Immediate and long-term plasticity in human somatosensory thalamus and its involvement in phantom limbs

This paper describes studies on plasticity that the author undertook with Patrick Wall in the mid '70s, and then reviews recent related studies in humans carried out in the author's laboratory. The human studies have shown that thalamic neurons frequently have subliminal receptive fields (RFs) and immediately following a reversible block of afferent activity from the RF some neurons develop increased sensitivity to tactile stimulation at sites outside their normal RF. Also described and discussed are novel findings in patients that had a limb amputated. The results suggested an expansion of the representation of the proximal limb into the thalamic region that used to represent the amputated part. Furthermore, in those patients that had a phantom limb, microstimulation in this region induced sensations perceived as originating on the phantom.