Audiovisual temporal sensitivity in typical and dyslexic adult readers as revealed by gamma oscillations
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2015-07-01
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en
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Abstract
Reading is an audiovisual process, which requires the development and automatization of grapheme-‐phoneme mapping. In order to occur in an adequate way letter-‐sound associations require a narrow temporal window of integration (Froyen, van Atteveldt, Bonte, & Blomert, 2008). Thus, if those mappings are established in a wider temporal window, this might lead to less appropriate letter-‐sound correspondences, which as a consequence could hamper and slow down the process of reading acquisition. Previous studies (Francisco, Jesse, Groen, & McQueen, submitted; Hairston, Burdette, Flowers, Wood, & Wallace, 2005) on audiovisual processing and developmental dyslexia have shown that dyslexic and typical readers differ in their audiovisual temporal sensitivity for both speech and non-‐speech events. Indeed, an audiovisual temporal deficit, reflected in an extended temporal window during which events out-‐of-‐synchrony are perceived as in-‐synchrony, might underlie reading impairments in developmental dyslexia.
The present study was designed to investigate whether an audiovisual temporal processing deficit might be reflected on differences in the oscillatory activity in the gamma-‐band frequency. We set out to test dyslexic versus typical adult readers while performing a simultaneity judgment task using audiovisual speech McGurk-‐type stimuli. The results suggest no significant differences in the oscillatory gamma-‐band responses between the groups. Though, we found higher gamma-‐band amplitude in dyslexic readers compared to typical adult readers. This pattern might reflect a wider window during which out-‐of-‐synchrony events are perceived as in-‐synchrony in dyslexic readers.
This finding does not allow us yet to complement previous behavioral studies, suggesting a general audiovisual temporal processing deficit in developmental dyslexia. Indeed, further research is needed to understand differential neurophysiological mechanisms involved in audiovisual temporal sensitivity in developmental dyslexia.
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Faculteit der Sociale Wetenschappen