Although translational motion (t-motion) is often used in motion-onset VEP studies, other types of motion such as radial motion (r-motion) have been shown to be efficient stimuli as well. However, the motion-onset VEPs are not well known in children. The aim of this study was to characterize and compare VEP responses to t-motion and r-motion in a large homogenous paediatric sample.
Motion-onset VEPs have been tested in a cohort of Inuit children (mean = 11,3 ±1 year) using left-right t-motion (n=125) and contraction-expansion radial motion (n=98). For both types of stimuli, motion-onset was evoked by an initial stationary period of 1120 ms follow by an abrupt and rapid motion (duration: 160 ms; velocity: 6,5 deg/s; contrast: 10%). Motion direction was unpredictable. Brain responses were recorded from 32 scalp electrodes according to the 10–20 system.
The amplitude of the P1 and the N2 components to r-motion were significantly stronger compare to t-motion. In both cases, the topographic mapping of the electrical activity shows a lateralized right hemisphere distribution over the occipito-temporal region, which was more important for r-motion. No significant difference was found for latency.
This study shows in school-age children that VEP responses evoked by r-motion are clearly more robust than those evoked by t-motion. This finding is consistent with previous reports in adults. Because r-motion is associated with a better signal and minimize ocular artefacts, this type of stimulus might therefore be more appropriate for paediatric motion-onset VEP assessment.