Tool Use Is Just a Trick of the Mind
By Michael Balter
ScienceNOW Daily News
28 January 2008

Don't take that hammer for granted. Using tools may seem like second
nature, but only a few animals can master the coordination and mental
sophistication required. 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.
Primates, with their four flexible fingers and opposable thumbs, have
a highly evolved ability to grasp and manipulate objects. Previous
research has shown that many of these actions are controlled by an
area of the brain called F5. As the hand opens and closes to grasp an
object, neurons in area F5 fire in a predictable sequence. In the
parlance of neuroscientists, the neurons are "coded" to control the
hand movements. When a primate learns to use a tool, its brain must
code neurons not only to move the hand but also to make the tool
manipulate an object, a much more cognitively complex task.

To investigate how the brain performs this sleight of hand, a team led
by neuroscientist Giacomo Rizzolatti of the University of Parma in
Italy recorded brain activity in two macaque monkeys. Each was trained
for 6 to 8 months to grasp items of food with pliers. The team
documented the activity of 113 neurons in F5 and in a brain area
called F1, which has also been implicated in the manipulation of
objects. 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.

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." As for how the same neurons could
affect both the opening and the closing of the hand, the team
speculates that they may be connected with other sets of neurons that
more directly control these movements. The authors also point out that
area F5 is rich in so-called mirror neurons, a type of nerve cell
discovered earlier by Rizzolatti that fires both when a primate
performs an action and when it observes another individual doing the
same thing (ScienceNOW, 13 July 2007). Mirror neurons in F5, the
authors suggest, may be involved in this transfer process as a monkey
learns how to use a tool by watching others.

The findings "fairly clearly show that monkey tool use involves the
incorporation of tools into the body schema, literally as extensions
of the body," says Dietrich Stout, an archaeologist specializing in
tool use at University College London. Scott Frey, a neuroscientist at
the University of Oregon, Eugene, says that in humans, this ability to
represent tools in the brain, combined with a capacity for innovation,
"was no doubt a fundamental step in the development of technology."

Source: Science
http://sciencenow.sciencemag.org/cgi/content/full/2008/128/2?etoc