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Abstract:
The ability to categorize actions is critical for
interacting in complex environments. Previous studies have
examined the neural correlates of categorization using
static stimuli. The goal of our study was to investigate
the neural substrates that mediate learning of complex
movement categories in the human brain. We used novel
dynamic patterns that were generated by animation of an
artificial skeleton model and presented as point-light
displays. We created prototypical stimuli that differed in
the spatial arrangement of their segments and their
kinematics. Intermediate stimuli between the prototypes
were generated by a weighted linear combination of the
prototypical trajectories in space-time. We compared fMRI
activations when the observers performed a categorization
vs. a spatial discrimination task on the same stimuli. In
the categorization task, the observers discriminated
whether each stimulus belonged to one of four prototypical
classes. In the spatial discrimination task, the observers
judged whether each stimulus was rotated (or translated)
leftwards vs. rightwards. These tasks were matched for
difficulty based on the observers? Performance during a
practice session. We observed significantly stronger fMRI
activations for the categorization than the spatial
discrimination tasks in the dorsal, inferior parietal and
the medial, inferior frontal cortex, consistent with
previous findings on the categorization of static stimuli.
Interestingly, we also observed activations in visual motion
areas (V3a, hMT+/V5), higher-order motion areas in the
intraparietal sulcus (VOIPS, POIPS, DIPSM, DIPSA) and
parieto-frontal areas (supramarginal gyrus, postcentral
gyrus, ventral and dorsal premotor cortex) thought to be
involved in action observation and imitation. These
findings suggest that categorization of complex dynamic
patterns may modulate processing in areas implicated in the
analysis of visual motion and actions.
