Decoding real and imagined actions: overlapping but distinct neural representations for planning vs. imagining hand movements

Patients with motor impairments learn to use brain-computer interfaces with training that consists of imagining what they want the effector to do. Neurologically intact individuals use motor imagery to improve performance of acquired skills and acquisition of new ones. The effect of motor imagery on real actions might be related to a shared neural representation of real and imagined actions. We explored whether areas implicated in hand actions and imagery tasks have a shared representation for planning and imagining hand movements. In a slow event-related functional magnetic resonance imaging (fMRI) paradigm participants (N=16) performed or imagined performing actions with the right dominant hand towards a centrally located object composed of a small shape attached on a large shape. The actions consisted of grasping the large shape, grasping the small shape, or reaching to the center of the object while fixating a point above the object. Each trial started with an auditory cue instructing participants about the task (Imagery, Movement) and the action (Grasp large, Grasp small, Reach-to-touch) to be performed at the end of the trial. A 10-s delay was followed by a go cue to perform or imagine performing the action (Go phase). Importantly, for both Imagery and Movement only the object, but not the hand, was visible to the participants. Using multi-voxel pattern analysis, we decoded action type in the planning phase of Movement tasks as well as in the Go phase of Imagery tasks in the anterior intraparietal sulcus (aIPS) and in early visual cortex (EVC). Moreover, we found cross-decoding between planning and imagery in aIPS, but not in EVC. Our results suggest a shared representation for planning and imagining specific hand movements in aIPS but not in low-level visual areas, such as the EVC. Therefore, planning and imagining actions have overlapping but not identical neural substrates.