Temporal memory is shaped by encoding stability and intervening item reactivation

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Memory Research

Background:

• The hippocampus and medial temporal lobe are crucial for episodic memory, including temporal order.
• Mechanisms of encoding and retrieving temporal information across extended sequences remain unclear.
• Understanding temporal order memory is key to comprehending how we make sense of past experiences.

Purpose of the Study:

• To investigate the type of information used for temporal order judgments.
• To elucidate the role of the hippocampus in encoding and retrieving temporal sequence information.
• To test predictions about associative retrieval processes in temporal order memory.

Main Methods:

• Functional magnetic resonance imaging (fMRI) during encoding and retrieval of image sequences.
• Recency discrimination tasks with intervening items, including category shifts.
• Machine learning classifiers to detect reactivation of item categories during retrieval.
• Behavioral priming experiments to assess item reinstatement.

Main Results:

• Hippocampal pattern similarity across intervening items predicted successful order memory.
• Reactivation of intervening item categories was observed during recency judgments, linked to hippocampal similarity.
• Behavioral data confirmed item reinstatement during temporal order judgments, irrespective of context boundaries.

Conclusions:

• The hippocampus plays a critical role in temporal order memory.
• Inter-item associative encoding and retrieval, mediated by the hippocampus, are key mechanisms for remembering event sequences.
• Reactivation of item content supports temporal order judgments.