Dementia is among the most daunting public health crises facing industrialized nations. Many countries, including the United States,1 have recently adopted comprehensive national dementia strategies.2 The US National Dementia Strategy (section 2B) has identified early diagnosis and links to community treatment services as pillars of its management plan. The availability of evidence-based outpatient treatment for progressive language impairments remains exceedingly sparse. In 2014, we began to address this void via a longitudinal intervention targeting maintenance of a core vocabulary consisting of 100 words over two years. This caregiver-friendly treatment is showing great promise for promoting the retention of key vocabulary in frontotemporal degeneration and Alzheimer's Disease. A secondary aim involved evaluating prediction of later language forgetting. We have learned much during this initial project period, and its renewal has the potential to tell us much more. Our current proposal consists of three aims, all of which directly align both with the US National Dementia Strategy and the mission of our funding institute (i.e., the National Institute on Deafness and Other Communication Disorders).3 In Specific Aim 1 (SA1), we will evaluate the long-term effectiveness of a regimen of noninvasive brain stimulation (transcranial direct current stimulation) delivered over the anterior temporal lobes as an adjuvant to our ongoing semantic behavioral treatment. We will do so using a crossover design where two groups of patients with semantic variant Primary Progressive Aphasia complete sham and active stimulation conditions paired with behavioral treatment (order counterbalanced). We will subsequently follow this patient cohort over two years to evaluate the durability of treatment gains. In SA2, we will evaluate predictors of emerging cognitive-linguistic impairment in a vastly underserved population (i.e., older African American adults). We will identify older adults who are at increased risk for conversion to mild cognitive impairment as indexed by global cognitive and language measures. We will then follow and characterize this prospective cohort using sensitive behavioral (gaze patterns during visual confrontation naming) and neuropsychological markers. Finally, in SA3 we will evaluate representation, processing, and shifts in abstract word meaning as functions of age, pathology, and individual differences (e.g., vocabulary size, years of education) using machine learning. This renewal reflects the continuation of a productive and rigorous line of research that will yield complementary data about human semantic memory, best practices in promoting language maintenance, and variability of age-associated language change.
We will investigate the effectiveness of pairing non-invasive brain stimulation with an ongoing behavioral treatment targeting maintenance of a small functional vocabulary in patients with progressive naming disorders. In a secondary sequence of aims, we will evaluate processing of abstract words (e.g., love, truth) and prediction of evolving language impairment in a prospective cohort of lower-income, predominantly minority older adults with the aim of improving early detection of cognitive-linguistic decline.
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