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Visual Neuroscience Lab

Maturation Research

Select Abstracts from Completed Projects

This research is funded by the Natural Sciences and Engineering Council of Canada (NSERC).

Giaschi, D., Narasimhan, S., Solski, A., Harrison, E. & Wilcox, L.M. (2013) On the typical development of stereopsis: Fine and coarse processing. Vision Research , 89, 65­71.

Stereoscopic depth perception may be obtained from small retinal disparities that can be fused for single vision (fine stereopsis), but reliable depth information is also obtained from larger disparities that produce double vision (coarse stereopsis). While there is some evidence that stereoacuity improves with age, little is known about the development and maturation of coarse stereopsis. Here we address this gap by assessing the maturation of stereoscopic depth perception in children (4­14 years) and adults over a large range of disparities from fused (fine) to diplopic (coarse). The observer’s task was to indicate whether a stereoscopic cartoon character was nearer or farther away than a zero-disparity reference frame. The test disparities were grouped into fine (0.02, 0.08, 0.17, 0.33, 0.68, 1.0 deg) and coarse (2.0, 2.5, 3.0, 3.5 deg) ranges based on an initial determination of the diplopia threshold for each observer. Next, percent correct depth direction was determined as a function of disparity. In the coarse range, accuracy decreased slightly with disparity and there were no differences as a function of age. In the fine range, accuracy was constant across all disparities in adults and increased with disparity in children of all ages. Performance was immature in all children at the finest disparity tested. We conclude that stereopsis in the coarse range is mature at 4 years of age, but stereopsis in the fine range, at least for small disparities, continues to mature into the school-age years.

Edwards V, Giaschi D, Low P, Edgell D (2005) Sensory and non-sensory influences on children’s performance of dichotic pitch perception tasks. Journal of the Acoustical Society of America,117, 3157-3164.

Dichotic pitch perception reflects the auditory system's use of binaural cues to perceptually separate different sound sources and to determine the spatial location of sounds. Several studies were conducted to identify factors that influence children's dichotic pitch perception thresholds. An initial study of school children revealed an age-related improvement in thresholds for lateralizing dichotic pitch tones. In subsequent studies potential sensory and nonsensory limitations on young children's performance of dichotic pitch lateralization tasks were examined. A training study showed that with sufficient practice, young children lateralize dichotic pitch stimuli as well as adults, indicating an age difference in perceptual learning of the lateralization task. Changing the task requirements so that young children made a judgment about the pitch of dichotic pitch tones, rather than the spatial location of the tones, also resulted in significantly better thresholds. These findings indicate that nonsensory factors limit young children's performance of dichotic pitch tasks.

Parrish E, Giaschi D, Boden C, Dougherty D (2005) The maturation of form and motion perception in school age children. Vision Research, 45, 827-837.

The purpose of the current study was to investigate the maturation of form and motion perception, speci€cally the component visual abilities involved in the identi€cation of motion-de€ned form, in children ranging in age from 3 to 12 years. Experiment 1 compared the maturation of motion-de€ned and texture-de€ned shape identi€cation. Minimum speed thresholds on the motionde€ned shape task decreased until age 7 years. Orientation difference thresholds on the texture-de€ned shape task decreased until age 11 years. Experiment 2 compared the maturation of global motion and global texture direction discrimination. Coherence thresholds on both tasks were similar in children of all ages and adults. Experiment 3 compared the maturation of direction discrimination on motion coherence and motion displacement tasks. Maximum displacement thresholds (Dmax) increased until age 7 years. The results are discussed with respect to the maturation of M/dorsal and P/ventral visual pathways.

 



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