The Influence of the Pretectum on the Visual Thalamus

PROJECT SUMMARY / ABSTRACT
The pretectum (PT) is a relatively unexplored brain area in mammals, and it is currently unknown
how the PT affects the visual properties of thalamic neurons that underly the complex integration
of vision and movement. Here, a team of investigators propose a multifaceted approach - from
synapse to behavior – to answer fundamental questions regarding PT circuits (Aim 1), the visual
and/or motor response properties of identified PT neurons (Aim 2), the effects of PT input on the
response properties of thalamic neurons (Aim 3), and the effects of the PT on visual behavior
(Aim 4). Each aim will utilize a combination of novel intersectional circuit labeling techniques,
neuronal activation, and recording strategies to probe two identified PT pathways: a GABAergic
pathway to the lateral geniculate nucleus (LGN) and the visual sector of the thalamic reticular
nucleus (vTRN), and a nonGABAergic pathway to the pulvinar nucleus (PUL) from PT neurons
that contain parvalbumin. Aim 1 will use cre-dependent monosynaptic rabies tracing to induce
the expression of the calcium indicator GCaMP to classify, using 2P imaging, the receptive field
properties and morphology of retinal ganglion cells that innervate PT-LGN/TRN and PT-PUL
neurons. Monosynaptic rabies tracing will also be used to characterize cortical and subcortical
brain inputs to PT-LGN/TRN and PT-PUL cells; identified PT inputs will subsequently be studied
using electron microscopy and in vitro whole cell recordings paired with optogenetic activation to
characterize their ultrastructure and synaptic properties. Aim 2 will use in vivo extracellular
recordings in awake animals paired with “opto-tagging” to determine the response properties of
PT-LGN/TRN and PT-PUL neurons. Aim 3 will use in vivo extracellular recordings from awake
animals paired with optogenetic activation of PT inputs to determine the effects of the PT inputs
on LGN, vTRN and PUL response properties. Finally, Aim 4 will use cre- and flp-dependent
chemogenetic activation of PT-LGN/TRN or PT-PUL neurons to determine if these cells affect
stereopsis and/or optokinetic responses. Collectively, these 4 lines of inquiry will provide key
information regarding the role of the PT in active vision.

Grant Number: 5R01EY035523-03
NIH Institute/Center: NIH
Principal Investigator: MARTHA BICKFORD