In-ear electroencephalography: a systematic review of technology, applications, challenges, and future directions

Electroencephalography (EEG) is widely used to monitor brain activity in both clinical and research settings. However, conventional scalp EEG systems require multiple electrodes, specialised equipment, and trained personnel, which limits their practicality for long-term monitoring in everyday environments. In-ear EEG has emerged as a promising wearable alternative that enables discreet and portable neural monitoring. This systematic review examines the current state of research on in-ear EEG technologies. Twenty-four studies met the inclusion criteria and were analysed thematically. The literature highlights rapid progress in device miniaturisation and wearable design, with reported applications including sleep monitoring, seizure detection, cognitive workload assessment, fatigue monitoring, and emotion recognition. Despite these advances, challenges remain related to signal quality, spatial coverage, and motion artefacts. Further research is required to validate in-ear EEG for broader clinical and real-world applications.