Fetus Tracking Stimulus (image) Cell Press Share Print E-Mail Caption This is a 4-D ultrasound of a fetus tracking the stimulus. Credit Kirsty Dunn & Vincent Reid Usage Restrictions Credit Required. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.