PONE-D-19-34387

Neurofeedback in ADHD: a qualitative study of strategy use in slow cortical potential training

PLOS ONE

Dear Mr. Hasslinger,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

The three reviewers make some valid points regarding framing and report of the results. Two of them also ask for additional report regarding the link between regulation strategies and training outcome (objective rather than subjective). I suggest that you consider those additional reports.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Partly

Reviewer #3: Partly

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: N/A

Reviewer #2: N/A

Reviewer #3: N/A

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3. Have the authors made all data underlying the findings in their manuscript fully available?

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

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Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The authors present a very interesting qualitative study into strategy use during SCP neurofeedback in ADHD. I agree that these kind of studies are important and long overdue, and I am hopeful that these insights will contribute to a better and more nuanced understanding of neurofeedback as treatment for ADHD. The manuscript is well written and the methods seem sound, I mostly have minor comments and ideas for additional discussion.

Introduction

1. In the explanation of neurofeedback (lines 75-77), you may add that other important ‘ingredients’ are learning principles, such as operant conditioning.

2. The first sentence of the paragraph (starting at line 90) does not really represent the rest of the paragraph, which mostly sums up the many limitations in neurofeedback research.

3. When discussing specific versus non-specific effects, which is at the core of the neurofeedback efficacy ‘debate’, you may want to consult the CRED-nf checklist. Recently, a consensus report was drafted on the reporting and experimental design of neurofeedback studies. The report contains a useful model that distinguishes multiple mechanisms that together may drive the total effect of neurofeedback, including (1) neurofeedback specific, (2) neurofeedback non-specific, (3) general non-specific, (4) repetition-related and (5) natural mechanisms.

Methods

1. Although the authors provide more details on the specific instructions that participants received during the neurofeedback session in the discussion, please also provide those in the methods section (were there any instructions in the protocol?): (a) How was the SCP training framed? As a way to treat ADHD, to self-regulate attention?, (b) How were the participants instructed concerning physiological artefacts?, (c) What instructions did they receive during the sessions?

2. On lines 241-242, it is described that mostly successful strategies were explored. Although this makes sense, do the authors think future research should also ask about what strategies did not work, and how many strategies were used during each session (as a measure of trial-and-error learning)?

Results

1. I think most results are presented well, but there is some inconsistent use of the words ‘theme’ and ‘sub-theme’ throughout the results section, and Table 2 (which ones are italic for example), making it more difficult to follow.

2. It may be useful to provide a ‘overview’ figure with all domains, and the themes and subthemes (this could be depicted using hierarchical boxes on top of each other).

3. Line 373: also name the number of themes and subthemes, including their names (like the other domain paragraphs).

4. I believe the subtheme ‘silence’ is not discussed in the text (of physiological strategies), while ‘breathing’ twice.

Discussion

1. It is fascinating to recognize many strategies, as reported in this manuscript, in my own experience with theta/beta neurofeedback research in ADHD and conversations I had with participants. Although SCP and theta/beta neurofeedback have different targets, both seem to affect (or regulate, in SCP) arousal. It may be interesting to discuss what the results mean for other neurofeedback protocols.

2. The authors discuss three different strategy ‘profiles’. The ‘state of mind’ profile is associated with intrinsic motivation, which may be an important factor in the ultimate efficacy of the training (although this is not studied in the current manuscript). It would be very interesting if the authors discuss the role of motivation more extensively. For example, the role of self-efficacy, locus-of-control, etc. in ADHD and as potential moderator for strategy use and efficacy of neurofeedback in ADHD.

3. Would you recommend exploring strategy use in EMG biofeedback (as sham-control condition for neurofeedback)? It may be interesting to see whether there is an overlap in strategies used, which may explain non-specific effects of neurofeedback.

4. Line 729: typo (the word ‘not’ is missing between ‘did’ and ‘benefit’).

Tieme Janssen

Reviewer #2: The manuscript entitled „Neurofeedback in ADHD: a qualitative study of strategy use in slow cortical potential training“ reports on the results of a qualitative explorative investigation of strategies during SCP-NF in 30 children and adolescents with ADHD. The authors derived strategy clusters covering cognitive, physiological, emotional and unspecified domains. Furthermore, from 14 participants, three strategy profiles could be differentiated: “State of Mind”, “Manifest and Concrete” and “Unaware”. This is an interesting study with the rationale to shed light on NF mechanisms. The manuscript is well written and clearly structured, and I believe that the results are of interest to other researchers in the field.

However, it would seem important to link the qualitative data (/subjective experience) at least to SCP regulation performance (i.e. amplitudes as an objective measure). The mere description of strategies doesn’t help evaluating how efficacious they are on NF performance. Thus, the final conclusion that the findings may help to facilitate more effective instructions in how to approach SCP is not supported by the data. From the data provided in the current version of the manuscript, we can’t see which strategies avail or hinder treatment effects or if using explicit strategies would be useful at all. Thus, we learn from the manuscript which strategies are used, but we do not know which of them are advantageous.

I believe that it would increase the informative value for the scientific community tremendously if the authors would build the bridge between the strategies or the strategy profiles and NF performance (cf., e.g., Kober et al., 2013) as well as symptom changes. This is, in my opinion, the most important part as it gives information on:

- Which strategies/ strategy profiles are (not) effective ((not) leading to negative or positive SCP shifts)? Can strategies predict outcome (Conners)?

- Are there differences in which strategies are particularly effective/feasible in everyday life (leading to more pronounced changes in Conners)?

o e.g., negative emotional strategies (anger, sadness) might be less feasible in everyday life as inducing negative emotions to take yourself into a state of attention might not be the appropriate approach

- Are there differences in which strategies are particularly effective depending on presentations of ADHD (Conners subscales)?

o e.g., the physiological strategies most probably constitute a general physical arousal regulation rather than regulation of a circumscribed disorder-specific brain region (thereby leading to specific ADHD-related symptom changes). Still, they might be particularly effective in reducing motor hyperactivity (by general relaxation).

- Is lack of insight an advantage (leading to more pronounced amplitudes and speaking in favor of an automatic learning process)?

Minor:

Reports from teachers or parents occurred by report of the children?

How did these reports coincide with the ratings by teachers or parents themselves?

In Figure 1 SCP Feedback. Looking at the feedback screen depicted in the middle, it looks as if a threshold would have been implemented during training, which is not mentioned in the manuscript and supposedly was not the case.

The authors should recheck spaces (e.g. line 50, 56, 94, 254) and misplaced words (e.g., line 152, 603).

In line 530, it should read “(…) frequently, showing that many strategies (…)”

Reviewer #3: In this manuscript, the authors analyzed quantitatively [editor: I think they meant qualitatively] the self-regulation strategies during specific and standardized neurofeedback training in ADHD patients. This is an important study which adds relevant and highly novel insights to the field of neurofeedback training. The main aims were to map the cognitive strategies, evaluate the changes over time and to investigate different profiles.

The manuscript is well written, but the result section is difficult to follow. In my opinion, it would be helpful to include some tables in which the proportion of subjects and the different strategies are stated and classified.

One major concern needs to be addressed to be suitable for publication and therefore to add novel insights to the field. In my opinion, the authors must include the factual self-regulation data of the NF training and performance. This is important to be able to answer the question of which cognitive or emotional strategy worked. Now the manuscript only is able to show in a quantitatively [editor: I think they mean qualitatively here] way that the participants tried something, but the key question remains unanswered! Did a specific strategy work? Did one work better? – In my opinion, this is really important and would lead to a very important paper. The authors might just look at the mean % of suns delivered by Theraprax?

If the self-regulation data is not included, the authors should address this issue in more detail during the discussion or even add a limitation section.

Minor:

Introduction

L70 Citation error

L81 ADHD symptoms as well as for medical conditions the authors may add a citation

L93 – The authors should cite more recent meta-analysis (ie. Cortese et al., 2016, Riesco-Mejias et al 2019)

L128 The authors should consider as well following manuscript when addressing the Placebo question in NF (Busalb et al 2019 https://www.frontiersin.org/articles/10.3389/fpsyt.2019.00035/full)

L131 The authors should specify that this study was done in Adults

Methods:

Did the participants receive some instruction prior to the SCP-NF training?

I miss the differentiation between strategies for the different conditions. SCP-NF has two conditions which are Negativity and Positivity trials. Did the authors look if there were different strategies during those different conditions? - What about the transfer vs. real-time feedback?

Discussion:

L 629 The authors state that they do not know if the subjects succeed in modulating their brain activity. This is a critical point and in my point of view if included it will enrich the manuscript and the conclusions.

L634 “While the other two groups also improvements were reported” I think that here is missing something.

L717 though we do not know whether these individuals were successful in manipulating their slow cortical potentials. The authors must analyse that.

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Reviewer #1: Yes: Tieme Janssen

Reviewer #2: No

Reviewer #3: No

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Neurofeedback in ADHD: a qualitative study of strategy use in slow cortical potential training

PONE-D-19-34387R1

Dear Dr. Hasslinger,

We are pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it complies with all outstanding technical requirements.

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Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

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Reviewer #2: All comments have been addressed

Reviewer #3: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #2: Yes

Reviewer #3: Partly

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: N/A

Reviewer #3: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #2: No

Reviewer #3: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #2: Yes

Reviewer #3: Yes

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #2: The authors addressed my comments adequately thus I would recommend publication of the MS in its current form in PLOS ONE.

Reviewer #3: The authors of this MS have been very responsive to my comments and have submitted an excellent revision.

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Reviewer #2: No

Reviewer #3: No