Modulating Default Mode Network Function: A Transcranial Direct Current Stimulation (TDCS) Pilot Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Modulating Default Mode Network Function: A Transcranial Direct Current Stimulation (TDCS) Pilot Study (NCT04598152), a na na study. The primary outcome is Blood Oxygen Level Dependent (BOLD) Response in the Precuneus During an Emotion Regulation Task Completed During fMRI Scanning..

2. Clinical Question

The study’s stated purpose was to gather information about brain responses to different types of pictures and to improve understanding of brain function in people who are depressed or anxious. The primary outcome narrows that broad purpose to a measured fMRI signal during an emotion regulation task. It is not a direct measure of a diagnosis, symptoms, or treatment benefit.

The registry’s primary-outcome population is particularly important for interpreting the question. It reports results for the Sham followed by Active sequence only, because no subjects completed the Active followed by Sham sequence. Thus the record does not describe a balanced comparison of the two sequences. The clinical question is best read as an exploratory question about BOLD response in a small group exposed to the listed stimulation conditions, rather than as a definitive comparison of active stimulation against sham.

3. Trial Design

NCT04598152 is a pilot study titled “Modulating Default Mode Network Function: A Transcranial Direct Current Stimulation (TDCS) Pilot Study.” The registry lists the study as terminated, with a start date of 2018-10-01 and primary completion on 2020-03-09. Enrollment is reported as 4. The phase and allocation are listed as NA; masking is listed as NONE, and the model is SINGLE GROUP.

The intervention is a device: transcranial direct current stimulation. The arm description states that each subject would undergo tDCS twice while completing a task during fMRI scanning. The primary-outcome description clarifies that the reported primary population consists of 3 individuals who completed Sham followed by Active tDCS; no subjects completed Active followed by Sham. These statements describe the recorded study experience, but do not establish a randomized crossover design. The record specifically warns that this is not a randomized comparison and that the arms are not a like-for-like control comparison.

The primary outcome is continuous: pre-post change in BOLD response in the precuneus during an emotion regulation task, expressed in arbitrary units. Its stated timeframe is 1 week between baseline and repeat scanning. A secondary outcome concerns the percentage of patients who reported a side effect in the active tDCS condition but not the sham condition.

The registry lists 2 outcome measures and 0 analyses. It does not report the numerical primary-outcome estimates or statistical analyses. The record also does not report the rationale for termination, a sample-size justification for the original study, or further details about the protocol. These omissions limit the conclusions that can be drawn from the design description alone.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Because no subjects completed the Active followed by Sham tDCS arm, results are reported for the 3 individuals who completed the Sham followed by Active tDCS arm only.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Blood Oxygen Level Dependent (BOLD) Response in the Precuneus During an Emotion Regulation Task Completed During fMRI Scanning., measured over 1 week (between baseline and repeat scanning).

The primary endpoint is pre-post change in blood oxygen level dependent (BOLD) response during an emotion regulation task completed during fMRI scanning. The target brain region is described as the precuneus/posterior cingulate gyrus. The outcome is a continuous measure reported in arbitrary units, with a mean and standard deviation specified as the summary format. The timeframe is 1 week between baseline and repeat scanning.

BOLD response reflects changes in regional blood flow. In general, fMRI researchers use this signal as a proxy for neural activity in particular brain regions; it is not a direct measurement of neuronal firing. The registry describes the endpoint as a way to assess how tDCS affects response in a region associated with the study’s focus on default mode network function.

The stated hypothesis was that applying tDCS to the target would decrease BOLD signal during critical components of the task, which the investigators characterized as normalizing function in the region. That is the investigators’ proposed interpretation, not a result established by the record. The numerical pre-post changes, group means, standard deviations, and any uncertainty estimates are not reported in the registry record. Consequently, the direction and precision of the observed endpoint cannot be assessed from the reported numerical information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a continuous endpoint represent?

The primary outcome is continuous: it records a quantity that can vary across a range, rather than simply classifying each participant into a category. The registry specifies the mean as the summary measure and the standard deviation as the measure of dispersion. In general, a mean describes the central value of a set of observations, while a standard deviation describes how spread out the observations are around that mean. Neither quantity is reported numerically for the primary outcome in the registry record.

The endpoint is a pre-post change in BOLD response, measured in arbitrary units. A change score represents how a measurement differs between the baseline and repeat scans for the relevant participant or participants. In general, analyzing change can focus attention on within-person movement over time, but a change score alone does not identify why the measurement changed. Effects of time, task performance, measurement variability, sequence, or other factors may also matter. The registry does not report enough numerical or protocol detail to assess those influences.

Why does the study design matter?

Statistical comparisons depend on how participants entered the conditions and whether the groups or periods are comparable. Here, allocation is listed as NA, masking as NONE, and the model as SINGLE GROUP. The record explicitly states that the study is not a randomized comparison and that its arms are not a like-for-like control comparison. The primary-outcome population is the 3 individuals who completed Sham followed by Active tDCS; no subjects completed Active followed by Sham. These features prevent the treatment contrast from being read as a randomized active-versus-sham effect.

In general, random allocation can help balance factors that might otherwise differ between treatment groups. Masking can reduce the influence of expectations on participant behavior or assessment. Those general safeguards should not be assumed when the record does not report them. Nor should a within-person sequence automatically be treated as a controlled comparison: order, carryover, task repetition, and timing can affect measurements. The registry does not report a statistical model addressing these issues.

How should uncertainty be understood?

In general, a standard error describes uncertainty in an estimate, while a confidence interval expresses that uncertainty as a range under specified assumptions. A p-value addresses compatibility between data and a stated null model, conditional on the analysis assumptions; it does not measure the size or practical importance of an effect. None of these inferential results is reported for the primary outcome. The registry lists 0 analyses, and its numerical primary-outcome estimates are not reported. Thus no confidence interval, p-value, or precision assessment can be reconstructed from the record.

Small samples generally yield less precise estimates and can be sensitive to individual observations. This is a general statistical consideration, not a new estimate of this study’s precision. The outcome population includes 3 individuals, but the record gives no participant-level observations or summary values. The data therefore do not allow an assessment of outliers, distribution shape, or how much an individual observation might influence the mean.

What do the planning assumptions mean?

The registry describes a sample-size planning illustration computed from the observed effect, rather than the trial’s own design. Its assumptions include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the intended effect is a stated fraction of the observed effect. In general, a sample-size illustration estimates the number of participants that a hypothetical design might require under its assumptions. It is not a report of actual enrollment needs established in the original protocol, and it is not observed power.

The illustration should be distinguished from this study’s recorded design. The registry lists a single-group model and warns that the arms are not a randomized, like-for-like control comparison, whereas the illustration assumes equal allocation between two arms. The original sample-size justification and the numerical planning outputs are not reported in the registry record. Since the primary outcome’s observed numerical effect is also not reported, the planning illustration cannot be independently interpreted from the information recorded.

In general, over-dispersion means that observed variability is greater than a statistical model expects. It matters because a model that understates variability can overstate precision. This is a general concept; the registry does not report a dispersion assessment or evidence of over-dispersion for this endpoint. For a continuous BOLD measure summarized by a mean and standard deviation, the spread of the measurements would be relevant to precision, but no numerical standard deviation is reported.

What can be inferred from the analysis record?

The record lists 2 outcome measures and 0 analyses. The primary outcome’s description includes a hypothesis and a defined timeframe, but a prespecified outcome description is not itself a statistical result. No adjustment method, model specification, handling of repeated observations, or inferential procedure is reported. Accordingly, the stated endpoint and hypothesis can be described, but no claim about statistical significance or the size of an estimated effect can be made.

The registry’s separate adverse-event counts are descriptive participant counts. They do not supply a statistical comparison for the BOLD endpoint, and the primary outcome is not an adverse-event measure. Keeping those outcome types distinct avoids treating safety counts as evidence about the fMRI response or treating a stated biological hypothesis as a reported finding.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Active vs Sham Transcranial Direct Current Stimula")
n   <- c(3)
m   <- c(-0.09)
sp  <- c(0.36)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Active vs Sham Transcranial Direct Current Stimula  3  -0.090  0.360  -0.984  0.804

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 2 outcome measures and 0 analyses. It identifies a primary BOLD response outcome and a secondary outcome concerning the percentage of patients reporting a side effect in the active condition but not the sham condition. However, it does not report a multiplicity strategy: no procedure for controlling the chance of false-positive findings across outcomes or analyses is reported in the registry record. With no analysis results posted, it is also not possible to determine whether multiple comparisons were performed or how any such comparisons were handled.

The record does not report a missing-data plan, an imputation method, or rules for excluding observations. The primary-outcome population is described as the 3 individuals who completed Sham followed by Active tDCS, and it states that no subjects completed Active followed by Sham. The reasons for noncompletion or the absence of observations for other participants are not reported in the registry record. It is therefore not possible to determine whether missingness was related to participant characteristics, treatment exposure, scan completion, or the outcome.

The analysis population is likewise not described using labels such as intention-to-treat or per-protocol. The stated primary population is limited to the specified sequence completers, but the record does not explain whether this was the planned analysis population or how participants were selected for analysis. No sensitivity analysis is reported to assess how missing observations might affect the findings.

In general, multiplicity matters because testing several outcomes or contrasts can increase the chance of a seemingly notable result arising by chance. Missing-data methods matter because conclusions may depend on why measurements are absent and on the assumptions used to handle them. These are general considerations; the registry does not report methods or results that would permit their evaluation for this study.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry records no serious adverse events in either listed condition: 0 of 4 at risk in the Active Transcranial Direct Current Stimulation During fMRI group and 0 of 3 at risk in the Sham Transcranial Direct Current Stimulation During fMRI group. Deaths are recorded as 0 in both groups. No serious adverse-event terms are listed.

The record also lists other, non-serious adverse events affecting 4 of 4 at risk in the active group and 3 of 3 at risk in the sham group. These are descriptive counts from the registry. They do not indicate severity beyond the serious-versus-other categorization, and the record does not provide event types or participant-level details for these other events. The counts should not be converted into a comparison of risk between conditions, particularly because the record cautions that the arms are not a randomized, like-for-like comparison.

The secondary outcome is phrased as the percentage of patients reporting a side effect in the active condition but not the sham condition. A numerical result for that specific within-participant outcome is not reported in the registry record. The group-level adverse-event counts above do not by themselves show which individuals experienced events in one condition, both conditions, or neither. Zero recorded serious events should be read as a description of the reported study experience, not as proof that serious events cannot occur.

13. What the Result Does, and Does Not, Mean

The record documents a pilot investigation of tDCS during fMRI and specifies a primary measure: pre-post change in BOLD response during an emotion regulation task. It also gives the investigators’ hypothesis that stimulation would decrease the signal during critical task components. The registry does not report the numerical primary-outcome results, however, so the posted information does not establish whether the signal increased, decreased, or remained similar, or how precisely any estimated change was measured.

The study’s small enrollment and the restricted primary-outcome population make the scope of interpretation narrow. Enrollment is reported as 4, while the primary-outcome description reports results for 3 individuals completing Sham followed by Active tDCS and says no subjects completed Active followed by Sham. The record does not report the reason for this pattern or provide a balanced randomized comparison. Any interpretation should therefore remain descriptive and should not attribute a difference to stimulation alone.

The fMRI measure is a proxy for regional neural activity, not a direct clinical outcome. Even if a BOLD change were reported, it would not by itself establish a change in depression or anxiety symptoms, diagnostic performance, or patient benefit. The study’s stated rationale connects the imaging question to broader understanding, but the record does not report clinical outcome results that would support conclusions about diagnosis or treatment.

The safety information records no serious adverse events and no deaths in the listed groups, alongside other adverse events recorded for participants at risk in both groups. Those descriptive counts do not establish comparative safety, especially given the nonrandomized, non-like-for-like design and the absence of detail about event types. The specific secondary outcome comparing side effects reported in active but not sham is not numerically reported.

In general, a pilot study can help characterize a research question and identify practical or measurement issues, but the registry record does not report its original sample-size rationale or detailed analysis plan. The planning illustration described in the registry is not observed power and should not be treated as proof that the study could detect a particular effect. The appropriate conclusion is limited to what is documented: the study’s design, endpoint, stated hypothesis, and adverse-event counts. The size, direction, and reliability of the primary result remain unreported.

14. Why This Trial Matters Statistically

This study illustrates why a clearly named endpoint does not, by itself, make a result interpretable. The registry defines a continuous fMRI measure, the brain region, the task context, the unit, the summary format, and the interval between scans. Those details help identify what was intended to be measured. But the numerical pre-post changes and statistical analyses are not reported, so readers cannot assess the estimated effect or its precision.

It also highlights the importance of aligning the intended comparison with the design actually recorded. Active and sham conditions may sound like a direct contrast, but allocation is listed as NA, the model is SINGLE GROUP, masking is NONE, and the record warns that the arms are not a like-for-like control comparison. Further, the primary-outcome description reports one sequence and says no subjects completed the other. Statistical interpretation must account for those features rather than treating the labels alone as evidence of a randomized control design.

The distinction between an observed estimate and a planning illustration is also important. The registry describes sample-size calculations based on the observed effect under assumptions of equal allocation, a two-sided significance level of 0.05, and a normal approximation. Such calculations can illustrate hypothetical planning needs, but are not observed power and do not show that the original study was adequately designed. The original design rationale is not reported.

Finally, this record demonstrates that safety summaries and efficacy-oriented biological measures answer different questions. Serious and other adverse-event counts are recorded, while the primary endpoint concerns BOLD response. Neither outcome can substitute for the other. Keeping design, endpoint, analysis, and safety evidence distinct is essential when interpreting a small pilot record with no posted primary statistical results.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The primary limitation is the absence of numerical primary-outcome results and analyses. The record gives no mean pre-post change, standard deviation, confidence interval, or p-value for BOLD response. As a result, the direction, magnitude, and precision of the outcome cannot be evaluated. The registry lists 0 analyses, so no reported statistical model or inferential procedure can be assessed.

The primary-outcome population is restricted to 3 individuals completing Sham followed by Active tDCS; no subjects completed Active followed by Sham. Enrollment is reported as 4, but the reason for the difference between enrollment and the described primary population is not reported in the registry record. There is no reported missing-data plan, account of exclusions, or sensitivity analysis.

The design does not support a like-for-like causal contrast. Allocation is NA, masking is NONE, and the model is SINGLE GROUP. The registry explicitly says the comparison is not randomized and the arms are not like-for-like controls. Sequence and other differences could therefore complicate any comparison, and the record does not report an analysis addressing them.

The record does not report detailed participant characteristics, the original sample-size justification, the rationale for termination, or a statistical analysis plan. The listed sample-size assumptions describe an illustration rather than the trial’s own design; specific planning outputs are not reported. Adverse-event information is also limited: no serious events or deaths are recorded, but the types and details of other adverse events are not given, and the secondary side-effect outcome has no reported numerical result.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Modulating Default Mode Network Function: A Transcranial Direct Current Stimulation (TDCS) Pilot Study — NCT04598152.
• Registry record last updated 2022-01-04; status last verified 2021-12.
• Results first posted 2022-01-04.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

NCT04598152 is a terminated pilot study of transcranial direct current stimulation during fMRI, focused on BOLD response during an emotion regulation task. The registry reports enrollment of 4, a SINGLE GROUP model, allocation listed as NA, and masking listed as NONE. The primary outcome is a continuous pre-post change in BOLD response in the precuneus/posterior cingulate gyrus, with a 1 week interval between baseline and repeat scanning.

The primary-outcome description reports the 3 individuals who completed Sham followed by Active tDCS and states that no subjects completed Active followed by Sham. The registry lists 2 outcome measures and 0 analyses; numerical primary-outcome results are not reported. No serious adverse events or deaths are recorded in either listed group. The record cautions that the arms are not a randomized, like-for-like control comparison.