Decoding intransitive actions in primary motor cortex using fMRI: toward a componential theory of 'action primitives' in motor cortex.

Multivoxel pattern analysis (MVPA) over functional MRI data can distinguish neural representational states that do not differ in their overall amplitude of BOLD contrast. Here we used MVPA to test whether simple intransitive actions can be distinguished in primary motor cortex. Participants rotated and flexed each of their extremities (hands and feet) during fMRI scanning. The primary motor cortex for the hand/wrist was functionally defined in each hemisphere in each subject. Within those subject-specific ROIs, we found that the average amplitude of BOLD contrast for two different movements of the contralateral hand (rotation, flexion) were higher than for the ipsilateral hand, as well as movements by both feet; however, there was no difference in amplitude between the two different types of movements for the contralateral hand. Using multivoxel pattern analysis (linear correlation), we were able to distinguish the two movements for the contralateral hand. These findings demonstrate that simple intransitive actions can be distinguished in primary motor areas using multivoxel pattern analysis.