The repeatability of cognitive performance: a meta-analysis

Behavioural and cognitive processes play important roles in mediating an individual's interactions with its environment. Yet, while there is a vast literature on repeatable individual differences in behaviour, relatively little is known about the repeatability of cognitive performance. To further our understanding of the evolution of cognition, we gathered 44 studies on individual performance of 25 species across six animal classes and used meta-analysis to assess whether cognitive performance is repeatable. We compared repeatability (R) in performance (1) on the same task presented at different times (temporal repeatability), and (2) on different tasks that measured the same putative cognitive ability (contextual repeatability). We also addressed whether R estimates were influenced by seven extrinsic factors (moderators): type of cognitive performance measurement, type of cognitive task, delay between tests, origin of the subjects, experimental context, taxonomic class and publication status. We found support for both temporal and contextual repeatability of cognitive performance, with mean R estimates ranging between 0.15 and 0.28. Repeatability estimates were mostly influenced by the type of cognitive performance measures and publication status. Our findings highlight the widespread occurrence of consistent inter-individual variation in cognition across a range of taxa which, like behaviour, may be associated with fitness outcomes.This article is part of the theme issue 'Causes and consequences of individual differences in cognitive abilities'.

Prevalence of word retrieval complaint and prediction of dementia in a population-based study of elderly subjects

There is agreement that elderly people complain about word finding difficulties, particularly proper names. However, few studies have focused on the prevalence of this complaint in the general population, nor is it clearly known whether it is predictive of dementia. The aim of this study was to fill this gap using the PAQUID cohort. 1,838 people aged 65 or more completed questionnaires and neuropsychological evaluation regularly during 13 years. Results show that the complaint about proper name retrieval concerns 64% of people aged above 65 years, and the complaint about common names 30%. The complaint was not associated with enhanced risk of dementia, whereas short naming tests were. Only a marginal relation was found between these naming tests and word retrieval complaint. This study emphasizes the importance of proper name retrieval complaint in the general population and suggests that elderly subjects can be reassured in the absence of other symptoms.

Comparison between PET template-based method and MRI-based method for cortical quantification of florbetapir (AV-45) uptake in vivo

PURPOSE

Florbetapir (AV-45) has been shown to be a reliable tool for assessing in vivo amyloid load in patients with Alzheimer's disease from the early stages. However, nonspecific white matter binding has been reported in healthy subjects as well as in patients with Alzheimer's disease. To avoid this issue, cortical quantification might increase the reliability of AV-45 PET analyses. In this study, we compared two quantification methods for AV-45 binding, a classical method relying on PET template registration (route 1), and a MRI-based method (route 2) for cortical quantification.

METHODS

We recruited 22 patients at the prodromal stage of Alzheimer's disease and 17 matched controls. AV-45 binding was assessed using both methods, and target-to-cerebellum mean global standard uptake values (SUVr) were obtained for each of them, together with SUVr in specific regions of interest. Quantification using the two routes was compared between the clinical groups (intragroup comparison), and between groups for each route (intergroup comparison). Discriminant analysis was performed.

RESULTS

In the intragroup comparison, differences in uptake values were observed between route 1 and route 2 in both groups. In the intergroup comparison, AV-45 uptake was higher in patients than controls in all regions of interest using both methods, but the effect size of this difference was larger using route 2. In the discriminant analysis, route 2 showed a higher specificity (94.1 % versus 70.6 %), despite a lower sensitivity (77.3 % versus 86.4 %), and D-prime values were higher for route 2.

CONCLUSION

These findings suggest that, although both quantification methods enabled patients at early stages of Alzheimer's disease to be well discriminated from controls, PET template-based quantification seems adequate for clinical use, while the MRI-based cortical quantification method led to greater intergroup differences and may be more suitable for use in current clinical research.

Identification of subgroups in amnestic mild cognitive impairment

The DMS48 is a visual recognition memory test designed to detect memory changes in early Alzheimer disease (AD). Patients with amnestic mild cognitive impairment (aMCI) who succeeded on this task exhibited frontal hypoperfusion on SPECT. In contrast, failure was associated with temporomesial and temporoparietal hypoperfusion, a pattern usually described in the early stages of AD. It may possible to detect patients at high risk for AD within a population of aMCI.