MOTOR FACILITATION DURING ACTION OBSERVATION - A MAGNETIC STIMULATIONSTUDY

1. We stimulated the motor cortex of normal subjects (transcranial mag netic stimulation) while they 1) observed an experimenter grasping SD- objects, 2) looked at the same 3D-objects, 3) observed an experimenter tracing geometrical figures in the air with his arm, and 4) detected the dimming of a light. Motor evoked potentials (MEPs) were recorded f rom hand muscles. 2. We found that MEPs significantly increased during the conditions in which subjects observed movements. The MEP pattern reflected the pattern of muscle activity recorded when the subjects ex ecuted the observed actions. 3. We conclude that in humans there is a system matching action observation and execution. This system resemble s the one recently described in the monkey.