PubMed · 13720206
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J R DAVIS, B SHACKEL. 1960. Changes in the electro-oculogram potential level.. https://doi.org/10.1136/bjo.44.10.606
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The emerging ability to represent an oscillating moving object over occlusions was studied in 7-21-week-old infants. The object moved at 0.25 Hz and was either occluded at the center of the trajectory (for 0.3 s) or at one turning point (for 0.7 s). Each trial lasted for 20 s. Both eye and head movements were measured. By using two kinds of motion, sinusoidal (varying velocity) and triangular (constant velocity), infants' ability to take velocity change into account when predicting the reappearance of the moving object was tested. Over the age period studied, performance at the central occluder progressed from almost total ignorance of what happened to consistent predictive behavior. From around 12 weeks of age, infants began to form representations of the moving object that persisted over temporary occlusions. At around 5 months of age these representations began to incorporate the dynamics of the represented motion. Strong learning effects were obtained over single trials, but there was no evidence of retention between trials. The individual differences were profound.
Onset of visual motion evokes a component in the EEG, the motion onset VEP. Exploring its motion specificity with a direction-specific adaptation paradigm, previous work demonstrated that less than 50% of the motion onset VEP represents actual motion detection. Here, we tested whether preadaptation of flicker-sensitive mechanisms can help to isolate motion-specific responses in the VEP. Flicker preadaptation was accomplished by limiting dot lifetime in the random-dot kinematograms that we used to study the direction specificity of motion adaptation. With unlimited dot lifetime, motion adaptation reduced the VEP amplitude to 35% (adapted direction) and 50% (opposite direction). With the shortest dot lifetime (40 ms), motion adaptation reduced the amplitude to 55% (adapted direction) and 70% (opposite direction). These findings suggest that random-dot kinematograms with short dot lifetimes could improve the investigation of human motion processing, be it in electrophysiology or other fields. While such stimuli successfully preadapt flicker-related components, they still evoke a sizable response, of which an estimated 70% is motion-specific.