Brain Imaging & Analysis Center

A Showplay paradigm parameter file (PPF) typically includes a parameter setting section and then a stimulus list table to specify the timing of stimulus events. The stimulus list is organized as a table, with one line for each event. The columns in the table specify the details of each event. The first column can be a text string, but all other columns are numbers (no decimal points). Words and numbers on each line in the stimulus list can be separated by spaces, tabs, commas, or the '|' character. Text words can be entered in upper or lower case. A semicolon (;) acts as a comment character; anything following the semicolon is ignored.

• Column 1: Stimulus name – the name of the stimulus. The stimulus name can be a file name, a text string, or a number (if it is a number it is treated as a pointer into a separate list of text). See Stimulus Names for more information.
• Column 2: Event ID – a user-defined number. You can use any numbering scheme you wish as code values to help identify important stimuli. This value can also be used as external stimulus code to send to another device at the moment this stimulus occurs. See EventCode for more information.
• Column 3: Event flag – a value indicating special processing options for this event. This is a bit-flag where each binary bit value controls a different option. Options can be combined by adding values. See EventFlag for more information.
• Column 4: Start time (ms) – when this event should be performed. The start time is specified in milliseconds since the beginning of the paradigm or the most recent RESET event. See Stimulus Start for more information.
• Column 5: Duration (ms) – how long the event should last. The duration time is specified in milliseconds since the onset of the event. If the duration is non-zero, the stimulus event will be terminated at that time. Termination typically involves erasing visual stimuli or stopping auditory stimuli. The termination behavior can be controlled by settings in the event's EventFlag. If the duration is 0, nothing is done to terminate the stimulus (e.g. if the next stimulus simply overwrites the previous one.) See Stimulus Duration for more information.

• Column 6: X position – for visual stimuli (images, text, graphics, movies) this specifies where the left side of the stimulus should appear on the screen, in pixels relative to the left edge of the display. A negative position value will cause the picture to be centered on the screen.
• Column 7: Y position – for visual stimuli (images, text, graphics, movies) this specifies where the bottom of the stimulus should appear on the screen, in pixels relative to the bottom of the display (if the ShowFlip variable has default value 1; if ShowFlip is 0, then the Y position is relative to the top of the display). A negative position value will cause the picture to be centered on the screen.

Example of a simple stimulus table

;Stimulus         ID  Flg  Onset(ms) Duration  LocationXY
"Press for faces"  1   0        0      4000    -1  -1  ; show text
fix                2   0     4000         0    -1  -1  ; central '+'
tones1.wav         3   0     6000         0            ; play auditory tone
face1.jpg         14   1     8000         0    -1  -1  ; show pictures (1/s)
face2.pcx         14   1     9000         0    -1  -1
face3.pcx         14   1    10000         0    -1  -1
face4.pcx         14   1    11000         0    -1  -1
scene1.jpg        15   1    12000         0    -1  -1
face5.jpg         14   1    13000         0    -1  -1
face6.jpg         14   1    14000         0    -1  -1
face7.jpg         14   1    15000      1000    -1  -1  ; erase after 1 sec
fix                2   0    16000         0    -1  -1
erase              0   0    18000
tones2.wav         3   0    18000
"End of task"      1   0    18000      2000    -1  -1  ; show text
quit               0   0    20000

See Paradigm Parameter File for more information.

See Also:

Paradigm Parameter File, Parameter Settings, EventCode, EventFlag

CIGAL Home, CIGAL Manual, ShowPlay Home, ShowPlay Manual, Introduction Topics, Manual Help