Perception of simulated forward and backward motion from optic flow at two different speeds in infants using high-density EEG : a longitudinal study
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High-density electroencephalogram (EEG) was used in a longitudinal study in infants at 4-5 months and later at 9-10 months to study brain electrical activity as the participants were presented with simulated forward and backward motion from optic flow at two different speeds, with a static inter-stimulus between each motion condition. The aim of the research was to investigate the evoked and oscillatory brain responses to the motion stimuli in infants, with particular attention directed at the N2 component, as well as to the oscillatory activity recorded in the occipital and parietal regions of the brain. The results showed a main effect of direction, indicating that infants had faster processing times for forward than the backward optic flow, as shown by longer latencies for the latter condition. Further, low speed was more easily processed than high speed, for both directions, but only by the older infants. Lower amplitudes were recorded for the older infants, and it was found that speed affected amplitude for backward motion only, with high speed displaying higher amplitudes, regardless of age. Additionally, direction affected amplitude for low speed only, with forward motion displaying higher amplitudes. Finally, observation of the oscillatory activity revealed theta- and alpha- desynchronizations at both ages when the TSEs for the motion conditions were compared to the static condition, with synchronizations being recorded for the static condition. However, no decrease in low-frequency activity was registered at the second testing, contrary to the expectations. It was concluded that the infant brain specializes and becomes more sensitive to visual motion stimuli as it matures.