# Retrosplenial Cortex Interactions with Entorhinal Cortex and the Visual Anchoring of Spatial Representations

> **NIH NIH F32** · BOSTON UNIVERSITY (CHARLES RIVER CAMPUS) · 2020 · $33,723

## Abstract

The hippocampus (HPC), medial entorhinal cortex (MEC), and retrosplenial cortex (RSC) are strongly
implicated in memory, and atrophy of all three structures serves as an early indicator of Alzheimer's disease. In
parallel to memory processes, these structures are important for spatial cognition and neurons within these
regions exhibit spatially-specific firing. HPC place cells fire when an animal occupies an explicit location in the
environment relative to distal visual landmarks. MEC neurons encode multiple forms of spatial information,
including grid fields, wherein a single neuron is active at multiple, equidistant locations that span the entire
environment and form a periodic grid. Critically,
dysfunction of MEC spatial patterning disrupts sequential
encoding in the HPC which is thought to underlie episodic memory.
Robust MEC spatially-related firing is known to require visual information which is likely routed to the region via
RSC. RSC forms a strong excitatory projection into the region, and like MEC, firing of RSC neurons can be
rhythmic and exhibit spatial periodicity. Further, individual RSC neurons encode sensory, motor, and spatial
variables that are known to modulate MEC activation. Although it is known that RSC is part of the visual
processing network, little is known as to how RSC spatial representations are influenced by the arrangement of
distal visual cues or how visually-related RSC activation in turn influences MEC activation. Given the
functional and anatomical relationship between RSC and MEC, it is pertinent to explore their connectivity and
joint neurophysiological dynamics at this time.
This proposal seeks to further our understanding of systems interactions between MEC and RSC in spatial
encoding. The proposed experiments will assay the influence of visual information in RSC and MEC spatial
representations through the implementation of visual cue manipulations that expand or compress the relative
angle between visual landmarks while rats perform a visually-guided navigation paradigm. Additionally, the
proposed experiments will utilize optogenetics to specifically inhibit RSC projections into MEC to test
hypotheses that RSC input is required for MEC visual sensitivity. Data collected in these experiments will be
utilized to test computational modeling predictions about distortions to position estimation and MEC spatial
representations following shifts to the known locations of familiar distal cues.

## Key facts

- **NIH application ID:** 10268956
- **Project number:** 5F32NS101836-04
- **Recipient organization:** BOSTON UNIVERSITY (CHARLES RIVER CAMPUS)
- **Principal Investigator:** Andrew S. Alexander
- **Activity code:** F32 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $33,723
- **Award type:** 5
- **Project period:** 2017-09-30 → 2021-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10268956

## Citation

> US National Institutes of Health, RePORTER application 10268956, Retrosplenial Cortex Interactions with Entorhinal Cortex and the Visual Anchoring of Spatial Representations (5F32NS101836-04). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10268956. Licensed CC0.

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