Abstract

Despite decades of research, there is still a lack of understanding of the role and generating mechanisms of the ubiquitous fluctuations and oscillations found in recordings of brain dynamics. Here, we used whole-brain computational models capable of presenting different dynamical regimes to reproduce empirical data's turbulence level. We showed that the model's fluctuations regime fitted to turbulence more faithfully reproduces the empirical functional connectivity compared to oscillatory and noise regimes. By applying global and local strength-dependent perturbations and subsequently measuring the responsiveness of the model, we revealed each regime's computational capacity demonstrating that brain dynamics is shifted towards fluctuations to provide much-needed flexibility. Importantly, fluctuation regime stimulation in a brain region within a given resting state network modulates that network, aligned with previous empirical and computational studies. Furthermore, this framework generates specific, testable empirical predictions for human stimulation studies using strength-dependent rather than constant perturbation. Overall, the whole-brain models fitted to the level of empirical turbulence together with functional connectivity unveil that the fluctuation regime best captures empirical data, and the strength-dependent perturbative framework demonstrates how this regime provides maximal flexibility to the human brain. Author summary How and why do complex, fluctuating, and oscillating dynamics characterise brain states? We combined a whole-brain model and strength-dependent perturbation frameworks to investigate the causal mechanistic explanation behind the human brain function. We demonstrated by fitting whole-brain models to the level of empirical turbulence together with functional connectivity that the fluctuation regime best captures empirical data. Furthermore, the strength-dependent perturbative approach allows us to assess the computational capabilities of different dynamical regimes. We showed that the fluctuations regime provides maximal flexibility to the human brain, a desirable property for brain dynamics to interact with the environment.