4. fMRI Task Protocols

4.1 Configurations for A/V and response systems:

At CCHMC, our 3T Philips MRI scanner is equipped with an Avotec audiovisual (AV) systems so that  visual and auditory fMRI stimuli can be conveniently presented to research participants.  We use a Silent Vision 6011 projection screen system for presentation of visual stimuli, and a Silent Scan 3100 systems for presentation of auditory stimuli.  These AV components are connected using an A/V switch that permits the desired input source to be easily selected from a numeric touchpad.  Available sources include Mac, PC, DVD player, and CD player inputs.  
 

For those fMRI paradigms that require patient response, a fiber optic response pad (fORP) interface unit is installed in the scanner from Current Designs, Inc.  The fORP interface accepts a variety of handheld button configurations and is compatible with many paradigm software programs including DirectRT, MacStim, Eprime, SuperLab, and Presentation.  For the C-MIND study we use DirectRT for the stimulus presentation and a Current Designs single-button wand in the dominant hand for responses. 

4.2. Tasks:

Both fMRI tasks for the C-MIND project involve alternating blocks of stimuli 64 seconds in duration.

The Story Processing Task involves passive listening to natural speech stories during the “stimulated” condition. The baseline condition is a non-speech broadband noise sweep with center frequencies ranging from 200-4000Hz . The duration of the sweep across this frequency range varies from 0.5-2.0 Hz. This baseline was designed be similar to the frequency range of speech but very non-speechlike because it avoids the rapid temporal transitions involved in speech. The task begins with a stories condition followed by a noise condition. A total of 5 blocks, each having 2 conditions, results in a total scan time of 10 minutes 40 seconds.

A timing file for fMRI analysis is availble here.

In the Sentence-Picture matching Task, the “stimulated” condition involves auditory presentation of a simple active or passive sentence simultaneously with visual presentation of a picture. The “baseline” condition involves single nouns also presented auditorily, repeated four times so that the noun stimuli are similar in duration to sentence stimuli. In both conditions, the participant’s task is to make a button-press response indicating when the auditory stimulus accurately describes the picture. Each condition includes 15 trials (4250 ms each), and these blocks are counterbalanced for yes/no responses, and sentence type. The task begins with a nouns condition followed by a sentences condition. A total of 5 blocks, each having two conditions ,results in a total scan time of 10 minutes 40 seconds.

Response accuracy for the button-press is logged, the format of the log files depends on the stimulus presentation software.

A timing file for fMRI analysis is availble here.

4.3 Implementation in stimulus presentation software:

Both tasks have been implemented in DirectRT, e-Prime, and Presentation software, and materials are available for download from the following page:

fMRI Task Files

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