Open the Record
Open the record \Samples\Grid\Clip.lay. Set the sensitivity to 70 uV, and turn the filters off.


This is a 64 channel recording on the grid, displayed below, which is stored in Clip.bmp. Grid 1 is at the bottom-left (hidden) and grid 8 is at the top left.

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Before using SpikeDetector, we will create the electrode map used to display the topographic plots of the grid recording.

Select Prism: VoltagePlot from Insight’s Tools menu. Select Design Electrode Map from VPlot’s View menu. Choose New Electrode Map from the tool palette.



Name the new map Grid64 and choose OK.



Select Properties from the tool palette. Select Browse and choose the bitmap clip.bmp and choose OK.

Important: your display needs to be set for > 256 colors in order to display topographs on a bitmap correctly. Select Display from the Control Panel to check your settings.



Now we are ready to place the electrodes. Select the Grid Guide tool and recall that grid 1 is at the bottom-left and grid 8 is at the top left. Click the left button of the mouse at the grid 1 position (bottom-left hidden), then the grid 8 position (top-left), then the grid 64 position (top-right) and finally the grid 57 position (bottom-right hidden).



You are prompted to select the electrodes to be placed on this grid. In this example, select the full set of electrodes (1-64) and choose OK.

Choose Opaque Electrodes from the toolbar, and you should see something like this.



Click an electrode to select it. Drag an enclosing rectangle to select one or more electrodes. Selected electrodes are repositioned by dragging them to a new position. (Click and move the mouse without releasing it until at the desired position.) Use the arrow keys for fine positioning.

In this example, it is easiest to start by selecting vertical columns and shifting them as a group. Finally, make small adjustments on the individual electrodes to match the bitmap.



Close the window and save your changes. This electrode map has now been saved (in the file pstopo.ini) for later use. Close VPlot and return to Insight

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Detections have already been saved in this example, but if they had not, here is what you would do. (Please refer to the User’s Guide for detailed instructions on using the SpikeDetector.)

Select SpikeDetector from Insight’s Tools menu. Select Start, select all 64 channels except 26, 32 and 36, which contain artifacts, and press the From EEG button to update the reading sensitivity set in Insight.



Note: the Depth Sensitivity can also be used to alter the reading sensitivity of scalp studies. For example, a record with very low output might need a reading sensitivity of 5 rather than the default 10.

This is the only difference required for an intracranial study. Select Cancel and close the SpikeDetector.

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Select SpikeReview from Insight’s Tools menu. Change the Electrode Map (on the lower toolbar) from 10-20 to Grid64, the map that we created above.

Select Contour Plots from the Format menu and change the Palette to Blue to Red.



Choose Cluster Spikes from the toolbar.



This dialog contains some options not yet described in the User’s Guide.

The Neighbors parameter allows the clustering of many more spikes than the original clustering algorithm. Spikes separated, in time, by more than Neighbors (e.g., spikes 20 and 527) are required to find an intervening similar spike between them before they are placed in the same group. The side effect of this is that the spikes tend to be clustered in time. If there are fewer than Neighbors spikes, then no change to the algorithm occurs. Reducing the number of neighbors reduces the time for the clustering and the required memory, but this number should probably not be reduced below 100 to maintain a good clustering.

Open theTree performs the same function as the Open Tree command available from the Tools menu. A Dissimilarity Level of ~2 will create groups with visually similar events. The focus of the Review Wizard is the splitting of groups to create good averages, so the dissimilarity level can be set higher than when used with the Open Tree command.

Run the Review Wizard places you in a new view, after clustering and opening the tree, that allows you to walk through all of the spike groups and decide whether they need to be expanded (for more detail) or deleted. After the wizard is done, you are placed in the Leaf Nodes: Traces view, which displays the remaining groups side-by-side.

Set the Tree Depth to 12 because intracranial records contain more focal points than scalp records. (You can leave this setting at this value unless you have a memory shortage.) Select OK to cluster the spikes, open the clustering tree and start the Review Wizard.

Toggle the Montage Bar, EEG Bar and Event List to see the complete view.



The average traces on the far left (n=64) displays group 1 of 10. (The groups displayed are the leaf nodes of the cluster tree.) This group is the parent of the two sets of child traces to the right (n=21 and n=43). If this group is expanded (as it should be), then the two child groups will be investigated. (This is equivalent to expanding the parent node in the Cluster Tree view.) To the right of the average traces are the iconic representations of the parent and children (from top to bottom).

Steps using the Wizard:

1. Delete the group if both its children are artifacts, or

2. Expand the group if its children look different, otherwise

3. Select Next (>) to move to the next group.

4. You may use any of the menu tools to look at individual spikes, then return to the Review Wizard

5. Select Done when you reach the last group (N of N).
Once you are done, the groups will be displayed side-by-side.


Select Save from the File menu to permanently mark the events you deleted. (This ensures that the deleted events will not be displayed in Insight, or in SpikeReview the next time you open it. Deleted events can be restored by selecting Restore Deleted from the Edit menu, even after the file has been saved.)

Finally, select Export Groups to EEG Page so that we can use Prism: Voltage Plot for a more in-depth analysis.

Note: you will not be able to save changes to clip.sd and clip.lay unless you have copied the file from the CD-ROM and removed its read only property via the Windows Explorer.

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By choosing Export Groups to EEG Page in SpikeReview, the non-deleted spikes have been stored in Insight as @VPlot events. These can be seen on the EEG Page, with each group a different color, and in the VPlot Groups dialog bar (Insert|VPlot Comments).


The advantage of using @VPlot events rather than the spike events for further analysis is the ability to move the @VPlot events. For example, if you are performing an advanced voltage plot or source dipole analysis, you may need to move the event slightly so it matches the peak of a different channel. (You can also place @VPlot events by hand and move them between groups.)

Select Prism: Voltage Plot from Insight’s Tools menu. Display the Montage Bar and select and delete the artifact channels 26, 32, 36.

Select Properties from the Format menu and make sure that the Voltage Plot and Template are enabled. Set the number of Grid Pts to 32 to account for the large number of electrodes.



Select Select Group from the Edit menu and choose group 4.



Change the display to show the propagation over time in a 3x3 grid with 5 msec resolution to see that the spike starts in grid 31 and them moves to grid 39.

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