# Neural Circuits that Process Visual Information

> **NIH NIH R01** · UNIVERSITY OF SOUTHERN CALIFORNIA · 2024 · $415,000

## Abstract

PROJECT SUMMARY:
Thalamic circuits are dominated by two sources of inhibition that have a profound influence on the type and
quantity of information that relay cells transmit from eye to brain: These are local interneurons within the dorsal
lateral geniculate nucleus of the thalamus (dLGN), and the visual sector of the thalamic reticular nucleus (TRN)—
a thin sheet of GABAergic cells that lies nearby. Local interneurons receive retinal input and synapse with relay
cells and each other to supply powerful feedforward inhibition. By contrast, relay cells make only sparse
connections within the main layers of dLGN. Rather, they contact neurons in TRN, whose dense axonal arbors
provide feedback inhibition in return. In addition to receiving ascending information, these three types of cells
(local interneurons, relay cells, reticular cells) in the dLGN/TRN complex are embedded in a larger network that
involves top-down input from cortex; this arrangement is repeated across primary thalamic nuclei in mammals.
Thus, learning how thalamic circuits operate is key to understanding sensory integration and, moreover, serves
studies of disorders such as amblyopia or the development of visual prosthetics by providing a blueprint for how
healthy brains function. Here we focus on TRN in mouse, a species that has become central to studies of vision
because of the many experimental advantages it offers, but whose visual system differs somewhat from those
of traditional experimental subjects like carnivore and primate. The design of the project is inspired by a
framework voiced by Francis Crick, who theorized that TRN might act as a searchlight that increases thalamic
activity in specific regions of interest, or as a thermostat that regulates levels of global activity. We evaluate
predictions of each hypothesis to explore visual processing per se, by combining comparative, optogenetic,
physiological, anatomical, and computational approaches. The project comprises three interrelated aims, as
follows. The searchlight hypothesis suggests that receptive fields in TRN are feature specific and localized and
we have shown that this is the case in carnivore; Aim 1 uses physiological and computational approaches to
analyze the spatiotemporal features encoded in mouse visual TRN across visual space. These results are then
incorporated into a model framework that ties the output of inhibitory cells, including TRN and local interneurons
(we have studied these previously) to patterns of inhibition recorded from the relay cell’s receptive field. Aim 2
explores the link between receptive field structures in dLGN and TRN mechanistically by exploring how input
from dLGN influences visual response properties in TRN and vice versa; opsins that suppress synaptic
transmission and statistical tools that reveal connectivity between neurons are used to approach this topic.
Finally, Aim 3 takes the general perspective of the thermostat hypothesis and asks how responses of TRN to
global stim...

## Key facts

- **NIH application ID:** 10981489
- **Project number:** 2R01EY009593-29
- **Recipient organization:** UNIVERSITY OF SOUTHERN CALIFORNIA
- **Principal Investigator:** Judith A Hirsch
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $415,000
- **Award type:** 2
- **Project period:** 1993-07-01 → 2028-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10981489

## Citation

> US National Institutes of Health, RePORTER application 10981489, Neural Circuits that Process Visual Information (2R01EY009593-29). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10981489. Licensed CC0.

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