Abrupt and ramped flicker-defined form shows evidence for a large magnocellular impairment in dyslexia

Laycock, R, Crewther, D and Crewther, S 2012, 'Abrupt and ramped flicker-defined form shows evidence for a large magnocellular impairment in dyslexia', Neuropsychologia, vol. 50, no. 8, pp. 2107-2113.


Document type: Journal Article
Collection: Journal Articles

Title Abrupt and ramped flicker-defined form shows evidence for a large magnocellular impairment in dyslexia
Author(s) Laycock, R
Crewther, D
Crewther, S
Year 2012
Journal name Neuropsychologia
Volume number 50
Issue number 8
Start page 2107
End page 2113
Total pages 7
Publisher Pergamon Press
Abstract Controversy still exists over whether there is a magnocellular deficit associated with developmental dyslexia. Here we utilised a magnocellular system-biased phantom contour form discrimination task defined by high temporal frequency contrast reversals to compare contrast sensitivity in a group of children with dyslexia and an age- and nonverbal intelligence-matched control group (9-14 years). Stimuli were either abruptly presented for 4 refresh frames (34 ms), or in two reduced transience conditions had contrast progressively ramped on and off over either 4 frames or 10 frames (86 ms). Children in the dyslexia group showed increased contrast thresholds compared with the control group in all three conditions, and thus strong evidence for a magnocellular deficit. Although the absolute size of the differences in threshold scores between control and dyslexic groups increased dramatically between the abrupt and the 4 and 10 frame ramped onset stimuli, the similar effect size across all tasks, and also the similar range of contrast change at the first frame of stimulus presentation across all tasks between groups suggests that a similar neural mechanism could provide the locus of the apparent magnocellular deficit in children with dyslexia for all tasks tested. These results suggest that threshold discrimination of stimuli with low contrast and high temporal frequencies designed to target the magnocellular system, and has great potential for early screening for children at risk of visually derived reading difficulties.
Subject Neurosciences not elsewhere classified
Psychology not elsewhere classified
Cognitive Science not elsewhere classified
Keyword(s) Contrast sensitivity
Magnocellular
Dyslexia
Flicker-defined form
DOI - identifier 10.1016/j.neuropsychologia.2012.05.012
Copyright notice © 2012 Elsevier Ltd. All rights reserved.
ISSN 0028-3932
Versions
Version Filter Type
Citation counts: TR Web of Science Citation Count  Cited 7 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 5 times in Scopus Article | Citations
Altmetric details:
Access Statistics: 135 Abstract Views  -  Detailed Statistics
Created: Wed, 30 Nov 2016, 07:55:00 EST by Catalyst Administrator
© 2014 RMIT Research Repository • Powered by Fez SoftwareContact us