The importance of ventral premotor cortex for body ownership processing.

Editor's Note: These short, critical reviews of recent papers in the Journal, written exclusively by graduate students or postdoctoral fellows, are intended to summarize the important findings of the paper and provide additional insight and commentary. For more information on the format and purpose of the Journal Club, please see Review of Zeller et al. The perception of one's own hand is an eminently coherent impression: proprio-ceptive, tactile, and visual inputs usually correspond perfectly. Current theoretical frameworks postulate that this multi-modal integration is required for a feeling of ownership of the body, and is ultimately accompanied by a sense of self. This might seem trivial; but actually, it is necessary for the discrimination between one's own body and its surroundings, as well as the distinction between self and other. However, how the brain manages the feeling of body integrity with all its parts remains an open question. The major mystery of body perception can be expressed by this simple question: Why do I perceive my hand as belonging to me? The ventral premotor cortex (PMv) seems to play a key role in this integrative process. Early studies showed that multimodal receptive fields in the PMv of primates appear to combine visual and somatosensory input to locate one's own limb in peripersonal space (Graziano et al., 2000). Botvinick and Cohen (1998) complemented these findings by showing that a visible rubber hand is experienced as belonging to the subject's body when both the rubber hand and the subject's own hand are stimulated congruently in terms of location and temporal consistency. The authors assumed an involvement of the PMv in this so-called rubber hand illusion (RHI), which was confirmed by Ehrsson et al. (2004) using functional magnetic resonance imaging, indicating that activity in PMv is positively correlated with the experience of body ownership. However, it remained unclear whether multisensory integration within the PMv is necessary to generate a feeling of body ownership, or whether the neuronal processes in the RHI paradigm are unique and different from usual body perception processes. This question was recently examined by Zeller and colleagues (2011). The authors assessed the experience of illusory ownership of an artificial limb in patients suffering from circumscribed unilateral ischemic strokes, which damaged the basal ganglia and periventricular white matter, affecting the putamen, precentral and postcentral cortices, and the thala-mus. To evaluate the importance of lesion side, the RHI was induced both for the …