Project 2: Susceptibility Factors for Primary Progressive Aphasia

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PROJECT 2 - ABSTRACT Primary progressive aphasia (PPA) is a collection of clinical syndromes characterized by gradual, selective decline in speech and language functions. It is caused by neurodegeneration in the brain regions that sustain language. PPA is a devastating disease affecting adults in the prime of their life, depriving them of the ability to communicate and function in society. In the last decade, the cognitive and neural bases of PPA have been studied thoroughly, and three clinic-anatomical variants of the disease have been described. Importantly, each variant is characterized by a different probability of underlying frontotemporal lobar degeneration (FTLD) or Alzheimer's disease (AD) pathology. Recent preliminary data suggest that different neurodevelopmental and biological factors are associated with each of the main PPA variants. In this project, we will further develop this line of research and investigate developmental, genetic and molecular factors that might determine susceptibility of the language network to each PPA subtype. We will recruit 125 new PPA patients and combine data with that of our large existing cohort to realize the following main goals: (1) Identify the presence of language-based learning disabilities, such as dyslexia, and determine their effect on cognitive and anatomical phenotypes. We hypothesize that language-based learning disabilities will be present most often in the logopenic variant PPA and will predict earlier age at onset and greater phonological impairment. (2) Measure hemispheric lateralization of language function an asses brain symmetry using magnetoencephalography and structural MRI. We predict that svPPA patients will show anomalous lateralization of language activation and decreased asymmetry of specific perisylvian language regions. (3) evaluate APOE allele status, inflammatory gene expression patterns and plasma cytokines levels. We expect to find a lower incidence of the APOE4 allele among logopenic patients with learning disabilities than those without, and to find biomarkers indicative of an altered immunological response in svPPA. This research will increase our knowledge about the pathogenesis of PPA and the neurobiology of language. Moreover, the results might serve as the foundation to develop early intervention strategies and personalized risk assessment for the prediction of neurodegenerative disease.