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.