Short-term changes of finger representation at the somatosensory cortex in humans.

The present study describes short-term modifications of the representation of the fingers at the cortex. Somatosensory evoked potentials were stimulated at the 1st, 3rd and 5th finger, and at the 1st and 5th fingers after anaesthesia of the 2nd, 3rd and 4th fingers. Somatotropic arrangement of the fingers was determined by dipole localization. After local anaesthesia significant changes of the 1st finger to lateral and of the 5th fingers to medial were found. Injection of the anaesthetic drug caused predominant burning pain at the basis of the fingers, suspected to result in a 'hyperactivation' of the connected somatosensory cortex, and giving rise to a shift of the locations towards the neighbouring cortex. This replicates results in animal studies, believed to be caused by an alteration of the excitatory-inhibitory balance at the somatosensory cortex.