Development of a PC-based system for recording flash electroretinograms in experimental animals

This report presents the results of a student design project, the goal of which was to develop a user-friendly PC-based system for recording flash electroretinograms (ERGs) in experimental animals. This system consists of an LED stimulator with associated driver circuitry, a differential amplifier, and a LabVIEW-based software package that controls data acquisition and handling. The system was designed to be applicable to multiple animal models, and is currently being tested on both rats and horseshoe crabs. The electroretinogram is the summation of electrical responses from both neuronal and non-neuronal cells in the retina in response to stimulation by a flash of light. In this system, ERGs are recorded using DTL-fiber electrodes stretched across a moistened cornea, and referenced to cornea of the opposite, unstimulated eye. ERG signals are differentially amplified and digitized using a National Instruments data-acquisition (DAQ) board. ERGs are elicited by a LED stimulator that is controlled by the software package through a driver circuit that limits current flow to the LED. A diffuser is located in front of the LED to ensure uniform illumination of the retina. Stimulus intensities are controlled by alteration of the duration of excitation of the LED by the TTL output of the software. The software package allows the user to customize stimulation and sampling settings. It also functions as a digital oscilloscope to display responses as they are obtained from the subject. This package also incorporates the ability to average signals, which is necessary for increasing signal-to-noise ratios when recording small ERG signals.