Investigating Electroencephalographic Predictors of Default Mode Network Anticorrelation in Healthy Adults: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Investigating Electroencephalographic Predictors of Default Mode Network Anticorrelation in Healthy Adults (NCT05592600), a na na study. The primary outcome is Association Between EEG Measurements and Default Mode Network Brain Activity Measured With fMRI.

2. Clinical Question

The study focuses on an association between measurements from two brain-recording methods, rather than a comparison of treatment outcomes between groups. Investigators generated within-participant model predictions of fMRI activity from EEG features and assessed temporal correlation between EEG and fMRI across two sessions. The registry describes a higher correlation as indicating that EEG was more predictive of fMRI, and a lower correlation as indicating that it was less predictive.

The scientific question is whether EEG measurements can approximate a signal derived from fMRI in this setting. The registry record does not report a numerical estimate of the primary correlation, its variability, or a confidence interval. It therefore does not establish how strong or precise the observed association was.

3. Trial Design

This is a completed, single-group behavioral study sponsored by Drexel University. The registry lists the phase as NA, allocation as NA, and masking as none. It reports an enrollment of 24. These features describe a study organized around measurements within one group, not a randomized trial comparing neurofeedback with a control intervention.

The brief summary describes two sessions. In the first, participants had simultaneous EEG and fMRI recordings while performing cognitive tasks assessing attention. The second involved fMRI-based neurofeedback during simultaneous EEG-fMRI recording. Participants viewed real-time feedback of brain signals and tried to control the activity represented by that feedback. The primary outcome timeframe is described as two sessions 3 to 62 days apart.

The study status is completed. The listed start date is 2023-10-06, and the primary completion date is 2025-02-24. These dates describe the registry timeline; they do not provide additional information about the numerical outcome or the timing of individual analyses.

The primary question concerns whether EEG features predict fMRI-measured default mode network activity. Because there is no separate comparator group, the design cannot estimate a randomized between-group effect. The registry record does not report a protocol-level sample-size justification, a detailed statistical analysis plan, or interim analyses. The sample-size illustrations associated with the posted material should be read as planning exercises, not as features of the observed single-group design or as evidence of observed power.

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.

Before assignment: Potential participants were excluded from the study if they were unable to provide consent, reported having a current or history of psychiatric/neurological disorders, a chronic medical condition, were pregnant, were prisoners, were unable to understand English, had metal in the body, were contraindicated for MRI, had allergies to saline gel, or had cold, flu or COVID-19 symptoms within the two weeks preceding participation.

Overall Study

Analysis population for the primary outcome, as defined in the registry: All participants were included in analysis.

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 Association Between EEG Measurements and Default Mode Network Brain Activity Measured With fMRI, measured over Two sessions 3 to 62 days.

The primary endpoint is the association between EEG measurements and default mode network brain activity measured with fMRI. It is expressed as a Spearman rank correlation coefficient, with the endpoint description identifying a mean and standard deviation as the summary measures. Investigators used multiple EEG features, including spectral power in Theta: 4-7 Hz, Alpha: 8-12 Hz, Beta1: 13-22 Hz, Beta2: 23-29 Hz, and Gamma: 30-50 Hz. Model predictions from EEG were compared with fMRI measurements, and the average temporal correlation across the two sessions was computed.

A correlation is used to describe how two measurements vary together. Spearman correlation assesses the consistency of their rank ordering and can capture a monotonic association without requiring a straight-line relationship. In general, a higher positive correlation indicates that larger or smaller values in one measure tend to correspond consistently with values in the other. It does not by itself establish that one measurement causes the other, nor does it show that the two methods are interchangeable.

The registry describes higher correlation as greater EEG prediction of fMRI and lower correlation as less prediction. However, it does not report the numerical endpoint estimate, its standard deviation, or an interval expressing precision. The endpoint definition is available, but the size and uncertainty of the observed association are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The endpoint combines predictions based on EEG with fMRI measurements of default mode network activity. Its stated summary measure is the Spearman rank correlation coefficient. The registry describes an average temporal correlation across the two sessions, with the endpoint type identified as continuous and summarized using a mean and standard deviation. It does not report the calculated estimate or a detailed analysis procedure.

What does Spearman correlation describe?

As a general statistical concept, correlation describes the degree to which two measurements vary together. Spearman correlation first considers the rank ordering of observations and then assesses how consistently those rankings align. It can describe a monotonic pattern even when the relation is not well represented by a straight line. A positive value indicates that higher ranks on one measurement tend to accompany higher ranks on the other; a negative value indicates that higher ranks tend to accompany lower ranks. Values closer to zero indicate weaker rank association. These general interpretations do not supply a result for this study: the numerical correlation is not reported in the registry record.

Correlation does not prove that one signal causes the other. Nor does correlation alone show that EEG can replace fMRI for other tasks, populations, or settings. The registry question is narrower: whether EEG features could approximate fMRI-measured default mode network activity during the described recordings and cognitive tasks.

Why use ranks?

In general, rank-based methods focus on ordering rather than the raw distance between values. This can be useful when an association is monotonic but not necessarily linear, or when the measurement distributions make a rank-based summary appropriate. The registry record does not state why Spearman correlation was chosen over another measure, whether assumptions were checked, or how ties and repeated measurements were handled.

How should a mean and standard deviation be read?

In general, a mean describes the center of a set of values, while a standard deviation describes their spread around that center. For participant-level correlations, the mean could summarize typical association and the standard deviation could indicate variation across participants. But the registry record does not specify the unit over which these summaries were calculated. It also does not report either summary numerically, so neither the typical association nor its variability can be assessed from the registry record.

What would uncertainty add?

In general, a confidence interval communicates the uncertainty of an estimate under the analysis assumptions. A narrow interval suggests greater precision, while a wide interval indicates that a broader range of values remains compatible with the data. A hypothesis test and p-value address a different question about compatibility with a null model, and should be interpreted alongside the effect estimate rather than on their own. No confidence interval, p-value, or other primary inferential result is reported in the registry record.

What do the planning illustrations represent?

Sample-size calculations are planning tools, not outcome results. The stated illustration assumptions use a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and effects expressed as fractions of the observed effect. The record also states that non-time-to-event illustrations are expressed as participants per arm. These are hypothetical planning assumptions and do not describe the single-group study design, which has no randomized two-arm comparison. The illustration is not observed power, and its numerical outputs are not reported in the registry record.

More generally, power is a design-stage probability of detecting a specified effect if that effect and the model assumptions are correct. A post hoc calculation based on an observed effect does not establish the probability that the study successfully detected a real effect. Since the registry does not report the numerical primary result or a protocol-level sample-size justification, the planning illustration cannot resolve the uncertainty around this study's observed association.

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("EEG-fMRI")
n   <- c(24)
m   <- c(0.09)
sp  <- c(0.07)
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  EEG-fMRI  24  0.090  0.070  0.060  0.120

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure and zero analyses. A single listed outcome does not, by itself, show whether investigators evaluated multiple EEG features, model specifications, time points, or other endpoints. The primary endpoint description mentions multiple EEG frequency bands, but a complete list of statistical tests and decisions is not reported in the registry record.

Multiplicity arises in general when many statistical comparisons are made: the chance of at least one apparently notable result can increase as the number of tests grows. Analysts may address this with prespecified primary comparisons, adjustment procedures, or a clear distinction between confirmatory and exploratory analyses. The registry record does not report whether any multiplicity adjustment was planned or used, or whether the set of analyses was prespecified.

The registry states that all participants were included in the primary analysis. It does not report how many had complete data for the endpoint, how missing or unusable EEG/fMRI recordings were handled, or whether any observations were excluded. Reasons for missing data and any imputation or sensitivity analyses are not reported in the registry record.

The analysis population is therefore described broadly, but its operational details are unclear. In general, a clear account of exclusions and missing-data handling helps readers understand which participants contributed to an estimate and whether the analysis could be affected by incomplete measurements. No further analysis-population definition or missing-data method is reported in the registry record.

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.

The registry lists a single EEG-fMRI group, with 24 participants at risk for serious adverse events and 0 affected. For other adverse events, it likewise lists 24 at risk and 0 affected. Deaths are listed as 0. These are the recorded counts for the group; they are not evidence that adverse events were impossible or that no events could occur outside the registry's reporting scope.

These safety figures should be read as counts, not as a comparison between treatments. The study is single-group and has no separate control arm. The registry does not provide serious adverse event terms, and its list of top serious terms is empty. Details about how adverse events were collected, how long participants were monitored, and what event types were included are not reported in the registry record.

In general, a zero count in a study does not establish the absence of risk. The ability to characterize uncommon events depends on study size, follow-up, and ascertainment. The posted counts describe what was recorded for this group; they do not support a broader safety conclusion.

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

The study addresses a measurement question: whether EEG features can predict fMRI-measured default mode network activity during the described cognitive-task recordings. The registry defines the primary endpoint as a mean temporal Spearman correlation across two sessions. This gives readers the intended target and the direction of its interpretation: higher correlation means EEG is more predictive of fMRI according to the endpoint description.

The numerical primary result is not reported in the registry record. Consequently, the posted information does not establish whether the association was strong or weak, positive or negative, or estimated precisely. The absence of a reported estimate should not be interpreted as evidence that EEG failed to predict fMRI; it leaves the result unknown from this record.

Even a reported correlation would answer a limited question. In general, association between two signals does not demonstrate causation, establish that one signal can replace another, or show an effect on health outcomes. The study has no randomized comparator, so its design does not support a treatment-effect comparison between groups. The registry describes neurofeedback as an activity participants undertook, but does not report an outcome showing whether it changed their ability to control brain activity.

The record also does not report uncertainty intervals, participant-level variation, completeness of data, or analysis details beyond the endpoint description. Those omissions limit assessment of precision, reproducibility, and how representative an average may be of individual participants. The outcome population is described as all participants, but the number with usable data is not reported in the registry record.

The most defensible interpretation is therefore methodological rather than quantitative: the trial was designed to examine EEG-fMRI correspondence in healthy adults in a two-session setting, and its registry record gives the measurement concept but not the numerical outcome needed to judge the observed association.

14. Why This Trial Matters Statistically

This study is statistically interesting because it asks whether a signal measured by EEG can track brain activity measured with fMRI. The endpoint is an association between predictions from multiple EEG features and fMRI-measured default mode network activity during cognitive tasks. Studying how closely distinct measurement modalities correspond can raise useful questions about prediction, repeated measurements, and the level at which results should be summarized.

The design also highlights why the unit of analysis matters. The registry refers to correlations within participants and an average across two sessions, but does not specify the precise unit used to calculate the reported mean and standard deviation. In repeated-measure settings, observations from the same person may be related; methods that account for that dependence can differ from methods that treat every observation as independent. The analysis details needed to assess this issue are not reported in the registry record.

Another statistical lesson is the distinction between an endpoint definition and an endpoint result. Naming Spearman correlation and describing its interpretation does not reveal the association's size or precision. Without the estimate and uncertainty, readers cannot tell whether the data support a consistent relationship or how much participant-to-participant variation there may be.

Finally, planning calculations and observed evidence serve different purposes. The stated sample-size illustration assumptions do not turn this single-group study into a two-arm trial, nor do they provide observed power. Clear separation of design, analysis, and result is essential when interpreting clinical and behavioral research. Here, the registry record makes the scientific question understandable, but leaves the numerical answer unreported.

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 main limitation for statistical interpretation is that the registry record does not report the primary outcome estimate, standard deviation, confidence interval, or test result. Without these values, the association's magnitude, direction, variability, and precision cannot be assessed.

The study is single-group, with allocation listed as NA and no masking. There is no randomized control comparison in the registry record. This limits what can be inferred about the effect of neurofeedback compared with an alternative condition. The registry describes participants trying to control real-time brain feedback, but does not report a specific behavioral or clinical outcome demonstrating change.

The outcome description refers to multiple EEG frequency bands and two sessions, but does not report how individual features were combined, how the temporal correlations were calculated, or how repeated observations were handled. Details on model specification, assumptions, and analytic choices are not reported in the registry record. These omissions make it difficult to evaluate reproducibility or determine how sensitive the result might be to alternative analysis choices.

Although the registry says all participants were included, it does not report the number with complete endpoint data, missing-data procedures, or participant-level results. The record also does not report a sample-size justification, a detailed statistical analysis plan, or interim analyses. The planning illustration uses two-arm assumptions that do not match the listed single-group design, so it should not be treated as a description of the trial's design or as observed power.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Investigating Electroencephalographic Predictors of Default Mode Network Anticorrelation in Healthy Adults — NCT05592600.
• Registry record last updated 2026-03-12; status last verified 2026-02.
• Results first posted 2026-03-12.
• 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

NCT05592600 is a completed, single-group behavioral study sponsored by Drexel University. The registry lists 24 enrolled participants, healthy adults, no masking, and allocation as NA. The study describes two sessions: simultaneous EEG-fMRI measurement during cognitive tasks and a neurofeedback session with real-time visual feedback during EEG-fMRI recording.

The primary outcome concerns the association between EEG features and default mode network activity measured with fMRI. It is described as a mean Spearman rank correlation, with standard deviation, across two sessions 3 to 62 days apart. Higher correlation is described as greater EEG prediction of fMRI.

The registry record does not report the numerical primary outcome or its uncertainty. It states that all participants were included in the analysis, but details about complete data and missing-data handling are not reported. Serious adverse events, other adverse events, and deaths are recorded as 0 in the listed group.