We present a protocol that allows investigation of the neural correlates of recollecting emotional autobiographical memories, using functional magnetic resonance imaging. This protocol can be used with both healthy and clinical participants.
Recollection of emotional autobiographical memories (AMs) is important to healthy cognitive and affective functioning 1 – remembering positive AMs is associated with increased personal well-being and self-esteem 2, whereas remembering and ruminating on negative AMs may lead to affective disorders 3. Although significant progress has been made in understanding the brain mechanisms underlying AM retrieval in general (reviewed in 4, 5), less is known about the effect of emotion on the subjective re-experience of AMs and the associated neural correlates. This is in part due to the fact that, unlike the investigations of the emotion effect on memory for laboratory-based microevents (reviewed in 6, 7-9), often times AM studies do not have a clear focus on the emotional aspects of remembering personal events (but see 10). Here, we present a protocol that allows investigation of the neural correlates of recollecting emotional AMs using functional magnetic resonance imaging (fMRI). Cues for these memories are collected prior to scanning by means of an autobiographical memory questionnaire (AMQ), therefore allowing for proper selection of emotional AMs based on their phenomenological properties (i.e., intensity, vividness, personal significance). This protocol can be used in healthy and clinical populations alike.
1. Collection and Selection of Memories, Imaged Task, and Experimental Protocol
Collection of the Emotional AMs
Figure 1. Illustration of AMQ Administration. For each cue, participants remember and briefly describe a specific event, and then date and rate it on 6 scales.
Selection of Highly Emotional AMs
The fMRI Task
Figure 2. Structure of the fMRI Trials. A. General Structure of the trials. B. Specific structure of the AM and SM trials.
2. Preparing the Subject for the Scan
All participants provide written informed consent prior to running the experimental protocol, which is approved by an Ethics Board. Typically, to avoid confounds in the lateralization of brain activations, scanned participants are right-handed.
Prior to Entering the Scanning Room
Entering the Scanning Room
3. Data Recording and Processing
Scanning Parameters
We collected MRI data using a 1.5 Tesla Siemens Sonata scanner for MRI recordings. Anatomical images were 3D MPRAGE anatomical series (repetition time (TR) = 1600 ms, echo time (TE) = 3.82 ms; number of slices = 112; voxel size = 1x1x1 mm), and functional images were series of 28 functional slices, acquired axially using an echoplanar sequence (TR = 2000 ms; TE = 40 ms; field of view FOV = 256×256 mm; voxel size = 4x4x4 mm), thus allowing for full-brain coverage.
Data Analysis
We used Statistical Parametric Mapping (SPM: http://www.fil.ion.ucl.ac.uk/spm) in combination with in-house Matlab-based tools. Pre-processing involved typical steps: quality assurance, TR alignment, motion correction, co-registration, normalization, and smoothing (8 mm3 Kernel). Individual and group-level statistical analyses may involve comparisons of brain activity according to memory type (AM vs. SM), emotional valence (positive vs. negative), and retrieval focus (emotional vs. non-emotional content).
4. Representative Results
Figure 3. Neural Correlates of AM Retrieval. Validating the present protocol, retrieval of AMs yielded increased activity in the AM retrieval network 4, 25, including hippocampal areas (a), involved in general memory retrieval, the medial prefrontal cortex (b), associated with personal engagement, the cuneus/precuneus regions and parieto-occipital junction (c, e, respectively), associated with processing visuo-spatial representation, and the frontal-temporal junction (d), involved in affective AM retrieval; similar effects to the latter were also found in the amygdala (not shown). The “activation maps” are superimposed on high resolution brain images displayed in coronal (left panel) and saggital (middle and right panels) views; the color bars indicate the gradient of t values of the activation maps (p < 0.005, 10 contiguous voxels 26), reflecting brain activity time-locked to the onsets of the memory cues. The line graphs illustrate the time courses of the fMRI signal (% signal change), for each trial type and TR (1 TR = 2 seconds). L = Left; R = Right.
The experimental design introduced here allows investigation of the neural correlates of remembering emotional autobiographical memories. This design has the potential to advance our knowledge of how the brain generates affective biases (positive or negative) in remembering personal memories, and how those biases may be modulated by the retrieval focus (on emotional or non-emotional aspects). This protocol has additional benefits in that it can also be used with clinical populations (e.g., in patients with depression and post-traumatic stress disorder), which allows investigation of alterations associated with negative affective biases in AM retrieval (e.g., rumination on negative experiences and uncontrollable recollection of traumatic events, respectively). Overall, the success of this design depends on careful AM collection and selection and proper experimental manipulations.
The authors have nothing to disclose.
This research was supported by a Young Investigator Award from the US National Alliance for Research on Schizophrenia and Depression and a CPRF Award from the Canadian Psychiatric Research Foundation (to FD). ED was supported by a Wyeth-CIHR Post-Doctoral Fellowship. The authors wish to thank Peter Seres for assistance with fMRI data collection and Kristina Suen for assistance with data analysis.