Phillip Gilley - US grants

During skilled reading, people recognize words from written character strings and combine words into a larger message-level interpretation. Reading is a pervasive part of modern human life, and impaired reading is highly detrimental to scholastic and professional success. Despite its importance, the neural processes that enable skilled readers to comprehend multi-word combinations remain poorly understood. In this research, Dr. Albert Kim and Dr. Phillip Gilley of the University of Colorado Boulder will use cutting edge neurophysiological methods to understand how the brain generates and uses predictions about the upcoming words within a text during reading, guided by prior linguistic context. Predictions are thought to support the fast pace of normal reading, which is typically 3-5 words per second, by allowing the brain to prepare in advance for anticipated text before it arrives in the retinal input. Predictions are also thought to be crucial to the common ability to perceive words accurately in the face of impoverished inputs, such as conditions of poor lighting, print quality, or visual acuity. The research in this project is expected to produce knowledge that guides the identification of reading disorders and distinctions between different sorts of disorders, which can in turn guide clinical and pedagogical approaches to reading disorders.

The project will use scalp-recorded encephalography (EEG) to observe neural oscillatory activity -- reflecting the dynamic coupling and uncoupling of neural networks -- while healthy young adults read sentences. The sentences that participants read will be manipulated so that some sentence contexts render a specific word likely to occur, according to computational language models. Under these conditions, brain activity that occurs before and after the appearance of a word in the linguistic input will be examined for evidence of predictions. The project will investigate the role of neural oscillations in conveying predictions about upcoming words from high level brain regions to low level visual cortical areas and also in assessing the match between predictions and the bottom-up sensory input. The researchers will also study the types of linguistic contexts and processing demands that engage such predictive activity. Results of this research are expected to contribute significantly to cognitive neuroscience by combining three critical areas of research that have typically been studied separately: language processing, prediction in cognition, and neural oscillations. The project will develop new analytic methods for characterizing neural oscillations in EEG data, which will be developed into a toolbox to be shared with other researchers. The project will also produce a rich database of brain activity during the reading of naturalistic stories, which will be shared with the scientific community as a resource for further research.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Human beings confront pervasive ambiguity in language as they listen and read. For example, two spoken words can sound nearly identical (e.g., ?beach? and ?peach?); sentences can be grammatically analyzed in multiple ways; and speech is often obscured by environmental sounds, as in a crowded restaurant. Although ambiguity routinely increases the risk of arriving at the wrong interpretation, or even no interpretation of a message, healthy young adults are marvelously adept at understanding language, vastly surpassing the capabilities of automatic systems despite major advances in machine learning. Explaining how humans understand language in the face of ambiguity, and why some populations fail, is a fundamental challenge for cognitive science, and is crucial for assisting people with language impairments that intensify under conditions of ambiguity, including stroke patients and healthy older adults with hearing loss. This research will use advanced neurophysiological and eye-tracking methods to illuminate how people regulate their interpretations of speech and language input by using executive functions (EF): the family of cognitive mechanisms that enable information processing in the brain and the flexible guidance of goal-directed behavior. EF are thought to be critical to helping people select among different interpretations of a sentence when more than one is possible, and for guiding the mind toward perceiving a word when the environment is ?noisy.? However, the neural and cognitive mechanisms that allow EF to contribute to language comprehension are poorly understood. This project will elucidate EF?s role in language comprehension.

This project will test the hypothesis that two particular forms of executive function ? attention control and cognitive control ? play fundamental and distinct roles in supporting language comprehension in the face of ambiguity. Attention control is hypothesized to regulate the collection of information by directing perceptual processing toward the intended signal, isolating it from noise under suboptimal listening conditions. Cognitive control is hypothesized to assist the revision of misinterpretations by guiding internal representations to align with relevant sources of evidence when multiple cues compete. The investigators will use neural oscillatory activity in scalp-recorded EEG to provide novel markers of cognitive control and attention control during cognitive task performance. Eye-movement patterns will be used to track participants? interpretations of language input in real time, by recording the millisecond-level dynamics of listeners? gaze while they listen to sentences and interrogate a scene before them. The combination of EEG and eye tracking will provide a multi-modal characterization of the neural processes and temporal nature of interpretation procedures during language comprehension. In order to illuminate how attention and cognitive control separately affect humans? ability to deal with ambiguity, the experiments will manipulate the engagement status of these EF subtypes just prior to processing language, by having participants perform tasks, such as the Flanker task, which are known to recruit cognitive-control processes. This experimental approach will establish causal relationships between EF and language processing and will identify the distinctive contributions of cognitive control and attention control to comprehension.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.