Mapping neural activity during naturalistic visual and memory search

In everyday life, individuals often search for one of several items stored in memory. This cognitive process, known as hybrid search, is critical for tasks like navigating using landmarks. While the behavioral aspects of hybrid search have been extensively studied, the underlying neural mechanisms remain less understood. In this study, we combined concurrent magnetoencephalography (MEG) and eye movement recordings to investigate the oscillatory and evoked neural dynamics supporting hybrid search under naturalistic viewing conditions. Twenty-one participants (12 males, 9 females) performed a free-viewing task involving visual search for targets embedded in memory (hybrid search) across structured, context-rich scenes. Time-Frequency analyses revealed specific neural signatures during memory encoding, retention, and visual search. During encoding and retention, posterior alpha-band power decreased with memory load, and frontoparietal beta-band activity scaled with memory load during visual search. By aligning MEG signals to eye movement events and applying source reconstruction, we identified an early visually evoked lambda response, localized to V1, followed by a distributed P3m component, with maximum activation in the right inferior parietal lobe, that discriminated target from distractor fixations. These findings were further confirmed by a deconvolution approach to account for overlapping neural signals linked to eye movements. These results show that distinct oscillatory and evoked signatures track the dynamic brain responses during hybrid search. Alpha-band modulation reflects heightened perceptual and mnemonic demands, whereas beta-band increases index cognitive control engaged during search. The fixation-locked responses highlight how classic electrophysiological signatures, such as target-related components, generalize to free viewing conditions. Together, these findings demonstrate how oscillatory and evoked responses dynamically support hybrid search under naturalistic viewing conditions, revealing how memory, attention, and visual processing interact during active vision.