Lectures and seminars Deep brain recordings in ambulatory humans during real-world and imagined navigation

Abstract:

Recollecting past events is central to episodic memory, and the internal manipulation of these recollections is essential for guiding future actions. Previous studies have pointed to a key role for the medial temporal lobe (MTL) in both spatial navigation and memory formation. Here, we ask whether real-world navigation and internal recollection or envisioning of learned routes engage similar dynamics in the human MTL.

Using recent advances in implanted neurotechnology, we recorded intracranial EEG from five freely moving humans as they learned to navigate two routes in an indoor room equipped with motion capture. After each real-world walk, participants walked on a treadmill while recollecting or envisioning the same routes. In every participant, we observed transient oscillations within the theta frequency range (4-9 Hz) that reliably preceded transitions between route sections at upcoming turns. During imagined navigation, theta bouts emerged at time points that reflected the routes' geometry, echoing the real-world neural patterns despite the absence of physical movement through space.

We then used these theta dynamics as priors to identify related components in simultaneously recorded scalp EEG, and by modeling the bioelectrical relationship between the MTL and scalp electrodes, we could replicate the main intracranial findings non-invasively. This scalp-based reconstruction opens a scalable approach for investigating MTL dynamics across larger populations and developmental and aging trajectories.

Together, these findings indicate that MTL theta dynamics support internal recollection and envisioning similarly as they support real-world navigation. Because these internal processes can be explicitly instructed and verbally reported in human participants, this framework offers a unique opportunity to probe the neural mechanisms underlying episodic memory, imagination, and the anticipation of hypothetical future scenarios.