Subicular spatial codes arise from predictive mapping

Area of Science:

• Neuroscience
• Computational Neuroscience
• Cognitive Science

Background:

• The successor representation (SR) explains mammalian navigation and memory, including hippocampal place and entorhinal grid cells.
• Subicular neurons, crucial hippocampal outputs, exhibit diverse spatial responses not yet unified by a single model.

Purpose of the Study:

• To develop a unified account for the heterogeneous activity patterns of subicular neurons.
• To investigate the role of behavioral biases within the SR framework for subicular function.

Main Methods:

• Incorporating rodent behavioral biases into the successor representation computational model.
• Analyzing and comparing the model's predictions against experimental data of subicular neuronal activity.

Main Results:

• The SR model, with behavioral biases, successfully reproduced the diverse activity patterns of subicular neurons.
• The framework predicted the emergence of boundary and corner cells in the subiculum, which are not found in upstream regions.
• Subicular firing patterns were better explained by the SR than by purely spatial or boundary vector cell models.

Conclusions:

• The successor representation provides a unified framework for understanding subicular neuronal function.
• Subicular processing involves encoding predictive representations over longer time horizons than CA1, capturing extended behavioral patterns and environmental affordances.
• This work highlights a temporal hierarchy in hippocampal-subicular information processing crucial for navigation and memory.