Hidden Spirals Reveal Neurocomputational Mechanisms of Traveling Waves in Human Memory

Traveling waves are neural oscillations that progressively propagate across the cortex in specific directions and spatial patterns, however, their underlying mechanisms remain elusive. To probe their mechanisms, we analyzed direct brain recordings from humans performing a working memory task using empirical statistical modeling and computational modeling. By using independent component analysis, we showed that traveling waves propagated along the cortex in complex spatial patterns that correlated with behaviors such as memory encoding, maintenance, and retrieval. We also applied a novel computational model to identify novel complex spatial patterns, using coupled phase oscillators to reveal hidden spirals that were not clearly visible in the original recordings. The orientation of these hidden spirals distinguished between separate cognitive states, such as memory encoding and retrieval. Our simultaneous empirical and computational modeling provides a general framework to probe the functional significance and neurocomputational mechanisms underlying a diverse range of spatial patterns of traveling waves. Importantly, our novel model-based analytical approach can identify new types of traveling waves in the brain that are missed with conventional analysis approaches.