Zoom link:
https://uni-sydney.zoom.us/j/8185360304
Oliver Cliff, Mike Li, Dennis Hernaus, Lianne Scholtens, Eli Müller, Brandon Munn, Gabriel Wainstein, Ben Fulcher, Joseph Lizier, James Shine
Cognition involves the dynamic adaptation of information processing resources as a function of task demands. To date, the neural mechanisms responsible for mediating this process remain poorly understood. In this study, we integrated cognitive neuroscience with information theory, network topology and neuropharmacology to advance our understanding of the fundamental computational processes that give rise to cognitive function in the human brain. In our first experiment, we consider the contrast between dynamic whole-brain blood oxygen level dependent (BOLD) data from both the resting state and a cognitively-challenging N-back task from the Human Connectome Project (N = 457) [1,2]. We translated the raw BOLD activity levels into time series that represent the dynamics of neural information processing by measuring information flows (pairwise between regions, using transfer entropy) and information storage (self-prediction in individual regions, using active information storage) as a function of time throughout the experiment [3]. Our results show that cognitive task performance alters the whole-brain information-processing landscape in a low-dimensional manner: during rest, information flowed from granular to agranular cortices, whereas this pattern was reversed during the performance of the N-back task. These contrasting gradients of information flow reflect the difference between a stronger "bottom-up" mode during rest (with inputs from sensory cortices sent up for interpretation as the dominant flow) versus a stronger "top-down" mode during task (where task performance is facilitated by higher level control and the increase of associated flows). To test a hypothesized mechanism for this switch [4], we modulated central noradrenaline levels in a double-blind, cross-over atomoxetine pharmacological fMRI study (N = 19) [5]. We found that potentiating the noradrenergic system altered the information processing dynamics by augmenting information transfer to and from the frontoparietal cortices. Together, our results provide a conceptual bridge between cognitive function, network topology, information theory and the ascending neuromodulatory arousal system. References 1\. Barch, D.M., Burgess, G.C., Harms, M.P., et al. Function in the human connectome: task-fMRI and individual differences in behavior. NeuroImage. 2013, 80, 169–189. 2\. Glasser, M.F., Sotiropoulos, S.N., Wilson, J.A., et al. The minimal preprocessing pipelines for the Human Connectome Project. NeuroImage. 2013, 80, 105–124. 3\. Lizier, J.T. JIDT: An information-theoretic toolkit for studying the dynamics of complex systems. Frontiers in Robotics and AI. 2014, 1, 11. 4\. Shine, J.M., Aburn, M.J., Breakspear, M., Poldrack, R.A. The modulation of neural gain facilitates a transition between functional segregation and integration in the brain. eLife. 2018, 7, e31130. 5\. Hernaus, D., Casales Santa, M.M., Offermann, J.S., Van Amelsvoort, T. Noradrenaline transporter blockade increases fronto-parietal functional connectivity relevant for working memory. Eur Neuropsychopharmacol. 2017, 27, 399–410.
