Preprocessing the data set:
The purpose of the preprocessing stage is to remove artifacts or unwanted segments from the data, as well as apply a filter. To begin preporcessing, click the "truncate” icon in the "Data Processing" Box. This option will open a window which allows you to remove specific sections of the data as you see fit. This can be done by selecting the portion of the data you wish to remove (either by mouse or entering the time points) and clicking “cut”. Once finished, click “save and close”.
The “Remove discontinuities” option allows for discontinuities in the data set (e.g. periods of empty data resulting from removing sections via truncating) to be removed this is done by clicking the “remove” option. The use of these options is determined by how the data collection process went and may not always be needed.
However, filtering the data is required for the analysis of all data sets. To accomplish this step, select the “apply” option, this will open the “Data filtering” page. Once this page is opened, select “band pass” from the filter options at the top of the screen and then click “filter”. The data will then be filtered, as indicated by a chance in the wave forms displayed in the window. When satisfied, click “save and close”.
Computing Hemodynamic states:
Once a filter has been applied to the data, a help dialog window will open notifying you that filtration has been completed and prompting you to compute the hemodynamic states.
To compute hemodynamic states, first click “set parameters” within the “Hemodynamic states” box. You will be directed to a page asking you to chose a spectum from the top center dropdown window to compare your data against. For the purposes of this lab, we have choses to use the spectrum from J.M. Schmitt. This can be chosen from the dropdown menue labeled “spectrum” (image: set parameters). Once the parameter has been set, click “save and close”.
At this stage, the data set has been prepared, filtering has been carried out, and the parameters for hemodynamic states have been set. You may now click the “compute option” in the “Hymodynamic states” box. This concludes the essential steps required for level 1 analysis of an individual participant.
Data Viewer box (Optional):
The Data Viewer box serves two functions, allowing you to manually review channels from data collection as well as map the hemodynamic states.
Manually selecting channels allows you to manually exclude or include channels. This can be of use if the computer interpritation of the cahnnels is not trusted, or to meet a specific parameter for the data. The second option, mapping hemodynamic states (Image:mapping hemodynamic states) allows you to visualise the changes that occurred during the duration of the test. From this menu it is possible to save a figure as well as an animation of participant’s brain. A completed file can be directly loaded thorugh the load option.
