How the brain suppresses unwanted memories and dampens emotion

How many participants were analyzed in the fMRI study, and what was the reason for excluding any participants?

The study analyzed data from 22 participants. Two participants were excluded because they did not have enough memory intrusions (less than 5% or fewer than 4 trials) in one of the emotional conditions.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

From which database were the scene stimuli selected, and how were they balanced for valence?

The 48 scene stimuli were selected from the International Affective Picture System (IAPS) database, with half of the critical scenes normed as negative and the other half normed as neutral.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

What training procedure was used to ensure that face-scene associations were strongly and comparably learned before the TNT task?

Participants learned all face-scene pairs using a drop-off/feedback cycle procedure, followed by a brief overtraining reminder session inside the scanner.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

In the Think/No-Think (TNT) task, how were participants cued to retrieve or suppress a memory?

Participants were shown face cues bounded by colored boxes: a green box cued them to retrieve the associated scene, while a red box cued them to suppress its retrieval.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

What strategy were participants instructed to use on No-Think trials to block thoughts of the scene?

Participants were instructed to blank their minds and concentrate on the face cue, avoiding replacing the scene with any other thoughts or mental images.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

How did the researchers track whether a memory entered awareness on a trial-by-trial basis?

After each trial, participants reported whether the associated scene entered awareness using a rating scale of "never", "briefly", or "often".

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

What purpose did the "Baseline" items serve in the final recognition and affect tests?

Baseline items were trained at the beginning but omitted from the TNT phase, serving as a control to measure the distinct effects of subsequent retrieval and suppression.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

Why did the researchers use a speeded associative recognition test instead of a recall test to assess memory retention after the TNT phase?

They used a speeded recognition test to prevent ceiling effects in accuracy that would likely occur because of the extensive overtraining of the face-scene pairs.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

How did the researchers adjust the Self-Assessment-Manikin (SAM) valence ratings to account for initial item differences?

They expressed each subject's SAM valence rating as a percentage relative to the scene's normative IAPS database value to control for pre-experimental differences.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

How did memory intrusion rates change over the course of the Think/No-Think blocks?

The proportion of intrusions significantly decreased across the blocks, showing that participants successfully gained control over unwanted memories over time.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

Did negative scenes show higher or lower intrusion rates than neutral scenes during suppression trials?

No-Think trials resulted in comparable intrusion reduction for both negative and neutral scenes, indicating that suppression was equally effective regardless of valence when encoding strength was equated.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

How did the ability to control memory intrusions correlate with subsequent affect suppression for negative scenes?

Participants who were more effective at preventing intrusions of negative scenes showed a greater reduction in negative affect for those scenes compared to baseline.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

What effect did attempting suppression have on negative scenes for participants with low memory control?

Participants in the low memory-control group judged suppressed negative scenes as significantly more negative than baseline scenes, indicating that failed suppression can increase negative affect.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

How did the researchers demonstrate that the relationship between intrusion control and affect suppression was not driven by item-specific biases?

They performed a split-half item analysis, showing that the intrusion rate of one random set of items still predicted the affect suppression score of a separate, independent set of items.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

What key stimulus limitation prevented the researchers from definitively ruling out that suppression simply adds positive valence to items?

The study did not include positively valenced scenes, meaning they could not verify if suppression increases positive valence or specifically disrupts negative affect.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

How did suppression affect subsequent recognition reaction times for negative versus neutral scenes?

Suppression significantly slowed subsequent recognition reaction times for negative scenes compared to baseline, but did not reliably slow reaction times for neutral scenes.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

Did actively retrieving scenes during "Think" trials alter their perceived emotional valence?

No, active retrieval during Think trials did not change the perceived emotional valence of the scenes on the final test.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

Which prefrontal cortex region was significantly engaged during suppression (No-Think > Think) across both negative and neutral conditions?

The right middle frontal gyrus (MFG), specifically the right dorsolateral prefrontal cortex.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

How did neural activity in the Medial Temporal Lobe (MTL) change during trials with intrusions compared to trials without intrusions?

The MTL structures, including the hippocampus, parahippocampus, and amygdala, showed significant downregulation (reduced activity) during intrusion trials.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

How did the downregulation of the amygdala during intrusions differ between negative and neutral scenes?

The amygdala exhibited significantly greater downregulation during the suppression of negative scenes than during the suppression of neutral scenes.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

Why did the researchers create participant-specific hand-drawn MTL masks in native space instead of normalized space?

To avoid spatial normalization errors that could mix voxels between adjacent, fine-grained structures like the amygdala and the hippocampus.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

What is the key advantage of using behavioral PLS correlation over standard univariate ROI-behavior correlations?

PLS is a multivariate technique that can identify whether a single, common set of voxels (rather than separate sets) mediates both memory and affect suppression.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI

What did behavioral PLS reveal about the prefrontal control network during the suppression of negative scenes?

It revealed a common set of voxels across the frontoparietal network where upregulation during intrusions predicted both better memory control and greater affect suppression.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

Did prefrontal voxels predict both intrusion control and affect suppression for neutral scenes in the PLS analysis?

No; for neutral scenes, the prefrontal voxel patterns predicted intrusion control but did not significantly correlate with affect suppression.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

What is the primary function of Dynamic Causal Modeling (DCM) in fMRI studies like this one?

DCM is used to explain changes in regional activity by modeling how experimental factors modulate the causal, directional connectivity between brain regions.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

In the DCM design, what three sub-hypotheses were compared in the "Regulation" family of models?

The models compared whether prefrontal modulation directly targeted only emotional regions (Emotion Regulation), only memory regions (Memory Regulation), or both in parallel (Parallel Regulation).

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

Which model family won the Dynamic Causal Modeling (DCM) selection, confirming the mechanism of prefrontal control?

The Parallel Regulation model, which showed that the right MFG modulates both memory-related (hippocampus/parahippocampus) and emotion-related (amygdala) sites in parallel.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

Why did the authors simplify their DCM model space by omitting other prefrontal regions like the ACC or right IFG?

They simplified the model space because the ability to estimate causal parameters effectively decreases as the model becomes more anatomically complex.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

Downregulation in which specific MTL regions predicted both better memory control and reduced negative affect?

Downregulated activity in both the hippocampus and the amygdala predicted fewer intrusions and lower negative valence for suppressed negative scenes.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

How many trials did participants need on average during the first and second drop-off training cycles to learn the face-scene pairs?

Participants took an average of about 1.6 trials in the first cycle and 1 trial in the second cycle, with no difference in learning speed between negative and neutral scenes.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

What limitation did the study have regarding the baseline measurement of scene valence?

The researchers lacked individual participant-specific valence ratings collected before the TNT phase, relying instead on standardized, group-level IAPS database norms.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

How did the researchers avoid circularity (double-dipping) when analyzing activation differences between intrusion and non-intrusion trials in their ROIs?

They defined the ROI masks using an orthogonal overall contrast (No-Think < Think) that collapsed across all trials, which did not pre-select based on intrusion status.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

Did the fMRI analysis show separate prefrontal networks for suppressing neutral versus negative memories?

No; there was no significant interaction between memory control and emotion, suggesting that a common frontoparietal network suppresses retrieval regardless of valence.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

What robust statistical measure did the researchers use to define and trim outliers in the reaction time and valence data?

They defined outliers as values more than 2 times above or below the median absolute deviation (MAD).

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified

In terms of general recognition speeds on the final test, how did negative scenes compare to neutral scenes?

Negative scenes showed significantly slower recognition reaction times overall compared to neutral scenes.

Source: Parallel Regulation of Memory and Emotion Supports the Suppression of Intrusive Memories · DOI · quote verified