6.3.2. How It Works
Charles Spence and colleagues1 have shown that we can update how we bind together vision and touch when we cross our hands over. They asked people to attend to and make judgments about vibrations that they felt on their hands, while ignoring lights presented at the same time. When feeling a vibration on their right hand, the lights on the right sideclosest to their right handinterfered much more (made people slower to carry out the task), than lights on their left side. That is, we tend to bind together vision and touch when they come from the same part of the outside world. So what happened when they crossed their hands over? The interaction between vision and touch changed over: lights over on the left side of their body were now closest to their right hand and interfered more with the right hand than the lights over on the right side. So, when we change where our hands are in space, we integrate different sets of visual and tactile signals.
But remapping can sometimes fail, even without intertwining our fingers. Two recent experiments2,3 have shown that we are particularly bad at dealing with information in quick succession. If your hands are in their usual uncrossed position and you are asked to judge which hand is touched first, it is relatively easy. On the other hand, if your hands are crossed, the same task becomes much more difficult. This difficulty in coping with stimuli presented in quick succession, suggests that remapping can be a time-consuming process. Shigeru Kitazawa4 has suggested we do not become conscious of a sensation on a particular part of our skin and then attribute it to a particular location in space. Rather, our conscious sensation of touch seems to be delayed until we can identify where it’s coming from.
So where in the brain do we remap and update our connections? Some clues have come from investigating the monkey brain. Cells that respond to both vision and touch have been found in the parietal and premotor cortexhigher areas, upstream of the somatosensory [Hack #12] and visual areas, which deal mainly with touch and vision alone.
The parietal cortex [Hack #8] contains areas that are concerned with visual and spatial representation. The premotor cortex is involved in representing and selecting movements
Taken from : Mind Hacks
