Unsupervised Online Paired Associates Learning Task from the Cambridge Neuropsychological Test Automated Battery (CANTAB®) in the Brain Health Registry.

BACKGROUND: Unsupervised online cognitive assessments have demonstrated promise as an efficient and scalable approach for evaluating cognition in aging, and Alzheimer's disease and related dementias. OBJECTIVES: The aim of this study was to evaluate the feasibility, usability, and construct validity of the Paired Associates Learning task from the Cambridge Neuropsychological Test Automated Battery® in adults enrolled in the Brain Health Registry. DESIGN, SETTING, PARTICIPANTS, MEASUREMENTS: The Paired Associates Learning task was administered to Brain Health Registry participants in a remote, unsupervised, online setting. In this cross-sectional analysis, we 1) evaluated construct validity by analyzing associations between Paired Associates Learning performance and additional participant registry data, including demographics, self- and study partner-reported subjective cognitive change (Everyday Cognition scale), self-reported memory concern, and depressive symptom severity (Patient Health Questionnaire-9) using multivariable linear regression models; 2) determined the predictive value of Paired Associates Learning and other registry variables for identifying participants who self-report Mild Cognitive Impairment by employing multivariable binomial logistic regressions and calculating the area under the receiver operator curve; 3) investigated feasibility by looking at task completion rates and statistically comparing characteristics of task completers and non-completers; and 4) evaluated usability in terms of participant requests for support from BHR related to the assessment. RESULTS: In terms of construct validity, in participants who took the Paired Associates Learning for the first time (N=14,528), worse performance was associated with being older, being male, lower educational attainment, higher levels of self- and study partner-reported decline, more self-reported memory concerns, greater depressive symptom severity, and self-report of Mild Cognitive Impairment. Paired Associates Learning performance and Brain Health Registry variables together identified those with self-reported Mild Cognitive Impairment with moderate accuracy (areas under the curve: 0.66-0.68). In terms of feasibility, in a sub-sample of 29,176 participants who had the opportunity to complete Paired Associates Learning for the first time in the registry, 14,417 started the task. 11,647 (80.9% of those who started) completed the task. Compared to those who did not complete the task at their first opportunity, those who completed were older, had more years of education, more likely to self-identify as White, less likely to self-identify as Latino, less likely to have a subjective memory concern, and more likely to report a family history of Alzheimer's disease. In terms of usability, out of 8,395 received requests for support from BHR staff via email, 4.4% (n=374) were related to PAL. Of those, 82% were related to technical difficulties. CONCLUSIONS: Our findings support moderate feasibility, good usability, and construct validity of cross-sectional Paired Associates Learning in an unsupervised online registry, but also highlight the need to make the assessment more inclusive and accessible to individuals from ethnoculturally and socioeconomically diverse communities. A future, improved version could be a scalable, efficient method to assess cognition in many different settings, including clinical trials, observational studies, healthcare, and public health.

Metabolic characteristics of cortical malformations causing epilepsy.

PURPOSE: Cortical malformations (CMs) are increasingly recognized as the epileptogenic substrate in patients with medically refractory neocortical epilepsy (NE). The aim of this study was to test the hypotheses that: 1. CMs are metabolically heterogeneous. 2. The structurally normal appearing perilesional zone is characterized by similar metabolic abnormalities as the CM. METHODS: Magnetic resonance spectroscopic imaging (MRSI) in combination with tissue segmentation was performed on eight patients with NE and CMs and 19 age matched controls. In controls, NAA, Cr, Cho,NAA/Cr and NAA/Cho of all voxels of a given lobe were expressed as a function of white matter content and thresholds for pathological values determined by calculating the 95% prediction intervals. These thresholds were used to identify metabolically abnormal voxels within the CM and in the perilesional zone. RESULTS: 30% of all voxels in the CMs were abnormal, most frequently because of decreases of NAA or increases of Cho. Abnormal voxels tended to form metabolically heterogeneous clusters interspersed in metabolically normal regions. Furthermore, 15% of all voxels in the perilesional zone were abnormal, the most frequent being decreases of NAA and Cr. CONCLUSION: In CMs metabolically normal regions are interspersed with metabolically heterogeneous abnormal regions. Metabolic abnormalities in the perilesional zone share several characteristics of CMs and might therefore represent areas with microscopic malformations and/or intrinsic epileptogenicity.

Measurement of hippocampal subfields and age-related changes with high resolution MRI at 4T.

Histological studies suggest that hippocampal subfields are differently affected by aging and Alzheimer's disease (AD). The aims of this study were: (1) To test if hippocampal subfields can be identified and marked using anatomical landmarks on high resolution MR images obtained on a 4T magnet. (2) To test if age-specific volume changes of subfields can be detected. Forty-two healthy controls (21-85 years) and three AD subjects (76-86 years) were studied with a high resolution T2 weighted fast spin echo sequence. The entorhinal cortex (ERC), subiculum, CA1, CA2 and CA3/4 and dentate were marked. A significant correlation between age and CA1 (r=-0.51, p=0.0002) which was most pronounced in the seventh decade of life was found in healthy controls. In AD subjects, CA1 and subiculum were smaller than in age-matched controls. These preliminary findings suggest that measurement of hippocampal subfields may be helpful to distinguish between normal aging and AD.

Spectroscopic evidence of hippocampal abnormalities in neocortical epilepsy.

Lesional neocortical epilepsy (NE) can be associated with hippocampal sclerosis or hippocampal spectroscopic abnormalities without atrophy (dual pathology). In this study, magnetic resonance spectroscopic imaging (MRSI) was used to determine the frequency of hippocampal damage/dysfunction in NE with and without structural lesion. Sixteen patients with NE [seven temporal NE (NE-T), nine extratemporal (NE-ET)] and 16 controls were studied with a 2D MRSI sequence (Repetition time/echo time (TR/TE) = 1800/135 ms) covering both hippocampi. Seven NE patients had MR visible lesions (NE-Les), nine had normal MRI (NE-no). In each hippocampus, 12 voxels were uniformly selected. In controls, mean (+/- SD) NAA/(Cr + Cho) values for each voxel were calculated and voxels with NAA/(Cr + Cho) < or = (mean in controls--2SD in controls) were defined as 'pathological' in patients. Eight of 16 NE patients had at least two 'pathological' voxel (mean 2.5, range 2-5) in one hippocampus. Four were NE-Les and four NE-no. Three (43%) NE-T patients, had evidence for hippocampal damage/dysfunction and five (56%) had NE-ET. The ipsilateral hippocampus was affected in six of eight NE patients. Evidence for unilateral hippocampal damage/dysfunction was demonstrated in 50% of the NE patients. The type of NE, i.e. NE-Les or NE-no, NE-T or NE-ET, had no influence on the occurrence of hippocampal damage/dysfunction.