Optically-pumped (OP) magnetometers allow magnetoencephalography (MEG) to be performed while a participant’s head is unconstrained. To fully leverage this new technology, and in particular its capacity for mobility, the
activity of deep brain structures which facilitate explorative behaviours such as navigation, must be detectable
using OP-MEG. One such crucial brain region is the hippocampus. Here we had three healthy adult participants
perform a hippocampal-dependent task – the imagination of novel scene imagery – while being scanned using OPMEG. A conjunction analysis across these three participants revealed a significant change in theta power in the
medial temporal lobe. The peak of this activated cluster was located in the anterior hippocampus. We repeated the
experiment with the same participants in a conventional SQUID-MEG scanner and found similar engagement of
the medial temporal lobe, also with a peak in the anterior hippocampus. These OP-MEG findings indicate exciting
new opportunities for investigating the neural correlates of a range of crucial cognitive functions in naturalistic
contexts including spatial navigation, episodic memory and social interactions
