Brain remodeling after chronic median nerve compression in a rat model

Carpal tunnel syndrome is the most common compressive neuropathy,presenting with sensorimotor dysfunction.In carpal tunnel syndrome patients,irregular afferent signals on functional magnetic resonance imaging are associated with changes in neural plasticity during peripheral nerve injury.However,it is difficult to obtain multi-point neuroimaging data of the brain in the clinic.In the present study,a rat model of median nerve compression was established by median nerve ligation,i.e.,carpal tunnel syndrome model.Sensory cortex remodeling was determined by functional magnetic resonance imaging between normal rats and carpal tunnel syndrome models at 2 weeks and 2 months after operation.Stimulation of bilateral paws by electricity for 30 seconds,alternating with 30 seconds of rest period（repeatedly 3 times）,resulted in activation of the contralateral sensorimotor cortex in normal rats.When carpal tunnel syndrome rats received this stimulation,the contralateral cerebral hemisphere was markedly activated at 2 weeks after operation,including the primary motor cortex,cerebellum,and thalamus.Moreover,this activation was not visible at 2 months after operation.These findings suggest that significant remodeling of the cerebral cortex appears at 2 weeks and 2 months after median nerve compression.

Altered intra- and inter-network brain functional connectivity in upper-limb amputees revealed through independent component analysis

Although cerebral neuroplasticity following amputation has been observed, little is understood about how network-level functional reorganization occurs in the brain following upper-limb amputation. The objective of this study was to analyze alterations in brain network functional connectivity(FC) in upper-limb amputees(ULAs). This observational study included 40 ULAs and 40 healthy control subjects;all participants underwent resting-state functional magnetic resonance imaging. Changes in intra-and inter-network FC in ULAs were quantified using independent component analysis and brain network FC analysis. We also analyzed the correlation between FC and clinical manifestations, such as pain. We identified 11 independent components using independent component analysis from all subjects. In ULAs, intra-network FC was decreased in the left precuneus(precuneus gyrus) within the dorsal attention network and left precentral(precentral gyrus) within the auditory network;but increased in the left Parietal_Inf(inferior parietal, but supramarginal and angular gyri) within the ventral sensorimotor network, right Cerebelum_Crus2(crus Ⅱ of cerebellum) and left Temporal_Mid(middle temporal gyrus) within the ventral attention network, and left Rolandic_Oper(rolandic operculum) within the auditory network. ULAs also showed decreased inter-network FCs between the dorsal sensorimotor network and ventral sensorimotor network, the dorsal sensorimotor network and right frontoparietal network, and the dorsal sensorimotor network and dorsal attention network. Correlation analyses revealed negative correlations between inter-network FC changes and residual limb pain and phantom limb pain scores, but positive correlations between inter-network FC changes and daily activity hours of stump limb. These results show that post-amputation plasticity in ULAs is not restricted to local remapping;rather, it also occurs at a network level across several cortical regions. This observation provides additional insights into the plasticity of brain networks after upper-limb amputation, and could contribute to identification of the mechanisms underlying post-amputation pain.