October 3, 2002
Hardwiring brain circuits
Connecting a monitor to the keyboard input on a computer’s CPU will result in neither the monitor nor keyboard functioning properly. The human brain has analogous, albeit much more complex, connections.
Some neurological diseases occur when the nerve cells in the cerebral cortex of the brain don’t connect properly during embryonic development. The cerebral cortex, consisting of many fine layers of organized nerve cells, is the outer shell of the brain controlling all voluntary muscle movement and sensory processing. Cerebral palsy, some forms of epilepsy and mental retardation may result when the layers of nerve cells are not organized properly, due to genetic mutation or other unknown factors.
“One of the things that goes wrong in these neurological diseases is the nerve cells are not sending their axons to the right place,” says Dr. Robert Hevner, assistant professor of pathology.
The axon of a nerve cell directs electrical messages to other nerve cells. In the cerebral cortex, nerve cells with similar functions are grouped together and often are formed at the same time during embryonic development — the cells have the same “birthdate,” and send their axons to the same target regions in the brain. But if the nerve cells grow their axons into the wrong targets, the brain wiring diagram is scrambled; just as the a computer keyboard does not function when plugged into the wrong input on a computer CPU.
Hevner’s lab studies the development of the cerebral cortex. Layer by layer the cerebral cortex forms with cells developing in one part of the brain and migrating to other parts. Using proteins marked with fluorescence, Hevner and his colleagues observe this cellular migration during development in embryonic mice.
“Ultimately we would like to understand and control the development of the nerve cells so that they can acquire the properties we want,” says Hevner.
One desirable property would allow using adult stem cell therapy to repair problematic nerve cell migration and connections. The Christopher Reeves Paralysis Foundation is supporting the Hevner lab’s work on identifying molecules involved in making connections between the nerve cells in the cerebral cortex and the spinal cord.
Hevner presents the first Science in Medicine Lecture in the 2002-2003 series at noon, Thursday, Sept. 26. The New Investigator Lecture, “Building the Cerebral Cortex: Neuron by Neuron, Layer by Layer,” will be in D-209, Turner Auditorium, Health Sciences Center. Everyone is welcome.
Hevner received received M.D. and Ph.D. degrees from the Medical Scientist Training Program at the Medical College of Wisconsin in Milwaukee. He completed a residency in pathology at Brigham and Women’s Hospital in Boston from 1992 to 1994. At Stanford University Medical Center from 1994 to 1997, Hevner completed a neuropathology fellowship and was an acting assistant professor of pathology for one year. He was an assistant adjunct professor of psychiatry (research) at the University of California San Francisco from 1998 to 2000, before joining the UW faculty.
Among his numerous honors, this year Hevner received the UW’s Marian E. Smith Junior Faculty Research Award and became the 40th Edward Mallinckrodt Scholar.