The Impact of State Depression on Proactive Control and Distractor Processing in a Memory Task: An Electrophysiological Study

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study is well-written, original, and presents an interesting contribution to the field. I have only a few suggestions to enhance clarity, organization, and transparency.

1. Introduction

• I recommend creating a subparagraph (e.g., The Current Study) to separate the background from the study description. Currently, the transition feels abrupt, as the discussion moves directly from theoretical perspectives and past research to the study’s methodology, which may be confusing for the reader.
• Reorganizing the introduction by presenting the theoretical framework first, followed by the study’s objectives, could improve coherence.
• The introduction is quite long; better structuring could help maintain the reader’s focus. If the study is introduced later in the section, it may be possible to avoid summarizing it again at the end, thus saving space.

2. Materials and Methods

• In the statistical analysis section, please specify the distribution test used to determine whether parametric or non-parametric tests were appropriate (e.g., Kolmogorov-Smirnov test).
• For transparency, I recommend including a table with the ANOVA results.

3. Discussion

• To improve organization and clarity, I suggest adding a separate Conclusion section at the end.
• A subparagraph dedicated to the study’s Implications would help emphasize its contributions.

Other Comments

• A Limitations section is missing and should be included.
• Unless the journal has specific formatting requirements, I suggest listing all author names (or at least the first six and the last one) in the references instead of only the first author.

Overall, this is a compelling and well-executed study. Addressing these minor structural and methodological points will further strengthen its impact and clarity.

Author Response

We would like to thank the anonymous reviewer for the useful comments, which have certainly improved the impact and clarity of the paper. All the new text in the article has been highlighted in yellow. 

Comment #1: I recommend creating a subparagraph (e.g., The Current Study) to separate the background from the study description. Currently, the transition feels abrupt, as the discussion moves directly from theoretical perspectives and past research to the study’s methodology, which may be confusing for the reader.

Response #1: Thank you for pointing this out. We agree with your comment. As you suggested, to improve coherence, we have re-structured the introduction and added a subparagraph titled: "The current study". The reorganized version of the introduction has at the beginning the literature review and explanation of the two fundamental theoretical frameworks (i.e., perceptual load theory and signal suppression hypothesis), and as part of new subparagraph, the hypotheses and overview of the visual paradigm.

Comment #2: The introduction is quite long; better structuring could help maintain the reader’s focus. If the study is introduced later in the section, it may be possible to avoid summarizing it again at the end, thus saving space.

Response #2: As the reviewer has anticipated, after improving the structure of the introduction, it was no longer necessary to offer a summary at the end of it. Thus, the following paragraph has been removed in the revised version of introduction saving space: 

"To summarize, this study evaluates the effects of loading and maintaining complex objects in VWM on distractor processing by leveraging ERP markers of selective attention. It tests the predictions of PLT, which suggests that the exhaustion of perceptual capacity in the high-perceptual load automatically reduces distractor processing (early selection), while low-perceptual load promotes bottom-up (stimulus-driven) attentional capture of a task-irrelevant distractor’s features. Additionally, it considers whether the ERP findings might align better with the predictions of SSH, which suggests that if a task-irrelevant distractor’s features interfere with those of the task-relevant stimuli part of the individual's active task set, then there would be the intervention of top-down (task-driven) proactive suppression mechanisms to actively suppress its features to prioritize the current task at hand". 

Comment #3: In the statistical analysis section, please specify the distribution test used to determine whether parametric or non-parametric tests were appropriate (e.g., Kolmogorov-Smirnov test).

Response #3:The following paragraph has been added at the beginning of the subheading: 2.4. Statistical analysis: "The Kolmogorov-Smirnov Test was employed to determine whether parametric tests were appropriate to be used".

Comment #4: For transparency, I recommend including a table with the ANOVA results.

Response #4: The following two sentences have been added at the end of the subheadings: 3.1. Electrophysiological results and 3.2. Behavioral results, respectively. "The output files of statistical analysis conducted on electrophysiological data can be found in the supplementary material" and "The output files of statistical analysis conducted on behavioral data can be found in the supplementary material".

Comment #5: To improve organization and clarity, I suggest adding a separate Conclusion section at the end.

Response #5: A separate conclusion section has been added at the end as suggested.

Comment #6: A subparagraph dedicated to the study’s Implications would help emphasize its contributions.

Response #6:  A separate subparagraph dedicated to the study’s Implications is in place now.   

Comment #7: A Limitations section is missing and should be included.

Response #7: Considering the reviewer's comment, a new "Limitations of the current study" section has been included in the revised version of the article. Please find below the full text of new section: 

Despite providing valuable insights into the relationship between state depression and attentional control mechanisms, the present study has several limitations that should be acknowledged. First, while ERP measures (early P_D and N2pc) reveal neural markers of attentional suppression and capture, the lack of behavioral differences between groups limits generalizability. HSD individuals may have used compensatory strategies to maintain performance, suggesting that ERP findings alone do not fully capture attentional control deficits. Future research should incorporate additional behavioral measures, such as eye-tracking, for a more comprehensive assessment. Second, the use of a unilateral distractor array raises concerns that the observed early lateralized waveform might reflect not only proactive suppression (early P_D) but also a posterior contralateral positivity (Ppc) component. Although our comparison between the two groups ruled out this possibility, future studies could employ bilateral distractor designs and experimental control conditions to better differentiate these effects. Finally, categorizing participants using the DASS-21 may not fully capture the complexity of depressive symptoms, as it assesses transient emotional states rather than clinical depression. Additionally, factors like trait anxiety and fatigue were not controlled, despite their known influence on attentional control and ERP responses. Future studies should account for these variables to refine our understanding of attentional deficits in depression.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

Thank you for providing me with the opportunity to review this interesting paper. Below, I have listed my comments:

1) Throughout the manuscript make sure to stay consistent with the terminology you are using. Fo rinstance, terms such as Singleton distractor, task-irrelevant distractor, and task-irrelevant stimulus features are used interchangeably.

2) In the introduction, it would have been nice to highlight the rationale for using ERPs.  why are these components (early PD, N2pc) relevant to studying attentional control in depression

3) What are the limitations of the study? They need to be stated.

4) Future research suggestions could be expanded. For example,  longitudinal studies to track how attentional control deficits evolve in depression could be suggested.

I hope this feedback is helpful.

Author Response

We sincerely appreciate the anonymous reviewer’s valuable feedback, which has significantly enhanced the clarity and impact of the paper. All newly added text has been highlighted in yellow.

Comment #1: Throughout the manuscript make sure to stay consistent with the terminology you are using. For instance, terms such as Singleton distractor, task-irrelevant distractor, and task-irrelevant stimulus features are used interchangeably.

Response #1:We have checked the manuscript and enhanced consistency in using the terminology "task-irrelevant singleton". 

Comment #2: In the introduction, it would have been nice to highlight the rationale for using ERPs. Why are these components (early PD, N2pc) relevant to studying attentional control in depression?

Response #2: We agree with the reviewer's comment. The following paragraph has been expanded and re-written:

Event-related potentials (ERPs) provide a time-sensitive method for examining attentional processes at the neural level, making them essential for understanding how individuals with depressive tendencies regulate attention. Traditional behavioral measures, such as reaction times and accuracy, may not fully capture the rapid and automatic nature of attentional mechanisms. ERPs, in contrast, allow researchers to directly measure the temporal dynamics of attentional suppression and selection, offering a more precise investigation of attentional control deficits in depression. A systematic evaluation of ERP studies has reported perceptual load effects as predicted by the PLT at all processing stages. Findings are, however, mixed, and this inconsistency is especially observed for earlier ERP components (i.e., C1, P1, and N1) but also seen during later stages (i.e., P2, and N2) (See for review [12]). However, the role of lateralized ERP components, such as the P_D (distractor positivity) and N2pc (N2-posterior-contralateral), as measures of distinct aspects of attentional selection and control under low- and high-perceptual load conditions has not been fully investigated in previous studies.

Comment #3: What are the limitations of the study? They need to be stated.

A new "Limitations of the current study" section has been included in the revised version of the article. Please find below the new section: 

Despite providing valuable insights into the relationship between state depression and attentional control mechanisms, the present study has several limitations that should be acknowledged. First, while ERP measures (early P_D and N2pc) reveal neural markers of attentional suppression and capture, the lack of behavioral differences between groups limits generalizability. HSD individuals may have used compensatory strategies to maintain performance, suggesting that ERP findings alone do not fully capture attentional control deficits. Future research should incorporate additional behavioral measures, such as eye-tracking, for a more comprehensive assessment. Second, the use of a unilateral distractor array raises concerns that the observed early lateralized waveform might reflect not only proactive suppression (early P_D) but also a posterior contralateral positivity (Ppc) component. Although our comparison between the two groups ruled out this possibility, future studies could employ bilateral distractor designs and experimental control conditions to better differentiate these effects. Finally, categorizing participants using the DASS-21 may not fully capture the complexity of depressive symptoms, as it assesses transient emotional states rather than clinical depression. Additionally, factors like trait anxiety and fatigue were not controlled, despite their known influence on attentional control and ERP responses. Future studies should account for these variables to refine our understanding of attentional deficits in depression.

Comment #4: Future research suggestions could be expanded. For example,  longitudinal studies to track how attentional control deficits evolve in depression could be suggested.

Response #4:Taking into account the useful comment provided by the reviewer, the following paragraph has been added at the very end of article:

Moreover, longitudinal studies should be conducted for understanding how attentional control deficits evolve over the course of depression, providing insights into whether these impairments are a consequence or a potential precursor of the disorder. By tracking individuals over time, researchers can examine how fluctuations in depressive symptoms influence attentional suppression and selection mechanisms, as measured through behavioral tasks and neurophysiological markers such as ERPs. This approach allows for the identification of causal relationships between depression severity and attentional control deficits. Additionally, longitudinal studies can assess the impact of therapeutic interventions, such as cognitive training or antidepressant treatments, on attentional control over time, offering valuable information on whether improvements in mood correlate with enhanced top-down attention regulation. Understanding these dynamics could help refine models of depression and guide the development of targeted interventions aimed at mitigating attentional dysfunction in affected individuals.