Perievent Rasters

This analysis shows the timestamps of the selected variable relative to the timestamps of the reference variable.

Parameters

Parameter	Description
Reference Type	Specifies if the analysis will use a single or multiple reference events.
Reference	Specifies a reference neuron or event (or a group of reference neurons or events).
XMin	Time axis minimum in seconds.
XMax	Time axis maximum in seconds
Markers	An option to display additional events (as markers - triangles, squares, etc.) in the perievent raster.
Background Intervals	An option to draw intervals in the raster background.
Trial Order	This option allows you to specify how the raster lines are drawn. The raster lines (corresponding to reference events) can be drawn in the order of reference events (with the first event on top, the last at the bottom of the perievent raster), or in the reverse order (the first event at the bottom of the raster display, the last event at the top). This option is ignored if Sort trials parameter is not None.
Sort trials	An option to sort raster lines. By default, the raster lines (corresponding to reference events) are drawn in the order specified by the Trial Order parameter. This option allows you to display reference events in a different order. For example, in behavioral experiments, you can sort the trials according to the latency of the response.
Sort event	Specifies how to identify the timestamps (in Sort ref. variable) that will be used in sorting.
Sort ref.	Specifies event variable that will be used to sort trials.
Histogram	An option to draw a histogram.
Bin	Histogram bin size in seconds.
Normalization	Histogram units (Counts/Bin, Probability or Spikes/Second). See Algorithm below.
No Selfcount	An option not to count reference events if the target event is the same as the reference event. Prevents a histogram to have a huge peak at zero when calculating PSTH versus itself.
Select Data	If Select Data is From Time Range, only the data from the specified (by Select Data From and Select Data To parameters) time range will be used in analysis. See also Data Selection Options.
Select Data From	Start of the time range in seconds.
Select Data To	End of the time range in seconds.
Int. filter type	Specifies if the analysis will use a single or multiple interval filters.
Interval filter	Specifies the interval filter(s) that will be used to preselect data before analysis. See also Data Selection Options.
Create filter on-the-fly	Specifies if a temporary interval filter needs to be created (and used to preselect data).
Create filter around	Specifies an event that will be used to create a temporary filter.
Start offset	Offset (in seconds, relative to the event specified in Create filter around parameter) for the start of interval for the temporary filter.
End offset	Offset (in seconds, relative to the event specified in Create filter around parameter) for the end of interval for the temporary filter.
Fix overlaps	An option to automatically merge the overlapping intervals in the temporary filter.
Smooth histogram	An option to smooth the histogram after the calculation. See Post-Processing Options for details.
Smooth Filter Width	The width of the smooth filter. See Post-Processing Options for details.

Summary of Numerical Results

The following information is available in the Summary of Numerical Results

Column	Description
Variable	Variable name.
Reference	Reference variable name.
NumRefEvents	The number of reference events used in calculation.
YMin	Histogram minimum.
YMax	Histogram maximum.
Spikes	The number of spikes used in calculation.
Filter Length	The length of all the intervals of the interval filter (if a filter was used) or the length or the recording session (in seconds)
Mean Freq.	Mean firing rate (Spikes/Filter_Length).
Mean Hist.	The mean of the histogram bin values.
St. Dev. Hist.	The standard deviation of the histogram bin values.
St. Err. Mean. Hist.	The standard error of mean of the histogram bin values.

Algorithm

Spike Trains

For the perievent histogram calculation,

Let ref[i] be the array of timestamps of the reference event, sortref[i] be the array of timestamps of the sort event.

If Sort Trials is selected, the following algorithm is used:

for each timestamp ref[k], NeuroExplorer finds the smallest sortref[i], such that

sortref[i] > ref[k]

the distance between two events is calculated:

dist[k] = sortref[i] - ref[k]

the trials ref[k] are sorted array sorted in ascending or descending order of dist[k].

Continuous Variables

Continuous variables can also be used in this analysis. However, you may prefer to use PeriEvent Rasters for Continuous Variables analysis.

For each ref[k], NeuroExplorer calculates a series of bins. The first bin is:

[ref[k]+XMin, ref[k]+XMin+Bin]

the second bin is [ref[k]+XMin+Bin, ref[k]+XMin+Bin+Bin], etc.

Then, the average value of a continuous variable is calculated within each of the bins and this average value is displayed using the color scale. If bin does not contain any timestamps of the continuous variable, the previous value of the continuous variable is used.