# Structure and function of corticogeniculate feedback

> **NIH NIH F31** · UNIVERSITY OF ROCHESTER · 2021 · $46,036

## Abstract

PROJECT SUMMARY
Corticogeniculate (CG) neurons that connect primary visual cortex (V1) to the lateral geniculate nucleus of the
thalamus (LGN) make up the first feedback circuit in the visual hierarchy. Although CG synapses onto LGN
neurons outnumber synapses coming from the retina, LGN receptive fields resemble those of their feedforward
retinal inputs and not their cortical inputs. The subtle, modulatory role of CG feedback has made understanding
its structure and function an enduring problem in visual neuroscience. This project proposes two sets of
experiments to establish the rules of connectivity between CG and LGN neurons and to examine the influence
of CG neurons on LGN ensemble activity in ferrets. Several studies in carnivore and primate have demonstrated
that CG feedback neurons are morphologically and physiologically heterogeneous, providing a substrate for
parallel streams of feedback that correspond with the feedforward parallel streams in the retino-geniculo-cortical
pathways. However, whether the functional connections between CG and LGN neurons are stream-specific or
mixed is not known. Aim 1 will investigate how CG neurons are functionally connected to LGN neurons.
Simultaneous recordings from functionally connected CG and LGN neurons in ferrets and a multidimensional
analysis of tuning properties will be used to rigorously classify these neurons and establish whether functional
connections are made preferentially between CG and LGN neurons with similar tuning. Aim 2 will examine the
composition of correlated LGN ensembles and how CG feedback influences the visual response dynamics and
ensemble tuning of small populations of LGN neurons. Previous work has established that CG feedback
regulates the timing, precision, and synchrony of LGN responses. We hypothesize that the effects of feedback
will depend on 1.) whether CG-LGN connectivity is feature-specific or mixed, and 2.) the cell-type composition
of LGN ensembles. Aim 2 will first determine whether ensembles of correlated LGN neurons are feature-specific.
Then, virus-mediated gene delivery targeting CG neurons will be used to optogenetically activate CG feedback
while recording from ensembles of LGN neurons. Together these experiments will advance knowledge of early
visual circuits by clarifying the connectivity between CG and LGN neurons and establishing the effect of CG
feedback on LGN ensemble activity. The training during this project will focus on increasing proficiency in
computational analyses, as well as improving experimental techniques and professional development for a
career as a future independent investigator, under the guidance of Dr. Farran Briggs, a leading researcher on
corticogeniculate feedback, and Dr. Krishnan Padmanabhan, an expert in computational systems neuroscience.
This research will be conducted at the University of Rochester, an institution with a strong Neuroscience
Graduate Program and a renowned Center for Visual Science, which will provide exc...

## Key facts

- **NIH application ID:** 10313616
- **Project number:** 1F31EY032332-01A1
- **Recipient organization:** UNIVERSITY OF ROCHESTER
- **Principal Investigator:** Allison Julia Murphy
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $46,036
- **Award type:** 1
- **Project period:** 2021-09-14 → 2023-09-13

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10313616

## Citation

> US National Institutes of Health, RePORTER application 10313616, Structure and function of corticogeniculate feedback (1F31EY032332-01A1). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10313616. Licensed CC0.

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