Revealing the neural fingerprints of a missing hand.

Sanne Kikkert,Irene Tracey,Saad Jbabdi,Heidi Johansen-Berg,Tamar R Makin,Christian F Beckmann,James Kolasinski

doi:10.7554/elife.15292

Abstract

The hand area of the primary somatosensory cortex contains detailed finger topography, thought to be shaped and maintained by daily life experience. Here we utilise phantom sensations and ultra high-field neuroimaging to uncover preserved, though latent, representation of amputees' missing hand. We show that representation of the missing hand's individual fingers persists in the primary somatosensory cortex even decades after arm amputation. By demonstrating stable topography despite amputation, our finding questions the extent to which continued sensory input is necessary to maintain organisation in sensory cortex, thereby reopening the question what happens to a cortical territory once its main input is lost. The discovery of persistent digit topography of amputees' missing hand could be exploited for the development of intuitive and fine-grained control of neuroprosthetics, requiring neural signals of individual digits.

Highlights

The hand area of the primary somatosensory cortex (S1) contains detailed digit maps, with physically adjacent digits represented next to each other
Digit topography is characterised in neuroimaging by two main principles: digit selectivity (Kolasinski et al, 2016) and inter-digit overlap (Ejaz et al, 2015)
We identified a typical inter-digit overlap pattern (Figure 4D), as confirmed in comparison with the control population described in Figure 3

Summary

Introduction

The hand area of the primary somatosensory cortex (S1) contains detailed digit maps, with physically adjacent digits represented next to each other. We identified a typical inter-digit overlap pattern (Figure 4D), as confirmed in comparison with the control population described in Figure 3 (average Spearman correlation with controls = 0.76, with 95% CI = 0.30–0.92) This result provides further evidence for the existence of preserved digit topography in the absence of peripheral input. For example following macular degeneration, the functional representation of the intact visual field was unchanged ([Baseler et al, 2011], see [Smirnakis et al, 2005] for similar results in non-human primates) Common to all these previous studies aiming to characterise reorganisation or the lack thereof, is that the authors probed the cortical neighbours of the area previously responsible for processing the lost input. By demonstrating persistence of topography despite input loss, our finding could be exploited to develop intuitive fine-grained control of neuroprosthetics (Bensmaia and Miller, 2014) (e.g. requiring representation of individual digits) in disabled populations

Participants

Findings

Funding Funder