Feb. 4, 1999 In the United States alone, 28 million people have some degree of hearing impairment. The problem is particularly severe in childhood, when deafness can have a profound impact on intellectual and emotional development. NYU neuroscientist Dan H. Sanes works to understand how deafness affects the growth and function of the central nervous system, and how these effects might be averted or reversed.
Sanes' research focuses on the development of inhibitory synapses. Although much is known about how malfunction of the excitatory synapses affects the auditory system's development, there is a dearth of such information on the inhibitory synapses.
Sanes is trying to fill this void. Previously, he has demonstrated that a developing organism's central auditory system can undergo striking changes when the inhibitory synapses malfunction for as little as 24 hours. For example, nerve cell dendrites produce extra branches, and excitatory connections from the intact ear become stronger than normal.
Sanes said, "We're trying to figure out what happens to the connections between nerve cells when they're deprived of stimulation during development, as occurs in hearing loss. Changes in the strength of inhibitory synapses can fundamentally alter how the central nervous system processes speech sounds or the location of a moving car. Broken inhibitory synapses probably play a pivotal role in many developmental disorders, including dyslexia and epilepsy."
Sanes lab is now examining how the activity of inhibitory synapses might influence neural development, and why the loss of this activity is so harmful. Dr. Vibhakar Kotak, a collaborator in Sanes's lab, discovered that the inhibitory synapses release a unique neurotransmitter during early development. This neonatal signal (an amino acid called GABA) activates a specific type of receptor, and it can depress the strength of neighboring connections. Understanding the normal signals that help inhibitory synapses form will be crucial to understanding how to deal with their loss or damage.
A second interest in Sanes' lab is the restoration of function following traumatic injury to nervous system pathways. For adult mammals, including humans, a major obstacle is that neuronal processes, called axons, will not regrow across the site of injury. In collaboration with Dr Aziz Hafidi, Sanes' lab has generated a model system to study this phenomenon. Relatively large pieces of the rodent central auditory system are kept alive in an incubator, where axon regeneration can be followed more easily. Although cut axons show some ability to grow, they are unable to cross the injury site, similar to the situation in the living animal. Sanes' lab is currently working on methods to modify the injury site in order to permit axons to grow across it.
Sanes is Director of NYU's Center for Neural Science. His research is supported by National Institute on Deafness and Other Communication Disorders and the National Science Foundation. Sanes teaches in both undergraduate and graduate programs, and is currently co-authoring an undergraduate textbook entitled Development of the Nervous System.
The Center for Neural Science is the focus for teaching and research in the brain sciences at the Washington Square Campus of New York University. Formed in 1987, the Center is a department of the Faculty of Arts and Science. The research interests of its faculty span a broad range of topics in neural science, and utilize techniques ranging from cellular analyses to fully integrated systems, computational, and cognitive studies.
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