How to Interpret and Use Mapfiles

How to Interpret and Use Mapfiles

Overview

In Central's Hardware Configuration utility, under the 'Location' header is a Bank assignment and a Pin number. Each Bank, which is lettered A to H, has 32 Pins, which are numbered 1-32. The number of Banks multiplied by 32 is your system's total channel count. A "channel" is the physical location on the amplifier stage that the signal is coming in from. Each electrode on your array will transmit data to your data acquisition system through a single channel. Therefore, each channel on your recording system has a single designated Pin on one Bank. "Pad Side" refers to looking down on the implanted array. 

Utah Array Channel Mapping

For Utah Array users, channel Banks and Pins correspond directly with the Bank and Pin numbers on the mapping Excel spreadsheet, which is included in the CD that came with your array (if this file is missing, please contact Blackrock Support). Because the data acquisition system can only understand channel and needs to be taught how electrodes on an Array corresponds to a given channel, these mapfiles are used to configure the Central software to display signals coming though each channel organized by array's electrode. A copy of the Excel sheet "Z-check" from the included file shows this mapping below.

Channel Labeling

It may be convenient to see the electrode numbering on your screen because the channel numbering does not give you an accurate visual representation of the electrode organization of the electrodes you are recording from. By default, Central Hardware Configuration numbers the channels sequentially, where Bank A gets channels 1-32, B gets 33-64, and so on. This is shown in the screen grab of Hardware Configuration before a mapfile is applied:


However, when a mapfile is applied, the electrode numbering becomes apparent. Using the same mapfile that was used in the Excel example above, note how the "Channel" labels in Hardware Configuration change to the numbers in the "Elec." column from the previous Excel example:

Mapfiles (.cmp files)

The mapfile (or .cmp file) is the one file that puts all of these factors pertaining to channels together: the channel's Bank and Pin as well as the Array Electrode number and organization that gets connected to that channel. Each row of a mapfile contains all of this information. Each row gets five columns, ordered left to right as:
col: the column in Central Spike Panel where the channel will appear, where 0 = left
row: the row in Central Spike Panel where the channel will appear, where 0 = bottom
bank: the channel's Bank (lettered A-H)
elec: the channel's Pin in its given Bank, numbered 1-32
label: a string to name the electrode, which is typically given a name such as "elecXX" where "XX" is the electrode number the channel connects to on an Array
A screenshot of the .cmp mapfile that corresponds to the data shown above is pasted below:



The layout that is generated in Spike Panel for this .cmp mapfile, which is loaded by going to File -> Load Mapfile... in Central's Spike Panel utility, is shown below. Note how this topography matches that of an Array with the electrodes labeled with the "label" column from the .cmp file shown above, and how this mapped display of Spike Panel matches the electrode numbering from the Excel file from earlier:

Making Your Own Mapfile

In order to make your own mapfiles in your own text editor, the first 10 lines of the .cmp file should be left unchanged. You can then create your own mapfile description on line 11. Line 12 should also be unchanged. All following lines should be tab-separated into five columns consisting of col, row, bank, elec (i.e. pin number), and label, in that order for each channel. The file must be saved with extension ".cmp" in order for Central to be able to load it. In Notepad, this is done by saving the files with File -> Save As.... When the saving window comes up, the "Save as type:" field must be "All Files" and the "Encoding" field must be "ANSI". Then in the "File name:" file, name the file "NameOfYourFile.cmp", and click "Save".
Conclusion
With this information, you should be able to understand the information on the CD delivered with your Array, how channels are understood by your Blackrock data acquisition hardware, how electrodes are mapped to channels, and how to make your own mapfile. If you have any further questions about channel mapping, please browse the Knowledge base or contact Blackrock Support.

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