Variability in Brain Activity and Cognitive Function
Summary
Variability in brain activity refers to the inherent fluctuations in neural signals observed across milliseconds to minutes, as captured by electrophysiological and neuroimaging techniques. Once considered undesirable noise, these dynamic patterns are now recognised as fundamental to cognitive flexibility, efficient information processing and behavioural adaptability. Across development, increasing signal complexity accompanies improvements in attention, memory and decision-making, whereas ageing and neurodegenerative disorders often coincide with reduced variability and cognitive decline. In psychiatric and neurological conditions, altered variability profiles mirror symptom severity and treatment response, offering new avenues for biomarker discovery. Advances in analytic approaches—such as entropy measures, fractal dimension and time-resolved connectivity—have enabled the mapping of variability across spatial scales, from single neurons to large-scale networks. Understanding these fluctuations holds global significance for diagnostic precision, prognostic assessment and personalised interventions, and deepens our insight into how the brain balances stability with flexibility to support cognition.
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Variability in Brain Activity and Cognitive Function publication trend
The graph below shows the total number of articles in variability in brain activity and cognitive function across all publications each year (not limited to Nature Index journals).
Technical terms
Blood-oxygen-level-dependent (BOLD) signal: The fMRI measure of changes in deoxyhaemoglobin concentration used to infer neural activity.
Brain signal variability (BSV): The moment-to-moment fluctuations in neural signals that reflect dynamic brain states.
Entropy: A nonlinear metric quantifying the unpredictability or complexity of a time series.
Dwell time: The duration spent in a specific signal state before transitioning to another.
Default-mode network (DMN): A set of interacting brain regions active during rest, associated with self-referential and introspective processing.
Repetitive and restrictive behaviours (RRBs): Core autism symptoms characterised by repetitive actions and limited interests.
References
- Increased Brain Signal Variability Accompanies Lower Behavioral Variability in Development. PLOS Computational Biology (2008).
- Decreased Complexity in Alzheimer's Disease: Resting-State fMRI Evidence of Brain Entropy Mapping. Frontiers in Aging Neuroscience (2017).
- The Promise of Investigating Neural Variability in Psychiatric Disorders. Biological Psychiatry (2025).
- Imbalanced temporal states of cortical blood-oxygen-level-dependent signal variability during rest in episodic migraine. The Journal of Headache and Pain (2024).
- Age-related changes in brain signal variability in autism spectrum disorder. Molecular Autism (2025).
- Brain entropy, fractal dimensions and predictability: A review of complexity measures for EEG in healthy and neuropsychiatric populations. European Journal of Neuroscience (2022).
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