An Introduction To Presentation MACCS

Transcription

1 An Introduction To Presentation MACCS

2 Outline Experiment structure Tabs SDL and PCL Script structure: Settings and setup in your script Events PCL, logic and loops page 2

3 Experiment Structure An overall 'Experiment' file Composed of one or a number of 'Scenario' files Scenario files are played in order one after another page 3

4 Experiment Structure Scenario files may be separate SDL and PCL files more on this later Experiment Scenario 1 (SDL) PCL 1 Scenario 2 (SDL) PCL 2 page 4

5 Experiment Structure Or both SDL and PCL can be encompassed in the one scenario file Experiment Scenario 1 (SDL/ PCL) Scenario 2 (SDL/ PCL) page 5

6 Experiment Structure Depends on personal preference/ style Having SDL and PCL scripts in the same file makes it easier for me to edit Easier to open all you need if all in one file I tend not to use SDL only as very limited, therefore will not be covered here page 6

7 Tabs The Experiment file contains tabs to cover all of the needed components and settings: page 7

8 Tabs The Main tab shows the name of the experiment and location to place log files, both of which can be edited in this tab: page 8

9 Tabs - Scenarios The Scenarios tab allows you to add stimulus directory and scenarios: page 9

10 Tabs Settings (General) Check 'Wait for return to start scenario': page 10

11 Tabs Settings (Response) Best to add buttons to 'default', then 'test': page 11

12 Tabs Settings (Video) Your PC will probably only have one video card available. This is fine for testing When you get to either the ERP or MEG lab this will need to be changed to the 'Radeon' driver 'Current setting' experiments should be fine for most page 12

13 Tabs Settings (Audio) 'Primary Sound Driver' is the typical setting page 13

14 Tabs Settings (Port) Port codes in the ERP and MEG labs are sent by parallel port Your PC probably won't have a parallel port so you will need to change these settings in the lab ask for help To test and run your script on your own PC, click 'Add' Select an available port, usually 'COM1' page 14

15 Tabs Settings (Logfiles) You can typically leave most of these settings alone A very useful function is the prompt for Subject ID When you run the experiment you will see a window in which to type the subject's ID, and press 'enter' It's not necessary to adjust any settings in the 'Advanced' tab page 15

16 Tabs - Summary Save your experiment name Add LOG and STIM folders Add scenarios 'Wait for return to start scenario' Add buttons Add an output port Select 'Prompt' for Subject ID page 16

17 SDL and PCL Two language styles implemented in Presentation script SDL is most useful for: Implementing initial settings Loading and preparing stimuli Creating 'Events' PCL is most useful for: Logic functions Loops Output files 'Doing the work' page 17

18 SDL and PCL SDL = WHAT PCL = HOW page 18

19 Script Structure - SDL Settings Load Stimuli Arrange Stimuli Define Events page 19

20 Script Structure SDL - example Settings example: ISI RGB Sends port codes Note comments marked with a # page 20

21 Settings and Setup Port code pulse width: Onset Pulse width page 21

22 Settings and Setup You can define your own parameters. Easy to find Make changes in only one location Here is the substitutions: same example with parameter page 22

23 Script Structure - SDL Settings Load Stimuli Arrange Stimuli Define Events page 23

24 Load Stimuli A visual stimulus example: Can be '.bmp' or '.jpg' Your own shortcut page 24

25 Load Stimuli An auditory stimulus example: Must be '.wav' file; up to 8 channels; 8, 16 or 24 bit page 25

26 Script Structure - SDL Settings Load Stimuli Arrange Stimuli Define Events page 26

27 Arrange Stimuli Back to our visual stimulus example... It can be very useful for easier later reference to arrange stimuli into arrays: An array is just a type of LIST page 27

28 Arrange Stimuli Instead of having to call up the right filename, simply call the next item in the appropriate array Can also call up an item based on it's reference number in the array Especially useful for randomisation page 28

29 Script Structure - SDL Settings Load Stimuli Arrange Stimuli Define Events page 29

30 Define Events Example including response dependent trials: Some text Picture within an event within a trial page 30

31 Define Events Note that you don't need a separate trial for each stimulus or stimulus type: Duration may be left as default, be some other fixed length, or depend on response This trial includes response commands only button 1 is correct page 31

32 Define Events We use a photodetector in the MEG lab for greater timing accuracy It detects a white box presented in the corner of the screen You should include a white box for any stimulus presentation that also has a port code Just add this box command to appropriate trials, as well as the $VISTRIG... parameters to the top of the script. We will ensure it works correctly in the lab page 32

33 SDL - Summary Provides settings, stimulus loading and arrangement, and events or trials # can be used for comments, or to temporarily remove lines Custom parameters can be used ( $ABC... ) Useful to arrange stimuli into arrays Stimulus commands are arranged within events, which are arranged within trials You don't need a separate trial for each stimulus or even each stimulus group Add 'box' command for MEG experiments page 33

34 PCL If you include PCL in the Scenario file, you must use the begin_pcl command Open an output port in order to send port codes Include a command to automatically name your logfile so it doesn't get lost You can use # as a line break or box If you keep your PCL separate, tell the scenario file about it in the header: page 34

35 PCL, Logic and Loops In this example, we will present each image twice, in random order A good way to accomplish this is to use an array, with index numbers representing categories Note that in PCL, many commands are in the form name.command(settings) ( sequencea is a name, not a command) We're filling an array with 8 ones and 8 twos. The remaining 8 will be zeros shuffle() randomises the array page 35

36 PCL, Logic and Loops Start item Increment End item First number page 36

37 A Word About Randomisation When you use random functions, you don't always get what you expect i.e. Clumping You generally won't get all your items shown about the same number of times You will therefore generally want to constrain the random! Here we have arrays of ones, twos threes and fours serving as indexes for our stimulus arrays We can now be sure all our images will be shown the same number of times each page 37

38 PCL, Logic and Loops We're ready to commence the main task of presenting stimuli The introduction screen and fixation cross are presented easily enough: Trials are generally presented using loops: page 38

39 PCL, Logic and Loops A typical loop: The index i is only valid inside the loop You must increment the index manually Has both pros and cons page 39

40 PCL, Logic and Loops Note that new lines and spacing are irrelevant in Presentation, so this is exactly the same loop: page 40

41 PCL, Logic and Loops We will need more indexes to loop through the arrays for each category: faces, cars and butterflies We set the picture to be one of the faces We give the logfile the description of that face from the beginning of the script We tell the port we want 1 to be sent for faces We present the face, increment the face index, and present a fixation cross == means is equivalent to * * * * page 41

42 PCL, Logic and Loops Note the use of elseif and else statements Repeat the above procedure using the arrays and indexes for cars and for butterflies Note that we want responses to be valid for butterflies, so we use the trial that includes a target button page 42

43 PCL Output File Stimulus manager && = logic and = logic or page 43

44 Testing and Debugging 'Analyze' 'Run Scenario' 'Error Box' page 44

45 Run Your Experiment 'Run Experiment' page 45

46 Experimental Design Considerations Repetition Signal-to-noise-ratio AT LEAST 60 trials per condition. Breaks Happy and comfortable subjects Tiring Procedure length Compromise between ideal number of trials and subject fatigue Performance of the conductive gel will decline with time About two hours or less. At MEG, maximum block length is 20 min page 46

47 Experimental Design Considerations Sufficient port codes Allocate different port codes to each category Err on the side of excessive port codes 256 in ERP lab, about 16 in MEG lab Visual offset and ISI Visual ERP component Do not overlap with epoch or pre-stimulus (baseline) interval. Assuming the allocation of a 200ms baseline interval, and adding to this the 100ms offset component, you need an ISI of at least 300ms. Add some more just to be sure! page 47

48 Resources Presentation help file is okay, but confusing Neurobehavioral Systems forum: ERP Lab Server Library: \\Currawong\ERP\LIBRARY page 48