Hippocampal time cell dynamics evolve with learning to reflect cognitive demands

Area of Science:

• Neuroscience
• Cognitive Science
• Behavioral Biology

Background:

• The hippocampus is crucial for forming cognitive maps, representing external world knowledge.
• Hippocampal time cells are hypothesized to encode the temporal structure of experiences (temporal context).
• It's unclear if time cell activity changes with learning to reflect improved understanding of temporal relationships.

Purpose of the Study:

• To investigate if hippocampal time cells exhibit learning dynamics related to temporal structure acquisition.
• To determine how time cell activity evolves as animals learn to discriminate temporal contexts.
• To explore the role of time cells in utilizing temporal relationships for cognitive tasks.

Main Methods:

• A behavioral paradigm with a shaping curriculum was used to teach mice temporal structure.
• Two-photon calcium imaging recorded activity of large neuronal populations in the CA1 region.
• Mice were trained on a temporal Delayed Non-Match to Sample (tDNMS) task.

Main Results:

• Time cells were present early in training and showed evolving activity patterns with experience.
• Single-cell and population-level dynamics of time cells changed throughout the learning curriculum.
• Time cell dynamics adapted to reflect context generalization versus discrimination by the mice.

Conclusions:

• Hippocampal CA1 time cells represent temporal context and its utilization during learning.
• Time cell activity evolves to reflect the cognitive demands of understanding temporal relationships.
• These findings suggest time cells contribute to the hippocampus's function as a cognitive map for temporal information.