Where am I?

Radio Lab had a great hour production called Where Am I?, all about how mind and body collaborate to determine where you and all your assorted parts are in space and how that can sometimes get out of whack. Audio is available for streaming and download, and well worth the listen.

It reminds me of the “That’s my hand!” illusion, where you can give someone the uncanny feeling that an obviously-plastic severed rubber hand is actually their own by simply hiding their real hand from view and then simultaneously touching each hand in the same spot at the same time. After about 20 seconds of such touching the illusion kicks in, and is a wonderfully eerie feeling. They have a station for trying this out at the SF Exploratorium, but my first introduction to it was from reading a recent study where scientists induced the illusion while the subject was being scanned by an MRI. What they found was that the illusion corresponds with activity in the premotor cortex, a part of the brain that receives input both visual and touch information, implying that we build our idea of where different parts of our body is in space by correlating our own sense of touch with what we can detect with our other senses. (They also have a more recent study showing that it’s not just vision combined with touch — you can get the same effect bindfolded by making the subject think she’s touching her left hand with her right when actually she’s touching the rubber hand.)