Nerve cells (neurons) process information for the brain using electrochemical signaling mechanisms that can be studied by biophysical methods. A nerve cell has a membrane with complex electrical properties, so that different sites on the membrane have different sensitivity, particularly where there are functional junctions called synapses with other cells. Local responses to subthreshold electrical potential signals are important because they are inputs that are integrated by the cell to produce the output 'action potential', which the nerve cell uses to propagate information over distance. This project will develop a novel technique combing intracellular voltage-sensitive dyes with optical imaging utilizing a high-performance low-noise charge-coupled-device (CCD) camera. The new higher sensitivity will allow monitoring of multiple smaller, subthreshold signals at local sites on the membrane. The preparation is in a crustacean with single large identifiable neurons, which offer an excellent model to develop this system. Interactions and propagation of transient local electrical signals and action potentials will be recorded at multiple sites, to analyze spatial and temporal dynamics of subthreshold synaptic signals from neuronal processes. Results will be incorporated into a computational model of the detailed functional organization of this giant cell. This project will have an impact in developing extremely useful new technology for cellular physiology as well as neurophysiology, and results will be important for understanding the computational properties of nerve cells. The project also will support training of one postdoctoral fellow.
