Difference: DocsSectionsBuildingExperiments (6 vs. 7)

Revision 726 Sep 2011 - Main.MarjoleinVanDerWaal

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Building Experiments

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  Sometimes a marker signals a time point around which data should be collected. For example, if you are building an ERP-based BCI, you might want to collect a certain amount of data after each stimulus. For that purpose, each marker can specify a segment of data that should come along with the event. The DataSelection table indicates which markers call for data selection and also the time period of data selection relative to marker onset.
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The DataSelection table consists of a marker column, a begindata column, and an enddata column. Data selection may start before or after onset of the marker, indicated by negative and positive numbers respectively. The end of data selection can again be before or after the onset of the marker specified in the marker column, or you can use a new incoming marker by entering the name of the new marker (with or without extra timing). If multiple endtimes, seperated by a comma, are specified, the one that happens first will end the data selection.
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The DataSelection table consists of a marker column, a begindata column, and an enddata column. Data selection may start before or after onset of the marker, indicated by negative and positive numbers respectively. The end of data selection can be before or after the onset of the marker specified in the marker column, when a new marker arrives (with or without extra timing), or when nothing happens for a specified period of time (timeout). If multiple endtimes, seperated by a comma, are specified, the one that happens first will end the data selection.
 
marker begintime endtime datasource
mrk1 -0.5 2  
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mrk2 0.5 mrk3  
mrk3 0 mrk3, mrk4  
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mrk2 0.5 mrk3+1  
mrk4 0 mrk4, mrk5, timeout(3)  
  Table 3: DataSelection table
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The table above shows an example of a data selection table. The data selection of mrk1 will start half a second before onset of the marker and end 2 seconds after the onset.The data selection of mrk2 will start half a second after the onset of mrk2 and will end when the new marker mrk3 arrives. mrk3 will start data selection immediately and this will end when a new marker mrk3 or the marker mrk4 arrives. For more examples of this data selection timing see Data-carrying events in the Architecture section.
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The table above shows an example of a data selection table. The data selection of mrk1 will start half a second before onset of the marker and end 2 seconds after the onset.The data selection of mrk2 will start half a second after the onset of mrk2 and will end one second after marker mrk3 arrives. Marker mrk4 will start data selection immediately and this will end when a new marker mrk4 arrives (in other words, after the first occurrence of marker mrk4, every new marker mrk4 will both end the previous period of data selection and start a new period). This sequence ends when marker mrk5 arrives or when no markers come in for 3 seconds. Note that if ending markers do not set the end of data selection and no timeout is specified, corresponding processing steps (with timepoint DATA) will never execute.

Timing offsets can also be specified in number of samples. In that case, the number should be followed by a '#' symbol (for example, 1024#). Of course, time points that are specified in seconds will also be rounded off to the nearest sample number by BrainStream's internal processing.

  The datasource column is optional. If multiple data sources are used in the experiment, the datasource column specifies from which source the data should be collected. If only one data source is involved, BrainStream will automatically collect data from this single source only.
 
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