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What Major Capabilities are in WinLTP 0.90
The Protocol Builder enables complicated protocols to be built using ‘building blocks’ pulled down from the green User Interface buttons. These building blocks include Loops, Delays, Runs and Sweeps (with various stimulations). WinLTP protocol flow of execution can be easily changed during runtime by checking or unchecking the Loop, Delay, Run and Sweep checkboxes. Sweep and Delay Periods can also be changed during runtime, as can all sweep stimulation values.
WinLTP can simultaneously execute two independent tasks, the Stimulation/Acquisition Sweeps task, and the Continuous Acquisition task. The Continuous Acquisition Task is a ‘tape recorder’ that saves continuously acquired data to a gap-free Axon Binary File (for later off-line analysis using other programs).
3. Fast Repeat (LTD) Sweep Stimulation with no time between sweeps Sometimes is is useful, particularly when recording long duration EPSCs during Fast Repeat (LTD) 1 or 2 Hz sweep (and pulse) stimulation, to record the whole 1000 or 500 msec sweep so as to record all of the EPSC tail current. In some data acquisition systems, it is impossible to stimulate and record whole contiguous sweeps (with no time delay between them) because of the time required to save the sweep before starting to stimulate another sweep. In WinLTP's multitasking/multithreaded program, stimulation output can precede at the same time as saving the sweep to disk. The figure below shows an example of this contiguous sweep stimulation and acquisition using Fast Repeat Sweep stimulation produced by 4 contiguous 1000 msec long P0sweeps every 1 second. This was produced by the following Protocol Builder script:
The traces in the bottom P0 Sweep Stimulation graph show a 1000 msec duration P0sweep with 1 S0 pulse/sweep and 20 S1 pulses/sweep at 50 msec pulse interval. The traces in the middle P0 Stimulus Sweep Acquisition graphs shows the recording of the last 1000 msec duration P0sweep showing the one S0 pulse in the AD0 trace and the 20 S1 pulses in the AD1 trace. The top traces in the Continuous Acquisition graphs show the output recorded for the S0 pulse at 1/sec in the AD0 trace and the S1 pulses at 20/sec in the AD1 trace.
4. PopSpike Amplitude and Latency WinLTP is somewhat unique in doing on- and off-line measurements PopSpike Amplitude and Latency, although one would expect this in an LTP program. The PopSpike Amplitude is calculated as the amplitude from the PopSpike peak to the intersection with an interpolated tangent dotted line drawn between the pre-PopSpike peak to the post-PopSpike peak (shown be the solid vertical line in the figure below). PopSpike Latency is calculated as the time between the occurrence of stimulus pulse and the PopSpike peak. PopSpike Amplitude and PopSpike Latency do not depend upon DC baseline or Peak Amplitude.
5.
Analyzing All S0- and S1-Evoked Synaptic Responses in a Sweep
Sometimes the experimenter is interested in examining each postsynaptic response evoked by a stimulus pulse in a train, in which case the baseline and synaptic response of each pulse is analyzed (as shown in the figure above). Alternatively, the synaptic responses evoked by train stimulation can be treated as a whole train object in a special manner by WinLTP.
Analyze every pulse in train using the baseline of first pulse as the
baseline for each pulse First,
the synaptic responses to each train pulse may be analyzed relative to the
baseline of the first pulse in the train as shown in the figure below.
Analyze whole train by analyzing only first pulse in train but detecting whole train Alternatively,
if
the baseline and response of only the first train pulse is used, all stimulus
artifacts are blocked, and the time of measurement is set sufficiently long to
encompass the whole train, then the synaptic response of the entire train will
be measured. With this analysis, the peak amplitude of the largest EPSP in the train
and the area of the synaptic
response of the entire train can be obtained.
Removal of stimulus artifacts is necessary to permit accurate calculation
of area and peak amplitude without contamination by stimulus artifacts occurring near the fEPSP peak.
Note the one measurement in the spreadsheet, one for the first pulse,
e.g. the whole train.
7. Stimulus Aritifact Blanking Stimulus artifacts can also be removed or blanked out, as shown by the figure above (Analyze whole train by analyzing only first pulse in train but detecting whole train), and the figure below. Stimulus artifact blanking is useful 1) for determining the area or peak amplitude of a whole train which could be seriously distorted by the stimulus artifact, 2) for determining the peak amplitudes of individual EPSPs when the stimulus artifacts are riding on top of the previous EPSP, and 3) 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.
In addition to capturing and analyzing raw sweeps, the WinLTP can also do on- and off-line signal averaging of these sweeps, blank out the stimulus artifacts if required, and low-pass filter the sweeps. Signal averaging occurs first, then stimulus artifact blanking, and finally low pass filtering. Single raw sweeps
can either be (i) low-pass filtered, (ii) stimulus artifact blanked, or (iii)
stimulus artifact blanked and then filtered (top part of the figure below), but
not first filtered and then stimulus artifact blanked.
The insets show a patch-clamp recording of an EPSC from one raw sweep
(left trace) showing substantial noise and a large stimulus artifact at the left
of the trace, the sweep that has been digitally filtered to reduce the noise
(note the large filtered artifact, right top trace), the sweep with the stimulus
artifact removed (middle trace), and the stimulus artifact blanked sweep that
has then been filtered (right bottom trace).
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