An efficient technique for determining characteristics of saccadic eye movements using a mini computer

Abstract

A new technique has been developed to quantify objectively certain characteristics of saccadic eye movements which can be used as indices of the effect of centrally-acting compounds. During a three minute test session subjects sit with their heads in a fixed position and are asked to follow horizontal step displacements of a spot on a CRT screen, driven by signals previously recorded on FM analogue tape. Displacements of the spot are produced at random intervals which result in saccadic eye movements having amplitudes 10 degrees to 40 degrees. The corneo-retinal potentials are d.c. amplified and stored on the same on the same tape, later sampled at 256 Hz, filtered, differentiated and compared to the spot-displacement signal. Reaction time, duration, peak velocity, post saccadic interval and saccadic accuracy are then determined. Efficient use of computer resources has been achieved with improvements in control of experimental conditions, in reliability and in accuracy of measurements. Automatic unbiased rejection of erroneous data has been achieved. The efficiency of the technique has made extensive clinical trials possible in an environment where computer power is not devoted to eye movement-measurements. In confirmation of previous work the peak velocity characteristic has been identified as a sensitive measure of the effect of several benzodiazepines.