Ryan T. Johnson

Having evolution and neuroscience as research interests is a difficult combination of macro and micro views that don't seem to work together, yet. However, there are options for combining these views and neuroendocrinology offers a fantastic approach:

During embryogenesis the "default" brain is a female one. However, adult males don't generally behave like females. Why not? We know that during neural development sex hormones serve to transform the default brain into one that will produce masculine behaviors. Neuroscience has begun identifying components of the brain that are sensitive to sex hormones, but we are still far from a complete understanding of the differences between the male and female brain. How is this re-wiring achieved? Neuroscience is also not fully aware of how sex hormones alter neural development. What biological machinery do androgens switch on to re-wire the brain? Why is this re-wiring necessary? This is a much more difficult question but an especially interesting one. At some very early point in evolution, sexual reproduction became advantageous and specialized. Some individuals began to store their genetic information in large energy-costly cells (eggs) and other individuals began to store their genetic information in small inexpensive cells (sperm). This process likely occurred long before anything like a modern brain could be found; yet it has had long lasting and continuous effects on brain structure and function.

During evolution, an intricate relationship has developed; sexual reproduction has sculpted our brains and our brains have influenced the way we reproduce. Which neural changes came first? Which changes were essential? Why were they necessary? Which came as by-products or as random noise? Through exploration of these types of questions, I hope to contribute to a more complete understanding of both what it means to be female or male and importantly what it means to be human.

Currently, I am examining possible sex differences in astrocytes in the amygdala. The amygdala can be thought of as evolutions highlighter, emphasizing evolutionarily significant information from the incoming sensory mileu. Interestingly, the amygdala is linked to several diseases and disorders, including anxiety, autism, and schizophrenia all of which show uneven distribution between the sexes. Interestingly, the amygdala is sexually dimorphic and the medial postero-dorsal portion (MePD) responds to changes in sex hormones even in adulthood. However, the details of this dimorphism are unclear. Given their acknowledged role in neuronal plasticity and established hormone responsiveness, it is likely that astrocytes may be involved in MePD sexual dimorphisms. By better understanding how hormones alter MePD cellular components I hope to learn more about how the amygdala functions differently in males and females, which may lead to a deeper understanding of neural evolution and may promote the development of new treatments for the many sex-biased amygdala-liked diseases.

I have many hobbies outside of academia including playing bass, composing music, painting, cooking, and willfully submitting myself to the torture of DIY home remodeling. I live with my wonderful wife Sarah and my bulldog, Frank.