6.3.2. How It Works (2)
These cells usually respond to stimuli coming from the same region of space: a cell might respond to a finger being touched and to a light close to that finger. The most fascinating thing about some of these cells is that when the monkey moves its arm around, the region of visual space to which the cell responds also moves. Such cells are thought to represent the space that is close to our bodies. It is particularly important for us to merge together information from our different senses about this, our peripersonal space, which is within our immediate reach.
Spence and colleagues5 gave a patient with a split brain (whose left and right hemispheres were disconnected [Hack #69] ) the same touch and vision distraction task as described earlier. The patient behaved as normal with his right hand in the right side of space. That is, the lights on the right side produced the greatest interference. In this case, both touch and vision arrived first at the left hemisphere of his brain. When he moved his right hand over to the left side of space, we would now expect his right hand to be disrupted most by the nearby lights on the left side. However, the lights on the right side still interfered most with touches to the right hand (despite being on the opposite side of space to his hand). In this case, the lights on the left arrived first at the right hemisphere and touches to the right hand at the left hemisphere, and without connections between the two halves of his brain, he was unable to update. This shows how important the long-range connections between distant cortical areas of the brain are for remapping.
The fact that the updating of our posture and remapping of our visual-tactile links appears to occur before conscious awareness could explain why we take them for granted in our everyday lives. Some people seem to find such processing easier than others. Could experience affect these abilities? Might drummers who spend many hours playing with their arms crossed find remapping easier?
6.3.3. End Notes
Maravita, A., Spence, C., & Driver, J. (2003). Multisensory integration and the body schema: Close to hand and within reach. Current Biology, 13, R531-R539.
Yamamoto, S., & Kitazawa, S. (2001). Reversal of subjective temporal order due to arm crossing. Nature Neuroscience 4, 759-765.
Shore, D. I., Spry, E., & Spence, C. (2002). Confusing the mind by crossing the hands. Cognitive Brain Research, 14, 153-163.
Kitazawa, S. (2002). Where conscious sensation takes place. Consciousness and Cognition, 11, 475-477.
Spence, C. J., Kingstone, A., Shore, D. I., & Gazzaniga, M. S. (2001). Representation of visuotactile space in the split brain. Psychological Science, 12, 90-93.
Ellen Poliakoff
Taken from : Mind Hacks
