(2008). Dorsal stream development in motion and structure-from-motion perception. NeuroImage, 39(4): [1815][1816][1817][1818][1819][1820][1821][1822][1823] Little is known about the neural development underlying high order visual perception. For example, in detection of structures by coherently moving dots, motion information must interact with shape-based information to enable object recognition. Tasks involving these different motion-based discriminations are known to activate distinct specialized brain areas in adults. Here, we investigate neural development of normally developing children using functional magnetic resonance imaging (fMRI) during perception of randomly moving point-light dots (RM), coherently moving dots that formed a 3D rotating object (SFM) and static dots. Perception of RM enhanced neural activity as compared with static dots in motion processing-related visual areas, including visual area 3a (V3a), and middle temporal area (hMT+) in 10 adults (age 20-30 years). Children (age 5-6 years) showed less pronounced activity in area V3a than adults. Perception of SFM induced enhanced neural activity as compared to RM in adults in the left parietal shape area (PSA), whereas children increased neural activity within dorsal (V3a) and ventral brain areas (lingual gyrus) of the occipital cortex. These findings provide evidence of neural development within the dorsal pathway. First, maturation was associated with enhanced activity in specialized areas within the dorsal pathway during RM perception (V3a) and SFM perception (PSA). Secondly, high order visual perception-related neural development was associated with a shift in neural activity from low level shape and motion specialized areas in children, including partially immature area V3a, to high order areas in the parietal lobule (PSA) in adults.

Visual perceptual skills are basically mature by the age of 7 years. White matter, however, continues to develop until late adolescence. Here, we examined children (aged 5-7 years) and adults (aged 20-30 years) using diffusion tensor imaging (DTI) fiber tracking to investigate the microstructural maturation of the visual system. We characterized the brain volumes, DTI indices, and architecture of visual fiber tracts passing through white matter structures adjacent to occipital and parietal cortex (dorsal stream), and to occipital and temporal cortex (ventral stream). Dorsal, but not ventral visual stream pathways were found to increase in volume during maturation. DTI indices revealed expected maturational differences, manifested as decreased mean and radial diffusivities and increased fractional anisotropy in both streams. Additionally, fractional anisotropy was increased and radial diffusivity was decreased in the adult dorsal stream, which can be explained by specific dorsal stream myelination or increasing fiber compaction. Adult dorsal stream architecture showed additional intra- and interhemispheric connections: Dorsal fibers penetrated into contralateral hemispheres via commissural structures and projection fibers extended to the superior temporal gyrus and ventral association pathways. Moreover, intra-hemispheric connectivity was particularly strong in adult dorsal stream of the right hemisphere. Ventral stream architecture also differed between adults and children. Adults revealed additional connections to posterior lateral areas (occipital-temporal gyrus), whereas children showed connections to posterior medial areas (posterior parahippocampal and lingual gyrus). Hence, in addition to dorsal stream myelination or fiber compaction, progressing maturation of intra- and interhemispheric connectivity may contribute to the development of the visual system.

Little is known about the functional development of dorsal and ventral visual streams. The right posterior superior temporal sulcus (pSTS) represents a pivotal point of the two streams and is involved in the perception of biological motion. Here, we compared brain activity between children (aged 5-7 years) and adults (aged 20-32 years) while they were viewing point-light dot animations of biological motion. Biological motion-related activation was found in right pSTS of adults, and in right fusiform gyrus and left middle temporal lobe of children. Group comparisons revealed increased activity in pSTS for adults and in fusiform gyrus for children. Only poorly performing children showed fusiform gyrus activity. These findings indicate that pSTS functioning is not adult-like at the age of 6 years. AbstractLittle is known about the functional development of areas within dorsal and ventral visual streams. The right posterior superior temporal sulcus (pSTS) represents a pivotal point of the two streams and is involved in the perception of biological motion (BM). Here, we compared brain activity between children (5-7 y) and adults (20-32 y) while they were viewing point-light dot animations of BM. Adults showed BM related activation in right pSTS, whereas in children right fusiform gyrus (FG) and left hMT+ was activated. Group comparisons revealed increased activity in right pSTS for adults and in right FG for children. Only poorly performing children showed FG activity. These findings indicate that dorsal stream and pSTS functioning is not adult-like at age six.

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