Using event-related potentials to monitor the time course of mental processing during eye fixations in reading
Reddix, Michael Douglas
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Permalink
https://hdl.handle.net/2142/22739
Description
Title
Using event-related potentials to monitor the time course of mental processing during eye fixations in reading
Author(s)
Reddix, Michael Douglas
Issue Date
1989
Doctoral Committee Chair(s)
McConkie, George W.
Department of Study
Education
Discipline
Education
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Education, Reading
Psychology, Experimental
Psychology, Physiological
Language
eng
Abstract
A new method for measuring the temporal course of processing events that take place during eye fixations in reading was tested. The method was employed to determine the earliest point in time that orthographic information is utilized during an eye fixation in normal reading. Right handed male and female university students silently read sentences presented one at a time on a CRT while their eye movements and scalp recorded electroencephalographic (EEG) brain activity were monitored. Average event-related potentials (ERPs) were derived separately for control and experimental conditions by time-locking ERP epochs to the beginning of the first fixation on critical word locations containing either a control word or orthographically inappropriate letter string (i.e., brain or iarnb). The most prominent effect of encountering orthographically inappropriate letter strings during reading was the generation of a late negativity similar to that observed by other researchers who have manipulated semantic aspects of the language. A primary purpose for conducting this study was to determine whether scalp recorded brain activity would show effects of encountering violations of language constraints earlier than they are revealed in eye movement recordings. To answer this question grand averages for control and experimental conditions at each of four recording sites (Cz, Pz, P$\sb3$, and P$\sb4$) were compared to see how soon, after the beginning of the initial fixation on a critical word location, they separated. The earliest point in time at which control and orthographic grand averages separated as a result of the late negative component (210 msec at lateral sites P$\sb3$ and P$\sb4$; 270 msec at midline sites Cz and Pz) was later than the point in time at which differences have been observed in eye movement data (as early as 140-159 msec). This thesis explains various possible sources of confounding variance that may be making an early ERP effect difficult to detect: EEG activity produced by making saccadic eye movements, ERP component latency jitter, and component overlap. This study did establish the feasibility of using ERPs to study mental processing in ongoing tasks, like reading, by time-looking ERP epochs to the beginning of critical eye fixations.
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