The overall goal of this procedure is to perform MR Imaging in children and adolescents during the performance of an emotional oddball task. This is accomplished by first designing a child appropriate emotional oddball task. The second step is to allow participants to practice performing the task in a mock scanner environment.
Next, the participants perform the same task in the MRI scanner. The final step is to analyze the behavioral and imaging data. Ultimately, functional imaging during the emotional oddball task.
In schizophrenia first degree relatives is used to show decreased activation in fronto striate circuitry and response to target stimuli in at-risk children and adolescents. The main advantage of this technique is that it allows for non-invasive imaging of the brains of children and adolescents while they are engaged in cognitive functions. Although this method can provide insight into schizophrenia, it can also be applied to other developmental psychiatric illnesses such as bipolar disorder or autism or other brain disorders such as post-traumatic stress disorder.
Generally, individuals new to performing this method will struggle because there are many steps to creating experimental design, acquiring the images, programming the analysis and image processing pipelines, and applying the correct experimental designs to their project. Participating children and individuals with neuropsychiatric conditions also experience difficulty because the procedures require them to remain still during a typical MRI session while completing behavior tasks. In addition, the procedures requires clear communication and information dissemination between experimenter and participant, which requires a considerable amount of training.
To begin, use Siegel software to generate an event-based behavioral task that presents infrequent target stimuli, such as a circle within a sequence of more frequent standard stimuli, such as scrambled images. Select a set of aversive stimuli and a set of neutral stimuli from the International Effective Picture System database. These images are rated on a scale of one to nine with higher numbers indicating a higher positive level of valence and arousal.
Select a set of images that are age appropriate to the study group, such as pictures of snakes, spiders, or other animals. Program the task script so that images are presented in a pseudo randomized order for 1, 500 milliseconds with a 500 millisecond mean inter present target stimuli and task irrelevant neutral images no more frequently than every 15 seconds and make each about 4%of the stimuli. Be sure to jitter the event onset times to provide better hemodynamic response function resolution, create a total of eight sets of images, one for each of eight functional runs.
Recruit participants between the ages of nine and 18 who are at familial high risk for psychosis, as well as healthy controls. Obtain informed consent from participants or legal guardians and ascent from minors who are taking part in the study. Begin by placing the participants in a mock MRI scanner to familiarize them with the MRI environment.
Then ensure they understand the task instructions and play an audio recording of scanner noise while they complete a practice run of the behavioral task. Have the participant use the same MRI safe input box that will be used during the real scan and instruct them to press one button with their index finger in response to all target stimuli and another button with your middle finger for all other stimuli. Once the subject is comfortable in the mock scanner, place them in a 3.0 Tesla MRI scanner.
First, acquire a set of structural images including a 3D co-planner anatomical T one weighted image, using a spoiled gradient recalled acquisition pulse sequence. Then acquire functional imaging data using a gradient echo echo planner imaging sequence with full brain coverage. To measure brain activity during the behavioral task, use this imaging sequence for each run of the behavioral task present the task in eight functional runs each lasting approximately four minutes and consisting of 120 imaging time points.
Begin analysis by pre-processing the images open FMRI expert analysis tool within FSL software and select first level analysis and pre stats. Then in the data tab, select the number of input images and the path to each of the MR images. Also set the output directory.
Enter the total volumes, the number of discarded acquisitions, and the TR.Next, in the pre stats tab, set motion correction to MFL spatial smoothing full with half maximum to five millimeters and select slice timing correction. Do not select B zero UN warping and intensity normalization and select BET brain extraction and high-pass temporal filtering. Then in the registration tab for the main structural image, enter the path to the subject's skull stripped T one scan.
Use a linear normal search with at least six degrees of freedom. Then select standard space and enter the path to the MNI Atlas image. Use normal linear search with 12 degrees of freedom, exclude participants with head motion greater than three millimeters.
Now, to compare data between task conditions within a single run, select first level analysis, stats, and post stats. In the data tab, set the number of inputs and enter the path to each of the MR images and the output directory. Enter the total volumes, number of discarded acquisitions and the TR.Next, in the stats tab, select use film, pre whitening and full model setup.
Set the number of original EVs to the number of task conditions. For each condition, select custom three column format from the basic shape menu and double gamma HRF from the convolution menu and select the text file containing the task timing format. This text file in three columns with one entry for each event.
The first column should contain the onset time. The second should contain the duration and the third, the event weight. Now in the contrast and F test tab, create one contrast for each test condition and comparison in post stats select cluster from the thresholding menu and set the Z threshold and cluster P threshold to 2.3 and 0.05 respectively.
Then in the registration tab, select main structural image and enter the path to the subject skull. Stripped T one image. Use a linear normal search with at least six degrees of freedom and select standard space.
Enter the path to the MNI Atlas image and use a normal linear search with 12 degrees of freedom. Next, for second level analysis, compare data between runs. For each task condition, select higher level analysis and stats, plus post stats.
Then in the data tab, select inputs are lower level feet directories. Set the number of inputs and enter the path to each of the MR images. Also, enter a path for the output directory and the total volumes number of discarded acquisitions and the TR.In the stats tab, change mixed effects flame one to fixed effects.
Using the model setup wizard, select single group average and process. Then in the post ads tab, select cluster in the thresholding menu and set the Z threshold and cluster P threshold to 2.3 and 0.05 respectively. Now to compare data between subjects for each task condition across all runs, select higher level analysis and stats plus post stats.
In the data tab, select inputs are 3D COPE images from feet directories. Set the number of inputs and enter the path to each of the images. Enter the output directory, total volumes, number of discarded acquisitions, and the TR.Then in the stats tab, select full model setup.
Set the number of EVs equal to the number of group variables and covariates. Enter the values for each subject for each ev. Finally, in contrast, send F tests.
Add a contrast for each test variable and for each contrast. For each test variable, set the contrast by selecting one in the column under the appropriate ev. For each contrast, set the first value to one and the second to negative one.
Then in post stats, select cluster in the thresholding dropdown menu and set the Z threshold and cluster P threshold to 2.3 and 0.05 respectively. Here we can see activation maps showing between group differences as seen. Here, the familial high risk group showed greater activation than controls during target processing.
In these areas, controls showed greater activation than the familial high risk group during the target processing. Here, the familial high risk group activated more than controls during the aversive, greater than neutral contrast, and here the controls activated more than the familial high risk group during the aversive, greater than neutral contrast, these activation maps showed age-related group differences. The areas seen here have a greater positive correlation with age in the familial high risk group than in controls during target processing.
Here we see areas with a greater positive correlation with age in controls than in the familial high risk group during the aversive. Greater than neutral contrast. Don't forget that working with individuals in the scanner environment can be extremely hazardous Precautions such as MRI, safety screening and appropriate safety and comfort precautions and training should always be taken while performing this procedure.
This techniques has also created a new method for visualizing abnormal neural processes in brain disorders such as schizophrenia, autism, and post-traumatic stress disorder. While attempting this procedure, it is important to remember to communicate with your participants to help keep them calm and focused. Once mastered, this technique can be done in two hours if it is performed properly.
Following this procedure, other methods like EEG can be performed in order to answer additional questions about neuro synchrony in similar cohorts.
