The Symbol Digit Modalities Test (SDMT) has been proposed to replace the Paced Auditory Serial Addition Test-3 (PASAT-3) in the Multiple Sclerosis Functional Composite because it has the same validity but easy and shorter administration. However, among the two tests, the one that is most affected by culture is still unknown. The purpose of this study was to compare the performance of Argentinian and North American populations on the SDMT and PASAT-3. The SDMT and PASAT-3 were administered to 137 healthy volunteers from Buffalo, NY, and 137 healthy participants from Buenos Aires, Argentina. Participants were matched by gender, age (±2), and education (±1). Significant differences were found on the SDMT but not on the PASAT-3. Significant and low correlations were found between the tests and years of education. The SDMT is more affected by culture than is the PASAT-3. Possible interpretations of this result are presented.

Early neuropathological changes characteristic of late-onset Alzheimer’s disease (LOAD) involve brain stem and limbic structures that regulate neurovegetative functions, including sleep–wake rhythm. Indeed, sleep pattern is an emerging biomarker and a potential pathophysiological mechanism in LOAD. We hypothesized that cognitively asymptomatic, middle-aged offspring of patients with LOAD (O-LOAD) would display a series of circadian rhythm abnormalities prior to the onset of objective cognitive alterations. We tested 31 children of patients with LOAD (O-LOAD) and 19 healthy individuals without family history of Alzheimer’s disease (control subjects, CS) with basic tests of cognitive function, as well as actigraphy measures of sleep–wake rhythm, cardiac autonomic function, and bodily temperature. Unexpectedly, O-LOAD displayed subtle but significant deficits in verbal episodic memory (Rey Auditory Verbal Learning Test delayed recall 10.6 ± 0.4 vs. 8.6 ± 0.6, t = 4.97, df = 49, p < 0.01) and language (Weschler’s vocabulary 51.4 ± 1.3 vs. 44.3 ± 1.5, t = 2.49, df = 49, p < 0.001) compared to CS, even though all participants had results within the clinically normal range. O-LOAD showed a phase-delayed rhythm of body temperature (2.56 ± 0.47 h vs. 3.8 ± 0.26 h, t = 2.48, df = 40, p = 0.031). Cognitive performance in O-LOAD was associated with a series of cardiac autonomic sleep–wake variables; specifically indicators of greater sympathetic activity at night were related to poorer cognition. The present results suggest sleep pattern deserves further study as a potential neurobiological signature in LOAD, even in middle-aged, at risk individuals.

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Background: Factors associated with early life educational performance can be related to neurodevelopment, cognitive functioning and, consequently, the risk for dementia, but have received less attention than adult biomarkers. Method:A systematic review of the evidence available up to October 2020 in PubMed and Scopus was carried out. Original articles addressing both developmental learning disorders (LD) and late-onset neurodegenerative diseases (NDD) were included.Result: A significant prevalence of LD was found in patients with atypical variants of Alzheimer's disease (AD). Furthermore, an association was found between primary progressive aphasia -logopenic variant and language-related LD, and also between posterior cortical atrophy and non-language-related LD. These results could be explained by the selective vulnerability hypothesis, which states that the vulnerability of a particular brain network or area could predispose both to developmental LD and late-onset NDD. Conclusion:Developmental LDs can be considered as risk factors for late-onset NDD, especially for atypical AD variants. Given the scarcity of results and the limitations reported, a greater number of studies are required, with larger samples and, preferably, of longitudinal design in order to address this issue.