Sara

Back to Psych 204B Projects 2012

Background

Major Depressive Disorder (MDD) is associated with self-focused rumination; people with tendencies to ruminate will focus repetitively on negative emotions and feelings of distress. These negative emotions often co-arise with memories of past experiences. Emotion regulation strategies are often a component of cognitive therapies for depression, such as reappraisal in CBT.

Methods

Subjects

Five individuals diagnosed with MDD and five non-depressed control subjects were included in the study. All participants were females between the ages of 18 and 59. The Structured Clinical Interview for the DSM-IV was administered to all participants to assess current and lifetime diagnoses for anxiety, mood, psychotic symptoms, alcohol and substance use, somatoform, and eating disorders. Participants who met DSM-IV criteria for current MDD were included in the MDD group; exclusion criteria included substance abuse within the prior 6 months and co-occurring psychosis and/or mania. Participants with no current or past Axis I disorder, and who were not taking any psychotropic medications, were included in the control (CTL) group. Exclusion criteria for the CTL group included prior substance abuse problems and previous use of psychotropic medications.

Task Design

Participants were trained to associate memory cue words with recall of specific negative autobiographical memories, which they had described in an initial screening session. A computer protocol was used in pre-scan training to ensure participants could quickly recall the associated memory when a cue word appears, i.e. within 10 seconds. Nine memories were used per subject, and memories were matched for ratings of valence and arousal.

Three repetitions of each of the three stimulus blocks (feel, accept, analyze) were presented to subjects in counterbalanced order. Each trial started with a 10-second memory cue phase, prompting the participant to bring to mind the cued autobiographical memory. Next, an instruction cue appeared on the screen, directing the participant to engage in either the feel, analyze, or accept strategy for 30 seconds. Subsequently, participants were prompted to rate how aroused they felt (Rating 1) and how negative they felt (Rating 2) on a 5-point scale. They were given 5 seconds for each question. After this, participants were given a spatial perception task for 30 seconds, in which they saw an arrow pointing right or left and indicated which direction it was pointing. The arrows task was chosen as an active baseline task that would not engage the emotional, regulatory, or memory processes of interest; this task has been used in prior research, and the prior work suggests it does not engage these processes.

fMRI task

MR Acquisition

Blood-oxygen level-dependent (BOLD) data were acquired with a 3 Tesla (T) strength General Electric Signa MR scanner (Milwaukee, Wisconsin), using a gradient echo EPI sequence (37 axial slices; field of view [FOV]=224mm, slice thickness=3.2mm, gap=0mm, repetition time [TR]=2000, echo time [TE]=30ms, flip angle [FA]=77°). A structural T1-weighted volume (186 sagittal slices, FOV=240mm, slice thickness=0.9mm, gap=0mm, TR=6200, TE=230, FA=12°) was performed following BOLD scanning runs. Head movement was minimized by using foam cushions.

MR Analysis

The MR data was analyzed using FSL software tools.

Pre-processing

The first 4 volumes (8s) in each functional scan were removed to allow for equilibrium effects. Functional and structural scans were processed with BET (Brain Extraction Tool) to remove the skull and nonbrain tissue. Motion correction was performed using MCFLIRT (part of FSL). Any subjects with motion exceeding 1.5mm were excluded from the analyses (N=1). Functional scans were slice-time corrected. High-pass temporal filtering was used to correct for baseline drifts, and data were spatially smoothed using a 5 mm full-width-half-maximum Gaussian kernel. Functional images were registered to the subjects' structural images using a 6 DOF transformation in FLIRT (FMRIB's Linear Image Registration Tool). Structural images were registered to MNI template space using a 12 DOF transformation in FLIRT, and this transformation was then applied to the functional images

PRF model fits

PRF models were fit with a 2-gaussian model.

MNI space

After a pRF model was solved for each subject, the model was trasnformed into MNI template space. This was done by first aligning the high resolution t1-weighted anatomical scan from each subject to an MNI template. Since the pRF model was coregistered to the t1-anatomical scan, the same alignment matrix could then be applied to the pRF model.
Once each pRF model was aligned to MNI space, 4 model parameters - x, y, sigma, and r^2 - were averaged across each of the 6 subjects in each voxel.

Et cetera.

Results

Accept Task

Accept Mean, MDD > CTL

Accept Mean, CTL > MDD

MDD > CTL for Accept Task

Accept Mean, MDD > CTL, Inferior Frontal Gyrus

Accept Mean, MDD > CTL, Subgenual Prefrontal Cortex

Retinotopic models in individual subjects transformed into MNI space

Some text. Some analysis. Some figures.

Retinotopic models in group-averaged data on the MNI template brain

Some text. Some analysis. Some figures. Maybe some equations.

Retinotopic models in group-averaged data projected back into native space

Some text. Some analysis. Some figures.

Conclusions

Here is where you say what your results mean.

References - Resources and related work

References

Software

Appendix I - Code and Data

Code

File:CodeFile.zip

Data

zip file with my data