A new brain imaging study from the European College of Neuropsychopharmacology has shown that the testosterone given to aid trans individuals in sex reassignment alters the brain structures and pathways involved in speech and verbal fluency—and may have just shown how men and women (both cis and transsexual*) experience language and communication differently.

The researchers from Vienna and Austria studied 18 trans individuals (average age of 27) who had been designated female at birth and had decided to transition. Before and after four weeks of testosterone therapy, the subjects underwent MRI brain scans.

Surprise stronger white matter

The results: The volume of grey matter (the part of the brain that processes information) had decreased in two key language areas of the brain. The regions, known as Broca’s and Wernicke’s areas, play important roles in language comprehension and communication. Simultaneously, the white matter pathways known as the extreme capsule connecting these two regions got stronger.

“It has been known for some time that higher testosterone is linked to smaller vocabulary in children and that verbal fluency skills decrease in female-to-male transsexuals after testosterone treatment,” explained researcher Dr. Andreas Hahn in a press release. “This fits in well with our finding of decreased grey matter volume. However, the strengthening of the white matter in these areas was a surprise. We think that when it comes to certain language skills, the loss of grey matter outweighs the strengthened white matter connection.”

Testosterone itself is known to exert a strong influence on human behavior and cognition—it has been linked to verbal fluency before—but is often hard to study for ethical reasons, making it impossible to see the direct effects is has on brain structure. However, studying trans individuals allowed researchers to overcome these hurdles.

“What we see is a real quantitative difference in brain structure after prolonged exposure to testosterone,” explained researcher Professor Rupert Lanzenberger. “This would have been impossible to understand without looking at a transsexual population. In more general terms, these findings may suggest that the genuine difference between the brains of women and men is substantially attributable to the effects of circulating sex hormones. Moreover, the hormonal influence on human brain structure goes beyond early developmental phases and is still present in adulthood.”

The research was presented at the 28th ECNP Congress.

*Used here to denote those who are actively transitioning, or who have transitioned.

—–

Feature image: Thinkstock

Comments

comments