Abstract
Functional brain mapping with direct cortical stimulation (DCS) may be required for patients undergoing stereotactic-EEG (SEEG), as workup towards epilepsy surgery. DCS has several limitations. Task-induced gamma-band-activity (GBA) is an emerging mapping technique that may complement or replace, mapping with DCS. Experience with SEEG-GBA mapping is currently limited.
Objective Provide a comprehensive review of the literature exploring functional mapping during SEEG, with GBA. Identify areas of opportunity that future research may explore to improve GBA-mapping.
Methods PubMed and EMBASE were searched for publications, 2000–2022. Inclusion criteria: SEEG-GBA studies mapping the following brain functions: language, memory, vision, audition, motor and sensory. Task-selection, signal-analysis methodology, and comparison against the ‘gold-standard’ were reviewed.
Results Language: 3 studies identified, two compared GBA mapping to DCS. In these, GBA mapping was highly specific but lowly sensitive for language localisation. Memory: 3 studies identified. Since there is no gold-standard for memory mapping, the clinical relevance of GBA memory mapping remains unknown. However, GBA was seen in brain regions thought to support memory from the existing PET, fMRI, DCS and WADA experience. Motor: one study identified; in this, GBA was highly congruent with DCS motor maps. No SEEG experience exists for mapping visual and sensory cortices. Task-selection and signal-analysis methods were heterogeneous across studies.
Conclusion SEEG-GBA mapping experience is limited, but promising for mapping language and motor networks. Memory mapping is shown to be possible but clinical relevance is stifled by the lack of a gold-standard. Standardised testing pipeline to map these and other un-investigated brain networks is needed.
