Neurons detect cognitive boundaries to structure episodic memories in humans

Continuous experience is segmented into discrete mnemonic episodes. The authors identify neurons in the human brain whose responses to cognitive boundaries predict memory encoding success and mark timepoints that are reinstated during retrieval. While experience is continuous, memories are organized as discrete events. Cognitive boundaries are thought to segment experience and structure memory, but how this process is implemented remains unclear. We recorded the activity of single neurons in the human medial temporal lobe (MTL) during the formation and retrieval of memories with complex narratives. Here, we show that neurons responded to abstract cognitive boundaries between different episodes. Boundary-induced neural state changes during encoding predicted subsequent recognition accuracy but impaired event order memory, mirroring a fundamental behavioral tradeoff between content and time memory. Furthermore, the neural state following boundaries was reinstated during both successful retrieval and false memories. These findings reveal a neuronal substrate for detecting cognitive boundaries that transform experience into mnemonic episodes and structure mental time travel during retrieval.

Automated summary

This study reveals that neurons in the human brain respond to cognitive boundaries, predicting memory encoding success and influencing subsequent recognition accuracy and event order memory. While experience is continuous, memories are organized discretely, with cognitive boundaries thought to play a key role in structuring memory.