User manual

4.5.1 Signal Averaging

If Signal Averaging is used, each sweep is first acquired and plotted in Gray, then the average of the

sweeps is then plotted in LightBlue. The setting for the number of sweeps to average for the Slow Repeat

Sweeps is set by the AvgLoop number of loops field - see Fig. 3.1.2.1 for a simple averaging protocol,

and Figs. 7.4.1.1, 7.4.9.1 and 7.4.10.1 for more complex averaging protocols.

You can also signal average during Fast Repetitive Pulse Sweep (LTD) Stimulation which is set by the

NumSweeps to Avg field (Fig. 4.4.2.1).

4.5.2 Stimulus Artifact Blanking

Fig 4.5.2.1 and Fig 4.13.2.1 show the effect of stimulus artifact blanking. If Stimulus Artifact Blanking is

chosen, stimulus artifact blanking is enabled, and a S0 or S1 Blank field appears on the Detection page

(see Fig. 4.5.2.1). Beginning at the time of the start of the S0 or S1 pulse to the time set in the S0 or S1

Blank field (1 ms in Fig. 4.5.2.1), the stimulus artifact data in the ADsweep array is (sometimes) set to the

Average of the 1 data point value just before blanking begins, and one point value just after blanking

ceases (Fig. 4.5.2.1a). If the time in the S0 or S1 Blank field is set too short, then the stimulus artifact is

not entirely blanked, if it is set too long (but not ridiculously long) generally there aren't any problems as

long as the peak amplitude is not clipped.

WinLTP can take the Average of the point just before blanking begins and the point just after blanking

ceases (Fig. 4.5.2.1a). However, WinLTP can also take the Slope between the point just before blanking

begins and the point just after blanking ceases (Fig. 4.5.2.1b), and can also take the point just before

blanking begins and then Hold that voltage until to the point just after blanking ceases (Fig.

4.5.2.1c). Setting the Average, Slope or Hold blanking method is accomplished by entering A, S or H

into the Average/Slope/Hold field next to Blank.

Stimulus artifact blanking is useful for determining the peak amplitudes of individual EPSPs when the

stimulus artifacts are riding on top of the previous EPSP, or when trying to determine the area or peak

amplitude of a whole train which could be seriously distorted by the stimulus artifact (Fig 4.13.2.1).

Stimulus artifact blanking has also turned out to be useful when trying to fit exponential curves to the

decay phase of closely spaced EPSCs when the artifact for the next EPSC occurs during this decay

phase. This approach has been used for exponential curve fitting of synaptic trains by the Synaptosoft

MiniAnalysis Program (www.synaptosoft.com). It's interesting how removal of stimulus artifacts allows

EPSPs and EPSCs to be analyzed as spontaneous events. The Slope method has proved particularly

useful for fitting exponential curves to synaptic potentials by having a smoother decay phase; in fact it is

almost impossible to see where the stimulus artifact was.

The Hold method has proved useful for blanking stimulus artifacts where the point just after blanking

ceases varies widely (such as blanking the stimulation in extracellular CA3 recording where the ntidromic

spike occurs right after the stimulus artifact).