The Origin of Sensory Representation: What we can learn from congenital limb deficiencies: a case-control study

Abstract Background There are arguments regarding the ontological or embryological origin of sensory representation in the literature. This study aimed to understand the origin of somatosensory organization by comparing participants with congenital limb deficiencies with healthy controls. Methods Four participants with congenital limb deficiencies (three participants with bilateral amelia, one participant with tetramelia, 19–31 years old, two females, two males), 15 healthy controls (three males, 12 females; mean age, 19.57 ± 1.34 years) in the quantitative electroencephalography (QEEG) experiment, and 10 healthy controls (seven male, three female; mean age, 23.9 ± 2.21 years) in the functional magnetic resonance imaging (fMRI) experiment, participated in this study. fMRI and QEEG data were recorded to determine the somatosensorial organization in both participants with congenital limb deficiency and healthy controls. For the QEEG data, one sample t-tests were conducted to evaluate whether the spectral power in the CZ, C3, and C4 electrodes in the participants with congenital limb deficiencies differed from that in healthy controls when they were touched on their cheek, shoulder, and foot. In fMRI recordings, the face and hand regions were stimulated using a non-magnetic stick with cotton attached. For the fMRI data, individual level and group level interferences were examined with one and two sample t-tests, respectively. Moreover, masked regions of interest were systematically compared using the Mann-Whitney U-test. Results Our findings showed that the somatotopic structure of participants with congenital limb deficiency and healthy controls have some common patterns and striking differences. In the QEEG results, the cortical activity was lower in participants with congenital limb deficiency than the activity in healthy controls during tactile stimulation and the participant with tetramelia had lower cortical activity levels than both the participants with amelia and healthy controls (p < 0.05). Furthermore, the representation of the face showed activation predominantly towards the upper somatosensory cortex according to the fMRI results. Conclusions Differences in the somatosensory organization of individuals with congenital limb deficiency and healthy controls show that both ontology and plasticity may have played a role in this status.