Interspike Interval Histograms
Interspike interval histogram shows the conditional probability of the first spike at time t0+t after a spike at time t0.
Parameters
Parameter |
Description |
|---|---|
Min Interval |
Minimum interspike interval in seconds. |
Max Interval |
Maximum interspike interval in seconds. |
Bin |
Bin size in seconds. |
Normalization |
Histogram units (Counts/Bin, Probability or Spikes/Second). See Algorithm below. |
Log Bins and X Axis |
An option to use Log10 interval scale (see Algorithm below for details). |
Bins per decade |
A bin size option if Log option is selected (see Algorithm below for details). |
Y Axis Limit (%) |
An option to ‘zoom in’ small histogram values. This parameter specifies the maximum of Y axis. If it is 100%, the Y axis maximum is equal to the maximum bin value. If it is, for example, 10%, Y axis maximum is set to 10% of the bin max and the small bin values have better visibility. |
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. |
Overlay Graphs |
An option to draw several histograms in each graph. This option requires that Int. filter type specifies that multiple interval filters will be used (either Table (row) or Table (col)). |
Smooth |
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 Bin Left to Results |
An option to add an additional vector (containing a left edge of each bin) to the matrix of numerical results. |
Add Bin Middle to Results |
An option to add an additional vector (containing a middle point of each bin) to the matrix of numerical results. |
Add Bin Right to Results |
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. |
Mean ISI |
The mean of the interspike intervals. |
St. Dev. ISI |
The standard deviation of the interspike intervals. |
Coeff. Var. ISI |
Coefficient of variation of the interspike intervals. |
Median ISI |
Median of the interspike intervals. |
Mode ISI |
Mode of the interspike intervals. |
Algorithm
If Use Log Bins and X Axis option is not selected
The time axis is divided into bins. The first bin is [IntMin, IntMin+Bin). The second bin is
[IntMin+Bin, Intmin+Bin*2), etc. The left end is included in each bin,
the right end is excluded from the bin. For each bin, the number of interspike intervals within this bin is calculated.
For example, for the first bin
bin_count = number of interspike intervals (isi)
such that isi >= IntMin and isi < IntMin + Bin
If Normalization is Counts/Bin, no further calculations are performed.
If Normalization is Probability, bin counts are divided by the number of interspike intervals in the spike train.
If Normalization is Spikes/Sec, bin counts are divided by NumInt*Bin, where NumInt
is the number of interspike intervals in the spike train.
If Use Log Bins and X Axis option is selected
The i-th bin (i=1,2,…) is [IntMin * 10 ^ ((i -1)/D), IntMin * 10 ^ (i/D)), where D is the Number of Bins Per Decade.
For each bin, the number of interspike intervals within this bin is calculated.
For discussion on using logarithm of interspike intervals, see:
Alan D. Dorval, Probability distributions of the logarithm of inter-spike intervals yield accurate entropy estimates from small datasets. Journal of Neuroscience Methods 173 (2008) 129-139