Ouch! My phantom leg jumps/hurts when you stab "my" virtual hand

Area of Science:

• Neuroscience
• Psychology
• Human Embodiment Studies

Background:

• Pain synaesthesia involves experiencing pain in response to observing or imagining another person in pain.
• Embodiment illusions, like the rubber-hand illusion, create a sense of ownership over an artificial limb.
• Lower-limb amputees were included to explore cross-modal sensory experiences and phantom limb phenomena.

Purpose of the Study:

• To investigate pain synaesthesia within an upper-limb embodiment paradigm.
• To explore whether lower-limb amputees with pain synaesthesia experience sensations in their phantom limbs.
• To further define the characteristics of synaesthesia for pain, including potential motor components.

Main Methods:

• A modified rubber-hand illusion was used to induce upper-limb embodiment.
• Lower-limb amputees and non-amputees participated as subjects and controls.
• Threatening stimuli and high-frequency stimulation were applied to the embodied hand, with participants reporting sensations in their phantom limbs.

Main Results:

• All subjects experienced topographic illusory sensations during the embodiment task.
• Lower-limb amputee pain synaesthetes reported pain or motor responses in their phantom legs when the embodied hand was threatened or stimulated.
• No association was found between pain synaesthesia and empathy scores.

Conclusions:

• Synaesthesia for pain may involve a motor component, including avoidance and withdrawal actions, in addition to sensory experiences.
• The findings suggest that engaged motor systems and hyper-vigilance to threatening stimuli contribute to phantom limb pain in synaesthetes.
• This research expands the understanding of pain synaesthesia and its manifestation in phantom limb phenomena.