  The human brain exhibits large-scale spontaneous fluctuations that account
for most of its total energy metabolism. Independent of any overt function,
this immense ongoing activity likely creates or maintains a potential
functional brain reserve to facilitate normal brain function. An important
property of spontaneous brain activity is the long-range temporal coherence,
which can be characterized by resting state fMRI-based brain entropy mapping
(BEN), a relatively new method that has gained increasing research interest.
The purpose of this study was to leverage the large resting state fMRI and
behavioral data publicly available from the human connectome project to address
three important but still unknown questions: temporal stability of
rsfMRI-derived BEN; the relationship of resting BEN to latent functional
reserve; associations of resting BEN to neurocognition. Our results showed that
rsfMRI-derived BEN was highly stable across time; resting BEN in the default
mode network (DMN) and executive control network (ECN) was related to brain
reserve in a negative correlation to education years; and lower DMN/ECN BEN
corresponds to higher fluid intelligence and better task performance. These
results suggest that resting BEN is a temporally stable brain trait; BEN in
DMN/ECN may provide a means to measure the latent functional reserve that
bestows better brain functionality and may be enhanced by education.
