Q. How and when does templating for sexual orientation occur in the brain?

A. Research is not yet sufficiently advanced to specifically describe in detail how and when sexual orientation is templated in the brain. What is clear is that the developing fetal brain does undergo templating (gender-patterning) for aspects of human sexuality including sexual identity, orientation, and preference. Nature plus nurture results in an individual’s personal sexual template.

During gestation, templating for sexuality appears to involve a region in the anterior hypothalamus; the INAH3 (the Third Interstitial Nucleus of the anterior hypothalamus) more specifically. This hypothalamic nucleus is on average more than twice as large in the brains of heterosexual males than it is in the brains of females or homosexual males. Critical time periods likely involve the last part of the first trimester and/or the 16 th-26th weeks of gestation. Templating may occur atypically if something interferes with any or all of the process. Research continues in this area. Dorner, Diamond, and Seligman are three individuals who have taken a position on this process. Each has his own way of describing templating.

Dr. Gunter Dorner, a German scientist, said templating of the brain for sexual identity and related behaviors occurs through the development of three centers:

  • The Sex Center—controls typical male characteristics or female characteristics
  • The Mating Center—controls attraction and exhibited sexual behaviors
  • The Gender-role Center—controls behaviors such as aggression that become more fully expressed under the hormonal influence of puberty.

Dr. Milton Diamond, an American scientist, said four stages of development are likely to be involved:

  • Stage 1 - basic sexual patterning (e.g., passivity or aggressiveness)
  • Stage 2 - sexual identity (the individual’s own gender mindset)
  • Stage 3 - sexual object choice (similar to Dr. Dorner’s mating center)
  • Stage 4 - control over one’s sexual equipment (including the mechanism of orgasm)

Martin Seligman, PhD, author of the book What You Can Change...and What You Can’t, defined five layers related to human sexuality and templating:

  • Core layer: Sexual identity – a personal perception of being male or female that usually is consistent with the person’s genitals but not always (e.g., the transsexual’s brain does not match the person’s genitals). Identity tends not to change, especially for exclusive heterosexuals or exclusive homosexuals.
  • Second layer: Sexual orientation – denotes who the individual is attracted to sexually. The basic sexual orientations are heterosexual and homosexual (either exclusive or bisexual-optional). Orientation is closely identified with sexual identity and strongly resistant to change. Some are able to make choices about whom to perform with sexually but may not be able to alter whom they want to perform with sexually.
  • Third layer: Sexual preference – the types of situations, things, articles of clothing, fetishes, and/or body parts that trigger sexual arousal. Preferences may surface in late childhood when the dormant brain templates that were created during pregnancy are triggered by hormonal surges in puberty. Sexual preferences developed by adolescence tend to continue, although new ones can be added. Some preferences can be altered with explicit therapy.
  • Fourth layer: Sex role – the exhibiting of behaviors that relate to sexual performance including stereotypical expectations related to role. Many sex differences exist but three types may be directly relevant to role: ability, personality, and social differences. Culture and choice play a part in sex roles. Some individual change can be achieved, within limits.
  • Fifth layer: Sexual performance – the adequacy of sexual performance with a suitable individual in a suitable environmental setting. Sexual dysfunctions in males include impotence and premature ejaculation; in females they include frigidity and inability to reach orgasm. A great deal of change can be achieved related to sexual performance although the process may be difficult.

According to Dr. Seligman the ability to change and/or the ease with which a person is able to change is related to the depth of the layer (e.g., the deeper the layer the more difficult it is to achieve change). Thus the core layer is the most resistant to any type of change while sexual performance is the easiest to alter, even though the process may be difficult and painful. He also made the point that while some can learn to exhibit a variety of sex-related behaviors (e.g., can engage in sexual relations with another person through the use of fantasy), the individual’s core identity and orientation toward the type of person he/she wants to be sexual with are likely to remain constant.

You may want to refer to Brain References—Sexuality and the Brain for additional brain facts.