RIGHT-HEMISPHERIC ASYMMETRY IN AUDITORY SPATIAL ATTENTION: INSIGHTS FROM EEG-BASED SPATIAL ANALYSIS

Accurately localizing sounds is critical for adaptive behavior, yet the hemispheric organization of auditory spatial attention remains debated. This study examined hemispheric asymmetries in auditory spatial processing of both task-relevant and task-irrelevant sounds. Electroencephalogram (EEG) data were recorded from 65 healthy young adults (19‒27 years old, 31 male) performing a monaural auditory oddball task. Participants indicated the spatial location of target sounds via button press. Behaviorally, right-ear sounds elicited higher sensitivity (d’) and shorter reaction times (RTs), indicating a right-ear advantage. At the neural level, event-related potential (ERP) analyses revealed a larger N1 amplitude (170‒190 ms) for right-ear targets than for left-ear targets, reflecting enhanced early sensory processing during target selection. Right-ear target sounds evoked comparable N1 component in both hemispheres, whereas left-ear target sounds showed pronounced right-hemispheric dominance with reduced left-hemisphere N1 amplitude. For nontarget sounds, no right-ear posterior N1 enhancement was observed; however, the right hemisphere consistently exhibited stronger N1 to ipsilateral sounds, suggesting an intrinsic, early hemispheric bias independent of task relevance. Multivariate pattern analysis (MVPA) further demonstrated higher decoding accuracy for target sound location in the right than left hemisphere, whereas decoding of nontarget location was uniformly low across hemispheres. Importantly, stronger right-hemispheric decoding dominance was associated with greater RT advantages for right-ear target sounds. Together, these findings demonstrate a tight link between hemispheric asymmetry in auditory spatial representations and spatially specific behavioral efficiency in human adults, extending prior work by incorporating nontarget processing into models of auditory spatial attention.