Proceedings of the National Academy of Sciences of the United States of America · 10 authors, 4 centres
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This longitudinal study of a partial facial transplant recipient shows that self-face recognition is neurocognitively plastic. Despite radical facial changes from injury and transplantation, the patient gradually incorporated his new face into his self-identity, as evidenced by behavioral and fMRI data. These findings demonstrate that the brain's self-processing network can adapt to a new facial appearance while preserving a sense of continuity with the pre-injury self.
**Background:** The ability to recognize one's own face is a hallmark of self-awareness, supported by a distributed neural network including the right inferior frontal gyrus (IFG), superior occipital cortex, postcentral gyrus, and midline structures such as the medial frontal cortex (MFC)/anterior cingulate cortex (ACC) and precuneus. Facial transplantation—first performed in 2005—radically alters a person's appearance, raising fundamental questions about the plasticity of self-face representations. While sensorimotor recovery after facial transplantation has been studied, the neurocognitive plasticity of self-recognition following such a procedure had not been examined.
**Methods:** The participant was a 25-year-old male who sustained a ballistic facial injury in June 2016 and underwent partial face, bilateral jaw, and teeth transplantation on January 6, 2018. He participated in five experimental sessions: two pre-transplant (T1 at 8 months pre-op; T2 at 2 months pre-op) and three post-transplant (T3 at 11 months; T4 and T5 at later time points up to 20 months post-transplant). In each session, he performed a self-recognition task while undergoing fMRI. He viewed morphed images containing varying percentages of his own face (pre-injury, post-injury, and post-transplant) and familiar others' faces, and indicated whether each image looked more like "self" or "other." Behavioral responses were modeled with logistic functions to estimate the point of subjective equality (PSE). fMRI data were analyzed using parametric contrasts corresponding to the percentage of self in each image, as well as contrasts based on the patient's overt self/other judgments.
**Key Results:** Behaviorally, the patient showed a liberal self-recognition bias toward the pre-injury face (PSE: T1 = 43.7, T2 = 46.4) compared to the post-injury face (PSE: T1 = 57.4, T2 = 59.2), indicating that less self-feature was needed to recognize the pre-injury face. Post-transplant, the pre-injury face continued to show the most liberal recognition, but the post-transplant face gradually aligned with it (PSE: T3 = 57.6, T4 = 62.7, T5 = 49.5). Wilcoxon tests showed a significant difference between pre-injury and post-injury PSEs (z = −2.02, P = 0.043), but no significant differences between pre-injury and post-transplant (z = −1.60, P = 0.109) or between post-injury and post-transplant (z = −1.60, P = 0.109). Accuracy for recognizing others' faces was at ceiling across all time points. Neurally, the pre-injury face consistently engaged midline structures (MFC, ACC, precuneus) associated with self-referential processing. The post-transplant face gradually engaged these same regions across T3–T5, including the ACC/MPFC and precuneus, as well as the right IFG and insula. By T5, the post-injury face no longer elicited significant activity in self-processing regions. ROI analyses confirmed increased activity in the right insula for pre-injury and post-transplant faces compared to the post-injury face. No significant amygdala activity was observed.
**Clinical Implications:** This study provides the first longitudinal evidence that self-face recognition is neurocognitively plastic following facial transplantation. The patient gradually incorporated his new facial appearance into his self-identity, while the post-injury face lost its neural representation. The findings suggest that successful facial transplantation can support positive psychological adaptation, with the brain's self-processing network capable of assimilating a radically new appearance. The results also highlight the importance of affective and evaluative factors—the post-injury face, associated with trauma, showed weaker identification despite comparable exposure time to the post-transplant face. These insights are critical for pre- and post-transplant psychological counseling and for setting patient expectations. The authors note that two additional transplant recipients tested showed unique patterns of self-recognition, underscoring individual variability in adaptation. Limitations include the single-subject design, potential MRI artifacts from maxillomandibular hardware (mitigated at T4/T5), and the use of only one photo per face condition.