Action recognition in the premotor cortex. By Vittorio Gallese, Luciano Fadiga, Leonardo Fogassi and Giacomo Rizzolatti. Brain 1996: 119; 593-609.

Abstract

Dogma—following Karl Brodmann's studies from the early 1900s—teaches that the agranular cortex of the primate frontal lobe consists of area 4 containing giant pyramidal neurons and area 6 which does not; to which can be added a functional classification of primary (area 4 and the lateral part of area 6) and supplementary motor cortex (the medial component of area 6). But this is overly simplified and a variety of anatomical methodologies (immunohistochemistry, neurochemistry and hodology, inter alia ) have revealed a mosaic of structures in the agranular frontal region to which distinct functional properties can be assigned. The classical view of the premotor cortex as the orchestrator strictly of motor control is now supplemented by evidence for its role in cognitive and behavioural functions—coding space, decoding the intrinsic properties of objects and contributing to associative learning. But special attention should be paid to F5, lying immediately caudal to the inferior arm of the arcuate sulcus, and concerned with hand and mouth movements in its dorsal and ventral portions, respectively. The hand neurons discharge during goal-directed movements, such as specific types of grasping, tearing, manipulating and holding; and they become active when 3D objects that are the same size as those activating that neuron during grip, are seen but not moved. Now the Italian team describe simian neurons that discharge not only with movement but also when the monkey observes meaningful movements made by the experimenter. They also provide a detailed description of the properties of these cells—designated ‘mirror neurons’—and some clinical implications arising from their discovery. Their method is to record from the rostral inferior part of area 6 in one or both hemispheres of two monkeys trained to observe and then reach for food and other objects of differing sizes and shapes—movements that require precision grip (index finger and thumb), …