Electrocorticographic coherence patterns

The availability of implantable subdural electrode arrays has made systematic studies of electrocorticographic (ECoG) coherence possible. Studies of coherence patterns recorded directly from human cortex are reviewed along with the presentation of original human clinical data, which reveal reliable and characteristic patterns of coherence. A data-driven technique for discriminating between reliable and unreliable coherence and phase values is described and used to reveal the relationship between coherence and cortical anatomy, such as in the region of the central sulcus, where low phase coherence declines and high phase-shifted coherence increases. Analysis of coherence magnitude and phase makes it possible to determine which signals likely arise from the cortical surface, and which arise from the depths of a sulcus. Alterations in coherence patterns caused by tumors or epilepsy are described and may be used to identify normal and pathological functional relationships between distant cortical areas. Some electrophysiologic/pathologic correlations indicate at least two types of epileptic abnormality, implying a sequence in breakdown of epileptic tissue. The relationship between coherence patterns and behavior and cognition is introduced and compared to similar studies of single-unit binding in animals.