Cortical focusing is an alternative explanation for improved sensory acuity on an amputation stump

The ability to localize a sensory stimulus on the body surface (locognosia) has been investigated in normal subjects in a quest to find an explanation for the reported findings of improved sensory acuity on an amputation stump. We have shown that when attending to a smaller area of skin, during the testing procedure, locognosia improves (P<0.001) by a similar degree to that seen in amputees. Such selective attention is likely to occur in upper limb amputees as they have a reduced area of skin on which to focus during sensory testing. This represents a further explanation for improved sensory acuity on an amputation stump without implicating plasticity of connections within the somatosensory cortex.