healthy community-dwelling older adults, whose cortical thickness was measured via MRI. HbO 2 levels in the PFC, measured via fNIRS, were assessed during active walking under STW and DTW conditions. Statistical analyses were adjusted for demographics and behavioral performance. Linear mixed-effects models revealed that the increase in HbO 2 from STW to DTW was moderated by cortical thickness in several regions. Specifically, thinner cortex in specific regions of the frontal, parietal, temporal, and occipital lobes, cingulate cortex, and insula was associated with greater increases in HbO 2 levels from single to dual-task walking. In conclusion, participants with thinner cortex in regions implicated in higher order control of walking employed greater neural resources, as measured by increased HbO 2 , in the PFC during DTW, without demonstrating benefits to behavioral performance. To our knowledge, this is the first study to examine cortical thickness as a marker of neural inefficiency during active walking.

Background Cognitive Reserve (CR) protects against cognitive decline, but whether CR influences the efficiency of cortical control of gait has not been reported. The current study addressed this important gap in the literature. Specifically, we determined the role of CR in moderating the efficiency of functional Near-Infrared-Spectroscopy (fNIRS)-derived HbO2 in the prefrontal cortex (PFC) assessed during active walking. We hypothesized that higher CR would be associated with more efficient brain activation patterns. Methods Participants were 55 (mean age=74.84; %female=49.1) older adults who underwent the combined walking/fNIRS protocol and had MRI data. We used an established dual-task walking paradigm that consisted of three task conditions: Single-Task-Walk (STW), Single-Task-Alpha (STA, cognitive task) and Dual-Task-Walk (DTW). Using the residuals approach, CR was derived from a word-reading test score by removing variance accounted for by socio-demographic variables, tests of current cognitive functions and a measure of structural brain integrity. Results CR moderated the change in fNIRS-derived HbO2 in the PFC across tasks. Higher CR was associated with smaller increases in fNIRS-derived HbO2 from the single tasks to dual task walking (CR x DTW compared to STW: estimate = .183; p < .001; CR x DTW compared to STA: estimate =.257; p < .001). The moderation effect of CR remained significant when adjusting for multiple covariates and concurrent moderation effects of measures of gait performance, current cognitive functions and structural integrity of the brain. Conclusion The current study provided first evidence that higher CR was associated with better neural efficiency of walking in older adults.

Intraindividual variability in gait and cognitive performance is distinct from central-tendency measures and associated with clinical outcomes in aging. Knowledge concerning intraindividual variability in neural activity, however, has been relatively scarce, and no research to date has reported on such variability during active walking. The current study addressed this major gap in knowledge. Participants were community-residing older adults (n = 394; mean age = 76.29 ± 6.65 years; %female = 55). Functional near-infrared spectroscopy (fNIRS) was used to measure oxygenated hemoglobin (HbO2) in the prefrontal cortex under three experimental conditions: single-task-walk, single-task-alpha (cognitive task), and dual-task-walk, which required the participants to perform the two single tasks simultaneously. Intraindividual variability in neural activity was operationalized using the standard deviation of fNIRS-derived HbO2 observations assessed during a 30-s interval in each experimental condition. The increase in intraindividual variability in neural activity in the dual-task-walk condition compared to both single-task conditions was associated with the presence of cognitive impairments and being a male. Furthermore, measures of intraindividual variability in neural activity and gait performance were positively correlated only under the dual-task-walk condition. Intraindividual variability in the neural activity of gait may be a novel marker for age-related impairments in mobility and cognitive function.

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Objective: Autoimmune encephalitis (AE) refers to a group of syndromes involving brain inflammation due to autoimmune activity and is associated with acute cognitive impairment. While several identified AE-associated antibodies (e.g., NMDAR) can be detected in cerebrospinal fluid and blood serum, many patients who respond well to treatment do not have the AE-associated antibodies. This causes challenges in diagnosis and treatment and has led to limited literature prognosticating cognitive outcomes following treatment in cases of suspected seronegative AE. We describe a case of seronegative AE in a patient with lingering cognitive symptoms after resolution of acute symptoms post-immunotherapy. Method: Patient is a 25-year-old female with a history of ulcerative proctitis who presented with suspected AE in the context of seizure, fever, balance difficulties, and personality changes. While antibodies were not detected, she was diagnosed with AE based on presentation, inflammatory markers, and neuroimaging and was treated with steroids, intravenous immunoglobulin, and plasma exchange. Patient presented for neuropsychological assessment 10 months later with lingering cognitive complaints. Results: Neuropsychological testing posttreatment revealed weaknesses/variability in attention, working memory, processing speed, and aspects of executive functioning including executive aspects of memory. Language, visuospatial functions, and retentive memory were preserved. Conclusion: This case suggested continued frontal-subcortical dysfunction likely related to residual effects of AE. Side effects of medications may have also contributed to her cognitive weaknesses. This case highlights the need for more research examining cognitive prognosis and expected timelines post seronegative AE treatment, given limited existing research. This is an important consideration for interpretations and recommendations from our neuropsychological evaluations.