## 4 Discussion
### Limb Laterality Discrimination and Psychological Variables in Fibromyalgiagia Pain Syndrome
On the other hand, the inability to discriminate the laterality of the hands, with no significant differences found for the feet, may be owing to the hand being one of the body regions with the largest area of representation in both the somatosensory and motor cortex, according to the somatotopic maps established by [PERSON] [70; 71]  
Some previous publications on other chronic pain conditions which studied the laterality discrimination task and psychological variables have found a relationship between them, whereas others have not [51; 52; 53]. [PERSON] et al. [51] carried out a study on patients with neck pain that correlated the laterality discrimination task with the Fear Avoidance Belief's Questionnaire, without finding a statistically significant association. [PERSON] et al. [52] conducted a study in patients with complex regional pain syndrome (CRPS), where subjects only showed longer RTs for the upper lip lift than other types of facial expressions. This reflects a deficit in mental rotation tasks, especially for lower-facial-region pain expressions in CRPS, which may be related to the psychosocial aspects of pain. However, they did not further study the comprehensive intra- and interpersonal influences of these aspects further (they used the BDI scale to assess depression). In the research by [PERSON] et al. [53] in populations with neck pain and whiplash-associated disorders (WAD), they found no correlation between laterality discrimination and the post-traumatic stress symptoms scale. In this study, the laterality discrimination ability of patients with WAD was not impaired. Our study is the first to delve into the study of the relationship between psychological variables (depression, anxiety, fear of movement, and catastrophizing) and the laterality discrimination task in patients with FMS by performing a statistical correlation analysis. Why Do Psychological Variables Not Influence Limb Laterality Discrimination? A Neurophysiological Explanation  
According to the current scientific literature, relationships have been found between psychological variables and functional alterations in brain activity. Studies had found elevated catastrophizing to be associated with reduced left amygdala connectivity with the supramarginal gyrus and increased left amygdala connectivity with the hippocampus, dorsal striatum, paracingulate, and motor regions. It was concluded that resting-state functional connectivity between the left amygdala (a core emotion hub) and the inferior parietal lobe (involved in appraisal and integration of bodily signals, as well as attentional reorienting) explains associations between daily-life relevant catastrophizing and threat/safety learning [72]. In addition, catastrophizing has been found to affect the relationship between clinical pain and resting-state functional connectivity among the anterior cingulate cortex (ACC), dorsolateral prefrontal cortex (dlPFC), insula, and S1 [73]. With regard to fear-related movement, studies using fMRI showed that greater fear-related movement was positively associated with greater activity in the cerebellum-frontal network [74]. Increasedfunctional connectivity between the right dIPFC and the right anterior insular cortex (aIC) is also significantly associated with increased TSK [75]. Negative emotional stimuli (anxiety or depression) activate a broad network of brain regions, including the medial prefrontal (mPFC) and ACC cortices [76]. During limb laterality discrimination, the participants must accomplish a process of implicit motor imagery (the patients are not asked to carry out imagined movements; therefore, the participants are not aware of carrying out this process of motor imagery). Neuroimaging studies using positron emission tomography have shown that this process involves the activation of different brain areas. Immediately after the presentation of the visual stimulus, the attentional process involves an activation of the ACC and the attentional parietal areas contralateral to the stimulated hemisphere.