Nicole R. Nissim

Background: African Americans experience a high dementia burden yet are critically underrepresented in observational studies and clinical trials in memory and aging. Lack of adequate representation increases the likelihood that research findings may not generalize to African Americans. A deeper understanding of the barriers and facilitators that influence participation by younger and older African American adults is needed to support recruitment and retention in studies focused on early‐ and late‐onset neurodegenerative diseases.Method: African American community leaders collaborated in design of an electronic survey that was distributed via social media focused on local zip codes. Survey respondents rated barriers and facilitators to research participation on a 0–3‐point Likert scale. Responses ≥2 corresponded with barriers/facilitators likely to influence participation decisions. Differences across age groups were evaluated using nonparametric Kruskal‐Wallis tests. Strategies to mitigate barriers and reinforce facilitators were further explored via community‐based focus groups.Result: Survey data included responses from 240 African Americans (18‐44‐years, n = 76; 45‐64‐years, n = 83; ≥65‐years, n = 81). Requirement to undergo a diagnostic lumbar puncture was a substantial barrier to research participation across all age groups. Attending weekday visits (median = 2.0), including visits ≥2 hours (median 2.0), was a substantial barrier for individuals 18‐44‐years, but not older respondents (p = 0.001). Compensation for meals/transportation was beneficial across all age groups (median = 2.0; pp = 0.001). Focus group results supported survey findings and showed slight variations in priorities across age groups. Older participants (≥65‐years‐old) more frequently cited the longstanding effects of racism as a barrier to research participation compared to younger participants (45‐64‐years‐old; p = 0.008), who more frequently cited concerns regarding testing requirements (p = 0.034).Conclusion: Perceived barriers and facilitators to research participation vary with age. Age‐specific strategies are needed to increase engagement, address disparities in recruitment, and promote retention of African American participants in studies of memory and aging across the lifespan.

Background Black/African Americans experience a high burden of Alzheimer disease and related dementias yet are critically underrepresented in corresponding research. Understanding barriers and facilitators to research participation among younger and older African Americans is necessary to inform age-specific strategies to promote equity in studies of early- and late-onset neurodegenerative diseases. Study Design Survey respondents (n = 240) rated barriers and facilitators of research participation. Age-specific differences were evaluated using nonparametric Kruskal–Wallis tests across respondents aged 18–44 years (n = 76), 45–64 years (n = 83), and ≥ 65 years (n = 81). Strategies to mitigate barriers and promote facilitators were further explored via community-based focus groups. Pooled frequency of common themes discussed in focus groups were evaluated and compared across different ages including ≥ 45 years, ≥ 65 years, and mixed ages ≥ 45 years. Results Younger respondents (aged 18–44 and 45–64 years) expressed a greater need for flexibility in when, where, and how research testing takes place versus adults ≥ 65 years. Focus groups emphasized long-lasting consequences of systemic racism and the need to build and foster trust to resolve barriers and promote research engagement amongst African Americans. Discussion Age-specific strategies are needed to increase engagement, address recruitment disparities, and promote retention of African American participants in memory and aging studies across the lifespan.

Age-related differences in dorsolateral prefrontal cortex (DLPFC) structure and function have each been linked to working memory. However, few studies have integrated multimodal imaging to simultaneously investigate relationships among structure, function, and cognition. We aimed to clarify how specifically DLPFC structure and function contribute to working memory in healthy older adults. In total, 138 participants aged 65–88 underwent 3 T neuroimaging and were divided into higher and lower groups based on a median split of in-scanner n-back task performance. Three a priori spherical DLPFC regions of interest (ROIs) were used to quantify blood-oxygen-level-dependent (BOLD) signal and FreeSurfer-derived surface area, cortical thickness, and white matter volume. Binary logistic regressions adjusting for age, sex, education, and scanner type revealed that greater left and right DLPFC BOLD signal predicted the probability of higher performing group membership (P values<.05). Binary logistic regressions also adjusting for total intracranial volume revealed left DLPFC surface area that significantly predicted the probability of being in the higher performing group (P = 0.017). The left DLPFC BOLD signal and surface area were not significantly associated and did not significantly interact to predict group membership (P values>.05). Importantly, this suggests BOLD signal and surface area may independently contribute to working memory performance in healthy older adults.

Noninvasive brain stimulation techniques, such as transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS), paired with behavioral language therapy, have demonstrated the capacity to enhance language abilities in primary progressive aphasia (PPA), a debilitating degenerative neurological syndrome that leads to declines in communication abilities. The aim of this meta-analysis is to systematically evaluate the efficacy of tDCS and TMS in improving language outcomes in PPA, explore the magnitude of effects between stimulation modalities, and examine potential moderators that may influence treatment effects. Standard mean differences for change in performance from baseline to post-stimulation on language-related tasks were evaluated. Six tDCS studies and two repetitive TMS studies met inclusion criteria and provided 22 effects in the analysis. Random effect models revealed a significant, heterogeneous, and moderate effect size for tDCS and TMS in the enhancement of language outcomes. Findings demonstrate that naming ability significantly improves due to brain stimulation, an effect found to be largely driven by tDCS. Future randomized controlled trials are needed to determine long-term effectiveness of noninvasive brain stimulation techniques on language abilities, further delineate the efficacy of tDCS and TMS, and identify optimal parameters to enable the greatest gains for persons with PPA.

Working memory is an executive memory process essential for everyday decision-making and problem solving that declines with advanced age. Transcranial direct current stimulation (tDCS) is a non-invasive form of brain stimulation that has demonstrated potential for improving working memory performance in older adults. However, the neural mechanisms underlying effects of tDCS on working memory are not well understood. This mechanistic study investigated the acute and after-effects of bilateral frontal (F3/F4) tDCS at 2mA for 12-minutes on functional connectivity of the working memory network in older adults. We hypothesized active tDCS over sham would increase frontal connectivity during working memory performance. The study used a double-blind within-subject 2 session crossover design. Participants performed an fMRI N-Back working memory task before, during, and after active or sham stimulation. Functional connectivity of the working memory network was assessed within and between stimulation conditions (FDR<.05). Active tDCS produced a significant increase in functional connectivity between left ventrolateral prefrontal cortex and left dorsolateral prefrontal cortex during stimulation, but not after stimulation. Connectivity did not significantly increase with sham stimulation. In addition, our data demonstrated both state-dependent and time-dependent effects of tDCS working memory network connectivity in older adults. tDCS during working memory performance produces a selective change in functional connectivity of the working memory network in older adults. These data provide important mechanistic insight into the effects of tDCS on brain connectivity in older adults, as well as key methodological considerations for tDCS-working memory studies.