Michael Balter writes in Science NOW Daily News, Tool Use Is Just a Trick of the Mind, about recent research led by Italian neuroscientist, Giacomo Rizzolatti of the University of Parma, head of the team responsible for discovering ‘mirror neurons’ (which I’ve been banging on about for a while, here and here). Rizzolatti’s team was looking at how primate brains managed to do the same tasks with hands and with tools. As Balter describes the research: ‘So how did primates learn to use tools in the first place? A new study in monkeys suggests that the brain’s trick is to treat tools as just another body part.’
Two monkeys were trained from six to eight months to grasp food with pliers. Then the team documented the activity of 113 neurons in areas F5 and F1, a region linked to manipulating objects. How did the monkeys’ motor areas act when using the tools?
The researchers first established the brain’s firing sequence when the monkeys grasped only with their hands. The experiment was then repeated while the monkeys used normal pliers that required first opening the hand and then closing it to grasp the food. The same neurons fired in the same order. Remarkably, the same neurons also fired, in the same order, when the monkeys used “reverse pliers” that required them to close their fingers first and then open them to take the food, the team reports online today in the Proceedings of the National Academy of Sciences.
Balter summarize their conclusions: ‘Rizzolatti and his co-workers conclude that when learning to use a tool, the pattern of neuronal activity is somehow transferred from the hand to the tool, “as if the tool were the hand of the monkey and its tips were the monkey’s fingers.”‘
One of my favorite bloggers, John Hawks, has some comments on the tool-related story. Hawks is not terribly caught up in the excitement surrounding mirror neurons (fair enough; some folks are saying some pretty outrageous stuff). As he puts it:
it would be far harder to build a brain capable of learning by observation if some of the same neurons weren’t involved in both observing and doing. Likewise, it would be a lot more complicated to learn to use a tool if the same neurons weren’t involved in planning the action using the hands compared to planning the action using a tool. So there ought to be a whole lot of neural overlap.
So, Hawks is not buying the hype around ‘mirror neurons,’ but he does find the discovery that the hand-tool re-mapping is happening in the same motor region of the brain where mirror neurons are located interesting.
Now, the fact that these are in a particular region (F5) is structurally important, since this region has other functions whose interrelations aren’t obvious logical necessities. And the fact that tool use is another example of a behavior that maps onto this region (at least in terms of learning) is also pretty important. It will be nice to see whether this “transfer” ability — from hand to tool — is a primate feature, or if instead it may be more widely distributed.
For me, though, the import of the material Rizzolatti produces on tool use is less the fact that they are proximal to (or even overlapping with) mirror neurons in the same regions of the brain. After all, many areas of the brain get co-opted into different functional networks in order to accomplish different functions, as Hawks puts it, even functions that don’t have ‘obvious logical’ relations (the brain works in weird ways). Rather, the interesting thing is that there’s significant material evidence in primates for something observed phenomenologically — the extension of the body’s sensory functions through tools — and some suggestion of a mechanism through which it is accomplished (or at least evidence that makes some explanations less plausible than others).
That is, phenomenologists starting with Maurice Merleau-Ponty have taken the use of a cane by the blind as one example of the way that the experiential body can be extended beyond the skin. Just as the blind man with a cane can perceive at the tip of the cane, monkeys appear to be able to perceive through, or at least to act in an extended fashion through, a pliers if trained to do so. Phenomenologically, we know that tools can become extensions of the body, so that part of the Parma group’s research is not too surprising.
But what we gain some intriguing insights into through this research is the elegant and uncanny way in which the brain may accomplish this. It doesn’t have a special ‘tool use module,’ it doesn’t create a new system, but rather, it simply reassigns the same neurons that it would use to grab things with a hand to pliers duty. Although logically, these may appear to be very different tasks, the brain learns to do them the same way, suggesting that the ‘body image’ in the brain is unstable, able to be reconfigured for certain tasks (‘grasping’ is one set of finger motions changing into ‘grasping’ is another set, depending upon whether or not I have a tool).
Of course, human brains and monkey brains are not identical, and like Hawks, I don’t want to be seen as buying into the type, but the data is certainly suggestive, leading me to think that the idea of a tool-use part of the brain is less likely than a tool-use ability to write new motor patterns onto the same parts of the brain, especially associated with certain functions.
(Thanks to Daniel for pointing this article out to me. As usual, he’s finding new stuff all over the place.)