Rate Histograms

Rate histogram displays firing rate versus time.

Parameters

Parameter	Description
XMin/XMax type	An option on how XMin and XMax values are specified.
XMin	Time axis minimum in seconds.
XMax	Time axis maximum in seconds
Bin	Histogram bin size in seconds.
Normalization	Histogram units (Counts/Bin or Spikes/Second). See Algorithm below.
Set Cont. Mean to Zero if Small Bin Count	If the number of continuous data points int a bin is too small, set cont. mean (bin value) to zero. See Algorithm below.
Cont. Min Bin Count Percent	Minimum number of continuous data points in a bin as percent of the expected number of data points. See Algorithm below.
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.
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.
Add to Results / Bin left	An option to add an additional vector (containing a left edge of each bin) to the matrix of numerical results.
Add to Results / Bin middle	An option to add an additional vector (containing a middle point of each bin) to the matrix of numerical results.
Add to Results / Bin right	An option to add an additional vector (containing a right edge of each bin) to the matrix of numerical results.
Send to Matlab	An option to send the matrix of numerical results to Matlab. See also Matlab Options .
Matrix Name	Specifies the name of the results matrix in Matlab workspace.
Matlab command	Specifies a Matlab command that is executed after the numerical results are sent to Matlab.
Send to Excel	An option to send numerical results or summary of numerical results to Excel. See also Excel Options .
Sheet Name	The name of the worksheet in Excel where to copy the numerical results.
TopLeft	Specifies the Excel cell where the results are copied. Should be in the form CR where C is Excel column name, R is the row number. For example, A1 is the top-left cell in the worksheet.

Summary of Numerical Results

The following information is available in the Summary of Numerical Results

Column	Description
Variable	Variable name.
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

The time axis is divided into bins. The first bin is [XMin, XMin+Bin). The second bin is [XMin+Bin, Xmin+Bin*2), etc. The left end is included in each bin, the right end is excluded from the bin.

Spike Trains and Events

For each bin, the number of events (timestamps) in this bin is calculated.

For example, for the first bin

bin_count = number of timestamps (ts) such that ts >= XMin and ts < XMin + Bin

If Normalization is Counts/Bin, no further calculations are performed.

If Normalization is Spikes/Sec, bin counts are divided by Bin.

Continuous Channels

For each bin, the average of continuous signal values in this bin is calculated. Normalization parameter is ignored.

When calculating the average of continuous signal, we may encounter a situation when the number of data points in a bin is very small. For example, with a 1 KHz signal and bin = 1 second, we typically have 1000 data points in each bin. If we have a bin in which we have only one data point, the average of the signal in this bin is equal to the single data point value. This value can be very different from the typical average of 1000 data points. Therefore, to avoid these spurious artifacts, we need to check how many data points are in the bin and set the average to zero if there are too few data points.