Thesis title: Virtual pleasant touch perception and Interoceptive processes in chronic clinical conditions: Immersive Virtual Reality, behavioural and psychophysiological evidence on Fibromyalgia and Spinal Cord Injured patients.
Interoception is classically defined as the sense of the physiological condition of the entire body, providing a moment-by-moment mapping of the body’s internal state across both conscious and unconscious levels (Craig, 2002; Khalsa et al., 2018). Along with exteroception and proprioception, interoception provides a complete set of information regarding the state of the body, thus contributing also to emotional processes and self-consciousness (Craig 2009; Berlucchi & Aglioti, 2010). Indeed, interoceptive processing occurs across all major biological systems involved in maintaining bodily homeostasis, involving, among the other, also the nociceptive systems, as proposed by some models that expanded the definition of interoception to other motivationally relevant physiological signals (e.g., pain, cutaneous light ‘sensual’ touch) (Craig, 2002). According to recent evidence alterations in interoceptive processes have been observed in numerous clinical conditions (Garfinkel et al., 2016b; Paulus & Stein, 2006, 2010; Rae, Larsson, Garfinkel, & Critchley, 2018). In particular, chronic pain has attracted the attention of research especially in recent years, leading to hypothesize a relationship between interoception and chronic pain, supported by both behavioural and neuroanatomical studies (Di Lernia et al., 2020; Duschek et al., 2015; Weiss et al., 2014; Mejier et al., 2022; Lu et al., 2016). In line with this recent evidence, the aim of the thesis was to investigate interoceptive related processes in two clinical populations affected by chronic pain and/or somatosensory deafferentation and de-efferentation. The first stream of research, comprising two studies, addressed Fibromyalgia (FM) patients. The general objective was to explore, through an innovative immersive virtual reality approach, the perception of virtual vicarious pleasant and social touch in this clinical population with a specific focus on the potential analgesic effect of virtual pleasant touch on pain perception. The second line of research focused on Spinal Cord Injuries (SCI) with the ultimate goal of providing an in-depth investigation of interoception (Experiment 1) and its relationship with bodily self-consciousness (Experiment 2) in this clinical population. In the attempt to overcome the limitations characterizing current research on interoception, the first part of the study on SCI assessed interoception along its three dimensions (i.e., sensibility, accuracy, and awareness) and across different domains. The second part of the study investigated how interoceptive signal, specifically breathing signals, shape bodily self-consciousness by means of an adapted version of a newly developed full body illusion, called the Embreathment illusion (Monti et al., 2020).