Functional Connectivity in Brain Networks

Functional connectivity refers to the statistical dependencies between spatially distinct brain regions, reflecting coordinated neural activity over time. This field has grown out of advances in neuroimaging—particularly functional magnetic resonance imaging (fMRI), magnetoencephalography and electrophysiological recordings—that permit non-invasive mapping of brain networks. At rest, the brain exhibits intrinsic networks characterised by coherent low-frequency fluctuations, while task performance engages dynamic reconfiguration of these connections. Graph theory has provided quantitative tools to characterise network topology, revealing small-world properties, modular organisation and the presence of hub regions critical for information integration. More recent work has emphasised the non-stationary nature of connectivity, showing that transient brain states assemble and dissolve on sub-second to minute timescales, and that these fluctuations underpin cognitive flexibility, disease phenotypes and individual differences in behaviour.

Research from Nature Portfolio

Recent studies have applied innovation-driven co-activation pattern analysis to resting-state fMRI, revealing that functional networks are composed of spatially overlapping building blocks whose activity overlaps in time. This approach demonstrates that conventional views of anti-correlated networks mask a richer spatiotemporal interplay among default-mode, attention and control systems. Complementing these findings, investigations into spectrally defined transient states using magnetoencephalography have shown that resting networks can be described as visits to short-lived brain states, each marked by distinct oscillatory power and coherence in specific frequency bands. Together, these works advance a dynamic view of connectivity in which brain networks emerge through coordinated bursts of activity rather than sustained coupling.

Functional Connectivity in Brain Networks publication trend

The graph below shows the total number of articles in functional connectivity in brain networks across all publications each year (not limited to Nature Index journals).

Technical terms

Functional connectivity: Statistical dependence between activities of distinct brain regions over time.

Resting-state fMRI: Imaging of spontaneous blood-oxygen-level-dependent signal fluctuations in the absence of explicit tasks.

Innovation-driven co-activation patterns (iCAPs): Spatially and temporally overlapping components extracted from resting-state fMRI that reveal dynamic network building blocks.

Phase-coupling: Synchronisation of oscillatory phases between neural populations, indicating functional interaction.

Fractional amplitude of low-frequency fluctuations (fALFF): Ratio of power within a low-frequency band to total power in the fMRI signal, used as a marker of regional spontaneous activity.

Time-varying functional connectivity (TVFC): Analysis of how functional connections change over time rather than assuming constant coupling.

References

1. Graph analysis of the human connectome: Promise, progress, and pitfalls. NeuroImage (2013).
2. Fast transient networks in spontaneous human brain activity. eLife (2014).
3. Transient brain activity disentangles fMRI resting-state dynamics in terms of spatially and temporally overlapping networks. Nature Communications (2015).
4. Spectrally resolved fast transient brain states in electrophysiological data. NeuroImage (2015).
5. Predicting tremor improvement after MRgFUS thalamotomy in essential tremor from preoperative spontaneous brain activity: A machine learning approach. Science Bulletin (2024).
6. Questions and controversies in the study of time-varying functional connectivity in resting fMRI. Network Neuroscience (2020).
7. Non-Stationarity in the “Resting Brain’s” Modular Architecture. PLOS ONE (2012).