Neuroplastic adaptation in somatosensory representation in congenital limb deficiency: A case-control study

Investigating somatosensory representation and sensory processing changes provides valuable information about the neuroplastic adaptation in handless individuals with congenital limb deficiency (CLD). Four participants with CLD (19-31 years old), 14 controls (mean age, 19.57 ± 1.34 years) in the quantitative electroencephalography (QEEG) experiment, and 10 controls (mean age, 23.9 ± 2.21 years) in the functional magnetic resonance imaging (fMRI) experiment, participated in this study to determine changes in sensory representation of the hand and sensory processing. For the QEEG data, significance tests of Crawford & Howell were conducted to evaluate whether the mu suppression in the Cz, C3, and C4 electrodes in the participants with CLD differed from that in the controls when their 17 body regions were touched. fMRI data were obtained during the tactile stimulation of the face and hand or the residual limb. For the fMRI data, individual-level and group-level inferences were examined with one and two-sample t-tests, respectively. Moreover, masked regions of interest were systematically compared using the Crawford & Howell test. Our findings showed that the representation of the face showed activation predominantly towards the upper somatosensory cortex towards the hand representation area and mu suppression was lower in individuals with CLD compared to the controls during tactile stimulation, with the exception of one participant, suggesting reduced sensitivity. In addition, according to the electrophysiological data, it was observed that the cortical representation of the face in individuals with CLD differed from that of the controls. Handless individuals with CLD exhibit altered somatosensory organisation with shifts in cortical activation and reduced mu suppression, suggesting neuroplastic adaptation that may be relevant to the hypothesis that intrauterine hand and face contact is important.