Deborah Giaschi

University of British Columbia - Vancouver, Vancouver, British Columbia, Canada

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Publications (56)153.42 Total impact

  • Kimberly Meier · Brian Sum · Deborah Giaschi
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    ABSTRACT: There are conflicting results on whether children with amblyopia have deficits in global motion perception. Differences in the stimulus parameters used in different studies may have led to these discrepancies. Specifically, the speed of a global motion stimulus can be broken down into a ratio of spatial (∆x) and temporal (∆t) displacement parameters. We have shown that coherence thresholds for global motion direction discrimination are immature in 4-6 year olds when smaller ∆x/∆t values are used to create the speed, but adult-like when larger values are used (Meier & Giaschi, 2014). We hypothesize that coherence thresholds in children with amblyopia will be elevated for parameters that take longer to mature, and similar to controls for parameters that mature earlier. Coherence thresholds were assessed in children with amblyopia (7--16 years, M = 11.21) and age-matched controls using a two-alternative forced choice direction discrimination task. Six combinations of spatial and temporal parameters were used: spatial displacement (∆x) was 1, 5, or 30 arc min; temporal displacement (∆t) was 17 or 50 ms. Children were assessed monocularly, and conducted one run per eye, for a total of 12 measurements. Children with amblyopia had elevated coherence thresholds in the amblyopic eye for ∆x = 1 and 5 arc min, but not ∆x = 30 arc min, at both ∆t = 17 and 50 ms. There was a similar trend in the fellow eye at ∆t = 17 ms, ∆x = 1 arc min. Children with amblyopia show deficits in global motion perception in each eye when they are tested with stimuli that use shorter spatial displacements, regardless of temporal displacement. This is consistent with the hypothesis that aspects of motion perception that take longer to mature are more susceptible to damage by amblyopia. Meeting abstract presented at VSS 2015.
    No preview · Article · Sep 2015 · Journal of Vision
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    ABSTRACT: Patients with the autosomal recessive disorder phenylketonuria (PKU) have elevated phenylalanine levels that impede production of tyrosine, a precursor to dopamine. Lowered dopamine levels lead to a number of deficits, including lowered visual contrast sensitivity (Diamond & Herzberg, 1996; Gramer et al, 2013; Stemerdink et al, 1999). In the present study we measured contrast sensitivity and blood phenylalanine and tyrosine levels on multiple visits in 10 PKU patients, 5 of whom began a course of sapropterin dihydrochloride (Kuvan®), which reduces phenylalanine levels (in some patients). The expectation was that initial contrast sensitivity would correlate with phenylalanine and tyrosine levels, and that in patients who responded well to sapropterin dihydrochloride, reduced phenylalanine levels would correspond to increased contrast sensitivity. Contrast thresholds for each PKU patient and age-matched controls were determined using a four-alternative forced-choice grating discrimination task with an adaptive staircase (the Freiburg Visual Acuity Test, Bach, 1996; 2007) at five spatial frequencies, on multiple visits (1-4 per patient). On Visit 1, prior to sapropterin dihydrochloride treatment, contrast thresholds were an average of 67% higher in PKU patients than in their age-matched controls, but no correlation between performance and phenylalanine or tyrosine levels was detectable. During sapropterin dihydrochloride treatment, however, phenylalanine levels dropped by half, and contrast sensitivity deficits disappeared entirely. Practice also played a role in improvement: threshold elevations were 10% lower on Visit 2 among those patients who had not begun treatment. Control participants displayed a similar degree of improvement on their second visit. Results during treatment suggest that sapropterin hydrochloride may be effective in reducing both phenylalanine levels and corresponding perceptual deficits in PKU patients. The practice effect, however, raises the possibility that only some of the contrast sensitivity deficit in PKU patients is the result of dopamine-related impairments in the retina or visual cortex. Meeting abstract presented at VSS 2015.
    No preview · Article · Sep 2015 · Journal of Vision
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    ABSTRACT: There is growing evidence for deficits in motion perception in amblyopia, but these are rarely assessed clinically. In this prospective study we examined the effect of occlusion therapy on motion-defined form perception and multiple-object tracking. Participants included children (3-10 years old) with unilateral anisometropic and/or strabismic amblyopia who were currently undergoing occlusion therapy and age-matched control children with normal vision. At the start of the study, deficits in motion-defined form perception were present in at least one eye in 69% of the children with amblyopia. These deficits were still present at the end of the study in 55% of the amblyopia group. For multiple-object tracking, deficits were present initially in 64% and finally in 55% of the children with amblyopia, even after completion of occlusion therapy. Many of these deficits persisted in spite of an improvement in amblyopic eye visual acuity in response to occlusion therapy. The prevalence of motion perception deficits in amblyopia as well as their resistance to occlusion therapy, support the need for new approaches to amblyopia treatment. Copyright © 2015. Published by Elsevier Ltd.
    No preview · Article · Jun 2015 · Vision research
  • Sae Kaneko · Deborah Giaschi · Stuart Anstis
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    ABSTRACT: Independent channels respond to both the spatial and temporal characteristics of visual stimuli. Gratings <3cycles per degree (cpd) are sensed by transient channels that prefer intermittent stimulation, while gratings >3cpd are sensed by sustained channels that prefer steady stimulation. From this we predict that adaptation to a spatially uniform flickering field will selectively adapt the transient channels and raise the apparent spatial frequency of coarse sinusoidal gratings. Observers adapted to a spatially uniform field whose upper or lower half was steady and whose other half was flickering. They then adjusted the spatial frequency of a stationary test (matching) grating on the previously unmodulated half field until it matched the apparent spatial frequency of a grating falling on the previously flickering half field. The adapting field flickered at 8Hz and the spatial frequency of the gratings was varied in octave steps from 0.25 to 16cpd. As predicted, adapting to flicker raised the apparent spatial frequency of the test gratings. The aftereffect reached a peak of 11% between 0.5 and 1cpd and disappeared above 4cpd. We also observed that superimposed 10Hz luminance flicker raised the apparent spatial frequency of 0.5cpd test gratings. The effect was not seen with slower flicker or finer test gratings. Altogether, our study suggests that apparent spatial frequency is determined by the balance between transient and sustained channels and that an imbalance between the channels caused by flicker can alter spatial frequency perception. Copyright © 2015. Published by Elsevier Ltd.
    No preview · Article · Feb 2015 · Vision Research
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    ABSTRACT: Self-report, when available, is considered the ideal way to assess the intensity and other aspects of pain in children. However, self-report scales are often too complex cognitively for preschool-aged children (2-4 years). The Rainbow Pain Scale (RPS) was developed to provide individualized self-reported pain ratings for preschool-aged children. The psychometric properties of this scale have yet to be evaluated. To ensure validity, our first step was to compare RPS scores to a well-validated scale in older children who were able to self-report their pain. The purpose of this study was to assess the concurrent validity of the RPS in children aged 5 to 10 years as proof of principle. We compared ratings of 49 children's pain using the RPS with those on the Faces Pain Scale-Revised (FPS-R). Participants suffering from pain related to cancer and cancer treatment were recruited to complete both scales at 3 time points, during both inpatient and outpatient clinic visits. Pearson's r and Cohen's κ were used to evaluate the level of association between the scales. The association between RPS and the FPS-R was greater than .7 at all 3 visits; r = .96 between the scales at the first clinic visit, .97 at the second visit, and .93 at the third visit. Cohen's κ between scales was 1.0 at the first clinic visit, .95 at the second visit, and .87 at the third visit. The RPS shows excellent concurrent validity with the FPS-R in school-aged children. The next step will be to examine the psychometric properties of the RPS in preschool-aged children. © 2014 by Association of Pediatric Hematology/Oncology Nurses.
    Full-text · Article · Nov 2014 · Journal of Pediatric Oncology Nursing
  • Kimberly Meier · Deborah Giaschi
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    ABSTRACT: The typical development of motion perception is commonly assessed with tests of global motion integration using random dot kinematograms. There are discrepancies, however, with respect to when typically-developing children reach adult-like performance on this task, ranging from as early as 3 years to as late as 12 years. To address these discrepancies, the current study measured the effect of frame duration (Δt) and signal dot spatial offset (Δx) on motion coherence thresholds in adults and children. Two Δt values were used in combination with seven Δx values, for a range of speeds (0.3-38 deg/s). Developmental comparisons showed that for the longer Δt, children performed as well as adults for larger Δx, and were immature for smaller Δx. When parameters were expressed as speed, there was a range of intermediate speeds (4-12 deg/s) for which maturity was dependent on the values of Δx and Δt tested. These results resolve previous discrepancies by showing that motion sensitivity to a given speed may be mature, or not, depending on the underlying spatial and temporal properties of the motion stimulus.
    No preview · Article · Dec 2013 · Vision research
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    ABSTRACT: 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). Here we assess the possibility that the early development of coarse stereopsis makes it resilient to the factors that cause amblyopia by comparing performance in children with a history of strabismic, anisometropic, or aniso-strabismic amblyopia and age-matched controls (5-12 years). The task was to indicate whether a cartoon character was nearer or farther away than a zero-disparity reference frame. Test disparities were grouped into fine and coarse ranges based on preliminary assessment of diplopia thresholds. In the fine range, accuracy increased with disparity for both groups, but children in the amblyopia group performed significantly worse than children in the control group, particularly when their amblyopia was associated with strabismus. In the coarse range, accuracy was constant across all disparities for both groups although performance appeared to be poorer in the aniso-strabismic group. These results suggest that, under some conditions, stereopsis for large disparities may be spared when stereopsis for small disparities is disrupted by early visual deprivation. This undetected residual binocular function has important clinical implications given recent efforts to improve amblyopia treatment outcomes by employing binocular treatment protocols.
    No preview · Article · Aug 2013 · Journal of Vision
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    ABSTRACT: 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 (4 to 14 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.
    Preview · Article · Jul 2013 · Vision research
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    ABSTRACT: The current study examined auditory processing deficits in dyslexia using a dichotic pitch stimulus and functional MRI. Cortical activation by the dichotic pitch task occurred in bilateral Heschl's gyri, right planum temporale, and right superior temporal sulcus. Adolescents with dyslexia, relative to age-matched controls, illustrated greater activity in left Heschl's gyrus for random noise, less activity in right Heschl's gyrus for all auditory conditions, and less activity in right superior temporal sulcus for a dichotic melody. Subsequent analyses showed that these group differences were attributable to dyslexic readers who performed poorly on the psychophysical task. Furthermore, behavioral performance on phonological reading was correlated to activity from dichotic conditions in right Heschl's gyrus and right superior temporal sulcus. It is postulated that these differences between reader groups is primarily due to a noise exclusion deficit shown previously in dyslexia.
    No preview · Article · Oct 2012 · Brain and Language
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    ABSTRACT: Background / Purpose: 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. We tested 114 children (4-13 years) and 18 adults (18-40 years) on a computerized stereopsis test where the participant’s task was to specify whether a Pokemon character was nearer or farther away than a reference frame at zero disparity. Main conclusion: In the fine range (disparity levels of 0.02, 0.1, 0.17, 0.33, 0.68, 1.0 deg), accuracy was lower in children under the age of 12 at the finest disparity only. There was no effect of age in the coarse range (disparity levels of 2, 2.5, 3, 3.5 deg). Our results suggest that coarse stereopsis matures before age 4, while fine stereopsis continues to develop into the school-age years.
    Preview · Conference Paper · Jul 2012
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    ABSTRACT: Background / Purpose: Stereoscopic depth percepts result from small retinal disparities within Panum’s fusional area (fine stereopsis) as well as from larger disparities that cannot be fused (coarse stereopsis). Recently we showed that coarse stereopsis is mature by age 4 when fine stereopsis is still developing (see “Narasimhan et al 2012” ;http://f1000.com/posters). We hypothesize that the early development of coarse stereopsis makes it less susceptible to amblyogenic factors. 17 children with strabismic or anisometropic amblyopia and 17 age-matched control children (5-12 years) were tested on computerized tests of fine (disparity levels of 0.02, 0.1, 0.17, 0.33, 0.68, 1.0 deg) and coarse (disparity levels of 2, 2.5, 3, 3.5 deg) stereopsis. Main conclusion: Participants were asked to indicate whether a Pokemon character was nearer or farther than a zero-disparity reference frame. Children with amblyopia performed significantly worse than control children at all fine disparities, but there was no significant difference in performance between the two groups at all coarse disparities. The early development of coarse stereopsis may provide its resilience to amblyogenic factors.
    Preview · Conference Paper · Jul 2012
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    Sathyasri Narasimhan · Emily R Harrison · Deborah E Giaschi
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    ABSTRACT: In this study we explored the possibility of using a dichoptic global motion technique to measure interocular suppression in children with amblyopia. We compared children (5-16 years old) with unilateral anisometropic and/or strabismic amblyopia to age-matched control children. Under dichoptic viewing conditions, contrast interference thresholds were determined with a global motion direction-discrimination task. Using virtual reality goggles, high contrast signal dots were presented to the amblyopic eye, while low contrast noise dots were presented to the non-amblyopic fellow eye. The contrast of the noise dots was increased until discrimination of the motion direction of the signal dots reached chance performance. Contrast interference thresholds were significantly lower in the strabismic group than in the anisometropic and control group. Our results suggest that interocular suppression is stronger in strabismic than in anisometropic amblyopia.
    Preview · Article · Jun 2012 · Vision research
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    Sathyasri Narasimhan · Deborah Giaschi
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    ABSTRACT: The purpose of this study was to investigate the effect of dot speed and dot density on the development of global motion perception by comparing the performance of adults and children (5-6years old) on a direction-discrimination task. Motion coherence thresholds were measured at two dot speeds (1 and 4deg/s) and three dot densities (1, 15, 30dots/deg(2)). Adult coherence thresholds were constant at approximately 9%, regardless of speed or density. Child coherence thresholds were significantly higher across conditions, and were most immature at the slow speed and at the sparse density. Thus, the development of global motion perception depends heavily on stimulus parameters. This finding can account for some of the discrepancy in the current developmental literature. Our results, however, caution against making general claims about motion deficits in clinical populations based on only a single measurement at a specific combination of speed and density.
    Preview · Article · Apr 2012 · Vision research
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    John Secen · Jody Culham · Cindy Ho · Deborah Giaschi
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    ABSTRACT: Deficits in multiple-object tracking have previously been reported in both the amblyopic and the clinically unaffected fellow eye of patients with amblyopia. We examined the neural correlates of this deficit using functional MRI. Attentive tracking of 1, 2 or 4 moving targets was compared to passive viewing and to baseline fixation in an amblyopic group and an age-matched control group in six regions of interest: V1, middle temporal complex (MT+), superior parietal lobule (SPL), frontal eye fields (FEF), anterior intraparietal sulcus (IPS), and posterior IPS. Activation in all regions of interest, except V1, increased with attentional load in both groups. MT+ was less active in both eyes of the amblyopic group relative to controls for passive viewing and each of the tracking conditions. Anterior IPS and FEF were less active with amblyopic eye viewing when tracking four targets. These results implicate both the low-level passive and high-level active motion systems in the multiple-object tracking deficit in amblyopia.
    Full-text · Article · Dec 2011 · Vision research
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    Jake Hayward · Grace Truong · Marita Partanen · Deborah Giaschi
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    ABSTRACT: We determined the effect of dot speed on the typical and atypical development of motion-defined form perception. Monocular motion coherence thresholds for orientation discrimination of motion-defined rectangles were determined at slow (0.1 deg/s), medium (0.9 deg/s) and fast (5.0 deg/s) dot speeds. First we examined typical development from age 4 to 31 years. We found that performance was most immature at the slow speed and in the youngest group of children (4-6 years). Next we measured motion-defined form perception in the amblyopic and fellow eyes of patients with amblyopia. Deficits were found in both eyes and were most pronounced at the slow speed. These results demonstrate the importance of dot speed to the development of motion-defined form perception. Implications regarding sensitive periods and the neural correlates of motion-defined form perception are discussed.
    Full-text · Article · Sep 2011 · Vision research
  • P. S. Paul · D. Giaschi · P. Cavanagh · R. Cline
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    ABSTRACT: We showed previously that children with amblyopia show significant deficits in motion-defined form perception (Giaschi et al., 1992, IOVS). These deficits are found in both the amblyopic and the nonamblyopic fellow eye. Performance on low-level direction-discrimination tasks is often normal in these children (Giaschi et al., 1998, ARVO). The purpose of this study was to examine performance of amblyopes on high-level motion tasks based on attentive tracking. We tested each eye of 8 children with unilateral anisometropic amblyopia (9 to 16 years old) and 20 age-matched controls on 1 low-level motion task and 4 high-level motion tasks. Children with amblyopia showed similar performance to controls in both eyes on the low-level motion coherence task and on two high-level motion tasks: the maximum number of targets that can be tracked in a multiple-item tracking task; and the perception of "long-range" apparent motion in a four-dot quartet display. However, they showed significantly worse performance than controls in both eyes on the maximum speed for tracking a single target, and in visual search for a biological-motion target, two tasks that are linked in other studies to limits of temporal attention (Battelli et al., 2000, VSS; Verstraten et al., 2000, Vis. Research). These results suggest that amblyopia may be accompanied by a loss in both eyes of some aspects of temporal attention. In contrast, a recent report finds deficits of spatial attention in the amblyopic eye of adults with strabismic amblyopia (Sharma et al., 2000, Nature Neuroscience).
    No preview · Article · Dec 2010 · Journal of Vision
  • A. Solski · D. Giaschi · L. Wilcox

    No preview · Article · Aug 2010 · Journal of Vision
  • M. Scheel · L. J. Lanyon · D. Giaschi · J. J. Barton

    No preview · Article · Aug 2010 · Journal of Vision
  • D. Giaschi · A. Zwicker · S. A. Young · B. Lee · B. Bjornson

    No preview · Article · Jun 2010 · Journal of Vision
  • D. Giaschi · K. MacKenzie · C. Boden · A. Solski · L. Wilcox

    No preview · Article · May 2010 · Journal of Vision

Publication Stats

1k Citations
153.42 Total Impact Points

Institutions

  • 1993-2015
    • University of British Columbia - Vancouver
      • • Department of Ophthalmology and Visual Sciences
      • • Department of Psychology
      Vancouver, British Columbia, Canada
  • 2009
    • Children's & Women's Health Centre of British Columbia
      Vancouver, British Columbia, Canada
  • 2005-2009
    • BC Children's Hospital
      Vancouver, British Columbia, Canada
  • 2006
    • University of California, San Diego
      • Department of Ophthalmology
      San Diego, California, United States
  • 2004
    • Government of British Columbia, Canada
      Vancouver, British Columbia, Canada
  • 1992
    • University of Toronto
      • Division of Neurology
      Toronto, Ontario, Canada
    • York University
      • Department of Psychology
      Toronto, Ontario, Canada