How can you create a customized overlay plot in BrainVision Analyzer 2?
by Dr. Filipa Campos Viola
Scientific Consultant (Brain Products)
Among the most appreciated features of BrainVision Analyzer 2 are the visualization options. Several nice graphical views are just a “mouse-click” away. The users can quickly explore the EEG data in a convenient and user friendly way. All views can be customized by changing settings either locally or globally. These customized plots can be further optimized by taking advantage of functionalities such as the placeholders.
The example described here explains how to create a customized overlay plot
The data shown is part of an auditory experiment with the goal of comparing auditory evoked potential (AEPs) in a control group with normal hearing and in patients with a cochlear implant. The data analysis was performed in BrainVision Analyzer 2 and AEPs were computed for each group. The user would now like to create a summary plot for channel Cz illustrating the grand average waveforms for the two groups. In this example, the node that corresponds to the grand average for the control group needs to be active so the waveform for channel Cz will be displayed using the default view (Grid View). The user can then “drag and drop” the grand average node that corresponds to the patient group on that plot.
The default overlay plot will show the waveform for the control group in black (Reference Node) and the patient group waveform will be shown in red (see figure 1).
Figure 1: Overlay plot for channel Cz.
The default labels correspond to the name of the channel and the name of the node, which is “Raw Data” in both cases. These nodes are the default result when using the transformation Grand Average. It would be desirable to change these labels in the plot in order to have a unique name for each group.
This leads us to the question in the title: “How can you create a customized overlay plot?”
The user needs to right-click on the overlay plot and select from the context menu the option “Settings of Grid View”. In order to customize the labels it is necessary to navigate to the tab Overlay (see figure 2). A table is displayed showing the list of overlays and the default settings. A list of placeholders is shown to the right. Placeholders can be regarded as shortcuts. The special character $ can be combined with a dedicated letter that will then be interpreted to create a label. For instance $h stands for history file name, $n stands for node name, and $c stands for channel name.
In this customized example (see figure 3) the control group will be displayed in black (Overlay No. 0) and the patient group will be displayed in green (Overlay No. 1).
The line width was set to 3 and the placeholder $h was selected as label. In the case of the Reference Node the placeholder $c was added because the channel label is also needed. The button Apply makes it possible to display the changes without closing the dialog. Other changes can be made and then confirmed with OK.
Figure 2: Overlay dialog.
Figure 3: Changing default settings locally.
The resulting overlay plot is shown in figure 4 below.
Figure 4: Overlay plot for channel Cz. Data is displayed using customized settings.
Placeholders are also particularly useful when applying the transformation Data Comparison or the Export functions. More details can be found in the User Manual.
It is also relevant to highlight that the example described here shows how to change settings locally, which means that the changes performed will only be valid for this particular plot. If the user wants to reconfigure the global settings, similar changes can be made using the menu View Settings available under “File -> Configuration”.
We hope that this brief explanation will help you to create nice customized plots with just a few “mouse clicks”.