Brain's “Reset Button” Found to Segment Memories into Separate Events

Researchers from the University of California, Los Angeles, and Columbia University have discovered that neurons in the brainstem's locus coeruleus act like a “memory reset button”, segmenting continuous experiences into distinct events. The study, published in Neuron, reveals that this mechanism plays a key role in how we store and organize memories.

In experiments, 32 participants underwent fMRI scans while viewing images, with alternating tones in each ear simulating environmental changes. Neural activity in the locus coeruleus spiked at event boundaries, reducing the ability to recall the order of items across these boundaries—indicating that memories were stored in separate segments. Pupil dilation data supported this finding, as pupils enlarged when a new event began.

The locus coeruleus also influences the hippocampus, the brain region responsible for encoding new memories and tracking environmental context. Researchers suggest it may send a “start” signal to initiate new event encoding. The locus coeruleus operates in two modes: a phasic mode that marks significant events, and a tonic mode that regulates alertness. Chronic stress can lead to overactivity in the locus coeruleus, blunting its sensitivity to event boundaries and disrupting memory organization.

Potential ways to reduce overactivity include medication, slow breathing, or stress-ball exercises, though long-term solutions require further research. Despite its small size, the locus coeruleus has a profound impact on memory and how we perceive life’s flow.