How our brain navigates using its cognitive map and place cell sequences – unraveling the brain’s fundamental spatial memory units.

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Hippocampal principal neurons display both spatial tuning properties and memory features. Whether this distinction corresponds to separate neuron types or a context-dependent continuum has been debated. We report here that the task-context (“splitter”) feature is highly variable along both trial and spatial position axes. Neurons acquire or lose splitter features across trials even when place field features remain unaltered. Multiple place fields of the same neuron can individually encode both past or future run trajectories, implying that splitter fields are under the control of assembly activity. Place fields can be differentiated into subfields by the behavioral choice of the animal, and splitting within subfields evolves across trials. Interneurons also differentiate choices by integrating inputs from pyramidal cells. Finally, bilateral optogenetic inactivation of the medial entorhinal cortex reversibly decreases the fraction of splitter fields. Our findings suggest that place or splitter features are different manifestations of the same hippocampal computation.

Highlights

• Memory and place field features of hippocampal neurons are a continuum
• Retrospective and prospective firing can vary even within a single field
• Interneurons also exhibit splitter activity preserved in a novel environment
• Bilateral medial entorhinal inactivation decreases the fraction of splitter cells

Viktor Varga, Peter C. Petersen, Ipshita Zutshi, Roman Huszar, Yiyao Zhang, György Buzsáki, Working memory features are embedded in hippocampal place fields. Cell Reports, March 26, 2024. [link] [pdf] [data] [code]

Shuhan’s thesis focused on A Population-level description of theta oscillations in the Medial Septum.

The presentation includes an introduction with slides and a demo in Matlab showing how to use the processing pipeline, CellExplorer, and NeuroScope2.

Peter received a Lundbeck Fellowship from the Lundbeck Foundation totaling DKK 10 million. With this grant, to be paid out over a period of five years, Peter can establish his own research group in the Neuroscience Department at the University of Copenhagen. He specializes in theta rhythms, which are part of the electrical activity in the brain. These rhythms are involved in learning and memory – as well as in spatial navigation in a physical environment. About the Lundbeck Foundation Fellowship 2022: https://lundbeckfonden.com/en/news/se…