Nerve cells in the brain send messages to each other using fast electrical pulses that are referred to as action potentials. A signal response is initiated in a nerve cell axon, and the resulting action potential travels forward along the axon which acts like a cable going to other nerve cells. In most brain cells, the action potential also travels backwards up the axon and into the nerve cell body and its dendrite projections. There are, however, three types of nerve cells in the auditory system, where, for unknown reasons, the action potential does not travel backwards. These auditory nerve cells encode information about sounds through the unusually precise timing of their action potentials. This project will investigate whether the lack of backward action potentials in these cells explains their notable ability to precisely time their forward action potentials. To investigate this distinct neurobiological problem, two laboratories, one in the US and another in Germany, have set up a collaboration. An existing computerized, real-time interface will be used to simulate backward action potentials in auditory cells that normally do not produce backward action potentials in response to sound. The results of this analysis will be used to determine whether sodium conductance disrupts the precise timing of the forward action potentials that are normally exhibited by these cells. The experimental data will be tested against a fully computational model of nerve cells to gain insight into the relationship between normal action potential initiation and the precise timing of action potentials, as well as to understand the enhanced capabilities of these three unusual cell types. The software for the computer interface that will be developed in this project will be made freely available online to other researchers. The project will provide significant training opportunities for undergraduate and graduate students in laboratories with differing, but complimentary, areas of expertise. Development of the computer interface will involve computer science undergraduates taking a course in Real-time and Embedded Operating Systems. (A companion project is being funded by the German Ministry of Education and Research (BMBF).
