Event related design question

AFNI Message Board
1

Dear AFNI experts,

I have some silly questions about event related design. Especially about the duration of the stimulus as well as the jitter.

I have an experimental design and there is a trial as shown below, specifically, the first screen is a fixation with a duration of 2s, and the second screen to the fourth screen are stimuli with a duration of 1.5s.The last screen is a 1 ~ 2s jitter of blank.

The second screen is stimulus ConA, the third screen is stimulus ConB, and the fourth screen is stimulus ConC. I want to compare the differences between conditions ABC, is there a problem with this experimental design? And is it reasonable to present conditions ABC continuously without jitter between them? Additionally, the TR is 2s.

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Sincerely,
Yang

2

Yang,

To effectively estimate and compare BOLD responses across the three conditions, the following prerequisites are essential from a modeling perspective:

  • Randomizing the sequence of the three conditions.
  • Incorporating intervals and jittering them between the conditions.
  • Increasing and jittering the inter-trial intervals for better separation of responses.

Without these key design elements, achieving your research goals is highly unlikely.

Gang Chen

3

If you're looking for the reasons behind these requirements, start with this good set of "classic" literature on event-related design: