Neural modifications in lower limb amputation: an fMRI study on action and non-action oriented body representations.

The loss of sensorimotor and visual information that follows limb amputation is known to affect both the action-oriented (body schema, BS) and non-action oriented (NA) body representations. However, the neural underpinnings of these effects have not yet been fully understood. We investigated the neural correlates of body representations in a group of 9 healthy right-handed individuals with left lower limb amputation (LLA) and 11 healthy age-matched controls (HC) by using event-related functional magnetic resonance imaging. Participants were scanned while performing mental rotation of body parts (i.e. hand, foot and eye) and objects (i.e. a rear-view mirror). Although the performance of LLA were similar to that of HC, they showed a different activation profile in relation to both BS and to NA within a wide range of brain areas. The bilateral intraparietal sulcus was less activated in LLA than HC, whereas the bilateral anterior insula as well as the fusiform body area, the precentral gyrus, the supplementary motor area in the left hemisphere and the inferior occipital gyrus in the right hemisphere were more activated during the mental rotation of left stimuli in the LLA. Also, the left EBA showed higher activation during the mental rotation of the foot than that of the eye in the LLA but not in the HC. Our results are consistent with the hypothesis that left LLA yields to a modification in the body representation network even when it does not lead to clear behavioral deficits.