Who Needs Emotions? The Brain Meets the Robot

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to the prefrontal cortex, which can then, on the basis of the current goals of
the organism and the recognition of the nature of the object, bias the AIP to
choose the affordance appropriate to the task at hand. Figure 12.1 gives only
a partial view of the FARS model, which also provides mechanisms for sequencing
actions. It segregates the F5 circuitry, which encodes unit actions
from the circuitry encoding a sequence, possibly the part of the supplementary
motor area called “pre-SMA” (Rizzolatti, Luppino, & Matelli, 1998).
The administration of the sequence (inhibiting extraneous actions, while
priming imminent actions) is then carried out by the basal ganglia (Bischoff-
Grethe, Crowley, & Arbib, 2003).
Bringing in the Mirror System
Further study revealed a class of F5 neurons that discharged not only when
the monkey grasped or manipulated objects but also when the monkey observed
the experimenter make a gesture similar to the one that, when actively
performed by the monkey, involved activity of the neuron (Rizzolatti,
Fadiga, Gallese, & Fogassi, 1995). Neurons with this property are called
“mirror neurons.” The majority of mirror neurons are selective for one type
of action, and for almost all mirror neurons there is a link between the effective
observed movement and the effective executed movement.
Two positron emission tomography (PET) experiments (Rizzolatti
et al., 1996; Grafton, Arbib, Fadiga, & Rizzolatti, 1996) were then designed
to seek mirror systems for grasping in humans. Grasp observation significantly
activated the superior temporal sulcus (STS), the inferior parietal
lobule, and the inferior frontal gyrus (area 45). All activations were in the
left hemisphere. The last area is of especial interest—areas 44 and 45 in the
left hemisphere of the human brain constitute Broca’s area, a major component
of the language mechanisms. Indeed, F5 is generally considered to be
the homolog of Broca’s area.
And on to Language
The finding that human Broca’s area contains a mirror system for grasping
led us (Arbib & Rizzolatti, 1997; Rizzolatti and Arbib, 1998) to explore the
hypothesis that the mirror system provided the basis for the evolution of
human language via seven stages:
1. Grasping.
2. A mirror system for grasping.