Neuroergonomic Analysis of a Brain-Computer Interface Device (BCI)

Background and Rationale

Brain-Computer Interfaces (BCIs) are increasingly employed in neurorehabilitation settings to assist individuals with motor impairments. While these systems enable direct neural control of assistive devices, there is a significant gap in understanding the cognitive demands they impose on users. Excessive mental workload can lead to frustration, disengagement, and suboptimal therapeutic outcomes. This study addresses this gap by applying a neuroergonomic approach-integrating objective neurophysiological measures with subjective user experience (UX) assessments.

Objectives

Primary Objective: To evaluate cognitive load during interaction with the Exobots BCI device by integrating neurophysiological metrics (EEG), psychometric UX scores, and subjective user perceptions.

Secondary Objectives:

1. To map neural activity patterns, focusing on theta, alpha, and beta frequency bands, during BCI interaction.
2. To correlate neurophysiological indicators of mental effort with usability and UX measures obtained via the NASA-TLX and UEQ.
3. To identify preliminary operational sensitivity threshold parameters established during individual device calibration.
4. To analyze participants' subjective perceptions of the physical BCI interface using a semi-structured questionnaire with open-ended questions and visual cards.
5. To formulate technical recommendations for BCI interface design based on the integrated analysis of neurophysiological, psychometric, and qualitative data.

Study Design

This is an interventional, single-group, experimental study without a control arm. All participants will undergo the same protocol, testing three distinct sensitivity levels (low, medium, high) in a within-subjects design, with the order of sensitivity levels counterbalanced to avoid order effects.

Study Population and Sample Size

Healthy adults (aged 18 years or older) who are students (undergraduate, graduate, technical level) or staff members from the Federal University of Paraná (UFPR) and the Federal Institute of Paraná (IFPR) will be recruited.

The minimum sample size was calculated using G*Power software (version 3.1.9.7) for a bivariate normal correlation model (Exact test, Family: Correlation). Considering an expected effect size of r = 0.50, a significance level of α = 0.05, and a statistical power of (1-β) = 0.80, the calculation indicated a minimum of 29 participants. To ensure statistical robustness and account for potential data loss due to EEG artifacts or voluntary dropouts, the target enrollment is set at 30 participants, with recruitment extended to up to 60 individuals if necessary.

Intervention and Procedures

Screening and Consent: Interested individuals will receive and sign the Informed Consent Form (TCLE). A screening questionnaire will be administered to verify inclusion/exclusion criteria (e.g., no neurological disorders, no recent head injuries).

Device and Preparation: Participants will interact with the Exobots device (provided by Neurobots). An elastic cap equipped with six dry/wet EEG electrodes will be placed on the participant's scalp. A water-based conductive gel will be applied to the contact points to ensure optimal signal quality. The robotic glove will be fitted to the participant's hand.

Calibration: The system will be calibrated to recognize each participant's specific neural patterns. Based on the calibration, three distinct sensitivity thresholds (low, medium, high) will be defined and tested individually.

Experimental Protocol: Each participant will complete a sequence of repeated cycles consisting of four sequential steps:

Prepare: The participant focuses attention on their hand in anticipation of the command.

Think: The participant imagines opening/closing their hand without physically executing the movement. The EEG system detects the motor imagery signal. If the signal is maintained above the predetermined threshold for three consecutive seconds, the robotic glove is activated.

Move: The robotic glove passively moves the participant's hand. The participant is instructed to voluntarily accompany this movement if possible.

Relax: The participant stops focusing and rests for a few seconds before the next cycle.

Each sensitivity level will be tested in blocks of approximately 10 minutes, totaling approximately 35 minutes of effective interaction per participant. Sessions will be scheduled in advance, with at least 48 hours' notice.

Outcome Measures

Neurophysiological: Continuous 6-channel EEG recording throughout the task. Spectral power analysis will focus on theta (4-8 Hz), alpha (8-12 Hz), and beta (12-30 Hz) bands, with particular emphasis on the theta/beta ratio as a validated marker of cognitive load.

Psychometric: Immediately after each sensitivity block, participants will complete the NASA Task Load Index (NASA-TLX) to assess perceived mental, physical, and temporal demands, effort, and frustration. At the end of the entire session, the User Experience Questionnaire (UEQ) will be administered to evaluate pragmatic and hedonic quality attributes.

Qualitative: A semi-structured interview with open-ended questions and thematic cards will be conducted to capture nuanced perceptions regarding the physical interface, comfort, and overall experience that standardized scales may not fully address.

Statistical Analysis

Pearson correlation coefficients will be calculated to assess the association between neurophysiological metrics (e.g., theta/beta ratio, alpha power) and UX scores (UEQ and NASA-TLX). A significance level of p < 0.05 will be adopted. Qualitative data will be analyzed using content analysis techniques to identify recurring themes and insights.

Ethical Considerations

The study protocol was reviewed and approved by the Research Ethics Committee of the Federal Technological University of Paraná (CEP/UTFPR) under Approval Number 8.558.948 (issued July 2, 2026; CAAE: 97426026.1.0000.0165). All procedures comply with Brazilian regulations (Resolution CNS 466/12 and LGPD - Lei Geral de Proteção de Dados).

Participants will be informed that no direct clinical benefits are expected, but that their participation will contribute to the scientific advancement of assistive technologies. Risks are minimal and include mild scalp discomfort from the EEG cap/gel, transient fatigue, or mild frustration. Participants may take breaks or withdraw at any time without penalty. All data will be anonymized, stored on a password-protected local hard drive, and kept confidential.

Data Monitoring Committee

A formal Data Monitoring Committee (DMC) will not be established, as this is a low-risk, non-clinical, academic study with healthy volunteers and no investigational drug or device under IDE regulations.