Abstract
Structured patterns of global visual motion called optic flow provide crucial information about an observer's speed and direction of self-motion and about the geometry of the environment. Brain and behavioral responses to optic flow undergo considerable postnatal maturation, but relatively little brain imaging evidence describes the time course of development in motion processing systems in early to middle childhood, a time when psychophysical data suggest that there are changes in sensitivity. To fill this gap, electroencephalographic (EEG) responses were recorded in 4- to 8-year-old children who viewed three time-varying optic flow patterns (translation, rotation, and radial expansion/contraction) at three different speeds (2, 4, and 8 deg/s). Modulations of global motion coherence evoked coherent EEG responses at the first harmonic that differed by flow pattern and responses at the third harmonic and dot update rate that varied by speed. Pattern-related responses clustered over right lateral channels while speed-related responses clustered over midline channels. Both children and adults show widespread responses to modulations of motion coherence at the second harmonic that are not selective for pattern or speed. The results suggest that the developing brain segregates the processing of optic flow pattern from speed and that an adult-like pattern of neural responses to optic flow has begun to emerge by early to middle childhood.
Highlights
Structured patterns of global visual motion called optic flow provide crucial information about an observer's speed and direction of self-motion and about the shape and trajectory of moving objects [1, 2]
To address the possibility that there were significant age-related effects, we carried out a multivariate analysis of variance (MANOVA) with the real and imaginary components from the 1F1 harmonic of the EEG as the response measure and pattern type, speed (2, 4, and 8 deg/s), channel (1–128), and participant age in weeks as predictors
The results indicate that children show evoked global and local motion responses that are similar in a number of respects to adult observers, but with some specific differences that are likely to reflect immaturity in motion processing systems
Summary
Structured patterns of global visual motion called optic flow provide crucial information about an observer's speed and direction of self-motion and about the shape and trajectory of moving objects [1, 2]. Optic flow patterns change in accordance with the observer's direction and speed of motion and the geometry of the environment. Forward locomotion produces a radially expanding flow pattern [1, 2]. Head and eye translations yield translational flow while head and eye rotations result in rotational flow. This mapping between optic flow and self-motion provides observers with visually-based proprioceptive information. By locating the central vanishing point in a radial pattern of flow
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