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Applications of Lesion-Deficit Mapping to Unresolved Problems in Aphasia

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NIDCD - National Institute on Deafness and Other Communication Disorders

PROJECT SUMMARY A detailed model of how focal damage to the brain affects long-term language abilities would be of enormous value to clinicians trying to minimize language deficits from brain surgery or predict long-term recovery from strokes. The principal tool for creating such a model is lesion-deficit mapping (LDM), which generates statistical relations between language impairments and damage at each point in the brain. Advances in LDM methodology and neurobiological theories of language processing have enabled significant progress toward this goal, but many fundamental questions remain. This project addresses four such problems. The first concerns the phenomenon of accurate but slowed word processing in some people with aphasia, which could explain isolated sentence comprehension and production impairments in these individuals. This project will for the first time identify the neural correlates of this ubiquitous phenomenon using a novel LDM approach based on reaction time measurements during simple word comprehension and retrieval tasks. The second problem concerns the phenomenon of semantic access impairment, in which some people with aphasia appear to have adequate knowledge of word meaning but cannot selectively access this knowledge due to either excessive ‘competition’ from activation of similar word meanings or to inability to ‘control’ activation of word meanings. This project will be the first large-scale attempt to use LDM to define the lesion correlates of this syndrome and the first LDM study to compare distinct behavioral measures of competition and control. The third problem concerns new evidence for a selective deficit in comprehending noun-noun phrases such as ‘dog dish’ despite preserved comprehension of single words like ‘dog’ and ‘dish’. Understanding noun-noun phrases is thought to require computation of specific functional relationships between the first (modifier) and second (head) noun, and the new evidence suggests that such computations can be selectively impaired by focal brain damage. LDM will be used to identify the neural correlates of this novel type of comprehension impairment and to assess four distinct types of relational computations. The final problem concerns the inability of some people with aphasia to express coherent narratives (e.g., scene descriptions or stories) despite relatively preserved single-word retrieval. The lesion correlates of this deficit in higher-level semantic organization are unknown. The proposed approach will use a large language AI model (GPT4) to assess the coherence of scene descriptions and personal narratives produced by people with focal brain damage, then perform LDM using these scores. These studies will fill important gaps in our understanding of fundamental processing deficits in aphasia and introduce several novel and potentially powerful LDM methods.

– $489K
2031-01-31
health research
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Applying novel tools to parse Plasmodium vivax relapses in clinical trials

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NIAID - National Institute of Allergy and Infectious Diseases

ABSTRACT Relapsing malaria species, such as Plasmodium vivax (Pv), remain major challenges to malaria elimination due to their propensity to form hypnozoites that cause chronic latent infection in the liver and give rise to frequent relapses. Pv relapses cause significant morbidity and mortality worldwide. Despite advances, genotyping to distinguish relapses from re-infections remains fraught, limiting the evaluation of anti-relapse interventions like primaquine and tafenoquine. This study applies novel genomic and bioinformatic tools to clinical trial data in Southeast Asia and introduces innovative approaches to parse Pv relapse outcomes. Our approach leverages molecular inversion probes (MIPs) to deeply sequence Pv infections, capturing the diversity across the vivax genome and complexity within infected individuals. We will use Tapestry, a new bioinformatics tool, to enable haplotype reconstruction and identity-by-descent (IBD) analysis within and across multiclonal infections. Finally, Bayesian statistical models will refine relapse predictions by integrating genetic complexity, IBD relatedness, and clinical factors. Aim 1 investigates primaquine failures observed in a Thai Pv relapse trial (NCT04228315). Suspected relapses occurred in four individuals despite chloroquine and primaquine treatment; host CYP2D6 polymorphisms were ruled out. We hypothesize that high initial hypnozoite burden drove these relapses. We will generate evidence for this via genomic analyses that enhance detection of circulating parasite variants and assess infection complexity as a proxy for liver-stage hypnozoite burden. Aim 2 evaluates malaria elimination interventions in a Cambodian military cohort. Aim 2A tests whether rebound infections after cessation of monthly prophylaxis (MMP with dihydroartemisinin - piperaquine and weekly primaquine) represent relapses due to high hypnozoite burden, as reflected by genetic complexity. Aim 2B classifies Pv recurrences in soldiers wearing permethrin-treated uniforms to estimate vector-prevention efficacy. Results will differentiate relapse from reinfection and recalibrate protective efficacy estimates. In summary, this proposal seeks to address a fundamental gap in our ability to use genotyping to evaluate anti-relapse and other interventions that are needed to decrease the global burden of Plasmodium vivax. Expected outcomes include refined relapse classification, improved understanding of hypnozoite dynamics, and insights into anti-vivax interventions across diverse settings. Future directions include scaling our approach to larger cohort studies across diverse settings to improve classification of relapse outcomes.

– $191K
2028-01-31
health research