The Anticipation and Perception of Affective Touch in Women with and Recovered from Anorexia Nervosa

Abstract

Disruptions in reward processing and anhedonia have long been observed in Anorexia Nervosa (AN). Interoceptive deficits have also been observed in AN, including reduced tactile pleasure. However, the extent to which this tactile anhedonia is specifically liked to an impairment in a specialised, interoceptive C-tactile system originating at the periphery, or a more top-down mechanism in the processing of tactile pleasantness remains debated. Here, we investigated differences between patients with and recovered from AN (RAN) and healthy controls (HC) in the perception of pleasantness of touch delivered in a CT-optimal versus a CT-non-optimal manner, and in their top-down, anticipatory beliefs about the perceived pleasantness of touch. To this end, we measured the anticipated pleasantness of various materials touching the skin and the perceived pleasantness of light, dynamic touch applied to the forearm of 27 women with AN, 24 women who have recovered and 30 HCs using C Tactile (CT) afferents-optimal (slow) and non-optimal (fast) velocities. Our results showed that both clinical groups anticipated tactile experiences and rated delivered tactile stimuli as less pleasant than HCs, but the latter difference was not related to the CT optimality of the stimulation. Instead, differences in the perception of CT-optimal touch were predicted by differences in top-down beliefs, alexithymia and interoceptive sensibility. Thus, tactile anhedonia in AN might persist as a trait even after otherwise successful recovery of AN and it is not linked to a bottom-up interoceptive deficit in the CT system, but rather to a learned, defective top-down anticipation of tactile pleasantness.

Keywords: affective touch; anhedonia; anorexia nervosa; interoception; pleasantness; reward.

Figure 1

Schematic representation of the study procedure. All participants completed the same experimental procedure. 1. First, they were asked to answer four hypothetical questions about imagined touch, such as “How pleasant would it be to be touched by velvet on your skin?” using the VAS scale ranging from 0, not at all, to 100, extremely pleasant. 2. Participants were then asked to put on a blindfold before the experimenter delivered the touch on the left forearm (dorsal part) at CT-optimal, borderline or non-CT optimal velocities (in randomized order). Each touch lasted 3 seconds and was repeated 3 times for each velocity for a total of 15 trials. After each touch, participants were asked to rate the pleasantness of the touch using the same rating scale of part 1.

Figure 2

Estimation of pleasantness (mean, represented as diamond, and 95% confidence interval, represented as error bars) of soft and rough materials/objects between the three groups: women with anorexia nervosa (AN), women who have recovered from anorexia nervosa (RE) and matched healthy controls (HC).

Figure 3

Pleasantness ratings (mean, represented as diamond, and 95% confidence interval, represented as error bars) for the five velocities for the three groups: women with anorexia nervosa (AN), women who have recovered from anorexia nervosa (RAN) and matched healthy controls (HC).