NIH R21DC01671: FUNCTIONAL REORGANIZATION OF THE READING SYSTEM FOLLOWING STROKE

SIMON FISCHER-BAUM (PI)

Many stroke survivors are impaired at reading, at least immediately following the stroke. Reading typically improves over years following the stroke, though some degree of impairment remains common. Improvements in reading during recovery are thought to depend on neural plasticity, or the damaged brain reorganizing to better support the impaired reading functions. The long-term objective of our research is to characterize this neural plasticity so that we can develop new interventions that will enhance the recovery of reading following stroke. The immediate goal is to map this neural plasticity using functional neuroimaging, comparing a group of patients with reading impairments following stroke to controls. First, we investigate the extent to which there are consistent patterns of activation during reading tasks that distinguish individuals with reading impairments following stroke from control participants. Second, we use functional magnetic resonance imaging (fMRI) decoding methods to determine whether patients and controls differ in what different parts of the brain are doing functionally. Neural plasticity has been argued to either reflect functional take-over, whereby the function previously performed by a damaged area is shifted to a different brain region, or reflect a compensatory masquerade, i.e., the refinement of an intact cognitive process not normally used to perform a task. To determine which type of neural plasticity is occurring in the reading network, new fMRI analysis techniques are needed that go beyond activity magnitude investigations of brain regions to decode the information present in the distributed patterns of activation. Our lab has been developing such techniques and we will apply them to our sample to determine the extent to which individuals with chronic reading problems show consistent types of neural plasticity.

 

NSF BCS1752751: CAREER: MAPPING THE NEURAL LOCUS OF COGNITIVE PROCESSES IN WORD READING 

SIMON FISCHER-BAUM (PI)

The ability to read written words depends on a complex series of transformations, ranging from patterns of stimulation on the eye to neural representations of a word’s spelling, pronunciation and meaning. These transformations occur quickly and automatically in literate adults, despite the fact that written language is a relatively recent cultural invention and that reading is something learned in school rather than acquired without formal teaching. Rapid advances have been made in the understanding of how people read words – both in terms of better models of the computational processes involved in these transformations and better understanding of how the brain responds to written stimuli. This project aims to bridge these computational and cognitive neuroscience approaches, using brain activity data from neuroimaging studies to answer some fundamental questions about how people read. What code does the brain use to recognize written words? How do individuals differ in how they process written words? Do people read words differently depending on the context in which they are read? In answering these questions, the ultimate goal of this research is to develop a neurocognitive theory of reading that can provide critical insights into how people read words. This in turn can benefit society by informing literacy education, the treatment of learning disabilities or the remediation of language loss after brain injury. This project’s goal will be achieved by collecting functional neuroimaging data while people read, and analyzing it with an approach that maps between different cognitive reading processes and different patterns of brain activity. By using this approach, our lab identifies the pattern of brain activity elicited by individual stimuli, and calculate the similarity in the pattern between all pairs of stimuli. We then compare these brain-based similarity measures to formal predictions of similarity derived from computational models of reading. Consider how DOUGH relates to the words TOUGH, SEW and BREAD; DOUGH is spelled similarly to TOUGH, sounds similar to SEW, and has a meaning related to BREAD. Using the logic of this analysis, brain regions in which DOUGH elicits a similar response to TOUGH, but not to BREAD or SEW can be interpreted as regions involved in the neural representation of word spellings. In this way, the current approach provides a tool for linking neural activity to cognitive operations. Using this technique, the research in the project will test competing computational models of the front end of the reading system, evaluate how differences in a task alter reading-related processes and assess individual differences in the cognitive processes used by skilled readers. This project will advance research methods in bridging computational theories of cognition and neuroscience data that could be useful for many questions in cognitive science.

 

NIH R01DC014976-03: LANGUAGE AND NEURAL RECOVERY FROM STROKE: ROLE OF SELECTION AND WORKING MEMORY

RANDI MARTIN (Co-PI, Tatiana Schnur, PI)

A fundamental aspect of our existence is that spoken language is our primary means of communication with others. Unfortunately, the ability to speak, and multiword (i.e., phrase and sentence) production in particular, is impaired following stroke. It is unclear what drives successful recovery of language production following stroke. This research program uses cognitive behavioral testing, neuroimaging, and statistical modeling to understand how multiword production and the neural structures that support it change during recovery by testing patients within 72 hours of stroke (acute stage) and again at 1, 6, and 12 months after stroke. Previous neuroimaging and neuropsychological studies, including several from our laboratories, have identified two cognitive abilities and associated brain regions that may be critical for multiword production. These abilities are the ability to resolve interference from word competitors during word selection and the ability to store semantic information in working memory, subserved by posterior and anterior regions of the left inferior frontal gyrus, respectively. However, conclusions about the role of these abilities have been drawn from data collected from chronic stroke cases, months and years following the onset of stroke. As a result, conclusions about brain-behavior relations are problematic due to significant reorganization of function that occurs during recovery. Because studies of chronic patients typically exclude people whose language disorders have resolved, they underestimate the impact of damage to small regions of the brain on multiword production. Further, the way selection and working memory capacities interact to support multiword production remains to be examined. We use recent innovations in the analysis of longitudinal data (Latent Change Score models) and structural neuroimaging (sequences and modeling approaches to assess damage and hypoperfusion to gray matter and integrity of white matter tracks) to test the hypothesis that selection and working memory and associated brain regions are critical to the recovery of multiword production. We are testing the hypothesis that selection and semantic working memory capacities are necessary for multiword production by assessing patients before reorganization occurs, i.e., at the acute stage, within 72 hours of stroke, which will include those with smaller lesions. We are further identifying the neural structures associated with selection and working memory. Finally, we are testing the hypothesis that recovery of selection and working memory capacities is critical to post stroke language outcome by assessing behavior and neuroanatomical changes across acute, 1, 6, and 12 months post stroke time points. This research is leading to a detailed theory of the cognitive-brain basis of multiword production. This knowledge will have important health implications because information about how language ability is impaired and subsequently recovers is essential for managing the consequences of stroke through the development of language rehabilitation strategies.

 

NSF EEC 1840636: PLANNING GRANT: ENGINEERING RESEARCH CENTER FOR AUDITORY BIOENGINEERING

SIMON FISCHER-BAUM (Co-PI, Rob Raphael, PI)

This planning grant brings together a diverse team of researchers from Rice University, Baylor College of Medicine, the University of Southern California and Oregon Health Science University with complementary expertise in auditory neuroscience, cochlear implants, speech perception and devices that connect directly to neurons. We will engage in a series of meeting and activities that will lay the foundation for an Engineering Research Center in Auditory Bioengineering. The proposed Center will work to develop new technologies, expand the engineering workforce and foster a culture of diversity and inclusion by supporting the deaf and hard of hearing, especially members of underserved populations. During the course of this grant, the planning team will critically evaluate the potential of recent technological advances to improve hearing health care and identify additional participants to perform center-scale research. The intellectual focus of this proposal will reside in a critical evaluation of the potential for the following thrust areas to serve as a foundation for convergent research in Auditory Bioengineering. Thrust 1: Enabling Technologies for Next Generation Auditory Implants. In this thrust, recent advances in engineering technologies such as carbon nanofiber electrodes for neural interfacing will be integrated into biomedical microsystems to produce an innovative design for a next generation auditory implant. Thrust 2: Speech Perception for Auditory Bioengineering. In this thrust, recent advances the cognitive aspects of speech perception will be harnessed to determine the relevant information that needs to be passed to auditory implants and how best to provide that information based on what is known about the neural code, with consideration that different languages are tuned to different acoustic features. Thrust 3: Global Health and Disparities Research in Auditory Rehabilitation. This thrust will seek to investigate and evaluate ways to expand access to auditory rehabilitation with hearing aids and cochlear implants, especially for underserved population. The goal will be to develop an ERC in Auditory Bioengineering that will serve a national resource for auditory researchers, neuroengineers, audiologists and clinicians. With a central location in Houston, TX, the center will have national outreach and serve as a way to pool patient populations for studies on outcomes and disparities in auditory rehabilitation. This proposal will fill a key need in workforce development in training more students at the interface of hearing and speech research, who are prepared to employ modern engineering approaches for auditory rehabilitation.