Sustained versus instantaneous connectivity differentiates cognitive functions of processing speed and episodic memory

Abstract

Synchrony of brain activity over time describes the functional connectivity between brain regions but does not address the temporal component of this relationship. We propose a complementary method of analysis by introducing the width of cross-correlation curves between functional MRI (fMRI) time series as a metric of the relative duration of synchronous activity between brain regions, or "sustained connectivity". Using resting-state fMRI, cognitive, and demographics data from 1,003 subjects included in the Human Connectome Project, we find that sustained connectivity is a reproducible trait in individuals, heritable, more transient in females, and shows changes with age in early adulthood. Sustained connectivity in sensory brain regions is specifically associated with differences in processing speed across subjects, particularly in men. In contrast, traditional functional connectivity was correlated with a measure of episodic memory, but not with processing speed. Individual differences in hemodynamic response function (HRF) are closely approximated by sustained connectivity and width of the HRF is also correlated with processing speed across individuals, suggesting that variability in hemodynamic response may be influenced by transient versus sustained neural activity rather than simply differences in vascularity and signal transduction. Sustained connectivity may provide new opportunities to study brain dynamics in clinical populations.

Dynamic lag analysis reveals atypical brain information flow in autism spectrum disorder

“…King et al found increased durations of functional connections in both individual brain regions and distributed networks in autism, which were associated with metrics of disease severity [King et al, ]. They used a complementary method of analysis by introducing the width of cross‐correlation curves between resting‐state fMRI time series as a metric of relative duration of synchronous activity between brain regions (“sustained connectivity”) [King & Anderson, ]. The persistence of brain connectivity in autism may limit the ability to rapidly shift from one brain state to another [King et al, ].…”

Evaluation of Differences in Temporal Synchrony Between Brain Regions in Individuals With Autism and Typical Development

“…16 Briefly, time series data from each of the 17 distributed brain networks were extracted for analysis with each network treated as a single region of interest (ROI).…”

“…35 When combined, this parcellation scheme incorporates major cortical, subcortical, and cerebellar gray matter ROIs numbering 361 regions in total. 16,36 …”

“…16 For 1 connection involving 2 time series of BOLD measurements, cross-correlation curves were constructed by using the Pearson correlation coefficient between the 2 time series at each of −20 to +20 lags by shifting one or the other of the time points forward in time by 1 volume. For a graphical representation of this process, see the study by King and Anderson 16 (Figure 1). Data points from volumes before and after volumes with a mean head motion value of 0.2 mm or greater were treated as missing data in sustained connectivity MRI calculations analogous to volume censoring or scrubbing in traditional functional connectivity analysis.…”

“…16 Sustained connectivity provides insight into separable components of cognition when compared with static functional connectivity. For instance, the study by King and Anderson 16 showed a significant negative relationship between processing speed and sustained connectivity in a large sample of typically developing adults. This relationship with processing speed was not evident with static traditional functional connectivity.…”