furthermore, we found a significant   i.e., abdomen and face; c) explore the relationship between body awareness and interoceptive 438 deficits with tactile experience at these varying body sites.

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The results show that, as expected, perception of touch varied across skin sites according 440 to both tactile pleasantness and intensity. Tactile pleasantness, measured by means of hedonic 441 ratings to three velocities of stroking, one CT-optimal (3 cm/s) and two non-CT optimal (0.3 442 cm/s and 30 cm/s), was similar in profile across the body sites investigated. However, we 443 found that there was a subtle difference in the ratings at the abdomen, so that participants 444 rated this body area the least pleasant when touch was delivered at CT-optimal (3cm/s) 445 velocity. However, this reduction in pleasantness for CT-optimal touch to the abdomen was 446 not supported by a parallel increase in the intensity sensation experienced by participants at 447 the same body site, given that overall, touch to the back but not to the abdomen was felt as 448 the least intense. Furthermore, and contrary to our prediction, we did not find evidence to 449 support the idea of an association between preference for CT-optimal (3 cm/s) touch when pleasantness of CT-optimal (3 cm/s) touch to the forearm. We will now proceed to discuss 456 specific findings in turn. Contrary to our expectations, however, we did not find evidence of a link between overall 559 touch intensity and self-report measures of EDs, BDD, BPQ and interoceptive deficits. This