PowerPoint Presentation

HowTo 03: stimulus timing design (hands-on)

•Goal: to design an effective random stimulus presentation

_end result will be stimulus timing files

_example: using an event related design, with simple regression to analyze

•Steps:

0. given: experimental parameters (stimuli, # presentations, # TRs, etc.)

1. create random stimulus functions (one for each stimulus type)

2. create ideal reference functions (for each stimulus type)

3. evaluate the stimulus timing design

•Step 0: the (made-up) parameters from HowTo 03 are:

_ 3 stimulus types (the classic experiment: "houses, faces and donuts")

_presentation order is randomized

_TR = 1 sec, total number of TRs = 300

_number of presentations for each stimulus type = 50 (leaving 150 for fixation)

"fixation time should be 30% ~ 50% total scanning time

_3 contrasts of interest: each pair-wise comparison

_refer to directory: AFNI_data1/ht03