## 1 Introduction
Finally, in FMS patients, negatively biased cognitions about their bodies and heightened awareness of internal body signals may be related to the inability of incoming sensory pathways to adequately update negatively biased somatic representations of body parts, which are stored as long-term memories [32]. Limb laterality discrimination is a cognitive task that allows evaluating interception of body schema (sense of the physiological condition of the body) [33]. The task consists of discriminating whether a part of the body belongs to the right or left side. This process requires the participant to perform a mental rotation of the internal representation of the body part to be identified. During laterality discrimination, observers imagine their own hand moving toward the orientation of the stimulus they are to identify. This implies that the participants must carry out a process of implicit motor imagery [34]. The complex mechanisms of pain can influence the state of the body schema of populations suffering from chronic pain. The notion of the body schema is unconscious, and these alterations may be linked to a deterioration in the cortical representation of a painful part of the body (for example, in chronic pain, the cortical representation of the affected part suffers changes in position, size, or shape) or absence of this representation [35; 36; 37]. In addition, the nerve pathways that transmit information can also be altered in patients with chronic pain. Thus, the sensory pathway of the posterior cord of the medial lemniscus, related to movement planning, may be influenced by chronic pain, resulting in movement planning that is different from that of healthy people [38]. Furthermore, the pyramidal motor pathway is affected by incoming information, which can lead to alterations in pain processing [39]. In the area of pain study and treatment, limb laterality discrimination has been widely used in different populations suffering from some type of chronic pain condition [37; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49]. Despite its broad use in the field of pain neuroscience, there are no standardized protocols for limb discrimination tasks, given that previous research has shown significant heterogeneity in the applied methodologies and in the characteristics of the study populations [50]. Moreover, very few investigations evaluating laterality discrimination studied the emotional and cognitive aspects presented by the patients [51; 52; 53]. Laterality discrimination in FMS patients has only been investigated in two previous studies, with FMS patients showing an impairment of this ability compared to healthy subjects [54; 55]. However, in none of these investigations did the emotional and cognitive aspects presented by patients with FMS establish a correlation between these and the laterality discrimination task. To the best of our knowledge of the current scientific literature, to date, no publication has described how psychological variables can influence the limb laterality discrimination in FMS patients. The main objective of this study was to assess the status of body schema using limb laterality discrimination tasks in women with FMS compared to healthy subjects. The secondary aim was to evaluate how emotional and cognitive factors influence the limb laterality discrimination task in patients with FMS and healthy subjects.