For second language (L2) learners, achieving processing speed and accuracy in auditory speech comprehension comparable to those of native speakers remains a major challenge. In recent years, advances in high-temporal-resolution electrophysiological techniques, such as electroencephalography (EEG) and magnetoencephalography (MEG), have provided a new theoretical framework for investigating L2 processing from the perspectives of neural oscillations and neural entrainment. This review systematically synthesizes recent research on neural oscillatory activity underlying auditory speech perception and comprehension in L2 learners, with a particular focus on the functional roles of different oscillatory frequency bands across hierarchical levels of speech processing, as well as the modulatory effects of language experience and environmental factors on neural oscillatory patterns. Accumulating evidence suggests that neural oscillations at different frequency bands encode speech information at multiple temporal scales, ranging from phonemes and syllables to phrasal structures. However, the relationship between cortical tracking strength in the first language (L1) and L2 remains unresolved, with inconsistent findings likely arising from differences in experimental paradigms, analytical approaches, and participants’ language experience. In addition, bilingual background, especially L2 proficiency, has been shown to significantly modulate neural oscillatory patterns during L2 auditory processing under both quiet and noisy listening conditions. As a common phenomenon in bilingual language use, language switching typically imposes increased demands on cognitive control, which are primarily reflected at the neural level by modulations in oscillatory power in the delta (δ) and theta (θ) frequency bands. Based on these findings, this review integrates converging and diverging evidence in the current literature and highlights the need for future studies to incorporate complex auditory environments and longitudinal designs, in order to further elucidate the neural mechanisms of L2 auditory speech processing from a neural oscillation perspective.
Zhu et al. (Thu,) studied this question.