This research program explores the novel hypothesis that many of the processes by which we produce and understand language also place high demands on and receive contributions from the hippocampal declarative memory system. This system is uniquely positioned to access and integrate discourse, contextual and experiential information that the language processing system relies on to resolve ambiguity and create meaning. Recent provocative work extends the traditional view of declarative memory as contributing exclusively to long-term memory, to include a critical role in the generation and use of on-line representations, created during ongoing and online information processing to support behavioral performance in the moment. The proposed studies build upon a set of exciting preliminary findings revealing language deficits at low levels of language processing (i.e., within a single noun phrase), and in the absence of any explicit demands on memory (e.g., no delays;when all the stimuli remain in view) in patients with severe and selective declarative memory impairment. Our studies are built around investigating three key areas of language processing where proposals of the memory determinants are central, but untested:
Aim 1 : To investigate the demands of interactive dialogue on declarative memory;
Aim 2 : To investigate the demands of referential processing on declarative memory;
Aim 3 : To investigate the demands of accommodation of talker variability on declarative memory. Our experimental approach capitalizes on a compelling opportunity to combine the study of patients with hippocampal amnesia with eye tracking and behavioral measures to examine the necessity of a form of memory in meeting the demands of language. We will therefore be uniquely able to determine the contributions of hippocampus and declarative memory to language processing and use across multiple levels of language production and comprehension providing crucial tests of hypothesized roles for memory in language use. Language disruptions are common in many neurological and psychiatric conditions where impairments in declarative memory are also prominent, including stroke, traumatic brain injury, Alzheimer's disease, and schizophrenia. Thus, our efforts to characterize the observed language deficits and link them to underlying memory mechanisms are necessary for understanding the broader neural network and cognitive processes that support language use and for developing more sensitive assessments and effective interventions. This application, and the findings generated, offers unparalleled insights and advancements for theories of language processing, clinical service delivery to individuals with concomitant disorders of language and memory, and understanding the organization and operation of language in the brain.

Public Health Relevance

Disruptions in language use are prevalent, debilitating, and costly in numerous neurological and psychiatric diseases where declarative memory deficits are also prominent. By detailing the demands of language use on the hippocampal declarative memory system and the impact on language functioning following hippocampal damage and declarative memory impairment, our findings will be directly relevant to the understanding, diagnosis, and treatment of these non-aphasic language disorders.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
Research Project (R01)
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Language and Communication Study Section (LCOM)
Program Officer
Cooper, Judith
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University of Iowa
Other Health Professions
Schools of Arts and Sciences
Iowa City
United States
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Hilverman, Caitlin; Clough, Sharice A; Duff, Melissa C et al. (2018) Patients with hippocampal amnesia successfully integrate gesture and speech. Neuropsychologia 117:332-338
Horecka, Kevin M; Dulas, Michael R; Schwarb, Hillary et al. (2018) Reconstructing relational information. Hippocampus 28:164-177
Covington, Natalie V; Brown-Schmidt, Sarah; Duff, Melissa C (2018) The Necessity of the Hippocampus for Statistical Learning. J Cogn Neurosci 30:680-697
Ryskin, Rachel; Qi, Zhenghan; Covington, Natalie V et al. (2018) Knowledge and learning of verb biases in amnesia. Brain Lang 180-182:62-83
Hilverman, Caitlin; Cook, Susan Wagner; Duff, Melissa C (2017) The influence of the hippocampus and declarative memory on word use: Patients with amnesia use less imageable words. Neuropsychologia 106:179-186
Yoon, Si On; Duff, Melissa C; Brown-Schmidt, Sarah (2017) Learning and using knowledge about what other people do and don't know despite amnesia. Cortex 94:164-175
Ryskin, Rachel A; Qi, Zhenghan; Duff, Melissa C et al. (2017) Verb biases are shaped through lifelong learning. J Exp Psychol Learn Mem Cogn 43:781-794
Warren, David E; Kurczek, Jake; Duff, Melissa C (2016) What relates newspaper, definite, and clothing? An article describing deficits in convergent problem solving and creativity following hippocampal damage. Hippocampus 26:835-40
Covington, Natalie V; Duff, Melissa C (2016) Expanding the Language Network: Direct Contributions from the Hippocampus. Trends Cogn Sci 20:869-870
Hilverman, Caitlin; Cook, Susan Wagner; Duff, Melissa C (2016) Hippocampal declarative memory supports gesture production: Evidence from amnesia. Cortex 85:25-36

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