Ryan Johnson

Faculty Advisor: Drs. S.M. Breedlove and C. Jordan
Entered Program in Fall 2005

 john2448@msu.edu

Student Background/Interests

Having evolution and neuroscience as research interests is a difficult combination of macro and micro views that don’t seem to work together, yet. But “research interests” is merely another way of saying, “What questions do I like to think about?” and my answer to that is touched upon below.

During embryogenesis the default brain is a female one. However, adult males don’t generally behave like females.

Why not?

We know that at key points in neural development sex hormones serve to transform the default brain into one that will produce “male” behaviors. Neuroscience has begun the process of identifying regions of the brain which are sensitive to sex hormones, but we are still very 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. This is where my current focus lies. By exploring the effects of androgens on neural development, I hope to elucidate what biological machinery androgens activate to play a role in the re-wiring of the brain.

Why is this re-wiring necessary?

This is a much more difficult question, but to me a very interesting one. At some very early point in human evolution, sexual reproduction became advantageous. A bit further down the evolutionary timescale, sexual reproduction became specialized. Part of the species began to store their genetic information in large energy-costly cells (eggs) and the other part of the species began to store their genetic information in small inexpensive cells (sperm). The brain began to change both to promote and in response to these specializations. Why was this necessary? Which neural changes came first? Which changes came as the result of necessity and 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 a female or male and what it means to be a human.

Selected Publications

Johnson, R. T., Burk, J. A. (2005) Effects of Gonadectomy and Androgen Supplementation on Attention in Adult Male Rats.  Neurobiology of Learning and Memory, 85(3), 219-227.