Anticipatory effects of multi-step action: a fMRI study

Theway we grasp objects (e.g., over- vs. under-hand) depends on sensoryinformation concerning the state of the body (e.g., posture) and the targetobject (e.g., location, orientation, form), as well as prediction of forthcomingtask demands (e.g., intended rotation of the target object). This abilityto predict the consequences of our own multi-step actions relies on theuse of internal models and reflects the temporally-extended nature ofinternal action representations (Johnson-Frey et al., 2004). Previous workshowed that a parieto-frontal circuit is involved in the transformation ofsensory information into a motor plan for grasping (Johnson et al., 2002).Are these same circuits involved in grip selection decisions influenced bypredicted demands of a forthcoming object rotation? Event-related fMRIwas used to ask this question in 15 healthy, right-handed adults. Participantswere asked to select the most comfortable way (over- vs. underhand)to grasp a handle using either hand with the intention of rotating itin a cued direction or to only grasp the handle. Even if movement executionwas not required, grip preferences were significantly affected by thepredicted demands of handle rotation. Preparation for an imagined anticipatorygrip selection activates the same parieto-frontal networksinvolved in both the rotation and no-rotation conditions. Specifically,brain regions involved are bilateral dorsal premotor cortex (dPMC), bilateralintraparietal sulcus (IPS) and cerebellum. Further, fMRI data suggestthat prediction of these demands is accomplished in the very same neuralstructures as grip selection based on available sensory information.