Large-scale interactions mediating cognitive processes: Non-linear and non-separable

Objective

The human brain's cognitive abilities arise from complex interactions among highly interconnected brain areas. We have recently argued that interactions between oscillations at the same frequency (coherence-through-communication) cannot fully explain this coordination, due to the heterogeneity in cortical oscillation frequency and amplitude, as well as rapid cognitive state changes linked to aperiodic transients. Instead, we propose that non-linear interactions, which enable pattern recognition and integration beyond simple information relaying, are essential for understanding large-scale integration. NONLIN will investigate how non-linear mechanisms coordinate large-scale cortical networks and mediate cognitive and brain state changes, and will determine the non-separable nature of information integration, where combined influences of multiple regions on a target area cannot be decomposed into independent effects, counter to traditional modular views of cognition. To move beyond bi-variate, linear measures like coherence and Granger causality, NONLIN develops new mathematical methods to isolate and characterize non-linear and non-separable interactions, separating them from linear correlations caused by simple linear information relaying. Using large-scale intracranial electrophysiological data from humans and non-human primates, NONLIN will analyze how non-linear interactions reflect whole-brain anatomical connectivity and exhibit emergent properties distinct from the linear functional connectome. NONLIN tests whether active, alert states enhance non-linear, non-separable information integration, and whether cognitive processes, including attention, working memory, and perceptual binding, are primarily mediated by transient, broad-band influences and cross-frequency interactions driven by non-linear interactions. These findings will advance our understanding of cognition and impact the diagnosis and treatment of brain disorders and altered states of consciousness.