Altered White Matter and Sensory Response to Bodily Sensation in Female-to-Male Transgender Individuals
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While most people take identification with their body for granted, conditions such as phantom limb pain, alien hand syndrome, and xenomelia suggest that the feeling of bodily congruence is constructed and susceptible to alteration. Individuals with xenomelia typically experience one of their limbs as over-present and aversive, leading to a desire to amputate the limb. Similarly, many transgender individuals describe their untreated sexed body parts as incongruent and aversive, and many experience phantom body parts of the sex they identify with (Ramachandran, 2008). This experience may relate to differences in brain representation of the sexed body part, as suggested in xenomelia (McGeoch et al., 2011). We utilized magnetoencephalography imaging to record brain activity during somatosensory stimulation of the breast—a body part that feels incongruent to most presurgical female-to-male (FtM)-identified transgender individuals—and the hand, a body part that feels congruent. We measured the sensory evoked response in right hemisphere somatosensory and body-related brain areas and found significantly reduced activation in the supramarginal gyrus and secondary somatosensory cortex, but increased activation at the temporal pole for chest sensation in the FtM group (N = 8) relative to non-transgender females (N = 8). In addition, we found increased white matter coherence in the supramarginal gyrus and temporal pole and decreased white matter diffusivity in the anterior insula and temporal pole in the FtM group. These findings suggest that dysphoria related to gender-incongruent body parts in FtM individuals may be tied to differences in neural representation of the body and altered white matter connectivity.
KeywordsGender dysphoria Body image Body representation Gender identity Parietal lobes Transgender
We thank Dr. Mingxiong Huang, Dr. Roland Lee, and Dr. Tao Song for support in collecting the MEG data and Dr. Eric Halgren and Burke Rosen for assistance in processing the MEG data. We thank Zack Taich, Dave Deriso, and Radhika Gosavi for assistance in carrying out the study and Rachel Case for assistance in preparing the figures. This work was supported by the University of California, San Diego, through an Academic Senate Award (2011) and through general support of several of the authors while the study was conducted. This work was also supported by research funds from Herb Lurie. Finally, the first author thanks NCCIH for support during the preparation of the manuscript. The views presented in this paper are solely those of the authors and do not necessarily reflect views of the National Center for Complementary and Integrative Health.
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