Importance of human right inferior frontoparietal network connected by inferior branch of superior longitudinal fasciculus tract in corporeal awareness of kinesthetic illusory movement

It is generally believed that the human right cerebral hemisphere plays a dominant role in corporeal awareness, which is highly associated with conscious experience of the physical self. Prompted by our previous findings, we examined whether the right frontoparietal activations often observed when people experience kinesthetic illusory limb movement are supported by a large-scale brain network connected by a specific branch of the superior longitudinal fasciculus fiber tracts (SLF I, II, and III). We scanned brain activity with functional magnetic resonance imaging (MRI) while nineteen blindfolded healthy volunteers experienced illusory movement of the right stationary hand elicited by tendon vibration, which was replicated after the scanning. We also scanned brain activity when they executed and imagined right hand movement, and identified the active brain regions during illusion, execution, and imagery in relation to the SLF fiber tracts. We found that illusion predominantly activated the right inferior frontoparietal regions connected by SLF III, which were not substantially recruited during execution and imagery. Among these regions, activities in the right inferior parietal cortices and inferior frontal cortices showed right-side dominance and correlated well with the amount of illusion (kinesthetic illusory awareness) experienced by the participants. The results illustrated the predominant involvement of the right inferior frontoparietal network connected by SLF III when people recognize postural changes of their limb. We assume that the network bears a series of functions, specifically, monitoring the current status of the musculoskeletal system, and building-up and updating our postural model (body schema), which could be a basis for the conscious experience of the physical self.