Abstract
The Landolt reading paradigm was created in order to dissociate effects of eye movements and attention from lexical, syntactic, and sub-lexical processing. While previous eye-tracking and behavioral findings support the usefulness of the paradigm, it remains to be shown that the paradigm actually relies on the brain networks for occulomotor control and attention, but not on systems for lexical/syntactic/orthographic processing. Here, 20 healthy volunteers underwent fMRI scanning while reading sentences (with syntax) or unconnected lists of written stimuli (no syntax) consisting of words (with semantics) or pseudowords (no semantics). In an additional “Landolt reading” condition, all letters were replaced by closed circles, which should be scanned for targets (Landolt's rings) in a reading-like fashion from left to right. A conjunction analysis of all five conditions revealed the visual scanning network which involved bilateral visual cortex, premotor cortex, and superior parietal cortex, but which did not include regions for semantics, syntax, or orthography. Contrasting the Landolt reading condition with all other regions revealed additional involvement of the right superior parietal cortex (areas 7A/7P/7PC) and postcentral gyrus (area 2) involved in deliberate gaze shifting. These neuroimaging findings demonstrate for the first time that the linguistic and orthographic brain network can be dissociated from a pure gaze-orienting network with the Landolt paradigm. Consequently, the Landolt paradigm may provide novel insights into the contributions of linguistic and non-linguistic factors on reading failure e.g., in developmental dyslexia.
Highlights
In reading, eye movements of children with developmental dyslexia differ from those of normal reading children (De Luca et al, 1999), e.g., more and longer fixations (Rayner, 1998; Hutzler and Wimmer, 2003)
Likewise, during FUNCTIONAL MAGNETIC RESONANCE IMAGING (fMRI) DATA the fMRI data are reported with respect to the macroanatomical structures, which were activated in each condition; for detailed information about the cytoarchitectonic localizations please refer to the figures and tables
Results are reported separately for each condition contrasted against the resting baseline and for contrasts representing the gaze orientation network, orthographic processing, processing in the Landolt paradigm, semantic processing, and syntactic processing
Summary
Eye movements of children with developmental dyslexia differ from those of normal reading children (De Luca et al, 1999), e.g., more and longer fixations (Rayner, 1998; Hutzler and Wimmer, 2003) This fact has been known for more than 20 years, little is known about the causalities here: do these abnormal gaze patterns lead to dyslexic reading, or are they a consequence of reading difficulties potentially reflecting compensatory mechanisms? Thesis/files/archive-2008.html; Zschornak et al, 2012; available at https://www.thieme-connect.de/ejournals/html/10.1055/ s-0032-1304900) This non-lexical reading task only maintains the visual structure of written language, i.e., number of “letters” and “words.” This is achieved by replacing letters by nonorthorgraphic circle-like symbols, the so-called Landolt rings, removing all lexical, syntactic, or orthographic-phonological information. Reading without words is stimulated, allowing to test whether the gaze patterns of the reader move over the Landolt sentences in a reading-like fashion
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