Monkey electrophysiological and human neuroimaging studies
indicate the existence of specialized neural systems for the
perception and execution of actions. To date, the dynamics of
these neural systems in humans have not been well studied. Here,
we investigated the spatial and temporal behavior of human neural
responses elicited to viewing motion of the face, hand, and
body. Scalp event-related potentials (ERPs) were recorded in
20 participants viewing videotaped mouth (opening, closing),
hand (closing, opening), and body stepping (forward, backward)
movements. ERP peak differences within the movements of each
body part were compared using topographical maps of voltage,
voltage difference, and Student's t-test at ERP
peak latencies. Predominantly temporoparietal negative ERPs
occurred to motion of all body parts within 200 ms postmovement
onset. Hand closure elicited a significantly greater negativity
than opening, particularly in the left hemisphere. Vertex positive
ERPs within 300 ms postmovement onset were elicited to hand
and body motion. A significantly greater positivity occurred
for the body stepping forward relative to stepping backward.
The ERP topography was consistent with observed activation foci
in human neuroimaging studies. Our data indicate that the neural
activity of a system dedicated to the perception of high-level
motion stimuli can rapidly differentiate between movements across
and within body parts.