Tamara Y. Swaab, PhD - US grants

This research will investigate the nature and organization of semantic (meaning) representations. Specifically, the research will employ physiological approaches to test whether the brain's organization of conceptual knowledge supports models that propose multiple semantic systems. The approach will combine functional magnetic resonance imaging (fMRI) and event-related potentials (ERPs) to investigate the cognitive-neural organization of semantic knowledge representations and to test the role of the right hemisphere in lexical-semantic processing. In this regard, the research will address two main questions. The first is whether specific and separable brain regions (and therefore perhaps cognitive architectures) are involved in the processing of verbal-based and image-based representations of words. The second is whether specific and separable brain regions are involved in the processing of close semantic relations versus more distant semantic relations between words.

Swaab's career goals are to develop an active, extramurally-funded research program in language and brain in an academic environment that includes teaching and training at the undergraduate, graduate and postdoctoral levels. This POWRE award will allow her to obtain training and to develop expertise in the use of modern brain-imaging tools for pursuing the cognitive mechanisms and brain organization that underlie normal language processes. She already has expertise in the use of ERPs to study language comprehension processes and semantic representations both in neurologically normal persons and in brain-damaged patients with and without aphasia. Because these tools are rapidly becoming essential to studies of normal human language, Swaab will obtain training and experience in the use of fMRI to study the neural instantiation of models that propose non-unitary semantic knowledge representations. Importantly, this award will allow her to integrate fMRI and ERP in language research. This integration of neuroimaging and electrophysiological methods is a recent development in cognitive research and will elucidate both the time course and the functional anatomy of brain systems involved in language. At present, few laboratories have the tools and specialized knowledge to integrate electrophysiology and neuroimaging in the study of human language. Hence, this POWRE award will provide Swaab with a significant opportunity to take her work to the cutting edge of the cognitive neuroscience of language.

The goal of this research project is to understand the representations and processes behind syntactic priming. Syntactic priming occurs when processing the syntax of one sentence facilitates the processing of a related syntactic structure in another sentence later in the discourse. This research will test the hypothesis that syntactic priming is caused by two different types of mental processes, one that operates over short time scales (a few seconds) and another that operates over longer time scales (a few minutes to several days). This dual-mechanism hypothesis proposes that 1) transient increases in activation of syntactic representations that are tied to specific words produce short-term priming effects and 2) reorganizations of long-term memory produce longer-lived changes in the relative strength of different syntactic representations, which in turn produce long-term priming effects.

The proposed experiments use behavioral and neurophysiological research methods to test the dual-mechanism account. These methods have complementary strengths but both are highly sensitive to momentary changes in cognitive processing load. Using both methods in parallel gives the potential to illuminate the mental processes that give rise to neurophysiological responses. In addition, the proposed research may contribute to our understanding of adult language learning, in particular, changes in the adult system of syntactic representations and parsing processes as learning proceeds. This in turn may suggest ways in which poor readers can improve their reading skill. The project will also provide training opportunities for graduate students.

DESCRIPTION (provided by applicant): Schizophrenia is a prevalent mental health disorder that creates enormous social, economic, and interpersonal hardships for patients and their families. Although hallucinations and delusions are the most salient symptoms of this disease, language abnormalities are among the most prominent cognitive deficits in schizophrenia. The proposed research will explore the processes and circuits that underlie impaired discourse comprehension in schizophrenia. Discourse comprehension deficits are likely to have important functional implications, but there has been relatively little investigation of real-time discourse processing in schizophrenia, particularly in relation to other impaired cognitive and psycho-social functioning. Previous research in schizophrenia has related cognitive deficits to impairments in the ability to control the maintenance of context representations. We will test the hypothesis that deficits in controlled integration and maintenance of discourse context in schizophrenia will lead to difficulties in discourse comprehension, but will relatively spare processing of meanings of words and sentence structures. To do so we will combine electrophysiological (EEG/ERP) measures of language comprehension with measures of cognitive, social and occupational functioning in schizophrenia. Our approach will allow us to examine whether discourse comprehension deficits in schizophrenia relate to impaired cognitive, social and occupational functioning, and the outcome of this research can be used in the development and assessment of new treatments for this disease.

Project Summary Efficient cognitive processing relies on the brain?s ability to engage in prediction and to use forward modeling to anticipate cognitive events, including during language processing. The central goal of this proposal is to test two competing hypotheses concerning how age influences prediction during auditory and visual language processing. Current evidence is contradictory and sparse, reflecting the need for systematic investigation. The project has three Specific Aims: Aim1: Determine whether older adults predict words in manipulated sentence contexts less or more than younger adults do by examining prediction during reading, using both electrophysiology (EEG) and eyetracking methods. Aim2: Determine whether, during spoken language processing, older adults predict words in manipulated sentence contexts less or more than younger adults do, using EEG and Visual World eyetracking methods. Spoken language processing merits targeted investigation because evidence suggests older adults have specific problems with auditory input. Moreover, in the young adult literature on prediction in language processing, relatively few studies have focused on spoken language, so little is known about whether prediction differs in the two modalities. Aim3: Determine whether older adults predict upcoming words in connected passages less or more than younger adults do, using fixation-related fMRI and EEG methods in reading, with prediction assessed by continuous measures of lexical surprisal and entropy. Surprisal and entropy measures permit the investigation of more naturally varying levels of predictability, more natural distributions of predictable and less predictable information, and allow the investigation of how natural texts (i.e., stimuli not specifically created for an experiment) are comprehended. Innovations: The project is innovative in (1) the use of converging eyetracking, EEG, and fMRI methods to systematically evaluate the extent of prediction during older adults' language comprehension, emphasizing replication across techniques and modalities; (2) the use of continuously varying surprisal/entropy in connected text to index age differences in prediction; (3) the use of a novel technique developed by PI Henderson, Fixation-Related fMRI, to relate neural activation to word-by-word surprisal and entropy during natural reading. Significance: The experiments will yield high temporal resolution information about prediction in older adults during online reading and spoken comprehension, together with detailed information about the neural bases of prediction operations. The findings have important implications for theories of normal cognitive aging. Translational significance: A psychometrically valid assessment of everyday language skills will be used to evaluate the relationship between prediction skills and a measure that has been shown to predict impairments associated with Alzheimer?s disease. Overall, prediction in language processing is potentially a model system for enhancing our scientific understanding of how cognitive and neural decline associated with aging trades off against greater knowledge and experience.