Abstract
Background
Executive functions (EF) decline during typical aging and are affected in age-related neurodegenerative conditions. These functions have long been associated with the integrity of the frontal lobe. While neuroimaging studies have frequently reported correlations between objective lab-based EF tasks and activity in diverse brain structures, the relationship between everyday naturalistic EF and regional brain activity has been less well-studied. We aim to evaluate the relationships between naturalistic “real-world” behavioral ratings of EF and resting state regional brain activity.
Methods
Participants were 80 (26M) healthy older adults (average 69.13, SD 8.70) and their informants (usually their spouse). We used Frontal Systems Behavioral Scale (FrSBe) to obtain ratings of subjects’ EF dysfunction symptoms from the informant, which produces three subscales of EF syndromes (the Apathic, Disinhibited, Dysexecutive syndromes). [18F]-FDG PET imaging quantified regional glucose metabolism, with regional standard uptake value ratio (SUVr) calculated using the CapAIBL platform1,2. In addition, participants completed a battery of cognitive tests including the Montreal Cognitive Assessment (MoCA), Digit Span Backwards, Trail Making Test B (Trails B), the Controlled Word Association Test (COWA), and 21-item version of the Depression Anxiety Stress Scales (DASS-21).
Results
Partial correlations controlling for APOE ε4 allele status and DASS-21 depression scale revealed that greater informant-reported EF dysfunction (total FrsBe score) was associated with lower levels of brain activity in the dorsolateral prefrontal (r=-0.28, p=0.025), orbitofrontal (r=0.28, p=0.026), and anterior cingulate (r=-0.39, p=0.001). These relationships appear to be driven by the Dysexecutive syndrome subscale (prefrontal r=-0.35, p=0.005; orbitofrontal r=-0.34, p=0.007, anterior cingulate r=-0.44, p<0.001). Conversely, greater everyday EF problems were not significantly correlated with other brain regions such as the temporal or parietal lobe, and measures such as MoCA, Digit span backwards, Trails B, and COWA verbal fluency were not significantly correlated with prefrontal metabolism.
Conclusions
We are able to specifly the link between EF and the frontal lobe by using FrSBe, a naturalistic behavioral rating, and the resting state glucose metabolism by FDG PET imaging. 1Zhou et al., PLOS ONE, 9:e84777 (2014). 2Bourgeat et al., Neurobiology of Aging, 36 Suppl 1:S159–66 (2015).