Long-term transverse imaging of the hippocampus with glass microperiscopes

• DOI: 10.7554/elife.75391
• Publication Date: 2022-07-01T08:00:37Z
• Authors: William T Redman; Nora S Wolcott; Luca Montelisciani; Gabriel Luna; Tyler D Marks; Kevin K Sit; Che-Hang Yu; Spencer Smith; Michael J Goard
• Keywords: 0301 basic medicine; Biomedical and clinical sciences; Mouse; hippocampus; QH301-705.5; place cell; Science; 610; Hippocampus; neuroscience; Mice; 03 medical and health sciences; Animals; Biology (General); mouse; Neurons; 0303 health sciences; Biomedical and Clinical Sciences; Pyramidal Cells; Q; Neurosciences; R; 500; Health sciences; Dendrites; Biological sciences; Mental Health; Neurological; Biomedical Imaging; Medicine; Biochemistry and Cell Biology; two-photon imaging; Neuroscience

The hippocampus consists of a stereotyped neuronal circuit repeated along the septal-temporal axis. This transverse circuit contains distinct subfields with stereotyped connectivity that support crucial cognitive processes, including episodic and spatial memory. However, comprehensive measurements across the transverse hippocampal circuit in vivo are intractable with existing techniques. Here, we developed an approach for two-photon imaging of the transverse hippocampal plane in awake mice via implanted glass microperiscopes, allowing optical access to the major hippocampal subfields and to the dendritic arbor of pyramidal neurons. Using this approach, we tracked dendritic morphological dynamics on CA1 apical dendrites and characterized spine turnover. We then used calcium imaging to quantify the prevalence of place and speed cells across subfields. Finally, we measured the anatomical distribution of spatial information, finding a non-uniform distribution of spatial selectivity along the DG-to-CA1 axis. This approach extends the existing toolbox for structural and functional measurements of hippocampal circuitry.