The overall goal of this procedure is to investigate the neural correlates of recollecting and re-experiencing highly emotional autobiographical memories using FMRI. This is accomplished by first collecting personal cues for emotional autobiographical memories individually from each participant based on general cues. Next, the most highly emotional autobiographical memories are selected, are matched in such phenomenological properties such as emotional intensity, age vividness, and frequency of rehearsal, along with others.
These individualized memories are then queued during the FMRI scanning session one at a time. This will trigger recollection and re-experiencing of autobiographical memories, which participants are asked to rate on scales for emotional intensity, vividness and reliving. Finally, the FMRI data can be analyzed to reveal neural networks associated with emotional autobiographical recollection, which can be distinguished from those associated with the recollection of other types of memories such as semantic memories or memories.
For knowledge, some of the main targeted regions are the medial temporal lobe and the midline cortical structures. Because this method allows investigation of emotional biases in the recollection of autobiographical memories, it might contribute to understanding mood disorders such as depression. Where is a tendency to recollect and ruminate negative personal memories?
The main advantage of this technique over existing methods is that it allows us to pre-select highly emotional, positive and negative memories that are otherwise closely matched on such basic properties as emotional intensity, amount of detail, vividness of recollection, and personal significance. Personal memory should be elicited from each participant during an interview performed prior to the FMRI session. Similar to the procedure employed for non-emotional autobiographical memories, the autobiographical memory questionnaire comprised a list of 115 verbal cues for distinct life events such as the birth of a family member or the death of a relative.
So here's the questionnaire for each prompt. I would like for you to remember a unique event in your life that happened in a specific time and place.Okay. Upon recollection, ask the participant to provide a brief description of the memory, which will later be used as a personalized memory cue during FMRI scanning.
Make sure the participants are naive to the specific purpose of the pre scanning interview. Now have the participant day each memory, and then rate it on six Likert scales to assess its phenomenological properties. The scale should include among others ratings of emotional valence, emotional intensity, the amount of contextual and visual perceptual details, the personal significance, and the frequency of retrieval or using a seven point scale.
Next, the 40 most emotional memories, half positive and half negative should be selected for each participant based on the ratings provided on the autobiographical memory questionnaire. The positive and negative autobiographical memories should then be matched in terms of age and phenomenological properties to ensure that eventual differences in brain activity during recollection are not confounded by differences in these basic properties. Now that specific details of the participant's autobiographical memories have been collected, the FMRR paradigm can be set up.
This should be designed to allow comparison of the autobiographical memory task with a semantic memory control task. Hence, both tasks should have a similar general structure seen here. Presentation software such as sigal, can be used to set up and display paradigms in the MS scanner, but other software can also be used.
Base the autobiographical memory test on the personalized cues collected prior to scanning. Begin each trial with a cue that triggers autobiographical recollection, which is indicated by the participant with a button press. Then the participant's task will be to remember details of the event until queued.
For ratings of the recollected memory, each trial should be followed by rating screens presented in a counterbalanced order using a five point like art scale. Similarly, the semantic memory task used as the control should have a similar structure. This task involves generation of exemplars from different semantic categories, and after a semantic category is queued, the participant should press a button as soon as they start recalling exemplars from that category, and then continue recalling until queued again for memory ratings, set up multiple runs each beginning with six seconds of fixation to allow stabilization of the MR signal.
Then the autobiographical memory and semantic memory conditions should be presented in a random order separated by an inter trial interval of variable duration of five to nine seconds. Run order should be counterbalance between participants when the subject arrives for the scanning session, have him or her fill out an MRI screening form and remove all metal. Also have the subject complete questionnaires that assess personality traits and current state of mind, which may influence the participant's responses during the study.
Prior to the scan. Inform the participant in detail of the scan procedures and give specific instructions for the behavioral task. Also, give the participant an abbreviated practice session to create increased familiarity with the task.
Now, bring the subject into the scanning room and instruct him or her to lie supine on the scanning bed. Provide ear protection as well as isolation headphones for communication during the scan. Additional cushioning for the head should be placed to ensure comfort during the scan and minimize movement.
Also, the non-adhesive side of a length of tape may be wrapped lightly around the participant's forehead to further minimize head movement. Finally, position the subject's right hand comfortably on the response box and check to make sure the buttons are working properly. Also, place an emergency stop button nearby so that the subject may indicate any urgent need to stop the scanner.
Make sure that the subject can see the screen projection clearly for stimulus presentation before sending him or her into the scanner. Now acquire a high resolution T one weighted structural image such as an SPGR or MP rage in our studies using a 1.5 Tesla scanner. Three dimensional MP rage.
Anatomical images were acquired for each functional slice in an axial orientation. Next, set up your functional runs to allow full brain coverage. In our studies, we acquire a series of 28 functional slices collected axially using an echo plane, our pulse sequence with a four by four by four millimeter voxel size, a TR of 2000 milliseconds, a TE of 40 milliseconds, a flip angle of 90 degrees, a matrix size of 64 by 64, and a field of view of 256 by 256 millimeters.
Inform the subject that the functional imaging is about to begin and briefly remind him or her of the tasks. Now start the scanner synchronously with the subject specific paradigm. When scanning is complete, help the subject out of the scanner and be sure to thank him or her for participating in the experiment.
Once collected, data can be analyzed using any FMRI processing software package, such as statistical parametric mapping, commonly known as SPM. Our lab uses this in combination in-house MATLAB based tools. Pre-processing in our group involves typical steps, quality assurance, image alignment, motion correction, co-registration, normalization, and spatial smoothing with an eight millimeter kernel.
When using SPM, the general linear model is implemented to assess the fit of the recorded data from each condition of interest to a predetermined hemodynamic response function. Individual and group level. Statistical analysis may involve comparisons of brain activity according to memory type, such as autobiographical memory and semantic memory compared to the semantic memory task.
Retrieval of emotional autobiographical memories yielded increased activity in the autobiographical memory retrieval network, including the hippocampal areas seen here. Increased activity was also seen in the medial prefrontal cortex seen here labeled B and the ous precuneus regions labeled C, as well as in the parietal occipital junction labeled E and the frontal temporal junction labeled D.These areas are involved in general memory retrieval, personal engagement, visual spatial representation, and effective autobiographical memory retrieval respectively. The color bar indicates the gradient of T values of the activation maps and the line graphs illustrate the time courses of the FMRI signal in percent signal change for each trial type and TR with the autobiographical memory task in red and the semantic memory task in blue.
When attempting this procedure, it's important to be careful in the collection and selection of the personal memories and in providing the subject instructions for the FMRI task. This basic procedure can be modified by instructing participants to focus on emotional or non-emotional aspects of their memories in order to address additional questions about how focusing on or diverting from the emotional component of the autobiographical memories might influence the re-experiencing of the associated emotions and the underlying neuro correlates.
