Figure 1: Overview of behavioural tasks and 5-s traces from hippocampal contacts during real-world conditions.

(a) Top view of the space patients navigated while searching for invisible sensors (thin square plate) underneath the carpet. (g, top) First person view of the virtual navigation task showing landmarks in the distance as well as views of the radial arms in the task. (g, bottom) Bird’s eye view of radial arms layout. Patients were instructed to search for target objects (denoted by the suns) at the bottom of a pit located at the end of the arm. In part 1, patients could only enter four arms to pick up the objects. In part 2, patients had to remember previously visited arms and avoid them in order to retrieve the target objects in the new arms. (b) Posterior hippocampal contact from patient #2 demonstrates high-theta oscillations during real-world search for the invisible sensors. (c) Hippocampal contact from patient #4 demonstrates low-theta oscillations during real-world search for an invisible sensor. (d) Hippocampal contact from patient #5 demonstrates low to mid-range theta oscillations during recall of spatial locations in the invisible sensor task. (e) Posterior hippocampal contact from patient #2 demonstrates theta oscillations during real-world random walking. (f) Hippocampal contact from patient #2 shows minimal oscillations when patient is stopped and standing still. (h–i) Five-second raw traces from hippocampal contacts during the VR task. (h) Hippocampal contact from patient #5 demonstrates low to mid-range theta oscillations during VR navigation. (i) Hippocampal contact from patient #2 shows minimal oscillations when patient is not moving.