Hippocampal sequences span experience relative to rewards.

Area of Science:

• Neuroscience
• Cognitive Science
• Computational Neuroscience

Background:

• Hippocampal place cells are crucial for spatial navigation and memory.
• These cells exhibit sequential firing patterns across environments and modalities.
• Behavioral salience, such as reward, may influence hippocampal activity anchoring.

Purpose of the Study:

• To investigate if hippocampal activity sequences can anchor to reward locations.
• To determine if the hippocampus uses reward as a salient reference point.
• To explore how the brain encodes multiple salient features simultaneously.

Main Methods:

• Two-photon calcium imaging of hippocampal CA1 neurons in mice.
• Mice navigated virtual environments with dynamically changing hidden reward locations.
• Analysis of neuronal firing fields in relation to spatial position and reward availability.

Main Results:

• A subpopulation of hippocampal neurons shifted their firing fields to maintain a consistent position relative to the reward.
• These reward-relative cells formed sequences that spanned the task structure.
• Neuronal recruitment to reward-relative sequences increased with task experience.
• A distinct neuronal subpopulation maintained stable, spatially-based place codes.

Conclusions:

• The hippocampus utilizes distinct neuronal ensembles to encode multiple salient reference frames.
• Hippocampal activity flexibly anchors to behaviorally relevant information, such as rewards.
• This dual coding strategy reflects the complex structure of experience and navigation.