Functional Anatomy of the Observation and Imagination of Unimanual and Bimanual Actions

D. Kingsley, A. Zaman, E. Franz, N. Roberts Department of Psychiatry, University of Liverpool, Liverpool, United Kingdom, MARIARC, University of Liverpool, Liverpool, United Kingdom, Walton Centre for Neurology and Neurosurgery (WCNN), Liverpool, United Kingdom, Department of Psychology, University of Otago, Dunedin, New Zealand Introduction Several studies have examined the functional equivalence of execution, action observation and imagination of motor actions (Grezes and Decety 2001), finding neural overlap associated with these different tasks, notably in SMA, premotor cortex and superior parietal lobe. This makes sense in terms of the known role of these neural areas for generating a motor plan appropriate to an intended goal. Recent studies have also identified an important link between properties of action observation and action execution, with the discovery of mirror neurons (MNs) (Gallese et al 1996, Rizzolatti et al 1996). MNs, located in area F5 in the ventral premotor cortex of the monkey, have shown increased firing patterns both when an animal manipulates objects and when an animal observes similar object manipulations produced by a human experimenter (Rizzolatti et al. 1998). The human homologue of F5 is believed to be Broca's area located in the left inferior frontal gyrus (IFG) (Passingham 1993). Neuroimaging studies on humans have demonstrated IFG activation during execution, observation, and imagination of unimanual hand actions (Shlaug et al 1994, Decety et al. 1994, Iacaboni 1999). However, possible differences in IFG related to unimanual versus bimanual actions have had limited description. A recent study by Nair et al (2003) used fMRI to study the neural activity of imagined and executed unimanual and bimanual finger movements. Activation in bilateral superior parietal lobules suggested an important role of these areas in coordinating bimanual sequences, but the study found no evidence of IFG activity. The present study took the next step in identifying the neural correlates of bimanual (and unimanual) action observation and imagination, using ecologically-valid goal-directed skilled hand movements as stimuli that are likely to elicit MN (IFG) activity.