New Method Measures Brain Memory Effects Across Wakefulness and Deep Sleep

A new computational framework known as the FDTest assesses local memory effects in multidimensional systems by measuring violations of a generalized fluctuation-dissipation theorem. Introduced by Sebastian Manuel Geli, Juan Manuel Monti, Adrián Ponce-Alvarez, Gustavo Deco, and Yonatan Sanz Perl, this mathematical method evaluates how individual brain areas retain past information fed back from the surrounding network rather than operating strictly according to their immediate internal state.

Investigating how the human brain flexibly balances local and distributed information processing to support diverse cognitive and conscious states represents a fundamental challenge in neuroscience. The investigators hypothesized that a primary signature of this operational balance is the presence of memory effects. In neural dynamics, memory effects manifest whenever a region’s future activity depends not only on its present condition, but also on historical signals returned from the broader brain network.

To evaluate this dynamic behavior, the team applied the FDTest framework to whole-brain computational models fitted to empirical human neuroimaging data. Their initial modeling experiments demonstrated that the brain’s local memory structure directly reflects its underlying structural connectivity. By detecting explicit violations of the generalized fluctuation-dissipation theorem, the testing procedure uncovers how network-level feedback shapes localized neural activity across different brain areas.

The researchers then expanded their computational analysis to individualized whole-brain models of subjects during wakefulness and deep sleep. Their comparisons revealed that memory effects are consistently stronger during wakefulness than in deep sleep. According to the study, these amplified memory signatures in the waking brain indicate richer inter-regional dependencies and substantially more integrated neural dynamics across active brain circuits.

These experimental modeling findings establish local memory as a dynamical marker of brain state. By demonstrating that thermodynamic fluctuation-dissipation violations capture network communication across sleep and waking conditions, the authors position the FDTest as a principled analytical tool for probing the hidden dynamical structure of neural systems.

Subject of Research: Measurement of local memory effects in brain dynamics using fluctuation-dissipation theorem violations

Article Title: FDTest: Fluctuation-dissipation theorem as a test for memory effects in brain dynamics

Article References: Geli, S. M., Monti, J. M., Ponce-Alvarez, A., Deco, G., & Sanz Perl, Y. (2026). FDTest: Fluctuation-dissipation theorem as a test for memory effects in brain dynamics. PLOS Computational Biology, 22(11), e1014883. https://doi.org/10.1371/journal.pcbi.1014883

Image Credits: AI Generated

DOI: 10.1371/journal.pcbi.1014883

Keywords: fluctuation-dissipation theorem, FDTest, brain dynamics, memory effects, computational neuroscience, wakefulness, deep sleep, neuroimaging, whole-brain models, neural connectivity, information processing, dynamical markers, brain states, inter-regional dependencies, integrated dynamics, multidimensional systems