Closed-loop modulation of remote hippocampal representations with neurofeedback

Humans can remember specific remote events without acting on them and
influence which memories are retrieved based on internal goals. However,
animal models typically present sensory cues to trigger memory retrieval
and then assess retrieval based on action. Thus, it is difficult to
determine whether measured neural activity patterns relate to the cue(s),
the memory, or the behavior. We therefore asked whether retrieval-related
neural activity could be generated in animals without cues or a behavioral
report. We focused on hippocampal “place cells” which primarily represent
the animal’s current location (local representations) but can also
represent locations away from the animal (remote representations). We
developed a neurofeedback system to reward expression of remote
representations and found that rats could learn to generate specific
spatial representations that often jumped directly to the
experimenter-defined target location. Thus, animals can deliberately
engage remote representations, enabling direct study of retrieval-related
activity in the brain.