Adaptive analysis of cortical plasticity with fMRI in full face and arm transplants

Delta waves as a sign of cortical plasticity after full-face transplantation

This study focused on detecting the reflections of healing and change in cortex activation in full-face transplantation and lesions patients on EEG activity. Face transplant patients have facial lesions before transplantation and, to identify pre-face transplant patients' brain activity in the absence of pre-transplant recordings, we used data obtained from pre-transplant facial lesion patients. Ten healthy, four facial lesion and three full-face transplant patients participated in this study. EEG data recorded for four different sensory stimuli (brush from the right face, right hand, left face, and left-hand regions) were analyzed using wavelet packet transform method. EEG waves were analyzed for standard bands. Our findings indicate significant change in the 2-4 Hz frequency range which may be a result of ongoing or previous cortical reorganization for face lesion and transplant patients. Alterations of the delta wave seen in patients with facial lesion and face transplant can also be explained by the intense central plasticity. Our findings show that the delta band differences might be used as a marker in the evaluation of post-transplant cortical plasticity in the future.

Complementary Phenomena: Phantom Hand and Phantom Face

After tissue or limb loss, the development of sensation and perception of the lost or deafferent tissue is defined as a phantom phenomenon. We investigated the presence of phantom phenomena in individuals who underwent a full face transplant as well as those who had a hand transplant. Specifically, we investigated sensory perception of the face on the fingers and sensory perception of the fingers on the face in three full face and four hand transplant patients. In all seven individuals, we used a brush to separately stimulate the right and left sides of the face or the palmar and dorsal faces of the hand. We then asked the individuals if they felt a sensation of touch on any other part of their body and, if so, to describe their perceptions. Changes in the regions of the primary sensory cortex representing the hand and face were defined using fMRI obtained via tactile sensory stimulation of the clinical examination areas. Two of the full face transplant patients reported sensory perceptions such as a prominent sensation of touch on their faces during sensory stimulation of their fingers. Three of the hand transplant patients reported sensory perceptions, which we referred to as finger patches, during sensory stimulation of the face area. In fMRI, overlaps were observed in the cortical hand and face representation areas. We consider the phantom hand and phantom face phenomena we observed to be complementary due to the neighborhood of the representations of the hand and face in the somatosensory cortex.