Postnatal Development of Functional Projections from Parasubiculum and Presubiculum to Medial Entorhinal Cortex in the Rat

Cathrin B. Canto, Noriko Koganezawa, Mariá José Lagartos-Donate, Kally C. O'Reilly, Huibert D. Mansvelder, Menno P. Witter

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Abstract

Neurons in parasubiculum (PaS), presubiculum (PrS), and medial entorhinal cortex (MEC) code for place (grid cells) and head direction. Directional input has been shown to be important for stable grid cell properties in MEC, and PaS and PrS have been postulated to provide this information to MEC. In line with this, head direction cells in those brain areas are present at postnatal day 11 (P11), having directional tuning that stabilizes shortly after eye opening, which is before premature grid cells emerge in MEC at P16. Whether functional connectivity between these structures exists at those early postnatal stages is unclear. Using anatomical tracing, voltage-sensitive dye imaging and single-cell patch recordings in female and male rat brain slices between P2 and P61, we determined when the pathways from PaS and PrS to MEC emerge, become functional, and how they develop. Anatomical connections from PaS and PrS to superficial MEC emerge between P4 and P6. Monosynaptic connectivity from PaS and PrS to superficial MEC was measurable from P9 to P10 onward, whereas connectivity with deep MEC was measurable from P11 to P12. From P14/P15 on, reactivity of MEC neurons to parasubicular and presubicular inputs becomes adult-like and continues to develop until P28-P30. The maturation of the efficacy of both inputs between P9 and P21 is paralleled by maturation of morphological properties, changes in intrinsic properties of MEC principal neurons, and changes in the GABAergic network of MEC. In conclusion, synaptic projections from PaS and PrS to MEC become functional and adult-like before the emergence of grid cells in MEC.SIGNIFICANCE STATEMENT Head direction information, crucial for grid cells in medial entorhinal cortex (MEC), is thought to enter MEC via parasubiculum (PaS) and presubiculum (PrS). Unraveling the development of functional connections between PaS, PrS, and MEC is key to understanding how spatial navigation, an important cognitive function, may evolve. To gain insight into the development, we used anatomical tracing techniques, voltage-sensitive dye imaging, and single-cell recordings. The combined data led us to conclude that synaptic projections from PaS and PrS to MEC become functional and adult-like before eye opening, allowing crucial head direction information to influence place encoding before the emergence of grid cells in rat MEC.

Original languageEnglish
Pages (from-to)8645-8663
Number of pages19
JournalThe Journal of neuroscience : the official journal of the Society for Neuroscience
Volume39
Issue number44
Early online date30 Oct 2019
DOIs
Publication statusPublished - 30 Oct 2019

Funding

This work was supported by the Dutch research council grant ALW-VENI 863.14.005 to C.B.C, the Kavli Foundation,EuropeanUnion7thFrameworkSpacebrainGrant200873,CentreofExcellenceGrants223262and145993,and NorwegianResearchCouncilEquipmentGrant181676andResearchGrants191929and227769.WethankJonathan J. Couey for advice in the initial phase of the experiments.

FundersFunder number
Kavli FoundationCentreofExcellenceGrants223262and145993, EuropeanUnion7thFrameworkSpacebrainGrant200873
Nederlandse Organisatie voor Wetenschappelijk OnderzoekALW-VENI 863.14.005

    Keywords

    • learning
    • memory
    • ontogeny
    • parahippocampal region
    • spatial navigation

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