Pain and the body schema: Evidence for peripheral effects on mental representations of movement

Abstract

Some accounts of body representations postulate a real-time representation of the body in space generated by proprioceptive, somatosensory, vestibular and other sensory inputs; this representation has often been termed the 'body schema'. To examine whether the body schema is influenced by peripheral factors such as pain, we asked patients with chronic unilateral arm pain to determine the laterality of pictured hands presented at different orientations. Previous chronometric findings suggest that performance on this task depends on the body schema, in that it appears to involve mentally rotating one's hand from its current position until it is aligned with the stimulus hand. We found that, as in previous investigations, participants' response times (RTs) reflected the degree of simulated movement as well as biomechanical constraints of the arm. Importantly, a significant interaction between the magnitude of mental rotation and limb was observed: RTs were longer for the painful arm than for the unaffected arm for large-amplitude imagined movements; controls exhibited symmetrical RTs. These findings suggest that the body schema is influenced by pain and that this task may provide an objective measure of pain.

Influence of imagined posture and imagery modality on corticospinal excitability

“…Patients have longer reaction times when the hand, which must be mentally rotated, corresponds to the limb in pain [45], in agreement with evidence for anatomical 'constraints' during mental rotation of body parts [39]. Inflow in this context refers to initial sensory information conveying sensation and proprioception [44] rather than muscular inflow [22,23].…”

Pain, body, and space: What do patients with complex regional pain syndrome really neglect?

“…After prism adaptation, visual body midline judgments erred in the opposite direct, towards the side of the unaffected side [35]. In contrast to previous studies [5][6][7]16,24,25,34], these latter experiments [35,36,38] demonstrated that the side for which there is a diminished representation of space does not always correspond to that of the affected limb.…”

“…pain, swelling and skin changes in the affected limb, some of these patients tend to ignore or have an altered mental representation of the affected limb (somatoparaphrenia); movements are smaller and less frequent (hypokinesia), and take conscious effort [5][6][7]16]. They have difficulties recognizing their own limb [24] and estimating its position [17], its size [25] and its orientation [34].…”

Does thumb posture influence the mental rotation of hands?

“…The use of motor imagery strategies in mental rotation of hands has been corroborated by many authors [e.g., 9,14,23]. Evidence for motor imagery being involved in mental rotation of body parts comes from clinical cases [e.g., 3,4,12,16] and from neuroimaging studies (see [22] for review). Further studies proposed that mental rotation tasks can be solved by different strategies, involving visual imagery or motor imagery [2,11], and that the choice of strategy might depend on the type of stimuli [21] or the instructions [20].…”