Process Settings

Before using Review menu, Process, WAVE or MEAN functions or Review menu, Include, SCREEN functions, Process settings must be correctly set. Additionally, the channel selection, shown by a 1 or 0 to the left of each channel in the multi-block Review, must be set so that only the channel/s which are to be processed are selected on (1).

Adjustment of WAVE process settings can be refined, if the settings initially chosen (e.g. while a macro was being recorded) were not optimal. The completed macro would be run to the point where the WAVE window appeared, then Halt in the macro window would be clicked to stop it. WAVE settings could then be changed by double clicking on the WAVE Review and selecting Process, Set parameters. to get the process settings panel. The WAVE sliders could be changed, then the Process Settings panel Closed and the >< button on the WAVE Review clicked so that the same block would be re-processed with the new settings. This could be repeated for different blocks (moving forward or back through the blocks using the > and < buttons) until a best compromise was reached. Process settings would then be saved from the Process settings panel using the name originally registered in the macro. From then on the macro would use the new settings.

Process settings relate to the Review the panel is opened from. If the Process settings panel is evoked from a particular Review, it will affect the settings of that Review only, and not Reviews previously opened. However, if a new Review is created (e.g. by using a Process function), it will use the Process settings of the Review it was created from.

 For example, if Review#3 is created from Review#2, Review#3 will adopt the process settings of Review#2. If the Process settings of Review#2 are changed after Review#3 is created, it will not affect the settings of Review#3, but the settings of Review#3 can be subsequently altered by evoking the Process settings window directly from Review#3.

Process settings are set to default values when PSYLAB starts. These values are contained in the PSYLAB configuration file. This file is changed by using Toolbar menu, File data, Save settings now, which will make it adopt the current Process settings. Other settings are also saved with this function, for example current Block settings and the position of each window).

Process settings may be stored or loaded using the File menu on the Process settings panel. This allows any number of different settings to be saved and loaded in when required. Only current Process settings and current process channel selection are stored with this operation. If 'macro record' is on when the Process settings panel is evoked, the system will require the File operation before closing the panel so that a file name (.PRO) can be recorded in the macro to load in required process settings when running under macro control.

Process settings are used to control the operation of PSYLAB's inbuilt processing functions. To date (May 1997), these are WAVE, MEAN, AVERAGE and USER PROCESS functions. There are no relevant Process settings for AVERAGE and USER PROCESS, but the 'Select screening range' panel may have relevance for either of these, as it allows the SCREENING function (found in Review menu, Include) to eliminate blocks before these functions operate on them.

The following is a brief example of how process settings may be set differently on two different process Reviews to allow WAVE processing of Skin Conductance and Respiration: If there is a multiblock Review#2, first select only the SC channel, then double click on Review#2 to get the review menu, select 'Process, Set parameters' to adjusted Wave parameters to analysis of Skin Conductance. Select File, Save process settings as, then close Process Settings. Select Process, Wave to generate Review#3 showing Wave processed SC. Now go back to Review#2, select only the respiration channel and change the process settings for Respiration analysis. Generate a Wave Review#4 for the respiration wave. The process settings for Review#3 and Review#4 will remain differently set. They can be viewed or adjusted by double clicking on Review#3 or Review#4 and selecting Process, Set parameters. The effect of changing parameters on the Wave function can be tested using the >< button on the Review, which re-processes the same blo using the new settings.

Select Wave Parameters

The WAVE parameters set by the four vertical sliders shown in the WAVE settings panel above are '2, 2, 2, 3%'. The 2s mean that the WAVE detection system will look for one point plus two others to establish each aspect of the wave. The + slope (second aspect) is the first part of a fluctuation that the wave detection system recognises. Thus, as in this example the second parameter is set to 2 (the middle one of the three 2s), two points in the wave will be compared with the adjacent point. If all three points describe a section which consistently increases, this will be recognised as a 'valid slope' and the WAVE detection system will then proceed to look for an associated peak and onset. Otherwise, it will move on to look at the next three points, and so on until it reaches the last point in the block.

If the value for detecting the slope is set to a high number, a lot of waves will be missed altogether as the criterion of finding that number of points which consistently increase will be harder to find: only one point needs to have the same value or a lower value than the adjacent point for the criterion not to be met. The criterion for the + slope is that one point plus the setting number of other points must all be found to change consecutively in a positive direction. The criterion for the onset and peak aspects is that the points must all change in a negative direction OR be of equal value.

The criterion for the onset and peak aspects is that the points must all change in a negative direction OR be of equal value. This criterion is slightly easier to meet than that fot the slope, as digital systems work incrementally, so in any wave-form the likelihood of two points having exactly the same value is finite (it is determined by the resolution of the digital conversion system). For this reason, these parameter settings may be put higher without necessarily imparing sensitivity to WAVE detection.

The fourth slider in this group controls the minimum allowable amplitude of a detected wave, expressed as a percentage of the full scale range. Full scale range is the position that the Scale switch is set to on the amplifier when the recording is made. It is useful to disallow very small changes, otherwise Waves can be detected when there is a small amount of noise in the wave-form.

The compression slider allows the system to use less points than were recorded, so that a shallow slope can effectively be made steeper by increasing compression. This can be helpful, as a small amount of noise in a shallow slope can continually cancel slope detection resulting in poor wave detection. Compression setting relates to sample rate: if a compression setting of 2 is recommended at 20 samples per second, increase it to 4 at 40/second, 10 at 100 per second etc.

Allow onset at block start allows an onset to be established even if the wave begins before the start of the block and therefore does not show a flat or negative going onset slope. This may or may not be desirable. It makes it more likely that the system will detect a wave early in the block, but if 'latency of onset' of the wave is a required parameter, the onset point will not be correct if this option is checked. Manual score only prevents the automatic Wave detection system operating.

The other controls relate to how the wave system works with the Results Format Program to put Wave information into the results file. They are discussed in the Results Format Program details.

Results Format Program details.

 A few typical WAVE settings for different purposes are as follows:

Respiration analysis:

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WAVE parameters: 2, 2, 2, 3%

Compression 2 (@ sample rate 20)

Only wave totals

Skin Conductance analysis:

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WAVE parameters 3, 2, 3, 2.5%

Compression 2 (@ sample rate 20)

Pulse Wave analysis

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WAVE parameters 2, 1, 2, 12.5%

Compression 1(@ sample rate 20 or 40)

Select MEAN parameters

The MEAN function produces Mean (average of all data points per channel in a block), Standard deviation, Bad timer value count, Maximum, Minimum, and Absolute deviation. These values are sent to the Results window for each channel selected in the MEAN Review. The RFP language is used to allow user control over how this information appears in the Results window using the following Dat functions to express the information:

Dat1     Mean

Dat2     Standard Deviation

Dat3     Out-of-range timer value count

Dat4     Maximum

Dat5     Minimum

Dat6     Absolute deviation

These Dat functions are filled with respective information when the OK button on the MEAN Review is clicked. This will also cause the RFP (Results Format Program) to run once. Information for each channel in the MEAN Review is produced, a subscript to the Dat functions allows selection of each channel, e.g. Dat1(01) is Mean of channel 1.

Results format program

The only adjustable parameters for the MEAN function are 'valid timer channel values'. The two horizontal sliders select maximum and minimum values, to define a range outside of which readings from the Interval Timer (e.g. I.B.I.) are considered as errors. The If the 'Omit bad timer values' box is checked, every value in the Interval Timer signal in each block which is outside the valid range causes an 'artifact counter' to increment, and the bad value is omitted from the MEAN calculation and the number of data points used in the calulation is reduced by one.

This allows removal of values in the timer channel that result from incorrect triggering of the Interval Timer, as when this occurs the value will generally be either double (if a trigger is missed), or a great deal less (if it double triggers) than expected values.

Values often used are 500 and 1500, which can be converted into Heart Rate values of 45 to 120 BPM. It is possible that there may be more than one Interval Timer channel in a record, e.g. I.B.I. (Inter Beat Interval), P.T.T. (Pulse Transit Time). and RT (Reaction Time). The out-of-range system currently only allows one set of values to be specified for all such channels.