Organization of feedback projections to mouse primary visual cortex

Mai M Morimoto,Emi Uchishiba,Aman B Saleem

doi:10.1016/j.isci.2021.102450

Abstract

SummaryTop-down, context-dependent modulation of visual processing has been a topic of wide interest, including in mouse primary visual cortex (V1). However, the organization of feedback projections to V1 is relatively unknown. Here, we investigated inputs to mouse V1 by injecting retrograde tracers. We developed a software pipeline that maps labeled cell bodies to corresponding brain areas in the Allen Reference Atlas. We identified more than 24 brain areas that provide inputs to V1 and quantified the relative strength of their projections. We also assessed the organization of the projections, based on either the organization of cell bodies in the source area (topography) or the distribution of projections across V1 (bias). Projections from most higher visual and some nonvisual areas to V1 showed both topography and bias. Such organization of feedback projections to V1 suggests that parts of the visual field are differentially modulated by context, which can be ethologically relevant for a navigating animal.

Highlights

Software pipeline for mapping labeled cell bodies to brain areas To identify cell bodies labeled by the tracer and quantify their occurrence across various brain areas, we developed a software pipeline that maps each labeled cell body to its corresponding brain area, based on the Allen Reference Atlas (ARA) (Wang et al, 2020)
Higher visual areas (HVAs), auditory cortex, and RSP cortex provide largest cortical inputs to V1 We identified more than 24 brain areas that provided inputs to V1 (Figures 2 and S3)
We found the general tendency for HVAs (V2), auditory cortex (Au), retrosplenial cortex (A29, A30), and temporal association area (TEa) having the highest cell counts to be unchanged

Summary

Introduction

Neural activity in the mouse primary visual cortex (V1) is known to be modulated by a variety of contextual signals, including arousal, locomotion, spatial context, spatial attention, or navigation (Niell and Stryker, 2010; Keller et al, 2012; Saleem et al, 2013, 2018; Vinck et al, 2015; McGinley et al, 2015; Poort et al, 2015; Fiser et al, 2016; Jurjut et al, 2017; Pakan et al, 2018; Speed et al, 2020). Perturbations of specific areas have been found to alter contextual modulations in V1. Optogenetic stimulation of mesencephalic locomotor region mimics the effects of locomotion in V1 (Lee et al, 2014), and optogenetic stimulation of anterior cingulate cortical projections to V1 alters sensorimotor signals in V1 (Leinweber et al, 2017). Such studies have been limited to investigating the involvement of specific areas projecting to V1. The first step toward addressing this question is knowing which areas of the brain project to V1. We use an unbiased approach to quantitatively characterize brain-wide projections to V1 using retrograde tracing

Methods

Results

Discussion

Conclusion