Network mechanisms of spatial memory pattern activation and update

Memories, thoughts, or higher sensory categories are believed to be characterized by distinct neural patterns within their respective brain neural networks. These patterns, acting as discrete attractor states, can accommodate subtle differences in input information. This ability allows for the completion of a range of similar input patterns into already stored activity states or memory engrams, facilitating their categorization or activation of the appropriate memory trace.Here we present set of experiments that question kinetics of fast changes in hippocampal spatial maps upon manipulating sensory inputs that define the identity of environments (teleportation or morphing experiments) or its orientation (rotation test). While sudden categorical changes in environment identity (teleportation) typically result in quick neural representation shifts, the slow progression of environmental cues often lacks the appropriate network response. Interestingly, manipulating only the polarity of spatial visual cues through sudden rotation (90°) significantly delays hippocampal map reorientation.Next, we explore the phenomenon of hippocampal representation instability. Not only does a shift between attractor states cause instability, but its reorientation alone within the same state (rotation exp.) also brings the network to a transient instable state. Such instability may then persist, enabling spontaneous off-context activation reminiscent of the recall of episodic memory, where context independence is a fundamental feature, yet its mechanisms are still poorly understood.