Purpose: Loss of brain synapses is an early pathological feature of Alzheimer's disease. The current study assessed synaptic loss in vivo with Positron Emission Tomography and an 18Flabelled radiotracer of the synaptic vesicle protein 2A, [18F]UCB-H. Methods: Twenty-four patients with Mild Cognitive Impairment or Alzheimer's disease and positive [18F]Flutemetamol amyloid-PET were compared to nineteen healthy controls. [18F]UCB-H brain uptake was quantified with Logan graphical analysis using an imagederived blood input function. SPM12 and regions-of-interest (ROI) analyses were used for group comparisons of regional brain distribution volumes and for correlation with cognitive measures. Results: A significant decrease of [18F]UCB-H uptake was observed in several cortical areas (11 to 18% difference) and in the thalamus (16% difference), with the largest effect size in the hippocampus (31% difference). Reduced hippocampal uptake was related to patients' cognitive decline (ROI analysis) and unawareness of memory problems (SPM and ROI analyses). Conclusions: The findings thus highlight predominant synaptic loss in the hippocampus, confirming previous autopsy-based studies and a recent PET study with an 11C-labelled SV2A radiotracer. [18F]UCB-H PET allows to image in vivo synaptic changes in Alzheimer's disease and to relate them to patients' cognitive impairment.

BackgroundResearch on cognitive control suggests an age-related decline in proactive control abilities whereas reactive control seems to remain intact. However, the reason of the differential age effect on cognitive control efficiency is still unclear. This study investigated the potential influence of fluid intelligence and processing speed on the selective age-related decline in proactive control. Eighty young and 80 healthy older adults were included in this study. The participants were submitted to a working memory recognition paradigm, assessing proactive and reactive cognitive control by manipulating the interference level across items.ResultsRepeated measures ANOVAs and hierarchical linear regressions indicated that the ability to appropriately use cognitive control processes during aging seems to be at least partially affected by the amount of available cognitive resources (assessed by fluid intelligence and processing speed abilities).ConclusionsThis study highlights the potential role of cognitive resources on the selective age-related decline in proactive control, suggesting the importance of a more exhaustive approach considering the confounding variables during cognitive control assessment.

Marine MANARD, Marine.Manard@ulg.ac.be, Allée du VI août, 8 (B30), 4000 Liège, BelgiqueBackground. Research on cognitive control suggests an age-related decline in proactive control abilities (an anticipatory form of control) whereas reactive control (consecutive to conflict detection) seems to remain intact [1]. As proactive and reactive control abilities were associated to specific brain networks [2], this study investigated age-related effects on the neural substrates associated to each kind of control.

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Jaspar M., Genon S., Muto V., Meyer C., Manard M., Dideberg V., Bours V., Salmon E., Maquet P., Collette F. (2013). Modulating effect of COMT genotype on the brain regions underlying proactive control process during inhibition. Cortex (in press). DOI: http://dx.doi.org/10.1016DOI: http://dx.doi.org/10. /j.cortex.2013 Modulating effect of COMT genotype on the brain regions underlying proactive control process during inhibition