The Tell-Tale Brain: A Neuroscientist's Quest for What Makes Us Human

As with somatoparaphrenia, distortions or mismatches in the SPL can also explain the symptoms of transsexuals. Many male-to-female transsexuals report feeling that their penis seems to be redundant or, again, overpresent and intrusive. Many female-to-male transsexuals report feeling like a man in a woman’s body, and a majority of them have had a phantom penis since early childhood. Many of these women also report having phantom erections.⁸ In both kinds of transsexuals the discrepancy between internally specified sexual body image—which, surprisingly, includes details of sexual anatomy—and external anatomy leads to an intense discomfort and, again, a yearning to reduce the mismatch.

Scientists have shown that during fetal development, different aspects of sexuality are set in motion in parallel: sexual morphology (external anatomy), sexual identity (what you see yourself as), sexual orientation (what sex you are attracted to), and sexual body image (your brain’s internal representation of your body parts). Normally these harmonize during physical and social development to culminate in normal sexuality, but they can become uncoupled, leading to deviations that shift the individual toward one or the other end of the spectrum of normal distribution.

I am using the words “normal” and “deviation” here only in the statistical sense relative to the overall human population. I do not mean to imply that these ways of being are undesirable or perverse. Many transsexuals have told me that they would rather have surgery than be “cured” of their desire. If this seems strange, think of intense but unrequited romantic love. Would you request that your desire be removed? There is no simple answer.

Privacy

In Chapter 4, I explained the role of the mirror-neuron system in viewing the world from another person’s point of view, both spatially and (perhaps) metaphorically. In humans this system may have turned inward, enabling a representation of one’s own mind. With the mirror-neuron system thus “bent back” on itself full-circle, self-awareness was born. There is a subsidiary evolutionary question of which came first—other-awareness or self-awareness—but that’s tangential. My point is that the two coevolved, enriching each other enormously and culminating in the kind of reciprocity between self-awareness and other-awareness seen only in humans.

Although mirror neurons allow you to tentatively adopt another person’s vantage point, they don’t result in an out-of-body experience. You don’t literally float out to where that other vantage point is, nor do you lose your identity as a person. Similarly, when you watch another person being touched, your “touch” neurons fire, but even though you empathize, you don’t actually feel the touch. It turns out that in both cases, your frontal lobes inhibit the activated mirror neurons at least enough to stop all this from happening so you remain anchored in your own body. Additionally, “touch” neurons in your skin send a null signal to your mirror neurons, saying, “Hey, you are not being touched” to ensure that you don’t literally feel the other guy being touched. Thus in the normal brain a dynamic interplay of three sets of signals (mirror neurons, frontal lobes, and sensory receptors) is responsible for preserving both the individuality of your own mind and body, and your mind’s reciprocity with others—a paradoxical state of affairs unique to humans. Disturbances in this system, we shall see, would lead to a dissolution of interpersonal boundaries, personal identity, and body image—allowing us to explain a wide spectrum of seemingly incomprehensible symptoms seen in psychiatry. For example, derangements in frontal inhibition of mirror-neuron system may lead to a disturbing out-of-body experience—as though you were really watching yourself from above. Such syndromes reveal how blurred the boundary between reality and illusion can become under certain circumstances.

MIRROR NEURONS AND “EXOTIC” SYNDROMES

Mirror-neuron activity can go awry in many ways, sometimes in full-blown neurological disorders but also, I suspect, in numerous, more subtle ways as well. For instance, I wonder whether a dissolution of interpersonal boundaries may also explain more exotic syndromes such as folie à deux, in which two people, such as Bush and Cheney, share each other’s madness. Romantic love is a minor form of folie à deux, a mutual delusional fantasy that often afflicts otherwise normal people. Another example is Munchausen syndrome by proxy, in which hypochondriasis (where every trifling symptom is experienced as a harbinger of fatal illness) is unconsciously projected onto another (the “proxy”)—often by a parent onto his or her child—instead of onto oneself.