Spike Detection
This analysis optionally subtracts reference channel, band-pass filters continuous variables and detects spikes using threshold crossing algorithm. Detected spikes are added to current data file as new waveform variables.
Parameters
Parameter |
Description |
---|---|
Subtract Reference |
An option to subtract reference channel before filtering and spike detection. |
Reference Channel |
Reference Channel to subtract before filtering and spike detection. |
Filter Before Detection |
An option to band-pass filter continuous variables (using Butterworth filter) before spike detection. |
Filter Order |
The Butterworth filter order. |
Filter Frequency From |
Minimum frequency (Hz) of the band-pass filter. |
Filter Frequency To |
Maximum frequency (Hz) of the band-pass filter. |
Threshold type |
An option specifying how the threshold is calculated (see Algorithm below). |
Custom Threshold |
Threshold value or number of standard deviations (can be negative, see Algorithm below). |
Threshold Crossing Type |
Type of threshold crossing to use. Auto (if threshold is nonnegative, detect a spike when the signal crosses the threshold when signal is going up, if threshold is negative, detect a spike when the signal crosses the threshold when signal is going down); Up (detect a spike when the signal crosses the threshold when signal is going up); Down (detect a spike when the signal crosses the threshold when signal is going down). |
Segment Before Threshold (mS) |
Signal segment before threshold to include into spike waveform. |
Segment After Threshold (mS) |
Signal segment after threshold to include into spike waveform. |
Minimum Time Between Spikes |
Minimum time between spikes. |
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(s) that will be used to preselect data before analysis. See also Data Selection Options. |
Summary of Numerical Results
The following information is available in the Summary of Numerical Results
Column |
Description |
---|---|
Variable |
Variable name. |
YMin |
Y axis minimum. |
YMax |
Y axis maximum. |
Threshold |
The threshold value used to detect spikes (in mV) |
Spikes Detected |
The number of spikes detected. |
Algorithm
The standard deviation of the signal (SD
) and the median of the signal absolute values (MA
) are calculated.
‘Median Sigma’ (MS
) is equal to MA/0.6745
(see eq. 3.1 in Reference).
If threshold type is Auto, the threshold is equal to
-4.0*MS
(see eq. 3.1 in Reference).If threshold type is Number of Median Sigma, the threshold is equal to
Custom_Threshold*MS
.If threshold type is Number of Standard Deviations, the threshold is equal to
Custom_Threshold*SD
.If threshold type is Absolute, the threshold is equal to
Custom_Threshold
.
The spike is detected if the signal crosses the threshold when signal is going up or down (depending on the value of the Threshold Crossing Type parameter).
Reference
Neural Comput. 2004 Aug;16(8):1661-87. Unsupervised spike detection and sorting with wavelets and superparamagnetic clustering. Quiroga R, Nadasdy Z, Ben-Shaul Y.