Atypical influence of biomechanical knowledge in Complex Regional Pain Syndrome-towards a different perspective on body representation

Abstract

Part of the multifaceted pathophysiology of Complex Regional Pain Syndrome (CRPS) is ascribed to lateralized maladaptive neuroplasticity in sensorimotor cortices, corroborated by behavioral studies indicating that patients present difficulties in mentally representing their painful limb. Such difficulties are widely measured with hand laterality judgment tasks (HLT), which are also used in the rehabilitation of CRPS to activate motor imagery and restore the cortical representation of the painful limb. The potential of these tasks to elicit motor imagery is critical to their use in therapy, yet, the influence of the body’s biomechanical constraints (BMC) on HLT reaction time, supposed to index motor imagery activation, is rarely verified. Here we investigated the influence of BMC on the perception of hand postures and movements in upper-limb CRPS. Patients were slower than controls in judging hand laterality, whether or not stimuli corresponded to their painful hand. Reaction time patterns reflecting BMC were mostly absent in CRPS and controls. A second experiment therefore directly investigated the influence of implicit knowledge of BMC on hand movement judgments. Participants judged the perceived path of movement between two depicted hand positions, with only one of two proposed paths that was biomechanically plausible. While the controls mostly chose the biomechanically plausible path, patients did not. These findings show non-lateralized body representation impairments in CRPS, possibly related to difficulties in using correct knowledge of the body’s biomechanics. Importantly, they demonstrate the challenge of reliably measuring motor imagery with the HLT, which has important implications for the rehabilitation with these tasks.

Prior knowledge biases the visual memory of body postures

“…Furthermore, if motor experience plays a role in the visual memory of body postures, we might also expect an influence of commonly self-experienced postures. 42 , 43 Accordingly, factors that influence an individual’s motor experience, including age, 44 obesity, 45 pain, 46 , 47 and other clinical conditions, could potentially influence the biases reported here.…”

Prior Knowledge Biases the Perception of Body Postures

“…Furthermore, if motor experience plays a role in the visual memory of body postures, we might also expect an influence of commonly self-experienced postures 42,43 . Accordingly, factors that influence an individual's motor experience, including age 44 , obesity 45 , pain 46,47 , and other clinical conditions, could potentially influence the biases reported here.…”

The self, its body and its brain

“…For example, people with schizophrenia often have disrupted body awareness 4 and people with eating disorders might have impaired multisensory processing 5 or experience reduced pleasure from touch 6 . Moreover, physical conditions, such as chronic pain and changes in the body that occur as a result of pregnancy and childbirth are also thought to be related to changes in our bodily experience 7 , 8 .…”