Brain Oscillatory Activity during Spatial Navigation: Theta and Gamma Activity Link Medial Temporal and Parietal Regions

摘要

Brain oscillatory correlates of spatial navigation were investigatednusing blind source separation (BSS) and standardizednlow resolution electromagnetic tomography (sLORETA) analysesnof 62-channel EEG recordings. Twenty-five participants wereninstructed to navigate to distinct landmark buildings in a previouslynlearned virtual reality town environment. Data fromnperiods of navigation between landmarks were subject to BSSnanalyses to obtain source components. Two of these corticalnsources were found to exhibit significant spectral power differencesnduring navigation with respect to a resting eyes openncondition and were subject to source localization using sLORETA.nThese two sources were localized as a right parietal componentnwith gamma activation and a right medial-temporal–parietalncomponent with activation in theta and gamma bandwidths.nThe parietal gamma activity was thought to reflect visuospatialnprocessing associated with the task. The medial-temporal–nparietal activity was thought to be more specific to the navigationalnprocessing, representing the integration of ego- andnallo-centric representations of space required for successfulnnavigation, suggesting theta and gamma oscillations may havena role in integrating information from parietal and medialtemporalnregions. Theta activity on this medial-temporal–parietalnsource was positively correlated with more efficient navigationnperformance. Results are discussed in light of the depth andnproposed closed field structure of the hippocampus and potentialnimplications for scalp EEG data. The findings of the presentnstudy suggest that appropriate BSS methods are ideally suitednto minimizing the effects of volume conduction in noninvasivenrecordings, allowing more accurate exploration of deep brainnprocesses.