Clampfit 9 has a new analysis option called Event Detection. There are three types of event detection.
1) Template Search (the events are extracted based on their shape)
2) Threshold Search (the events are extracted based on their amplitude)
3) Single-channel search (the events are extracted based on the half-amplitude method).
This note describes Threshold Search for the file cut1a.abf.
In the Threshold Search dialog box, one sets the parameters that Clampfit will use to find events. In this case only the baseline (7.569 mV) and threshold level (54.05 mV) were set. The other options are used to refine the search, such as setting a re-arming value or noise rejection. Please consult the on-line help for details on each of these options.
Once the OK button is clicked, Event Detection begins. The data is scanned until a threshold crossing is detected. If the event is acceptable, one would click on the blue check mark button in the Event Detection toolbar, otherwise an event may be rejected by clicking on the button marked with a blue X. Detection may also be done nonstop by clicking the button marked with two white triangles.
The peak of each event is marked with a symbol and the event is noted above the trace with a mark. Each event’s statistics is also written to the Results window under the Events sheet. Each individual event is also extracted as a sweep to a temporary buffer – the Event Viewer. The Event Viewer shows the events as sweeps. They can be saved and analyzed later if the need arises.
The result of nonstop analysis on the cut1a.abf file.
At the end of the analysis, global Event Statistics provide averages to many parameters.
After the analysis is finished, additional analyses may be performed. With the Events page of the Results worksheet as the active window, one can elect to do Burst Analysis.
Since this is extracellular data, Peak time was selected as the Data Format. A conventional detection method was chosen with the minimum number of events per burst set to 4 and the Burst delimiting interval set to 600 ms. This number was chosen after carefully observing the data file. Looking at the first screenshot, events are clearly clustered in bursts. The longest interval between the main bursts is more than three seconds. Within one section, some peaks are separated by more than one second. In this case, it is a judgment call where to set the interburst interval.
Clicking OK starts the analysis. The results of the analysis are placed in the Bursts sheet in the Results window. In this case, Clampfit 9 identified 7 bursts in the data set. The number of events per burst, Start Time, End Time, Duration, and Frequency are given in the Sheet.
This is the first burst of 5 events bracketed by the cursors.
You can create graphs from the Burst data. Select Analyze / Event Analysis / Fast Graph.
(note the selections for X and Y data).
Clicking OK generates the burst frequency scatter plot.