Conference on Cognitive Computational Neuroscience

Macroscopic traveling waves (MTWs) in the cortex (>15cm) have been associated with cognitive processes such as perception, attention and working memory, as well as revealing single-trial relationships to event-related potentials (ERPs). However, their status remains unresolved, with some studies suggesting they result from localized oscillatory sources and blurring artifact from extra-cranial measurements. We apply a novel method to estimate the spatial frequency (SF, i.e., the characteristic scales) of phase-gradients in sEEG (stereotactic electro-encephalography). In humans, these intra-cranial depth contacts offer good spatial resolution and often-times good spatial coverage of the cortex with minimal blurring artifact. We find the spectral power of phase-gradients is highest at the longest wavelengths, up to the size of the measurement array (40cm). This means that MTWs dominate activity in the cortex and suggests that M/EEG are suitable tools for their study since they primarily distort high (and not low) SF components. We interpret this large-scale coherent field as evidence for phase-gradients maintaining a distinct global organization.