Layer 6 corticocortical neurons are a major route for intra and interhemispheric feedback

The neocortex comprises anatomically discrete yet interconnected areas that are symmetrically located across the two hemispheres. Determining the logic of these macrocircuits is necessary for understanding high level brain function. Here we have mapped the areal and laminar organization of the ipsilateral and contralateral cortical projection onto the primary visual, somatosensory and motor cortices in mice. We find that although the ipsilateral hemisphere is the primary source of cortical input, there is substantial contralateral symmetry regarding the relative contribution and areal identity of input. Laminar analysis of these input areas show that excitatory Layer 6 corticocortical cells (L6 CCs) are a major projection pathway within and between the two hemispheres. Analysis of the relative contribution of inputs from supra- (feedforward) and infra-granular (feedback) layers, reveals that contra-hemispheric projections reflect a dominant feedback organization compared to their ipsi-c..., Whole-brain retrograde tracing., , # Data from: Layer 6 corticocortical neurons are a major route for intra and interhemispheric feedback

[https://doi.org/10.5061/dryad.8kprr4xzd](https://doi.org/10.5061/dryad.8kprr4xzd)

## Description of the data and file structure

This is the explanation of the data structure and CSV files for the manuscript:

Layer 6 corticocortical neurons are a major route for intra and interhemispheric feedback

Simon Weiler, Manuel Teichert and Troy W. Margrie

Data_structure: Data_SW_20-02-Apr-2024.mat

Explanation of 12 fields in mat structure:

1\) animal_name: name of animal

2\) recording_date: date of recording of serial2p data

3\) virustype: 1=retro; 10=retro outlier example

4\) area=injection area; 0=mono VISp, 1=bino VISp, 2=SSpfb, 3=MOp

5\) hemisphere=injection hemisphere; 0= right 1= left

6\) gender= male or female; 0= F; 1= M

7\) age= age of perfusion in weeks

8\) area_names_1-xx= brain area name

9\) ipsi_cellnr_1_xx = cell numbers ipsi in the given area

10\) contra_celln...,