## 3 Motor and Somatosensory Disturbances in COFP  
As said earlier, somatosensory alterations in terms of epicritic and discriminative sensitivity are present in COFP patients. Normal _tactile acuity_ depends on a competent epicritic sensory system and an adequate central processing of the efferent signals. For example, in chronic neck [40], low back pain [41] and complex regional pain syndrome [42], activity levels are changed in the somatosensory cortex (S1). In comparison with healthy subjects, TMD patients suffering from myofascali pain have a decreased S1 grey-matter volume as defined by structural MRI, which may be expressed in a reduced sensory function [43], supported by the results obtained at the two-point discrimination test, which indicates a decrease in the discriminative threshold [34]. Tactile acuity depends strictly on the correct functioning of the somatosensory system; thus, the two-point discrimination test has been suggested as a good assessment tool to evaluate S1 area and the somatosensory function [34]. Another aspect found related to the altered somatosensory system is the _auditory acuity_, which consists on the localization of sounds, pitches and muting of background noises [44]. This ability may be \"blurred\" during chronic pain, since there are sensory convergence points at the thalamus and brainstem centers, such as the locus coeruleus. This can lead to difficulty at discrimination of different noises, hyperacusis and tinnitus [45; 46]. Clinically it is observed that in face-pain auditory acuity disturbances appears together with changes in tactile acuity and a left/right judgment task [47]. Reduced accuracy and prolonged response time in patients with head and face pain when performing the laterality judgment task have been found [48; 49; 50]. _Laterality recognition_ or left/right judgment is the ability to recognize that a part of the body belongs to the left or the right side of the body; it is needed for conscious access to the content of the intention of a movement, which is usually performed unconsciously during a normal motor planning process of the movement preparation [51; 52] and differs from motor execution, which is related with the (pre)motor cortex [53]. To be able to judge the laterality of a picture it is believed that the subjects mentally needs to rotate an internal representation of their own body part examined to mentally match it with the presented one. This process, therefore, would be influenced by the motor and somatosensory areas, in terms of recognition of the position of the body parts in space (proprioception) and the visual stimuli [54]; indeed, when the laterality discrimination is in conflict, it may be associated with a distorted proprioception cortical scheme of the body [55]. In fact, neural activity has been found in the sensorimotor, posterior parietal and occipital areas during the lateral recognition task [56]. Moreover, the activity of the superior precentral sulcus and intraparietal sulcus areas, predominantly on the left, were associated with accuracy of the imagery task performance [57]. All of these findings help to explain what could be happening at the CNS when performing tasks that relay on implicit motor imagery. Finally, it is important to mention that _motor control disturbances_ are frequent in COFP patients. Face pain or induced nerve blocks or (long-term) anesthesia of the orophnx may be associated with impaired facial motor, tongue and larynx function expressed by impaired facial expression, speech and swallowing, which may be associated with changed facial motor cortex neuroplasticity [58]. To be able to perform an accurate movement, precise sensory information is required for an efficient and adaptive motor function [59]. In this line, activity at primary sensory and motor areas, parietal operculum, anterior and posterior cerebellum, caudal premotor areas and fronto-parietal areas has been found related to movement execution [57].