Passive Language Mapping With High-Gamma Modulations

SUMMARY: Passive language mapping using high-gamma modulation (HGM) has emerged as a valuable tool in both presurgical evaluation for epilepsy and neuroscientific discovery. HGM mapping leverages task-related synchronization in high-gamma frequencies to identify language areas without the risks associated with electrical stimulation mapping. This review outlines the principles and techniques used in the field of HGM-based mapping, including electrode types, referencing schemes, power analysis, and localization techniques. We survey a range of cognitive tasks-speech production, auditory processing, reading, and memory-that elicit language-related HGM responses and discuss their relevance to comprehensive language mapping. We examine perspectives on methodologic challenges, including artifact management, variability across patients, and spatial sampling. We assess validation studies comparing HGM with electrical stimulation mapping and neuropsychological outcomes, noting HGM's unique role in identifying language cortex in pediatric and cognitively impaired populations. Finally, we speculate on the future directions of the field, including integration with corticocortical evoked potentials and the potential for HGM-informed speech synthesis. As the field matures, HGM mapping is poised to contribute to improved clinical outcomes and enhance our understanding of the dynamics and development of the human language network.