Multi-neuronal signals from the retina: acquisition and analysis.

Throughout the central nervous system, information about the outside world is represented collectively by large groups of cells, often arranged in a series of 2-dimensional maps connected by tracts with many fibers. To understand how such a circuit encodes and processes information, one must simultaneously observe the signals carried by many of its cells. This article describes a new method for monitoring the simultaneous electrical activity of many neurons in a functioning piece of retina. Extracellular action potentials are recorded with a planar array of 61 microelectrodes, which provides a natural match to the flat mosaic of retinal ganglion cells. The voltage signals are processed in real time to extract the spike trains from up to 100 neurons. We also present a method of visual stimulation and data analysis that allows a rapid characterization of each neuron's visual response properties. A randomly flickering display is used to elicit spike trains from the ganglion cell population. Analysis of the correlations between each spike train and the flicker stimulus results in a simple description of each ganglion cell's functional properties. The combination of these tools will allow detailed study of how the population of optic nerve fibers encodes a visual scene.