The Origin of Sensory Representation: What we can learn from congenital limb deficiencies

We aimed to understand ontology on the organization of the somatosensory representation. Therefore we compared the arrangement of the homunculus in individuals with congenital limb deficiencies (CLD) who have no face and hand co-activation and control subjects. Three of the participants with congenital limb deficiencies (S2, S3, S4) and 15 healthy controls participated in a QEEG experiment. S2 and S3 had bilateral amelia while S4 had tetramelia.

We analysed the spectral powers in the electrodes during tactile stimulation of three regions (cheek, shoulder, and foot) and two sides (right and left) to test our specific hypothesis. It is assumed that electrodes C3 and C4 represent the hand area and Cz represents the foot area in healthy controls.
In the QEEG analysis, one sample t-tests were performed to compare the spectral powers of the control group and the cases in each electrode. P value was considered significant at 0.05.

We measured the alpha activity during left side stimulation of the face, shoulder, and foot, since the C4 electrode is located over the right hemisphere.
Since the C3 electrode is located above the left hemisphere, the alpha activity during right-side stimulation of the face, shoulder, and foot was measured.
Since the Cz electrode is located centrally, the alpha activity during stimulation of both the left and right face, shoulder, and foot was measured.
In general, the alpha activity in the cases was lower than that of the controls in all tactile conditions according to QEEG results. This might be due to being exposed to less tactile stimulation during both prenatal and postnatal periods of their life.