Center for Brain and Cognition, University of California, McGill Hall, 9500 Gilman Dr. M/C 0109, La Jolla, San Diego, CA 92093, USA.
Med Hypotheses. 2012 May;78(5):626-31. doi: 10.1016/j.mehy.2012.01.041. Epub 2012 Feb 22.
Between the two extreme ends of human sexuality - male and female - lie a poorly understood and poorly studied spectrum of ambiguously defined sexual identities that are very much a part of the human condition but defy rigid classification. "Bigender" is a recently formed sub-category of transgenderism, describing individuals who experience a blending or alternation of gender states. While recognized nominally by the APA, no scientific work to our knowledge has addressed this fascinating condition, or proposed any physiological basis for it. In addition, the alternation aspect has not been proposed as a nosological entity distinct from blending. We present descriptive data suggesting that many bigender individuals experience an involuntary switching of gender states without any amnesia for either state. In addition, similar to transsexual individuals, the majority of bigender individuals experience phantom breasts or genitalia corresponding to the non-biologic gender when they are in a trans-gender state. Finally, our survey found decreased lateralization of handedness in the bigender community. These observations suggest a biologic basis of bigenderism and lead us to propose a novel gender condition, "alternating gender incongruity" (AGI). We hypothesize that AGI may be related to an unusual degree or depth of hemispheric switching and corresponding callosal suppression of sex appropriate body maps in parietal cortex- possibly the superior parietal lobule- and its reciprocal connections with the insula and hypothalamus. This is based on two lines of reasoning. First, bigender individuals in our survey sample reported an elevated rate of bipolar disorder, which has been linked to slowed hemispheric switching. We hypothesize that tracking the nasal cycle, rate of binocular rivalry, and other markers of hemispheric switching will reveal a physiological basis for AGI individuals' subjective reports of gender switches. Switching may also trigger hormonal cascades, which we are currently exploring. Second, we base our hypotheses on ancient and modern associations between the left and right hemispheres and the male and female genders. By providing a case of sharp brain-sex shifts within individuals, we believe that the study of AGI could prove illuminating to scientific understanding of gender, body representation, and the nature of self.
在人类性行为的两个极端——男性和女性之间——存在着一个理解和研究都很差的模糊定义的性身份光谱，这些性身份在很大程度上是人类状况的一部分，但难以进行严格的分类。“双性人”是跨性别者的一个新形成的亚类，描述的是经历性别状态混合或交替的个体。虽然被 APA 名义上承认，但据我们所知，没有科学工作研究过这种迷人的情况，也没有提出任何生理基础。此外，交替方面也没有被提出作为一种与混合不同的分类实体。我们提出了描述性数据，表明许多双性人会经历不由自主的性别状态切换，而对任何一种状态都没有记忆缺失。此外，与跨性别者类似，大多数双性人在跨性别状态下会经历与非生物性别相对应的幻影乳房或生殖器。最后，我们的调查发现，双性人群的左右利手偏向性降低。这些观察结果表明双性人存在生物学基础，并促使我们提出一种新的性别状态，即“交替性别不一致”（AGI）。我们假设，AGI 可能与半球切换的程度或深度异常有关，以及与之对应的胼胝体对顶叶皮层中性别适当身体图谱的抑制——可能是上顶叶——及其与岛叶和下丘脑的相互连接。这基于两个推理思路。首先，我们调查样本中的双性人报告了双相情感障碍的发生率较高，这与半球切换速度减慢有关。我们假设，跟踪鼻周期、双眼竞争的速度和其他半球切换的标志物，将揭示 AGI 个体主观报告的性别转换的生理基础。转换也可能触发激素级联反应，我们正在对此进行探索。其次，我们的假设基于左右半球与男性和女性之间的古老和现代联系。通过在个体内部提供尖锐的大脑性别转换的案例，我们相信对 AGI 的研究可以为性别、身体表现和自我本质的科学理解提供启示。
