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Neural Interaction of Reading Words and Spatial Attention
Poster Session B, Friday, September 12, 4:30 - 6:00 pm, Field House
Lauren E. Magliocco1, Sage G. Placer1, Sofia E. Ortega1, Katherine J. Midgley1, George R. Mangun2, Tamara Y. Swaab2, Karen Emmorey1, Phillip J. Holcomb1; 1San Diego State University, 2University of California Davis
Previous research has found that visual-spatial selective attention is modulated by a host of neural mechanisms that unfold over the course of stimulus processing. The P1 event-related potential (ERP) is characterized by a positive deflection occurring around 100-130 ms and is the earliest brainwave that has been consistently shown to be sensitive to spatial attention (the ability to focus on a particular region in space while ignoring others). More specifically, the amplitude of the P1 is larger to stimuli when they occur at an attended as opposed to an unattended location. However, there is limited research on how the P1 to visually presented words is modulated by selective spatial attention. Another ERP component, the N400, has also been shown to be sensitive to attention - e.g. it is usually larger when words are attended – although only a few studies have examined the N400 when spatial attention was manipulated. The current ERP study used a blocked cueing paradigm with four-letter English words and symbol strings, to explore how the P1 and N400 differ as a function of visual spatial attention. Data were collected from a sample of right-handed, native English speakers. The experiment contained 900 trials consisting of 240 words (e.g., desk – referred to as standards) and 60 four-character symbol strings (e.g., &*!#, referred to as targets) each presented three times. The location of stimuli was rapidly alternated (150 ms duration, average ISI = 275 ms, range 75-475 ms) across three left-to-right screen locations (5.15° left, 0° center and 5.15° right) each 4.58° above a central fixation cross which remained on screen throughout the experiment. Prior to each of the 12 blocks of trials, participants were randomly cued to direct attention to one of the three locations (i.e., left, center, right) while maintaining fixation on the central cross. The cued location was changed prior to each block. The task was to press a button whenever a symbol string target occurred at the cued location but to ignore all stimuli at the other locations. This design allowed us to compare ERPs to the so-called “standard” (word) stimuli, presented in the same location when attended vs. unattended. Overall, we found larger P1 and N400 amplitudes to attended words compared to unattended words, reinforcing the notion that spatial selective attention modulates both the earliest perceptual as well as later cognitive processing of language stimuli. Furthermore, we found that for the P1 this effect of attention was greater over left occipital sites for words presented in the right visual field which is consistent with a very early sensitivity to either the superior language processing abilities of the left hemisphere or the right visual field advantage observed in readers of left to right languages. The latter possibility was bolstered by the finding of a larger N400 attention effect for RVF words but no difference in its lateral distribution.
Topic Areas: Control, Selection, and Executive Processes, Reading