Hidden Spirals Underlie Cortical Traveling Waves

Neural traveling waves exhibit diverse spatial patterns, but the neural dynamics that generate them remain unknown. Here, we asked whether the apparent diversity of traveling waves reflects distinct dynamical processes or a common underlying organization obscured in recorded brain activity. We analyzed intracranial recordings from humans performing a working memory task and developed FOCUS (Frequency-flattened Oscillators in Cortex Unmask Spirals), a coupled phase oscillator framework that accounts for spatial heterogeneity in local frequencies to uncover latent dynamics underlying the observed waves. FOCUS revealed covert spiral dynamics underlying traveling waves whose recorded spatial patterns showed no overt spiral organization. These hidden spirals emerged only after accounting for heterogeneous local frequencies, exposing dynamical structure that was inaccessible from the recorded wave patterns alone. The centers of the hidden spirals shifted across the cortex between memory encoding and retrieval, linking their spatial organization to distinct memory states. Together, these findings reveal that apparently complex spatial patterns of traveling waves can conceal latent spiral attractors, uncovering a previously inaccessible layer of neural organization in human memory.