Hack 64. Mold Your Body Schema (3)
These disorders suggest that the brain’s system for representing body schema can operate (and be damaged) independently from the sensory feedback provided by the body itself. Sensory feedback must play a role of course, and it seems that it is used to update and correct the model to keep it in check with reality. In some situations, like the ones in the previous exercises, one type of sensory feedback can become out of sync with the others, leading to the experience of mild confusion of the body schema.
Ramachandran and Rogers-Ramachandran applied an understanding of the relationship between sensory feedback and the body schema to create a novel method to help people with phantom-limb pain.2 They used a mirror to allow people who were experiencing a phantom limb to simulate visual experience of their amputated hand. In the same way as the earlier exercise, the image of their amputated hand was simply a reflection of their remaining hand, but this simulated feedback provided enough information to the brain so they felt as if they could control and move their phantom limb. In some cases, they were able to “move” their limb out of positions that had been causing them real pain.
An fMRI [Hack #4] study by Donna Lloyd and colleagues3 might explain why visual feedback of body position might have such a dramatic effect. They scanned people while they were receiving tactile stimulation to the right hand, either while they had their eyes closed or while they were looking directly at their hand. When participants had the opportunity to view where they were being stimulated, activation shifted dramatically, not only to the parietal area, known to be involved in representing the body schema, but also to the premotor area, a part of the brain involved in planning and executing movements. This may also explain why the earlier exercises confuse our body schema enough to make accurate movement seem difficult or feel unusual. Visual information from viewing our body seems to activate brain areas involved in planning our next move.
6.4.3. End Notes
Ramachandran, V. S., & Blakeslee, S. (1998). Phantoms in the Brain: Human Nature and the Architecture of the Mind. London: Fourth Estate.
Ramachandran, V. S., & Rogers-Ramachandran, D. (1996). Synaesthesia in phantom limbs induced with mirrors. Proceedings of the Royal Society of London. Series B. Biological sciences, 263(1369), 377-386.
Lloyd, D. M., Shore, D. I., Spence, C., & Calvert, G. A. (2002). Multisensory representation of limb position in human premotor cortex. Nature Neuroscience, 6(1), 17-18.
6.4.4. See Also
Tool use extends the body schema with its reach, altering the map the brain keeps of our own body: Maravita, A., & Iriki, A. (2004). Tools for the body (schema). Trends in Cognitive Sciences, 8(2), 79-86.
Vaughan Bell
Taken from : Mind Hacks
