Definition: Event boundaries are moments in time when the brain segments continuous experience into discrete units called “events.” These transitions typically occur at changes in context, such as shifts in location, characters, goals, or perceptual features during real-world or narrative experiences (e.g., movies or stories).

• Perceptual shifts: Sudden changes in visual, auditory, or spatial context.
• Conceptual shifts: Changes in characters' goals, social interactions, or narrative structure.
• Temporal markers: Often correspond to natural pauses or breaks (e.g., scene cuts, silence, fade-outs).
• Detected by the brain: Even without explicit instruction, observers show consistent segmentation of events.

• Hippocampus: Exhibits increased activation at event boundaries, associated with memory encoding.
• Posterior medial cortex (e.g., precuneus, retrosplenial cortex): Active during transitions, suggesting involvement in context updating.
• Default Mode Network (DMN): Modulated by narrative boundaries and self-referential processing.
• Ripple-like activity: Intracranial EEG studies show increased ripple events around event boundaries, possibly reflecting mnemonic updating.

• Memory formation: Boundaries serve as anchors, organizing episodic memory into structured units.
• Prediction error: Boundaries often coincide with violations of expectation, prompting neural updating.
• Narrative comprehension: Helps maintain coherent models of ongoing events in naturalistic settings.

• Movie segmentation tasks: Participants indicate when one meaningful event ends and another begins.
• fMRI and iEEG alignment: Neural activity is time-locked to annotated event boundaries to study brain dynamics.
• Naturalistic stimuli: Used increasingly to examine cognition in ecologically valid scenarios.

• Impaired segmentation is linked to memory fragmentation, especially in aging, schizophrenia, or brain injury.
• Understanding event boundary processing may inform rehabilitation strategies for episodic memory dysfunction.