(Non)sensory reorganisation following arm amputation

Abstract

Arm amputation has been shown to result in dramatic unisensory reorganisation within the sensorimotor homunculus. However, little is known about the consequences of sensorimotor deprivation on global brain organisation. We studied the interplay between reorganisation within the primary sensorimotor cortex and reorganisation across large-scale brain networks in arm amputees and controls. Unisensory reorganisation was measured as medial shifts in lip representation in the deprived homunculus using task-based fMRI, reflecting the well-documented invasion of the lip representation into the missing hand area. Network-level reorganisation was assessed as changes in functional connectivity strength between the deprived hand area and fMRI resting-state networks, using independent component analysis. Functional connectivity between the deprived cortex and its network of origin (the sensorimotor network) was reduced in amputees, compared with controls. This was associated with greater coupling of the deprived cortex with the non-sensory default mode network, from which the primary sensorimotor cortex is normally decoupled. The degree of this new (non)sensory coupling was correlated with the degree of unisensory remapping within the sensorimotor homunculus and with decoupling of the deprived hand area from the resting-state sensorimotor network. Our results demonstrate that, following amputation, plasticity is present in, but not restricted to, the sensorimotor network, highlighting the role of sensory deprivation as a driving force for both sensory and non-sensory plasticity.