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The brain is considered one of the most intricate organs and the desire to untangle its complex function is unflagging. It is being studied at different scales from the molecular to the behavioral level using a wide palette of tools2,3,4,5,6,7,8. The amount of non-homogeneous experimental data grows with unprecedented speed. The awareness of the need for experimental data sharing, organization and standardization grows with the amount of acquired data. It has become evident that neuroinformatics will play a critical role in integrating experimental data across scales into models of brain function and dysfunction9,10.
To this end some studies, especially larger-scale studies, were able to earmark resources to make their results available via extensive databases11,12,13,14,15. However, a vast amount of experimental data from individual studies and regular-sized laboratories never reached the wider research community. This is mainly for two reasons: first, more dedicated time is needed to build a database and create tools that would enable the user to interact with the database; and second, more money is needed to support these tasks. Motivated by these challenges, a MATLAB based graphical user interface (GUI) engine called the Neurovascular Network Explorer 2.0 (NNE 2.0)16 was developed as a simple and low-cost tool for databasing, sharing and exploring of vascular imaging data. This manuscript provides a manual for operation of NNE 2.0 and the associated database of experimental data.
NNE 2.0 is already a second-generation software engine. The first generation, called Neurovascular Network Explorer 1.0 (NNE 1.0)17 was built to interact with a database of sensory-evoked vasodilation in rat primary somatosensory cortex (SI) in vivo measured by 2-photon microscopy18. NNE 1.0, its source code as well as the associated database are freely downloadable as a zipped file called ‘NNE 1 Tian’ from UCSD Neurovascular Imaging Laboratory website1. More information about NNE 1.0 and the associated database can be found in17.
The second generation, the NNE 2.0, interacts with a database of optogenetically-evoked dilation of individual vessels in mice SI in vivo measured by 2-photon microscopy20. The user can browse, select and visualize data based on selection categories such as cortical depth, branching order, vessel diameter, animal subject or a particular arteriolar tree. The GUI further performs simple mathematical operations such as averaging and peak-normalization in selected categories. NNE 2.0 enables to view and browse through images capturing 3D volumes of vasculature as well as identify the location of the functional measurement within the vascular trees. This feature can be used to reconstruct vascular morphologies in 3D and populate them with real single-vessel vaso-motion measurements. These reconstructions can in turn be incorporated into computational models of brain function21,22. NNE 2.0, its source code and the associated database are freely downloadable as a zipped file called ‘NNE 2.0 HDbase v1.0’ from UCSD Neurovascular Imaging Laboratory website1.
NNE 2.0 works with a database called 'vdb.mat'. This database is a matrix containing temporal profiles (time-courses) of single vessel diameter changes evoked by an optogenetic stimulus and measured at different locations of arteriolar trees. Each time-course was computed using custom-written software. It calculates the relative change of a vessel diameter from expansion of a fluorescent intensity profile acquired by scanning across the vessel. The fluorescent contrast was presented by intravascular injection of fluorescein isothiocyanate (FITC)-labeled dextran. For more information about the data and analysis procedures, please see20,23. The database has 305 time-courses (i.e. database entries) in total. In addition to the diameter change, each entry to the database holds an array of additional metadata which (1) quantify the time-course (2) describe the measured vessel and (3) identify the measurement location within a 3D volume of cortical vasculature. The metadata include the onset time, peak amplitude, peak amplitude time, cortical depth, branching order, vessel diameter at baseline, path to original reference images and 3D image stacks for each measurement and low-magnification maps of brain surface vasculature. Please see all parameters in the metadata listed and described in detail previously in Table 116.
NNE 2.0 interacts with reference images that are X-Y scans of a plane where the diameter measurement occurred. Each database entry has one corresponding reference image with a reference name displayed in the GUI. Each database entry also has an associated stack of images (3D stack) capturing a 3D volume of the vascular tree within which the measurement occurred. The GUI enables to choose a particular database entry and display the corresponding reference image as well as the 3D stack. It also guides the user to find the matching reference image and frame in the 3D stack (the same features can be found in both images). All stack and reference images in their full resolution (1024 pix x 1024 pix) are included in folders hana_stk and hana_refs, respectively. Low-magnification maps of brain vasculature are included in folder 'maps'. All three folders as well as the database matrix ‘vdb.mat’ are downloaded in the zipped file ‘NNE 2.0 HDbase v1.0’ from the UCSD Neurovascular Imaging Laboratory website1 and saved to the root folder of NNE 2.0 during the installation process.
The GUI has been designed as a set of four panels (Panel 1 (Main Panel) – Panel 4) which open sequentially as the user explores the database and selects specific data based on selection categories. Each panel is divided into two main parts: (1) the right column provides the possibility to interact with the database by selecting parameters and categories of the data and displays important information from the metadata; (2) the left column displays the data in the form of time-courses (diameter change in time) and scatter-plots. There are four types of scatter plots displaying (1) dilation onset time (2) time of the dilation peak (3) maximum diameter change (peak amplitude) and (4) baseline diameter (diameter before stimulation) as function of cortical depth. The user has the possibility to display average time-courses and values for selected data grouped either by cortical depth or branching order. This is to highlight the feature of gradient diameter-change behavior with increasing depth and branching order20. NNE 2.0 allows the user to export the selected subset of data in the format of '.xls', '.csv' or '.mat'.