Regularity Analysis

This analysis estimates the regularity of neuronal firing after the stimulation.

Parameters

Parameter	Description
Reference	Specifies a reference event or spike train.
XMin	Time axis minimum in seconds.
XMax	Time axis maximum in seconds.
Bin	Bin size in seconds. Used if Bin Type is set to User defined.
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.
Interval filter	Specifies the interval filter that will be used to preselect data before analysis. See also Data Selection Options.
ISI Graph	This parameter determines how the mean ISI values is displayed in the graph.
SD Graph	This parameter determines how the standard deviation of ISI is displayed in the graph.
CV Graph	This parameter determines how the CV (coefficient of variation) values are displayed in the graph.
CV Graph Max	This parameter determines the scale for the CV values in the graph. CV values are scaled from zero (bottom of the graph) to CV Graph Max (top of the graph).
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.

Summary of Numerical Results

The following information is available in the Summary of Numerical Results

Column	Description
Variable	Variable name.
NumRefEvents	Number of reference events.
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 (ISI values).
St. Dev. Hist.	The standard deviation of the histogram bin values.
St. Dev. ISI	The mean value of the SD ISI graph.
CV	The mean value of the CV ISI graph.

Algorithm

This analysis estimates the regularity of neuronal firing after the stimulation. The time axis is divided into bins with the first bin starting at the stimulus sync pulse. Interspike intervals are computed and interval values are placed in time bins according to the latency of the first spike in the interval (if the end of the ISI is more than XMax, the interval is not used in the analysis). Then the mean and standard deviation in each bin are calculated. CV is equal to standard deviation for the bin divided by the mean ISI for the bin.

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

ts[i] be the spike train (each ts is the timestamp)

For each timestamp ref[k]:

1a) calculate the distances from this event (or spike) to all the spikes in the spike train:

d[i] = ts[i] - ref[k]

1b) calculate the interspike interval

isi[i] = ts[i+1] - ts[i]

1c) for each i:

if d[i] is inside the first bin (d[i] >= XMin and d[i] < XMin + Bin) and d[i] + isi[i] < XMax, add isi[i] to the series of intervals for the first bin.

if d[i] is inside the second bin (d[i] >= XMin+Bin and d[i] < XMin + Bin*2) and d[i] + isi[i] < XMax, add isi[i] to the series of intervals for the second bin

and so on… .

2. for each bin, calculate mean and standard deviation of the series of interspike intervals for this bin.

Reference

E.D. Young, J.-M. Robert and W.P. Shofner. Regularity and latency of units in ventral cochlear nucleus: implications for unit classification and generation of response properties. J. Neurophysiology, Vol. 60, 1988, 1-29.