Experiment Details


The experiment protocol is located on Dropbox at: DJW_Projects/02_FOOD_REG/PAPERWORK/fMRI_Food_Regulation_Experiment_Protocol.gdoc

The fMRI scan protocol is here.

Main Task

The main task involved three discreet phases.

  1. Pre-Scan
    • Food liking ratings
    • Main task training
  2. Scan
    • In-scanner trials
      • 9 runs
  3. Post-Scan
    • Food liking ratings (repeated)
    • Food taste ratings
    • Food health ratings

The code for the Main Task (including the instructions) was written in MATLAB and uses Psychtoolbox.

The Main Task Code includes many files, but the key scripts are:

  • runPreMRI.m
    • Launches the experiment instructions and the initial Food Liking Rating
  • runSession.m
    • Launches a run of the experiment in-scanner
  • runPostMRI.m
    • Launches the post task ratings of Liking, Taste, and Health


The localizer task invovled two discreet phases.

  1. Pre-Scan
    • Localizer task training
  2. Scan
    • In-scanner trials
      • go-nogo: 2 runs
      • switching task: 1 run

The code for the Localizers was written in Python, using the Psychopy toolbox.


The Go-NoGo task scripts include both a practice and fMRI version. The main difference is that the fMRI version waits for the scanner to send a 5 to progress.

The Go-NoGo task was based on Wager et al. 2005. We used the letters ‘m’ and ‘w’ as the ‘go’ and ‘no-go’ stimuli, requiring the execution or withholding, respectively, of a keypress response (counterbalanced).

After presentation of a 500ms fixation cross, participants had 450ms to respond to the stimulus.

There were two types of blocks presented: low-go blocks, in which 20% of the trials required a response, and high-go blocks, in which 50% of trials required a response. The beginning and ends of these blocks were not indicated to participants.

A total of 24 blocks (12 of each condition), containing 12 trials each–a total of 288 trials–were presented. The rapid event-related design with clustered events is expected to maximize power (Liu 2004). The task was broken into two equal (144 trial) sessions for scanning to reduce fatigue.

Switching Task

The switching task scripts also include both a practice and fMRI version. The main difference is that the fMRI version waits for the scanner to send a 5 to progress.

The attention switching task showed subjects a pair of images, one face and one house, on each trial. The images were overlaid directly on top of each other with each image’s opacity reduced so that both images could be clearly deciphered. On each trial subjects were directed to focus their attention either on the Face or the House image, which was indicated both by text on screen indicating “Face” or “House” and the background color of the image (i.e. a different background color for Faces andHouses). On Face trials, subjects had to determine the face’s gender, using a keypress to indicate their response. On House trials, subjects had to indicate whether it was an old or modern house, using a keypress to indicate their response.

There were four total response possibilities, and four corresponding buttons to press. Participants had up to 1 second to respond. The inter trial interval was between 1s and 6s, uniformly distributed. A total of 80 trials were presented in a single session.


Upon completion of all tasks we asked subjects to complete the following questionnaires:

  1. Three-Factor Eating Questionnaire
  2. Rapid Food Screener
  3. Barrat BIS 11
  4. Perceived Stress Scale

There is also a questionnaire key, that will be helpful for data analysis.