Representation of memories in the cortical-hippocampal system: Results from the application of population similarity analyses

- Neurons in the medial temporal lobe system show multi-modal tuning curves.
- Representational similarity analysis can shed light on such a complex coding scheme.
- RSA reveals divergent memory organizations across cortico-hippocampal networks.

Here we consider the value of neural population analysis as an approach to understanding how information is represented in the hippocampus and cortical areas and how these areas might interact as a brain system to support memory. We argue that models based on sparse coding of different individual features by single neurons in these areas (e.g., place cells, grid cells) are inadequate to capture the complexity of experience represented within this system. By contrast, population analyses of neurons with denser coding and mixed selectivity reveal new and important insights into the organization of memories. Furthermore, comparisons of the organization of information in interconnected areas suggest a model of hippocampal-cortical interactions that mediates the fundamental features of memory.