Metacontrast masking as a measure of change detection: Children with poor reading fluency show impaired change detection for both letters and shapes

Crewther, David P.; Rutkowski, Jacqueline S.

doi:10.1101/697870

Cited by 3 publications

(4 citation statements)

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“…a reversal of the normal causality (see the different points of view: (Goswami, 2015b;a;Lobier and Valdois, 2015)). The current paper regarding early cortical physiology, and another 24/7/19 parallel one on rapid attention measured though change detection in a gap paradigm (Crewther et al, 2019) add significantly to this debate.…”

Section: Discussion 24/7/19mentioning

confidence: 81%

“…In terms of upper versus lower visual field stimulation, the clear bias for lower visual field VEP responses at first seems at odds with the reported poorer LVF vs UVF change detection (Rutkowski et al, 2003). However, reflection on the nature of the distraction provided by the dynamic mask flicker as introduced by Crewther et al (2019) or the sudden appearance of a high contrast static frame surrounding letters in the second stimulus in the gap paradigm used (Rutkowski et al, 2003) suggests that the effect of masking may be greater in the lower visual field precisely because of the increase in magnocellular sensitivity there.…”

Section: Discussion 24/7/19mentioning

confidence: 99%

“…The literature on change detection also implicates visual masking as making a contribution to change blindness (Rensink, 2002). Pertinent to this finding, Crewther et al (2019) 24/7/19 showed that metacontrast masking (with dynamic random dot annuli around each item of the change detection stimuli) provides a measure of change detection performance with higher contrast masking causing greater distraction, as evidence by poorer performance. These metacontrast change detection studies showed superior change detection for upper visual field locations.…”

Section: Introductionmentioning

confidence: 94%

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Dyslexic children show altered temporal structure of the nonlinear VEP

Rutkowski

Crewther

2019

Preprint

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The neural basis of dyslexia remains unresolved, despite many theories relating dyslexia to dysfunction in visual magnocellular and auditory temporal processing, cerebellar dysfunction, attentional deficits, as well as excessive neural noise. Recent research identifies perceptual speed as a common factor, integrating several of these systems. Optimal perceptual speed invokes transient attention as a necessary component, and change detection in gap paradigm tasks is impaired in those with dyslexia. This research has also identified an overall better change detection for targets presented in the upper compared with lower visual fields. Despite the magnocellular visual pathway being implicated in the aetiology of dyslexia over 30 years ago, objective physiological measures have been lacking. Thus, we employed nonlinear visual evoked potential (VEP) techniques which generate second order kernel terms specific for magno and parvocellular processing as a means to assessing the physiological status of poor readers (PR, n=12) compared with good readers (GR, n=16) selected from children with a mean age of 10yr. The first and second order Wiener kernels using multifocal VEP were recorded from a 4° foveal stimulus patch as well as for upper and lower visual field peripheral arcs. Foveal responses showed little difference between GR and PR for low contrast stimulation, except for the second slice of the second order kernel where lower peak amplitudes were recorded for PR vs GR. At high contrast, there was a trend to smaller first order kernel amplitudes for short latency peaks of the PR vs GR. In addition, there were significant latency differences for the first negativity in the first two slices of the second order kernel. In terms of peripheral stimulation, lower visual field response amplitudes were larger compared with upper visual field responses, for both PR and GR. A trend to larger second/first order ratio for magnocellularly driven responses suggests the possibility of lesser neural efficiency in the periphery for the PR compared with the GR. Stronger lower field peripheral response may relate to better upper visual field change detection performance when target visibility is controlled through flicking masks. In conclusion, early cortical magnocellular processing at low contrast was normal in those with dyslexia, while cortical activity related to parvocellular afferents was reduced. In addition, the study demonstrated a physiological basis for upper versus lower visual field differences related to magnocellular function.

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Section: Discussion 24/7/19mentioning

confidence: 81%

Section: Discussion 24/7/19mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 94%

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Dyslexic children show altered temporal structure of the nonlinear VEP

Rutkowski

Crewther

2019

Preprint

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“…Since that time, the evidence that many dyslexics have mildly impaired development of this visual magnocellular/transient processing system has become much stronger, although it still remains controversial [ 7 ]. Psychophysically, many dyslexics are found to display lower flicker fusion frequencies [ 8 ], reduced motion sensitivity [ 9 ], impaired focussing of visual attention [ 10 ], abnormal metacontrast masking [ 11 ] and unsteady binocular control [ 12 ]. Thus, the development of visual M- cells seems to be impaired in many, but probably not all, dyslexic people.…”

Section: Introductionmentioning

confidence: 99%

Reduced Visual Magnocellular Event-Related Potentials in Developmental Dyslexia

Stein

2021

Brain Sciences

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(1) Background—the magnocellular hypothesis proposes that impaired development of the visual timing systems in the brain that are mediated by magnocellular (M-) neurons is a major cause of dyslexia. Their function can now be assessed quite easily by analysing averaged visually evoked event-related potentials (VERPs) in the electroencephalogram (EEG). Such analysis might provide a useful, objective biomarker for diagnosing developmental dyslexia. (2) Methods—in adult dyslexics and normally reading controls, we recorded steady state VERPs, and their frequency content was computed using the fast Fourier transform. The visual stimulus was a black and white checker board whose checks reversed contrast every 100 ms. M- cells respond to this stimulus mainly at 10 Hz, whereas parvocells (P-) do so at 5 Hz. Left and right visual hemifields were stimulated separately in some subjects to see if there were latency differences between the M- inputs to the right vs. left hemispheres, and these were compared with the subjects’ handedness. (3) Results—Controls demonstrated a larger 10 Hz than 5 Hz fundamental peak in the spectra, whereas the dyslexics showed the reverse pattern. The ratio of subjects’ 10/5 Hz amplitudes predicted their reading ability. The latency of the 10 Hz peak was shorter during left than during right hemifield stimulation, and shorter in controls than in dyslexics. The latter correlated weakly with their handedness. (4) Conclusion—Steady state visual ERPs may conveniently be used to identify developmental dyslexia. However, due to the limited numbers of subjects in each sub-study, these results need confirmation.

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