A contingent CRT display for saccadic adaptive control experiments

William Payne, Chris Harris, Peter West
ECEM, August 2005

SensoriMotor Laboratory, Neuroscience, University of Plymouth, Drake Circus, Plymouth, PL4 8AA
Cambridge Research Systems, 80 Riverside, Sir Thomas Longley Road, Rochester, Kent, ME2 4BH

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Abstract

Keywords: contingent display saccade adaptive control

Understanding saccade adaptive control requires an intra-saccadic stimulus change to be performed during the ongoing saccade. Unfortunately, the limited availability of saccade contingent displays has limited research in this area. An obvious choice for a stimulus presentation system is a computer controlled CRT display. However, this potentially suffers from artifacts caused by frame-period quantization.

We explore a method for saccade contingent display on a CRT is described which has been developed and tested using Scalar IRIS infra-red limbus tracker and a Cambridge Research Systems Visage Visual Stimulus Generator.

A prosaccade task was used to illicit the eye movements which controlled a 167 Hz CRT display. A video frame-synchronized digital signal processing system was used to sample, filter and differentiate the eye movement data, which was then evaluated against a simple velocity threshold. Upon saccade detection, the stimulus display was modified according to the experimental protocol.

Preliminary data indicates a variable frame update delay of 15-25 ms. Thus, this novel technique allows an arbitrary change in the visual display during saccades of modest amplitudes. This study suggests that it will be possible to investigate saccade adaptive control using readily available technology, and to have unprecedented flexibility in the control of the contingent image properties.

William Payne was formerly a Student Staff Scientist at Cambridge Research Systems, studying with an Industrial Fellowship from the Royal Commission for the Exhibition of 1851.
Professor Chris Harris runs the SensoriMotor Lab at the University of Plymouth.
Peter West is a Director of Cambridge Research Systems.

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