As we move through physical space, various sensory modalities including proprioception and the vestibular sense contribute to the formation of spatial representations. We investigate the role of the medial temporal lobe in human navigation and how it is influenced by the multisensory input during physical locomotion, using the approach of Mobille Brain-Body Imaging (MoBI) to combine mobile EEG with immersive virtual reality. We implemented a human-scale Morris watermaze task in stationary and MoBI setups to test 10 participants that underwent right medial temporal lobe resection (MTLR), each with two matched control (CTRL) participants.
A previous work on the data set (Iggena et al., in prep) showed boosted spatial memory performance in the MoBI condition in both participant groups. Notably, the analysis of motion data indicated that the two groups use different strategies to make use of the additional multisensory information in MoBI setup, where MTLR group showed heavier reliance on the body-based (egocentric) strategy and the CTRL group displayed more active sampling of environment-centered (allocentric) information.
As the medial temporal lobe houses critical structures for formation of allocentric spatial representations, the difference in strategy may originate from MTLR group recruiting egocentric information formed in intact areas other than the medial temporal lobe as a compensatory mechanism to keep robust representations. We present the relevant change in EEG power dynamics on the source level, localized to the parietal cortex as a basis of processing of body-based information, and the retrosplenial complex, the hub for conversion between ego- and allocentric reference frames.