Recording Neural Signals

Preparing NeuroRighter for Neural Recordings

Chances are, after configuring your hardware settings and hitting 'okay', you are greeted with the following display:

We've got a couple more things to do before we can record neural signals.  First, select the 'Input Settings' tab at the upper right part of the screen.

this will open up a new panel of controls within NeuroRighter

For a basic recording, there are three fields here that we care about.  The first is the number of channels you are recording from.  If '16' is selected, for instance, then NeuroRighter will record and display the data being recorded off of the first 16 analog input channels on the first input device (defined in the Hardware Settings-> Neural Input tab).  Because there are only 32 channels of analog input per device, selecting 64 channels will record and display data from two devices.  

The rate at which voltages are sampled from the electrodes is also set on this menu, and different sampling rates can be used for different neural streams (such as LFP and MUA band, which don't need to be sampled as quickly as they don't contain frequency components as high as those in the raw data or 'spike' band).  

Additionally, you can use this menu to change the precision of the A/D converter.  The default option in NeuroRighter is to sample analog values with a range of +/- 10 volts, divided up into 16 bits worth of precision.  An A/D gain of 2 means that you are reducing your range by a factor of 2, with the benefit of decreasing the size of the minimal voltage change you can represent (reducing quantization error). So, with a digital gain of 2, we have an effective range of +/- 5 volts divided into 2^16 = 65,536 pieces. That corresponds to 0.0001525 volts = 0.1525 mV per division. Since the neural signals that you are recording are amplified by a gain typically ranging from 100-1000, this is plenty of precision. 

The advantage of using a high digital gain is that you get more precision on your recorded waveforms by reducing the dynamic range of the allowed A/D input. This means, for instance, that action potential waveforms will be smoother.

The advantage of using a low digital gain is that large signals will not saturate the A/D conversion circuitry (for instance movement artifacts or electrical stimulation). This means that neural signals can still be recovered during an 'artifact'. That is exactly what the SALPA algorithm does for stimulation artifacts.

Note that nothing visible will happen upon changing the sampling rate, number of channels or A/D gain.  These changes will not be noticeable until recording actually starts.  Also, note that NeuroRighter saves these settings between sessions, so you won't necessarily have to redo this step every time you record. 

Performing Neural Recordings

OK, now we are ready to record some neural signals. After you've done everything above, go ahead and hit that green 'start' button at the lower right corner of the screen.  

The timer next to the Note/Start/Stop buttons will begin timing, and the number of channels displayed will now reflect the number of channels you selected in the 'input settings' tab.

Note that the display will start by showing the full range of the A/D converters.  Chances are, you will need to zoom in significantly to see any neural activity.  To do this, use the helpful magnifying glass buttons to zoom in or out by a factor of 2.

An example of what recordings look like on the 'spikes' tab with 

nothing connected to an MCS preamp (+/- 40mv):

And there is your data (and hopefully spikes, if you've connected your electrodes to something neural)!  Hit the red 'Stop' button once you are done enjoying the sight of your raw traces.

Now that we've got everything set up, lets record something.  Tools for basic recording are in the 'recording' box just above the Note/Start/Stop buttons:

First, click the '...' button to select a file name using the standard windows 'Save As' dialog box.  Then, click the 'Set Recording Streams' button directly underneath the file name box to select what data types you want to save.

You have the option of selecting from any or all of the data streams that NeuroRighter produces, ranging from unfiltered raw data to just information about detected spikes.  Data types that are not available due to your hardware or filtering settings (ie, LFP data is only available if you are doing LFP filtering, same for SALPA data) will appear in this menu but their associated check boxes will be greyed out.  You can also use this dialog box to tell NeuroRighter to add a timestamp to the end of the files you save.  Note that decisions you made in this dialog will be saved between sessions, but BE CAREFUL.  It is a huge pain to do a long or otherwise expensive experiment and only realize at the end that you weren't saving the appropriate data type.  Note that all files will be save with the same prefix but different extensions (.spk, .raw, etc).  Only one file name/extension will be shown in the filename box, even if you record multiple file types.

After you've set all of your recording settings, click the little switch next to the file name dialog.  

Recording is now enabled (note that the LED next to the switch is now 'on').  Hit the green start button and NeuroRighter will begin displaying and saving your data until you hit the red stop button.

Note that if you have an experiment that requires a specific amount of data, you can configure NeuroRighter to stop automatically after a specified amount of time has elapsed.  Do this by checking off the box next to 'Enable Timed Recording' (in between the 'file setup' box and the Note/Start/Stop buttons). Additionally, if you want to record a very long experiment but break the files up into chunks, you can have enable 'Repeat Timed Recording.'  With this option, NeuroRighter will record files of a specified length, and then re-start recording after each file finishes.  You will then need to stop this repeated record manually by hitting the red 'Stop' button.  

Finally, you can hit the 'Note' button to access a text editor. This will create a log file with the same name as your neural recordings. Any note you enter into the text box will be saved along with a time stamp that can be referenced back to the header information in your neural recording files later on.