A critical review of high-frequency activity for functional mapping in SEEG

Mapping functional brain networks is a critical component of stereo-electroencephalography (SEEG) evaluations. Although direct cortical stimulation (DCS) is the clinical gold standard, it has important limitations-particularly in mapping distributed, complex functions such as language and memory, where deficits may still occur despite preservation of DCS-positive sites, impacting quality of life. More broadly, there is increasing emphasis on preserving cognitive function in epilepsy surgery. The growing use of minimally invasive treatments-such as laser interstitial thermal therapy and radiofrequency thermocoagulation-reflects this shift. This trend highlights a need for adjunctive mapping techniques that provide anatomically precise and clinically relevant information about cortical functions, complementing existing mapping methods. Task-induced high-frequency activity (HFA), broadly defined as neural activity above 30 Hz, reflects localized cortical processing and has emerged as a physiologically plausible signal for functional mapping. As an activation-based technique, HFA may complement DCS by providing additional information about cortical function to inform surgical planning and outcome prediction. Despite growing interest, clinical uptake of HFA mapping in SEEG remains limited. This likely reflects methodological heterogeneity across published studies, lack of standardized analysis pipelines, and limited validation through outcome-linked research. Together, these challenges create uncertainty around the clinical utility of HFA. In this narrative review, we describe the neurophysiological basis of HFA, review key mapping findings across functional domains, outline practical requirements for clinical implementation, and examine major barriers to clinical translation. In doing so, we aim to provide clarity on the current evidence base and identify opportunities for future research that may support the integration of HFA mapping into clinical workflows.