Typically, the design of an fMRI experiment is completely fixed in advance. Dynamically Adaptive Imaging allows the task, stimuli, MRI acquisition parameters or the subject’s behaviour to be contingently modified online, making imaging studies more sensitive and more robust. The system is currently in the piloting stages. This page includes SOPs for the pilot experiments which have been successfully run.
For comments or questions please contact RhodriCusack or MicheleVeldsman.
DAI set up
A simple overview of the current hardware and software set-up (relevant to the pilot studies) is illustrated below. Overall control and processing is handled by the stand-alone Linux machine, between the scanner console and stimulus delivery machines.
Configuring the Siemen's console
Enable Advanced User. Using ctrl+esc access 'run' in the start menu and input <ideacmdtool>. Check the send IMA switch is turned on (option 5). This allows the siemens machine to send images to the real-time machine.
Configuring the DAI Linux machine and Stimulus Delivery machines
SOP: Visual Response Contrast Function
Brief Description
Adaptive staircase procedures efficiently characterise perceptual thresholds. We adapt this for BOLD imaging using a Bayesian maximum likelihood estimation of the BOLD response threshold in V1 ROIs as a function of contrast. Participants viewed varying levels of contrast in sine-wave gratings presented as dynamic moving images surrounding a central fixation target-spotting task (see VisualContrastResponse for experimental details and program).
To provide a known answer rather than measuring true response contrast thresholds, the stimulus delivery program superimposed a sigmoidal function with a 50% point at one of two contrasts (2.5 or 6.5, arbitrary units). The real-time machine then attempted to discover this contrast using the participant's own BOLD response.
The adaptive procedure presents the stimuli around the contrast level of the model best describing the threshold at that point. The constant stimulus procedure presents stimuli in a randomised order, irrespective of threshold estimates.
Operating Protocol
SOP: Searching Broad Stimulus Sets
Brief Description
Operating Protocol