Steroid hormones have profound effects on human physiology and behaviour. They are critical for the nervous system to develop and function normally, and play a role in psychiatric and neurological diseases. The levels of one steroid hormone, DHEA (dehydroepiandrosterone), drop dramatically as people age. DHEA supplements have been promoted in the media as a “fountain of youth” that can reverse brain aging and cognitive decline. However relatively little is known about the actions of DHEA on the nervous sytem and how DHEA acts at the cellular and molecular level. In earlier research, Dr. Soma showed that DHEA increases aggressive behaviour and the size of specific brain regions. Now Dr. Soma is further clarifying the effects of DHEA on behaviour and neuroplasticity (the brain's natural ability to form new nerve cells and new connections after a change in the environment). He is assessing whether DHEA must be converted to sex steroids such as testosterone and estrogen to affect the brain. The research could improve understanding of the physiological functions of DHEA in humans, and help determine how DHEA treatment could be used to alleviate mental illness and increase neuroplasticity.