Intelligent and inclusive EEG-driven authentication for gender fairness and cognitive impairment

User authentication plays a key role in user modelling within computing systems, particularly for both normal control (NC) and Alzheimer’s disease (AD) users. Conventional authentication methods are vulnerable to external attacks and often rely on memory, which poses challenges for AD users experiencing cognitive decline. Electroencephalography (EEG) signals offer an alternative due to their subject-specific and difficult-to-replicate properties. However, differences in EEG patterns between NC and AD populations require intelligent authentication approaches that can generalise across heterogeneous user groups. This study proposes Biometric using microstates of EEG (Bio-MEEG), an intelligent EEG authentication framework that integrates EEG microstate analysis, one-dimensional convolutional neural networks (1D-CNNs), and ensemble learning based on echo state networks (ESNs) for user authentication under a closed-set, repeated-sample identification setting. The model is evaluated on 1,015 samples from 203 participants across multiple countries and EEG configurations. Results show that Bio-MEEG achieves stable authentication performance with minimal accuracy fluctuation across demographic subgroups and remains robust under feature-space adversarial perturbations. By supporting both NC and AD users without significant performance disparity, the proposed framework contributes toward more accessible, intelligent, and reliable EEG-based authentication systems.