Multichannel Systems NeuroExplorer - Manual (Page 100)

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.
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