Ethics

I think, therefore my tools are are part of my corporeal body (Reiner)

By Peter Reiner

Not so long ago, I spent a pleasant morning watching my friend Fred Stevens move and shape an impressive amount of earth with his backhoe.  Most remarkable was the delicate agility with which he used his mechanical arm.  When he was finished, I asked him what he thought about when he moved the arm.  Fred's first answer was that he had never really considered that question.  Once he thought about it for a second or two, he told me that there was really no explicit thinking involved; he merely looked at the object, thought about moving the mechanical arm to it, and it all just happened.

Fred's experience is a salient example of how our body image can extend beyond our corporeal body.  A new paper by Umilta et al. in PNAS entitled "When pliers become fingers in the monkey motor system" strongly suggests that Fred's experience is deeply encoded in his motor cortex.  The authors recorded neurons in primary motor cortex (F5 and F1) and found that when monkeys are trained to use a pair of pliers, the same pattern of activity that is seen with hand grasping is observed when pliers are used for grasping. In their discussion they conclude that,

"the end effect of training has been the transfer of the temporal discharge pattern that controls hand grasping to the tool use, as if the tool were the hand of the monkey and its tips were the monkey?s fingers."

These observations have substantial implications for theories of how we perceive of the self; while the concept can be directly traced back to the musings of William James, our understanding of the neuronal basis of self perception has been evolving quite handsomely of late, including such phenomena as the 'rubber hand illusion' (in which simultaneous stroking of a subjects hand and a rubber hand in the field of vision causes the fake hand to be attributed to one's own body) and a remarkable study which used virtual reality to extend the sense of self to a virtual own body.  Umilta et al.'s observations in monkeys represent a major stride in moving the classical concept of body schema from a theoretical construct to one defined in discrete neurobiological terms.  Such observations provide strong support for the notion that our sense of self is directly embodied in the neural apparatus.

Full post as published by Neuroethics and Law on February 14, 2008 (boomark / email).