Brain Mechanisms Underlying Human Motion Perception

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The ability to see objects in motion is a fundamental aspect of vision in all species. The overall goal of my research is to understand how the perception of motion is normally achieved by the human brain. It is rare for a person to totally lack the ability to perceive motion, but certain developmental disorders affect the ability to perceive specific types of motion. In addition, the development of motion perception in children differs for different types of motion. We study typical and atypical visual development to clarify normal mechanisms of motion perception. It is common to interpret our type of research in terms of the underlying pathways or streams in the brain. Form and colour perception are typically linked to the ventral stream and motion perception to the dorsal stream. It has been suggested that the dorsal stream is more vulnerable to damage during childhood than the ventral stream. However, the dorsal/ventral view of visual processing is probably too simplistic, and more recent evidence implicates the ventral stream in motion perception for slow speeds. This brings into question the usefulness of the dorsal stream vulnerability idea. The specific goal of this proposal is to address this controversy by identify the brain regions involved in the processing of fast and slow motion using two non-invasive techniques. With a behavioural technique called psychophysics, computer "games" will be used to measure a child's ability to perceive different types of motion. With functional magnetic resonance imaging (MRI), regions where brain activity changes while a child watches different types of motion will be determined. Our approach is unique in combining information about the typical maturation of motion perception in children (3 to 17 years old) with information about the changes in motion perception caused by lazy eye, dyslexia or preterm birth, and in the linking of psychophysical and functional MRI data in these populations. This work will provide new challenges for existing models of motion perception and help resolve some current controversies. There will be practical implications for the treatment and rehabilitation of Canadian children and adults with visual problems caused by neural disorders or brain injury.