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Previous functional magnetic resonance imaging (fMRI) research on action observation has emphasized the role of putative mirror neuron areas such as Broca's area, ventral premotor cortex, and the inferior parietal lobule. However, recent evidence suggests action observation involves many distributed cortical regions, including dorsal premotor and superior parietal cortex. How these different regions relate to traditional mirror neuron areas, and whether traditional mirror neuron areas play a special role in action representation, is unclear. Here we use multi-voxel pattern analysis (MVPA) to show that action representations, including observation, imagery, and execution of reaching movements: (1) are distributed across both dorsal (superior) and ventral (inferior) premotor and parietal areas; (2) can be decoded from areas that are jointly activated by observation, execution, and imagery of reaching movements, even in cases of equal-amplitude blood oxygen level-dependent (BOLD) responses; and (3) can be equally accurately classified from either posterior parietal or frontal (premotor and inferior frontal) regions. These results challenge the presumed dominance of traditional mirror neuron areas such as Broca's area in action observation and action representation more generally. Unlike traditional univariate fMRI analyses, MVPA was able to discriminate between imagined and observed movements from previously indistinguishable BOLD activations in commonly activated regions, suggesting finer-grained distributed patterns of activation.

The processing of Navon figures (Navon, 1977), i.e.,hierarchical letter stimuli, has been studied in experimentalsettings for many years. In particular, they have been studiedin the context of visual hemifield studies and yielded aninteraction between hemifield and whether a target is at thelocal or global level, with a right hemisphere advantage forthe global level, and a left hemisphere advantage for thetargets at the local level (Sergent, 1982). This is a ventralstream process, however, and we were interested in whetherthere might be a similar interaction for hierarchical motionstimuli, presumably a dorsal stream process. Hence wedeveloped a series of dynamic geometric Navon figures inorder to study global/local rotation processing. These figuresconsist of a global figure (a triangle or a square) made up oflocal figures (also triangles or squares). Both global and localfigures can rotate in either clockwise or counterclockwisedirections independently. We found that there is no right orleft visual field perceptual advantage for either the global orlocal levels of these figures. However, curiously enough, wefound that there is a significant processing advantage forclockwise motion compared to counterclockwise motion. Wealso found a highly significant interaction between thedetection of a particular rotational motion and the presence orabsence of that motion in the figure being examined. Finally,our data strongly support the Global Precedence Hypothesiswhich says that people generally tend to focus on the globalproperties of an object before local properties and thatprocessing proceeds in a global-to-local direction.