# Dendritic Computation and Representation of Head Direction in Retrosplenial Cortex

> **NIH NIH R01** · MASSACHUSETTS INSTITUTE OF TECHNOLOGY · 2020 · $412,837

## Abstract

The mammalian cortex plays a critical role in integrating multiple streams of information to guide adaptive
behavior. For example, head direction (HD) information is combined with visual and spatial input in the mouse
retrosplenial cortex (RSC). Accurate integration of these signals is a necessary component of navigation:
recognizing a distant landmark while facing north vs. facing south has very different interpretations for one's
position and future actions. However, the mechanisms by which any cortical association area integrates different
inputs at the level of individual neurons during behavior is unknown. RSC is therefore a compelling model system
in which to test general associative computations during a complex behavior: the combination of visual and HD
information during navigation.
 Anatomical evidence suggests that HD inputs computed in the anterior thalamus make their synapses at
distal apical dendrites in RSC, while visual and motor synapses are located closer to the somas of RSC principal
neurons. This arrangement suggests that nonlinear dendritic integration may be used by RSC to combine HD
with other inputs. Active dendritic integration is theorized to allow single neurons to respond flexibly to different
combinations of input, where the state of one input nonlinearly influences the impact of another input. Our
overarching hypothesis is that such mechanisms could work in concert with neural circuit computations to
implement context-dependent cortical computations. Congruent with this idea, RSC neurons in navigating rats
exhibit complex conjunctive receptive fields, a feature that is lacking from commonly studied primary sensory
cortices. RSC is therefore an ideal area to evaluate the role of dendrites in associative computations during
navigation. However, current methods are not well-suited to this level of investigation: they either allow mice to
behave freely or they achieve sub-cellular resolution. This has led to a critical gap in our understanding of
navigation, and by extension, associative cortex function. We have recently developed technology that bridges
this gap: an animal-actuated rotating headpost that allows mice to engage in 2-D navigation by freely turning
their head during conventional 2-photon imaging. We will use this new approach to test the hypothesis that
neurons in RSC use sub-cellular processing to flexibly combine HD and visual information during navigation
behavior. These experiments will provide new insights into cellular- and circuit-level mechanisms of navigation,
and of associative cortical function in general. Results from this project will be valuable for understanding brain
disease states as well as for building biologically-inspired artificial neural networks.

## Key facts

- **NIH application ID:** 9993577
- **Project number:** 5R01NS113079-02
- **Recipient organization:** MASSACHUSETTS INSTITUTE OF TECHNOLOGY
- **Principal Investigator:** Mark Thomas Harnett
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $412,837
- **Award type:** 5
- **Project period:** 2019-08-15 → 2024-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9993577

## Citation

> US National Institutes of Health, RePORTER application 9993577, Dendritic Computation and Representation of Head Direction in Retrosplenial Cortex (5R01NS113079-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9993577. Licensed CC0.

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