Saccades are rapid eye movements employed during active vision to bring the target of interest onto the fovea, the retinal area of highest visual acuity. They are critical to essential human behaviors such as reading and visual exploration of the environment, with recent perceptual studies emphasizing their active role in regulating the flow of visual information. The impact of saccades on word recognition remains little understood, however, because most studies have focused on static visual processing wherein visual stimuli are presented during constant fixation.
The aim of this research proposal is to investigate the spatial temporal dynamics of brain activity as words are processed following saccades, using a multimodal imaging approach that combines whole-head magnetoencephalography (MEG), electroencephalography (EEG), anatomical magnetic resonance imaging (MRI), and psychophysical methods. Integrating MEG/EEG with MRI provides a powerful tool for human brain imaging by allowing source localization of the magnetic and electrical signal on a millimeter spatial scale, with the high temporal resolution (milliseconds) inherent to MEG/EEG recordings. Our working hypothesis is that word processing is facilitated within a narrow time window following an eye movement and we aim to uncover the neuronal mechanisms involved. To distinguish between different postsaccadic effects (visual, motor, and attentional influences), we will compare the brain activations to words presented following saccades vs. externally generated image motion that mimics that during an eye movement. Word frequency and repetition priming effects within a lexical decision task will be used to investigate postsaccadic effects on different aspects (visual feature, orthographic, phonological, semantic) of language processing. To our knowledge, this is the first study to investigate saccadic modulation of word processing using multimodal MEG/EEG/MRI recordings. This work will contribute to elucidating the neural processes underlying control of eye movements and attention, and will advance our understanding of how active vision influences brain activity and visual processing during reading. Furthermore, results are expected to have important implications for clinical research in dyslexia, attention-deficit hyperactivity disorder (ADHD) and schizophrenia, where eye-movements have been shown to be abnormal. ? ? ?
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