Abstract
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Objectives There is increasing evidence that memory systems are modulated as part of the default mode network (DMN). In the present study, we examined whether connectivity within the DMN is related to working memory performance in young healthy adults.
Methods Independent component analysis of [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) data from 35 young adults (27.1±5.1 years) captured a coherent activity of the posterior cingulate (PCC), medial prefrontal (MPFC) and inferior parietal cortices bilaterally, i.e. major nodes of the classical DMN. Metabolic activity in these nodes was extracted and compared between groups of subjects with (relative to median) low (n=18) and high (n=17) performance on digit span backward test. In addition, we conducted fiber tractography in a subgroup of subjects from whom diffusion tensor imaging data were available (9 low and 10 high performers).
Results There was no difference in relative metabolic activity between high and low performers. However, low performers showed significantly lower metabolic connectivity between PCC and all other DMN nodes (p’s < 0.05). Tractography based on PCC and MPFC nodes as seed regions resulted in reconstruction of the cingulate bundles (CB) in all subjects. As compared to high performers, low performers showed smaller volume (one-sided p<0.05) and lower fractional anisotropy (one-sided p=0.053) of the left CB.
Conclusions Our data provide direct evidence that working memory performance is related to connectivity within the DMN in young healthy adults. Connectivity as quantified with FDG-PET might be a sensitive marker of the variability in normal cognitive function