How to Store Analog Data

NeuroExplorer up to version 5.020 always stored analog data internally as 16-bit integers. The reason? Most data acquisition systems use analog to digital converters that have 12-bit or 16-bit resolution and store A/D data as 16-bit integers.

To display real signal values, we use scaling. For example, if analog to digital converter has input range from -1000mV to +1000mV and 10X amplification was used, then maximum 16-bit value 32767 corresponds to 1000mV/10 (non-amplified signal value). This means that 32767*ScalingFactor = 100, and ScalingFactor is 100.0/32767.

16-bit storage model seems perfect — we do not loose any signal resolution and we save on storage space. However, if we import data from Matlab (where the data values are stored as floating point numbers), we have to calculate ScalingFactor to fit floating point values into 16-bit range. As a result, we loose signal resolution (especially when the signal has a few large peaks and lots of small values).

There are also clipping issues when we try to modify signal values in NexScript. If we try to assign the value that is outside the original  non-amplified  range, we would have to clip the value since we have hard limits for 16-bit internal representation of signals.

Things, however, are changing with NeuroExplorer 5.021. Now NeuroExplorer can store analog data both as 16-bit integers and as 32-bit floating point numbers.

Analog signals imported from data files created by data acquisition system are still stored as 16-bit integers.

Continuous channels imported from Matlab or generated in NeuroExplorer (using frequency filtering, etc.) are now stored as 32-bit floating point values. Both data representations can be saved and loaded using .nex5 data files.

Matlab scripts for reading and writing .nex5 files ( have been updated and can be used to read and write .nex5 files with analog data stored as 32-bit floats.

Dealing with Noise and Artifacts in Data Viewer

Often you can visually identify periods of noise or artifacts in 1D Data Viewer:

scratching artifact2

In NeuroExplorer version 5.014 or later, you can identify time intervals corresponding to artifacts using mouse:

– Right-click in 1D View to invoke context menu:


– Specify ‘Select Interval Variable…’ menu command. NeuroExplorer will display the following dialog:

Specify Interval Variable to Add Intervals to

– Click ‘Create New Interval Variable…’ button:

New Variable Name

– Let’s create a new interval variable with the name noise. Type ‘noise’ (without quotes) and click OK to close this dialog, then click OK to close Select Interval Variable dialog.

– Note that the cursor now has ‘plus interval’ graphic:


– Press the left mouse button at the start of the noise interval, then drag the mouse until the end of the noise interval and release left mouse button. The new interval is added to noise interval variable:

added interval

– Add a second interval:


– Hit ESC key to exit Add Interval mode

– We want to analyze data that is NOT in the noise intervals. To make this possible, right-click in 1D view again and select ‘Invert Interval Variable’ menu command:


– In the Invert Interval Variable dialog, select noise variable to be inverted:

Invert Interval Variable

– Now noise_inverted interval variable contains time intervals corresponding to our data without noise:


– We can use noise_inverted variable in a Data Selection page of analysis properties dialog:

Analysis Properties data sel

and the data in noise intervals will be ignored.

There is also a faster way to get rid of noisy data — you can delete all the data in specified time intervals. To do this, right-click in 1D view and select ‘On Mouse Click and Drag, Delete…’ menu command:


– Now when you click and drag with the left mouse button, all the data in selected time interval are deleted:



Note that delete operation cannot be undone right away. You will need to reload the data file to restore original data.


How to Save and Restore Your Work in NeuroExplorer

When you work in NeuroExplorer, the program creates a number of data and analysis results windows.  By default, these windows are not restored when you close and reopen the program.  If you would like to save and restore all your current work in NeuroExplorer, use File | Save NeuroExplorer State and File | Restore NeuroExplorer State menu commands:


You can also restore the last analysis of this or previous NeuroExplorer analysis session using File | Restore Last Analysis menu command.  The program will do the following:

  • Load the data file used in last analysis
  • Select the variables used in last analysis
  • Run the analysis

See also Working with Results Files.


Working with Results Files

NeuroExplorer can save both graphical and numerical results of the analysis in a NeuroExplorer results file. Since each result has both graphics and numerical values, the results are saved in a set of files with common file name and different extensions.

You can use SavedResults | Quick Save Results menu command to save all the current results:


For example, if you run Perievent Rasters analysis on data file TestD21.plx and select Quick Save Results, the results will be saved in the following 5 files:

  • TestD21_plx Perievent Rasters.nexresult (text file with links to other files of this result)
  • TestD21_plx Perievent Rasters numres.txt (text file with numerical results)
  • TestD21_plx Perievent Rasters numres summary.txt (text file with the summary of numerical results)
  • TestD21_plx Perievent Rasters.png (.png file with graphical analysis results)
  • TestD21_plx Perievent Rasters.ntp (template file with analysis parameters)

By default, these files be saved in the folder:
C:\Users\<your_user_name>\Documents\NeuroExplorer 5\Results.

The .nexresult file is the file containing description of the analysis and the links to other result files. You can open this file in NeuroExplorer using SavedResults | Open Saved Results File menu

When you open results file, NeuroExplorer loads graphics and numerical results files and shows a window with 4 tabs:


This window looks similar to the Graphical results window, but the results are not ‘live’ — you cannot adjust analysis parameters and recalculate the results.

However, you can replicate the results saved in the results file. Use SavedResults | Restore Analysis in NeuroExplorer menu command:


NeuroExplorer will do the following:

  • Open data file used in the calculation of results
  • Select variables for analysis exactly as they were selected in the saved results
  • Run the analysis used in the calculation of results (using the same analysis parameters)

You can also use SavedResults | Results Folder Summary menu command to view all the saved results in a grid:


In this Results Folder Summary view you can:

  • Sort results by any of the columns by clicking at the column header
  • Open results file by double-clicking the row representing the file
  • Convert selected results to PowerPoint slides using right-click and selecting Add Slides… context menu command
  • Select results using Find combo box in the NeuroExplorer toolbar. The text in all the columns will be used when filtering the results. For example, to view only results saved in 2015, type 2015 in Find box:




How to Customize Analyses Panel

There are two ways to select an analysis in NeuroExplorer – you can click at the analysis you want to run in the Analyses panel:


or select an analysis via Analysis | Select Analysis Type menu command:


The fastest way is to use Analyses panel. However, now that NeuroExplorer has more than 30 analyses to choose from, you may have to scroll the panel to get to many of the analyses. To speed up the access to the analyses you use most often, you can rearrange the order of the analyses in the All Analyses list by dragging the analyses up and down in the list:


There is also Recently Used Analyses list that shows the last 10 analyses that were used.

The layout of the Analyses panel is saved in the file

C:\Users\<user_name>\Documents\NeuroExplorer 5\Layouts\AnalysesPanelLayout.layout

If you want to standardize the order of analyses on all computers in your lab, you can rearrange the analyses on one of the computers, exit NeuroExplorer and copy AnalysesPanelLayout.layout file to C:\Users\<user_name>\Documents\NeuroExplorer 5\Layouts folders on other computers.