May 2014
Volume 55, Issue 5
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Eye Movements, Strabismus, Amblyopia and Neuro-ophthalmology  |   May 2014
Audiovisual Perception in Adults With Amblyopia: A Study Using the McGurk Effect
Author Affiliations & Notes
  • Cindy Narinesingh
    Program in Neuroscience and Mental Health, The Hospital for Sick Children, Toronto, Canada
  • Michael Wan
    Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Canada
  • Herbert C. Goltz
    Program in Neuroscience and Mental Health, The Hospital for Sick Children, Toronto, Canada
    Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Canada
  • Manokaraananthan Chandrakumar
    Program in Neuroscience and Mental Health, The Hospital for Sick Children, Toronto, Canada
  • Agnes M. F. Wong
    Program in Neuroscience and Mental Health, The Hospital for Sick Children, Toronto, Canada
  • Correspondence: Agnes M. F. Wong, Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, 555 University Avenue, Toronto, ON, Canada M5G 1X8; agnes.wong@sickkids.ca.  
Investigative Ophthalmology & Visual Science May 2014, Vol.55, 3158-3164. doi:10.1167/iovs.14-14140
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      Cindy Narinesingh, Michael Wan, Herbert C. Goltz, Manokaraananthan Chandrakumar, Agnes M. F. Wong; Audiovisual Perception in Adults With Amblyopia: A Study Using the McGurk Effect. Invest. Ophthalmol. Vis. Sci. 2014;55(5):3158-3164. doi: 10.1167/iovs.14-14140.

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      © 2016 Association for Research in Vision and Ophthalmology.

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Abstract

Purpose.: The effects on multisensory integration have rarely been examined in amblyopia. The McGurk effect is a well-established audiovisual illusion that is manifested when an auditory phoneme is presented concurrently with an incongruent visual phoneme. Visually healthy viewers will hear a phoneme that does not match the actual auditory stimulus, having been perceptually influenced by the visual phoneme. This study examines audiovisual integration in adults with amblyopia.

Methods.: Twenty-two subjects with amblyopia and 25 visually healthy controls participated. Participants viewed videos of combinations of visual and auditory phonemes, and were asked to report what they heard. Some videos had congruent video and audio (control), whereas others had incongruent video and audio (McGurk). The McGurk effect is strongest when the visual phoneme dominates over the audio phoneme, resulting in low auditory accuracy on the task.

Results.: Adults with amblyopia demonstrated a weaker McGurk effect than visually healthy controls (P = 0.01). The difference was greatest when viewing monocularly with the amblyopic eye, and it was also evident when viewing binocularly or monocularly with the fellow eye. No correlations were found between the strength of the McGurk effect and either visual acuity or stereoacuity in subjects with amblyopia. Subjects with amblyopia and controls showed a similar response pattern to different speakers and syllables, and subjects with amblyopia consistently demonstrated a weaker effect than controls.

Conclusions.: Abnormal visual experience early in life can have negative consequences for audiovisual integration that persists into adulthood in people with amblyopia.

Introduction
Amblyopia is defined as a unilateral or bilateral loss of visual acuity due to abnormal visual experience early in life. 1 It is the leading cause of monocular blindness worldwide, affecting approximately 3% to 5% of the population. 2,3 Although amblyopia is classically defined by a loss of visual acuity, 4 there is an accumulating body of research showing that it also is associated with a number of complex perceptual impairments. 58 Patients with amblyopia exhibit deficits in tasks including visual noise segregation, 6 real world scene perception, 7 visuospatial attention, 9 motion processing, 5,10 and attending to multiple simultaneous visual stimuli. 8  
Audiovisual integration is a fundamental component of natural speech perception and underlies an individual's ability to learn and communicate. 11 The McGurk effect is a well-established audiovisual illusion that occurs when the visual signal of one phoneme is presented concurrently with the auditory signal of a different phoneme. 12 With specific audiovisual pairs, visually healthy individuals will hear a phoneme that does not match the actual auditory signal, having been influenced by the incongruent visual phoneme. The McGurk effect is such a dominant perceptual effect that participants will continue to report hearing the same illusionary phoneme even after the full nature of the effect has been explained to them. 13 Electrophysiological studies have shown that the McGurk effect is based on a complex process of audiovisual integration and, as such, provides a valuable tool to examine how this process is affected in a neurovisual disorder such as amblyopia. 13,14  
According to the maximum likelihood estimate model, during multisensory integration, visual dominance occurs when the perceived variance of the visual estimate is lower than the variance associated with the other sensory modality. 15 When adding noise to the visual signal in a multisensory task, the influence of the visual signal varied based on the extent to which the signal was degraded. It is reasonable to hypothesize that audiovisual integration could operate similarly in amblyopia, with auditory input dominating over less reliable visual input. Indeed, reduced McGurk effect and deficits in similar audiovisual illusions (e.g., Colavita effect, a visual dominance effect that reflects a lower-level audiovisual function 16 ) have been found in patients with early visual deprivation. Patients treated for bilateral congenital cataracts demonstrated a reduced McGurk effect when compared with visually healthy controls. 17 Similarly, when tested for the Colavita effect, patients with monocular enucleation failed to show visual dominance when presented with audiovisual stimuli compared with controls, indicating that visual impairment in only one eye can modify multisensory processing. 18 A recently published abstract on a small case series using the McGurk effect demonstrated that children with amblyopia responded differently to integrated visual-auditory signals compared with visually healthy controls, even when viewing binocularly (Burgmeier RJ, et al. IOVS. 2012;53:ARVO E-Abstract 3895). 
Reduced McGurk effect also has been reported in patients with various neurological “integration” disorders. Adolescents with schizophrenia showed a reduced McGurk effect compared with healthy adolescent controls; however, adults with schizophrenia show no difference from age-matched controls. 19 Similarly, children with autism spectrum disorder have a weaker effect at younger ages, but showed results similar to controls at older ages, implying a developmental delay in multisensory integration, rather than a permanent deficit. 20 These studies suggest that multisensory deficits can resolve when development is complete or they can persist into adulthood, depending on the nature and timing of sensory impairment. A key factor may be whether or not deprivation occurs during the critical period for multisensory development, as is the case with amblyopia. To date, there have been no studies of the McGurk effect in adults with amblyopia. We hypothesize that the multisensory deficits found in children with unilateral amblyopia (caused by strabismus and/or anisometropia) will continue into adulthood, similar to patients treated for bilateral congenital cataracts (visual deprivation) who also experienced abnormal visual input during the critical period of development. 17 We predict that sensory reweighting in amblyopia will cause a reduced (but not absent) McGurk effect, indicating that multisensory integration is present but impaired. 
Methods
Participants
All participants were fluent English speakers with no known auditory or neurological disorders, and no eye pathology other than amblyopia, strabismus, or ametropia. Participants were assessed by a certified orthoptist for visual acuity (Early Treatment Diabetic Retinopathy Study chart), stereoacuity (Randot test), and eye alignment (cover-uncover test and alternate prism cover test). Amblyopia was defined as a visual acuity of 0.18 logMAR (20/30) or worse in the amblyopic eye, as well as an intraocular difference (IOD) of 0.2 logMAR (two chart lines difference). Anisometropia was defined as a difference of 1 diopter in either the sphere or astigmatic correction between the two eyes. Strabismic amblyopia refers to amblyopia in the presence of a manifest deviation (heterotropia) on cover test. Mixed amblyopia refers to the presence of both anisometropia and manifest strabismus. 
Twenty-two subjects with amblyopia were tested (19 female, mean age: 32.8 ± 10.9 years; age range, 20–56 years). Clinical details for all subjects with amblyopia are shown in the Table. Twenty-five visually healthy controls were tested (16 female, mean age: 31.8 ± 9.4 years; age range, 19–56 years). To be considered visually healthy, controls were required to have corrected-to-normal visual acuity of 0.1 logMAR (20/25) or better and stereoacuity of 40 seconds of arc or better. Informed consent was obtained from all participants. The study was approved by the Research Ethics Board at The Hospital for Sick Children. All protocols adhered to the guidelines of the Declaration of Helsinki. 
Table
 
Characteristics of Subjects With Amblyopia
Table
 
Characteristics of Subjects With Amblyopia
Participant Age Type of Amblyopia Visual Acuity, logMAR Refractive Correction Stereoacuity, Seconds of Arc
Right Eye Left Eye Right Eye Left Eye
1 24 Mixed −0.1 0.18 −1.25 −2.50+0.50×175 200
2 30 Strab 0 0.3 −1.00+0.75×022 −1.00+0.50×169 3000
3 35 Strab 0.7 0.1 +4.00+0.75×15 +4.00+0.25×065 Neg
4 20 Aniso 0 0.48 −1.50+0.50×080 +1.00+1.25×095 200
5 27 Mixed 0 1 Plano Plano+1.50×130 Neg
6 23 Strab 0.3 −0.1 +1.50+1.50×065 +1.25+1.00×110 Neg
7 20 Mixed 0 0.4 −4.25+1.50×088 −3.00+2.25×90 3000
8 27 Aniso 0 0.4 −1.50+0.50×080 −3.00+1.50×080 120
9 34 Strab 0.2 0 +4.25 +4.25 Neg
10 22 Aniso 0.48 −0.1 −11.25 −3.25 Neg
11 20 Aniso −0.1 1 −0.50 +5.00 3000
12* 37 Mixed 0.06 0.24 −5.50+0.50×163 −7.25 Neg
13 27 Aniso 0 0.3 +0.25 +2.75 140
14 46 Aniso 0.7 0 +2.25+0.25×174 −0.75 3000
15 44 Strab 0.1 0.6 −7.00+1.75×063 −7.00+2.50×110 Neg
16 36 Aniso 0.4 0 −1.00 +1.25 140
17 47 Aniso 1 −0.1 +4.50 Plano 3000
18 38 Mixed −0.1 0.2 −4.25 −3.25 3000
19 56 Mixed 0.1 0.9 +1.00 +2.00 Neg
20 52 Aniso 0.6 0 +3.25+0.75×020 Plano+0.75×175 400
21 36 Strab 0.4 0.1 +6.50 +7.00 3000
22 21 Strab 0.2 0.6 +0.75+2.00×67 +1.00+2.00×104 Neg
Stimuli
Video and audio stimuli were recorded with a tripod-mounted camera (CyberShot DSC-TX10; Sony Corporation, Tokyo, Japan) and edited and synchronized using video editing software (VideoStudio Pro X4; Corel Corporation, Ottawa, Canada). Each video consisted of one of five syllables repeated three times. Videos were approximately 5 seconds in length. Two young adult female speakers were used, both were fluent in English. Speaker 1 was Asian and Speaker 2 was Caucasian. Their faces and voices were recorded against a plain black background, with only head and shoulders visible. Videos were sized to 720 × 480 pixels and audio was sampled at 48 kHz. The face portion of the stimuli subtended a visual angle of approximately 6.7° vertically and 4.8° horizontally, at an approximate viewing distance of 60 cm. 
The five syllables used were “ba,” “da,” “ga,” “tha,” and “va.” Congruent trials in which the video and audio were matched served as control stimuli. Incongruent McGurk trial videos were made by using video of “da,” “ga,” tha,” and “va,” combined with audio of “ba.” Audio and video were synchronized to the nearest frame (frame rate of 29 frames per second, corresponding to approximately 34 ms accuracy). 
Each control and McGurk trial from each speaker was repeated twice in an experimental session, for a total of 36 trials ([5 control videos + 4 McGurk videos] × 2 speakers × 2 repeats). Each trial consisted of a single presentation of a control or McGurk video, containing the three repeats of a single syllable. Control and McGurk trials were interleaved within a single block. Trials were randomized within each experimental session. 
Apparatus and Procedure
Stimuli were viewed on a 15.6-inch laptop screen (X53E; ASUSTeK Computer, Inc., Taipei, Taiwan) with a screen resolution of 1366 × 768 pixels. A custom script (Matlab; MathWorks, Natick, MA, USA) was used to display the videos and to record the responses. The audio was played through a portable speaker (Z305; Logitech International S.A., Romanel-sur-Morges, Switzerland) at a mean volume of 76 dBA, equivalent to a loud conversational level. 
Before beginning the experiment, participants were shown a sheet of paper displaying the five syllables and the phrase “something else” in large, high-contrast type to familiarize them with the response options. During the experiment, participants were instructed to maintain their gaze on the speaker in the video for the entire duration of the trial before responding. After each video was displayed, a screen was presented instructing the participants to make their response. Participants responded by pressing one of the six labeled keys on the laptop keyboard, corresponding to the five syllables or the “something else” option if they heard something that did not match any of the syllables listed. In cases in which poor acuity in the amblyopic eye prevented key press responses, participants were instructed to point to a syllable on the sheet of paper. The experimenter then made the key presses on the participant's behalf. No time limit was imposed for responses. Reaction time was not recorded due to the variations in response method. After the participant made a response, the next trial was triggered. An optional break was offered to each participant halfway through the experiment. 
Participants were tested during three viewing conditions: monocularly during amblyopic eye viewing, monocularly during fellow eye viewing, and binocular viewing for a total of three experimental sessions. Monocular testing was done by patching the nonviewing eye with an opaque patch. Binocular testing was done first and the order of monocular testing was randomized for each participant. 
Analysis
All visually healthy controls and subjects with amblyopia performed at ceiling for congruent trials, with mean accuracy for both groups exceeding 98% across all viewing conditions. Congruent trials were, therefore, not included in any subsequent analyses. For analysis purposes, any non-“ba” responses to an incongruent trial were considered incorrect and grouped together. Response accuracy was the outcome measure indicating the effect strength of the McGurk phenomenon. Lower accuracy indicates a strong McGurk effect, implying that auditory input was influenced strongly by visual input, causing incorrect responses. Greenhouse-Geisser correction was used for any statistical test in which the assumption of sphericity was violated. For monocular viewing conditions, the amblyopic eyes in subjects with amblyopia were compared with left eyes in controls, and fellow eyes in subjects with amblyopia compared with right eyes in controls. Left and right eyes in controls were analyzed with a paired t-test and no significant differences were found (t 24 = 1.9, P = 0.07). Eye dominance information was available for 14 of 25 control subjects (10 right eye dominant, 4 left eye dominant). A paired t-test was performed on the dominant eye (5.8%) versus nondominant eye (6.3%) performance, and there was no statistically significant difference (t 13 = −0.268, P = 0.79). 
Response accuracy was analyzed using a 3 × 2 repeated measures ANOVA, with Group (two groups: amblyopia and visually normal) as a between-subjects factor and Viewing Condition (three conditions: binocular, monocular amblyopic/left eye, and monocular fellow/right eye) as a within-subjects factor. A separate repeated measures ANOVA was performed with Group as a between-subjects factor and two within-subjects factors: Speaker (speaker 1, speaker 2) and Viewing Condition. Another repeated measures ANOVA was performed with Group as a between-subjects factor and two within-subjects factors: Syllable (da, ga, tha, va) and Viewing Condition. 
Results
There were significant main effects for both Group (F 1,45 = 7.02, P = 0.01; Fig. 1) and Viewing Condition (F 1.54,69.4 = 5.56, P = 0.01). The interaction of Group and Viewing Condition was not statistically significant (F 1.54,69.4 = 2.18, P = 0.13). Mean accuracy (±SE) of subjects with amblyopia (Fig. 2) was 15.8% ± 3.5% during binocular viewing (versus 7.5% ± 2.7% in controls), 25.6% ± 5.5% during amblyopic eye viewing (versus 8.8% ± 2.9% in controls during left eye viewing), and 16.4% ± 4.4% during fellow eye viewing (versus 6.0% ± 2.0% in controls during right eye viewing). 
Figure 1
 
Accuracy of incongruent trials across all viewing conditions. Lower accuracy indicates a stronger McGurk effect.
Figure 1
 
Accuracy of incongruent trials across all viewing conditions. Lower accuracy indicates a stronger McGurk effect.
Figure 2
 
Accuracy of incongruent trials by viewing condition. For monocular viewing conditions, amblyopic eyes in subjects with amblyopia were compared with left eyes in visually healthy controls, while fellow eyes in subjects with amblyopia were compared with right eyes in controls.
Figure 2
 
Accuracy of incongruent trials by viewing condition. For monocular viewing conditions, amblyopic eyes in subjects with amblyopia were compared with left eyes in visually healthy controls, while fellow eyes in subjects with amblyopia were compared with right eyes in controls.
The effects of visual acuity and stereoacuity on response accuracy in subjects with amblyopia were analyzed with separate Spearman correlation analyses. No significant correlations were found between accuracy and visual acuity (r 20 = −0.25, P = 0.26 for binocular viewing; r 20 = 0.24, P = 0.27 for amblyopic eye viewing; Fig. 3), or between accuracy and stereoacuity (r 20 = −0.13, P = 0.58 for binocular viewing; r 20 = 0.07, P = 0.74 for amblyopic eye viewing; Fig. 4). 
Figure 3
 
(a) Accuracy of incongruent trials for subjects with amblyopia under binocular viewing condition, plotted against visual acuity in the amblyopic eye. Each triangle represents an individual subject with amblyopia. (b) Accuracy of incongruent trials for subjects with amblyopia under amblyopic eye viewing condition, plotted against visual acuity in the amblyopic eye. Each triangle represents an individual subject with amblyopia.
Figure 3
 
(a) Accuracy of incongruent trials for subjects with amblyopia under binocular viewing condition, plotted against visual acuity in the amblyopic eye. Each triangle represents an individual subject with amblyopia. (b) Accuracy of incongruent trials for subjects with amblyopia under amblyopic eye viewing condition, plotted against visual acuity in the amblyopic eye. Each triangle represents an individual subject with amblyopia.
Figure 4
 
(a) Accuracy of incongruent trials for subjects with amblyopia under binocular viewing condition plotted against stereoacuity. Each triangle represents an individual subject with amblyopia. (b) Accuracy of incongruent trials for subjects with amblyopia under amblyopic eye viewing condition plotted against stereoacuity. Each triangle represents an individual subject with amblyopia.
Figure 4
 
(a) Accuracy of incongruent trials for subjects with amblyopia under binocular viewing condition plotted against stereoacuity. Each triangle represents an individual subject with amblyopia. (b) Accuracy of incongruent trials for subjects with amblyopia under amblyopic eye viewing condition plotted against stereoacuity. Each triangle represents an individual subject with amblyopia.
The main effect of Speaker (F 1,45 = 6.33, P = 0.016) was significant, but there were no significant interactions between Speaker and Group (F 1,45 = 0.3, P = 0.59) or between Speaker and Viewing Condition (F 1.86,83.7 = 0.41, P = 0.65). Speaker 1 elicited higher accuracy in both visually healthy controls and subjects with amblyopia than speaker 2 across all viewing conditions (Fig. 5). Similarly, there was a significant main effect for Syllable (F 1.42,62.5 = 24.21, P < 0.0001) with “ga” and “da” eliciting higher accuracy than “va” and “tha” (Fig. 6), but no significant interactions were found between Syllable and Group (F 1.42,62.5 = 2.05, P = 0.15), or between Syllable and Viewing Condition (F 4.4,193.6 = 0.31, P = 0.89). 
Figure 5
 
Accuracy of incongruent trials by speaker under binocular viewing condition (collapsed across all syllables).
Figure 5
 
Accuracy of incongruent trials by speaker under binocular viewing condition (collapsed across all syllables).
Figure 6
 
Accuracy of incongruent trials by video syllable under binocular viewing condition (collapsed across both speakers). All video syllables were merged with an audio syllable of “ba.” Note: Accuracy of “tha” for visually healthy controls is 0%.
Figure 6
 
Accuracy of incongruent trials by video syllable under binocular viewing condition (collapsed across both speakers). All video syllables were merged with an audio syllable of “ba.” Note: Accuracy of “tha” for visually healthy controls is 0%.
Discussion
The main finding of this study is that adults with amblyopia exhibit an impaired ability to integrate visual and auditory signals. This deficit is not only apparent during monocular amblyopic eye viewing, it is also present during binocular viewing and monocular fellow eye viewing. Although the increased magnitude of the deficit during amblyopic eye viewing may be due to a simple lack of visibility, the persistence of the deficit in all viewing conditions demonstrates that the underlying causes are more complex. This finding, together with a lack of correlation between the strength of the McGurk effect and visual acuity/stereoacuity of subjects with amblyopia, suggest that abnormal visual experience early in life is associated with abnormalities in real-world perceptual processing that is beyond visual acuity. Our study is the first to demonstrate lasting deficits in audiovisual integration in a large number of adults with amblyopia. 
The impaired audiovisual integration we have shown here adds to the growing body of evidence that amblyopia is not only associated with low-level deficits, such as visual acuity and contrast sensitivity, it is also associated with an array of deficits in complex perceptual processes. Although animal studies have shown that experimentally induced amblyopia is associated with abnormalities in the architecture and functional properties of area V1, 21,22 the observed changes in V1 are not sufficient to fully explain the myriad of higher-level perceptual deficits seen in amblyopia. 510,2325 Indeed, numerous studies in humans suggest that there are also abnormalities in downstream extrastriate and later specialized cortical areas, indicating abnormal integration over relatively large regions of space and/or time. 6,26,27 Although the effects of amblyopia on visual perception are well documented, evidence for cross-modality effects is scarce. Experimental studies on the McGurk effect using functional magnetic resonance imaging 2830 and positron emission tomography 29 have suggested that the left superior temporal sulcus, as well as other regions within the temporal and frontal cortices, 31 are critical areas for audiovisual integration during speech perception. Our findings suggest that amblyopia also may affect the development of these specialized cortical areas for audiovisual integration. 
The finding that subjects with amblyopia show persistent deficits in audiovisual integration well into adulthood differentiates it from other conditions, such as autism or schizophrenia, which appear to only delay the development of audiovisual integration, rather than causing permanent deficits. 19,20 This may be explained by the difference in pathophysiology underlying these diverse conditions. For example, autism involves widespread neural abnormalities, as well as specific “top-down” cognitive impairments including difficulties with face processing and maintaining eye contact 32 that may adversely affect the performance of the McGurk task. In contrast, because the spatiotemporal deficits in amblyopia begin as early as the primary visual cortex (V1), 3336 the reduced McGurk effect we observed likely reflects the “bottom-up” effects of amblyopia on audiovisual integration during the critical period of visual development. 
Although the relation of McGurk phenomenon to “real-world” abilities, such as speech perception and learning, are incompletely understood, 37 speech perception and sensory integration have a profound impact on learning and communication, 38 and have implications for treatment. For instance, a form of “sensory integration therapy” has been shown to help improve the reading ability of children with learning disability who have poor sensory integration and processing skills. 3941 Similarly, the findings from the present study may have important implications for the treatment of amblyopia. At present, the treatment of amblyopia focuses primarily on visual acuity and involves patching or penalizing the good eye, as has been practiced for centuries. 42 By investigating the effects of amblyopia on the integration of vision and other sensory/motor modalities, 4349 this research represents our continuous effort to provide a new framework for the expansion of current amblyopia treatment: from one that focuses on visual rehabilitation alone to one that also addresses the effects of amblyopia on other motor and sensory systems. 
Although adults with amblyopia exhibit a persistent deficit, a few important questions remain unanswered. At what age do children with amblyopia exhibit a reduced McGurk effect? Does the reduced McGurk effect change over time in children with amblyopia? Does the finding in the present study represent a relative auditory dominance over vision due to reweighting as a result of a less reliable visual input? Or does it represent a failure of audiovisual integration in general? Studies are currently under way to answer these questions. 
Acknowledgments
We thank Kiran Bassi, OC(C), and Linda Colpa, OC(C), for providing orthoptic screening, and Rana Arham Raashid for statistical assistance. 
Supported by grants from the Canadian Institutes of Health Research (MOP 106663), Leaders Opportunity Fund from the Canada Foundation for Innovation, the John and Melinda Thompson Endowment Fund in Vision Neurosciences, and the Department of Ophthalmology and Vision Sciences at The Hospital for Sick Children. 
Disclosure: C. Narinesingh, None; M. Wan, None; H.C. Goltz, None; M. Chandrakumar, None; A.M.F. Wong, None 
References
The American Academy of Ophthalmology Pediatric Ophthalmology/Strabismus PPP Panel HCfQEC. Amblyopia: Preferred Practice Pattern Guideline . San Francisco: American Academy of Ophthalmology, 2012.
Attebo K Mitchell P Cumming R Smith W Jolly N Sparkes R. Prevalence and causes of amblyopia in an adult population. Ophthalmology . 1998; 105: 154–159. [CrossRef] [PubMed]
Buch HH Vinding TT La Cour MM Nielsen NVN. The prevalence and causes of bilateral and unilateral blindness in an elderly urban Danish population. The Copenhagen City Eye Study. Acta Ophthalmol Scand . 2001; 79: 441–449. [CrossRef] [PubMed]
Levi DM Harwerth RS. Spatio-temporal interactions in anisometropic and strabismic amblyopia. Invest Ophthalmol Vis Sci . 1977; 16: 90–95. [PubMed]
Ho CSC Giaschi DED Boden CC Dougherty RR Cline RR Lyons CC. Deficient motion perception in the fellow eye of amblyopic children. Vision Res . 2005; 45: 1615–1627. [CrossRef] [PubMed]
Mansouri B Hess RF. The global processing deficit in amblyopia involves noise segregation. Vision Res . 2006; 46: 14–14. [CrossRef] [PubMed]
Mirabella G Hay S Wong AMF. Deficits in perception of images of real-world scenes in patients with a history of amblyopia. Arch Ophthalmol . 2011; 129: 176–183. [CrossRef] [PubMed]
Sharma V Levi DM Klein SA. Undercounting features and missing features: evidence for a high-level deficit in strabismic amblyopia. Nat Neurosci . 2000; 3: 496–501. [CrossRef] [PubMed]
Ho CS Paul PS Asirvatham A Cavanagh P Cline R Giaschi DE. Abnormal spatial selection and tracking in children with amblyopia. Vision Res . 2006; 46: 3274–3283. [CrossRef] [PubMed]
Simmers AJA Ledgeway TT Hess RFR McGraw PVP. Deficits to global motion processing in human amblyopia. Vision Res . 2003; 43: 729–738. [CrossRef] [PubMed]
Brunellière A Sánchez-García C Ikumi N Soto-Faraco S. Visual information constrains early and late stages of spoken-word recognition in sentence context. Int J Psychophysiol . 2013; 89: 136–147. [CrossRef] [PubMed]
McGurk H MacDonald J. Hearing lips and seeing voices. Nature . 1976; 264: 746–748. [CrossRef] [PubMed]
Saint-Amour DD De Sanctis PP Molholm SS Ritter WW Foxe JJJ. Seeing voices: high-density electrical mapping and source-analysis of the multisensory mismatch negativity evoked during the McGurk illusion. Neuropsychologia . 2007; 45: 587–597. [CrossRef] [PubMed]
Sams MM Aulanko RR Hämäläinen MM Seeing speech: visual information from lip movements modifies activity in the human auditory cortex. Neurosci Lett . 1991; 127: 141–145. [CrossRef] [PubMed]
Ernst MO Banks MS. Humans integrate visual and haptic information in a statistically optimal fashion. Nature . 2002; 415: 429–433. [CrossRef] [PubMed]
Colavita FB. Human sensory dominance. Percept Psychophys . 1974; 16: 409–412. [CrossRef]
Putzar L Hotting K Röder B. Early visual deprivation affects the development of face recognition and of audio-visual speech perception. Restor Neurol Neurosci . 2010; 28: 251–257. [PubMed]
Moro SS Steeves JK. No Colavita effect: equal auditory and visual processing in people with one eye. Exp Brain Res . 2012; 216: 367–373. [CrossRef] [PubMed]
Pearl D Yodashkin-Porat D Katz N Differences in audiovisual integration, as measured by McGurk phenomenon, among adult and adolescent patients with schizophrenia and age-matched healthy control groups. Compr Psychiatry . 2009; 50: 186–192. [CrossRef] [PubMed]
Taylor N Isaac C Milne E. A comparison of the development of audiovisual integration in children with autism spectrum disorders and typically developing children. J Autism Dev Disord . 2010; 40: 1403–1411. [CrossRef] [PubMed]
Kiorpes L Kiper DC O'Keefe LP Cavanaugh JR Movshon JA. Neuronal correlates of amblyopia in the visual cortex of macaque monkeys with experimental strabismus and anisometropia. J Neurosci . 1998; 18: 6411–6424. [PubMed]
Wiesel TNT. Postnatal development of the visual cortex and the influence of environment. Nature . 1982; 299: 583–591. [CrossRef] [PubMed]
Hess RF Howell ER. The threshold contrast sensitivity function in strabismic amblyopia: evidence for a two type classification. Vision Res . 1977; 17: 1049–1055. [CrossRef] [PubMed]
Levi DM Klein SA. Vernier acuity, crowding and amblyopia. Vision Res . 1985; 25: 979–991. [CrossRef] [PubMed]
Levi DM Yu C Kuai SG Rislove E. Global contour processing in amblyopia. Vision Res . 2007; 47: 512–524. [CrossRef] [PubMed]
Levi DM. Image segregation in strabismic amblyopia. Vision Res . 2007; 47: 1833–1838. [CrossRef] [PubMed]
Simmers AJ Bex PJ. The representation of global spatial structure in amblyopia. Vision Res . 2004; 44: 523–533. [CrossRef] [PubMed]
Nath AR Beauchamp MS. A neural basis for interindividual differences in the McGurk effect, a multisensory speech illusion. NeuroImage . 2012; 59: 781–787. [CrossRef] [PubMed]
Sekiyama K Kanno I Miura S Sugita Y. Auditory-visual speech perception examined by fMRI and PET. Neurosci Res . 2003; 47: 277–287. [CrossRef] [PubMed]
Szycik GRG Stadler JJ Tempelmann CC Münte TFT. Examining the McGurk illusion using high-field 7 Tesla functional MRI. Front Hum Neurosci . 2012; 6: 95. [CrossRef] [PubMed]
Bristow D Dehaene-Lambertz G Mattout J Hearing faces: how the infant brain matches the face it sees with the speech it hears. J Cogn Neurosci . 2009; 21: 905–921. [CrossRef] [PubMed]
Saalasti S Katsyri J Tiippana K Laine-Hernandez M von Wendt L Sams M. Audiovisual speech perception and eye gaze behavior of adults with Asperger syndrome. J Autism Dev Disord . 2011; 42: 1606–1615. [CrossRef]
Hubel DH Wiesel TN. Binocular interaction in striate cortex of kittens reared with artificial squint. J Neurophysiol . 1965; 28: 1041–1059. [PubMed]
Hubel DH Wiesel TN. Receptive fields and functional architecture of monkey striate cortex. J Physiol . 1968; 195: 215–243. [CrossRef] [PubMed]
Hubel DH Wiesel TN. Anatomical demonstration of columns in the monkey striate cortex. Nature . 1969; 221: 747–750. [CrossRef] [PubMed]
Hubel DH Wiesel TN. Ferrier lecture. Functional architecture of macaque monkey visual cortex. Proc R Soc Lond B Biol Sci . 1977; 198: 1–59. [CrossRef] [PubMed]
Brancazio L Miller JL. Use of visual information in speech perception: evidence for a visual rate effect both with and without a McGurk effect. Percept Psychophys . 2005; 67: 759–769. [CrossRef] [PubMed]
Hayes EAE Tiippana KK Nicol TGT Sams MM Kraus NN. Integration of heard and seen speech: a factor in learning disabilities in children. Neurosci Lett . 2003; 351: 46–50. [CrossRef] [PubMed]
May-Benson TAT Koomar JAJ. Systematic review of the research evidence examining the effectiveness of interventions using a sensory integrative approach for children. Am J Occup Ther . 2010; 64: 403–414. [CrossRef] [PubMed]
Nelson A Copley J Flanigan K Underwood K. Occupational therapists prefer combining multiple intervention approaches for children with learning difficulties. Aust Occup Ther J . 2009; 56: 51–62. [CrossRef] [PubMed]
Polatajko HJ Cantin N. Exploring the effectiveness of occupational therapy interventions, other than the sensory integration approach, with children and adolescents experiencing difficulty processing and integrating sensory information. Am J Occup Ther . 2010; 64: 415–429. [CrossRef] [PubMed]
Stewart CE Moseley MJ Fielder AR. Amblyopia therapy: an update. Strabismus . 2011; 19: 91–98. [CrossRef] [PubMed]
Gonzalez EG Wong AM Niechwiej-Szwedo E Tarita-Nistor L Steinbach MJ. Eye position stability in amblyopia and in normal binocular vision. Invest Ophthalmol Vis Sci . 2012; 53: 5386–5394. [CrossRef] [PubMed]
Niechwiej-Szwedo E Chandrakumar M Goltz HC Wong AM. Effects of strabismic amblyopia and strabismus without amblyopia on visuomotor behavior, I: saccadic eye movements. Invest Ophthalmol Vis Sci . 2012; 53: 7458–7468. [CrossRef] [PubMed]
Niechwiej-Szwedo E Goltz HC Chandrakumar M Hirji Z Crawford JD Wong AM. Effects of anisometropic amblyopia on visuomotor behavior: II. Visually-guided reaching. Invest Ophthalmol Vis Sci . 2011; 52: 795–803. [CrossRef] [PubMed]
Niechwiej-Szwedo E Goltz HC Chandrakumar M Hirji Z Wong AM. Effects of anisometropic amblyopia on visuomotor behavior, III: temporal eye-hand coordination during reaching. Invest Ophthalmol Vis Sci . 2011; 52: 5853–5861. [CrossRef] [PubMed]
Niechwiej-Szwedo E Goltz HC Chandrakumar M Hirji ZA Wong AM. Effects of anisometropic amblyopia on visuomotor behavior, I: saccadic eye movements. Invest Ophthalmol Vis Sci . 2010; 51: 6348–6354. [CrossRef] [PubMed]
Niechwiej-Szwedo E Goltz HC Chandrakumar M Wong AM. The effect of sensory uncertainty due to amblyopia (lazy eye) on the planning and execution of visually-guided 3D reaching movements. PLoS One . 2012; 7: e31075. [CrossRef] [PubMed]
Niechwiej-Szwedo E Kennedy SA Colpa L Chandrakumar M Goltz HC Wong AM. Effects of induced monocular blur versus anisometropic amblyopia on saccades, reaching, and eye-hand coordination. Invest Ophthalmol Vis Sci . 2012; 53: 4354–4362. [CrossRef] [PubMed]
Figure 1
 
Accuracy of incongruent trials across all viewing conditions. Lower accuracy indicates a stronger McGurk effect.
Figure 1
 
Accuracy of incongruent trials across all viewing conditions. Lower accuracy indicates a stronger McGurk effect.
Figure 2
 
Accuracy of incongruent trials by viewing condition. For monocular viewing conditions, amblyopic eyes in subjects with amblyopia were compared with left eyes in visually healthy controls, while fellow eyes in subjects with amblyopia were compared with right eyes in controls.
Figure 2
 
Accuracy of incongruent trials by viewing condition. For monocular viewing conditions, amblyopic eyes in subjects with amblyopia were compared with left eyes in visually healthy controls, while fellow eyes in subjects with amblyopia were compared with right eyes in controls.
Figure 3
 
(a) Accuracy of incongruent trials for subjects with amblyopia under binocular viewing condition, plotted against visual acuity in the amblyopic eye. Each triangle represents an individual subject with amblyopia. (b) Accuracy of incongruent trials for subjects with amblyopia under amblyopic eye viewing condition, plotted against visual acuity in the amblyopic eye. Each triangle represents an individual subject with amblyopia.
Figure 3
 
(a) Accuracy of incongruent trials for subjects with amblyopia under binocular viewing condition, plotted against visual acuity in the amblyopic eye. Each triangle represents an individual subject with amblyopia. (b) Accuracy of incongruent trials for subjects with amblyopia under amblyopic eye viewing condition, plotted against visual acuity in the amblyopic eye. Each triangle represents an individual subject with amblyopia.
Figure 4
 
(a) Accuracy of incongruent trials for subjects with amblyopia under binocular viewing condition plotted against stereoacuity. Each triangle represents an individual subject with amblyopia. (b) Accuracy of incongruent trials for subjects with amblyopia under amblyopic eye viewing condition plotted against stereoacuity. Each triangle represents an individual subject with amblyopia.
Figure 4
 
(a) Accuracy of incongruent trials for subjects with amblyopia under binocular viewing condition plotted against stereoacuity. Each triangle represents an individual subject with amblyopia. (b) Accuracy of incongruent trials for subjects with amblyopia under amblyopic eye viewing condition plotted against stereoacuity. Each triangle represents an individual subject with amblyopia.
Figure 5
 
Accuracy of incongruent trials by speaker under binocular viewing condition (collapsed across all syllables).
Figure 5
 
Accuracy of incongruent trials by speaker under binocular viewing condition (collapsed across all syllables).
Figure 6
 
Accuracy of incongruent trials by video syllable under binocular viewing condition (collapsed across both speakers). All video syllables were merged with an audio syllable of “ba.” Note: Accuracy of “tha” for visually healthy controls is 0%.
Figure 6
 
Accuracy of incongruent trials by video syllable under binocular viewing condition (collapsed across both speakers). All video syllables were merged with an audio syllable of “ba.” Note: Accuracy of “tha” for visually healthy controls is 0%.
Table
 
Characteristics of Subjects With Amblyopia
Table
 
Characteristics of Subjects With Amblyopia
Participant Age Type of Amblyopia Visual Acuity, logMAR Refractive Correction Stereoacuity, Seconds of Arc
Right Eye Left Eye Right Eye Left Eye
1 24 Mixed −0.1 0.18 −1.25 −2.50+0.50×175 200
2 30 Strab 0 0.3 −1.00+0.75×022 −1.00+0.50×169 3000
3 35 Strab 0.7 0.1 +4.00+0.75×15 +4.00+0.25×065 Neg
4 20 Aniso 0 0.48 −1.50+0.50×080 +1.00+1.25×095 200
5 27 Mixed 0 1 Plano Plano+1.50×130 Neg
6 23 Strab 0.3 −0.1 +1.50+1.50×065 +1.25+1.00×110 Neg
7 20 Mixed 0 0.4 −4.25+1.50×088 −3.00+2.25×90 3000
8 27 Aniso 0 0.4 −1.50+0.50×080 −3.00+1.50×080 120
9 34 Strab 0.2 0 +4.25 +4.25 Neg
10 22 Aniso 0.48 −0.1 −11.25 −3.25 Neg
11 20 Aniso −0.1 1 −0.50 +5.00 3000
12* 37 Mixed 0.06 0.24 −5.50+0.50×163 −7.25 Neg
13 27 Aniso 0 0.3 +0.25 +2.75 140
14 46 Aniso 0.7 0 +2.25+0.25×174 −0.75 3000
15 44 Strab 0.1 0.6 −7.00+1.75×063 −7.00+2.50×110 Neg
16 36 Aniso 0.4 0 −1.00 +1.25 140
17 47 Aniso 1 −0.1 +4.50 Plano 3000
18 38 Mixed −0.1 0.2 −4.25 −3.25 3000
19 56 Mixed 0.1 0.9 +1.00 +2.00 Neg
20 52 Aniso 0.6 0 +3.25+0.75×020 Plano+0.75×175 400
21 36 Strab 0.4 0.1 +6.50 +7.00 3000
22 21 Strab 0.2 0.6 +0.75+2.00×67 +1.00+2.00×104 Neg
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