Abstract
Arm-amputation involves two powerful drivers for brain plasticity-sensory deprivation and altered use. However, research has largely focused on sensory deprivation and maladaptive change. Here we show that adaptive patterns of limb usage after amputation drive cortical plasticity. We report that individuals with congenital or acquired limb-absence vary in whether they preferentially use their intact hand or residual arm in daily activities. Using fMRI, we show that the deprived sensorimotor cortex is employed by whichever limb individuals are over-using. Individuals from either group that rely more on their intact hands (and report less frequent residual arm usage) showed increased intact hand representation in the deprived cortex, and increased white matter fractional anisotropy underlying the deprived cortex, irrespective of the age at which deprivation occurred. Our results demonstrate how experience-driven plasticity in the human brain can transcend boundaries that have been thought to limit reorganisation after sensory deprivation in adults. DOI: http://dx.doi.org/10.7554/eLife.01273.001.
Highlights
After losing a hand, simple tasks such as tying your shoelaces become a daily challenge, resulting in serious implications for quality of life and employment (Jang et al, 2011)
Most accounts of plasticity following arm amputation focused on sensory deprivation, and in particular on apparently passive remapping of adjacent face or arm representation into the deprived cortex (Lotze et al, 1999; Ramachandran and Altschuler, 2009; Nava and Röder, 2011)
When considering usage across both 1-handed groups we found that greater usage of the residual arm was associated with less activation during intact hand movements in the deprived cortex (r(26) = −0.43, p=0.021), even when accounting for age of sensory deprivation (r(25) = −0.36, p=0.032)
Summary
Simple tasks such as tying your shoelaces become a daily challenge, resulting in serious implications for quality of life and employment (Jang et al, 2011). Longer-range remapping has been reported, such as intact hand representation in the deprived cortex (Bogdanov et al, 2012), this is usually explained as a passive result of inter-hemispheric dis-inhibition (Werhahn et al, 2002; Ramachandran and Altschuler, 2009; Simões et al, 2012). These accounts ignore substantial adaptations in motor behaviour that accompany absence or loss of a limb, which could be powerful drivers for plasticity (Scholz et al, 2009)
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