Spatiotemporal analysis of EEG rhythms during a visual working memory task with anticipated within- and cross-modal distractors

Working memory (WM) temporarily maintains and manipulates information, supporting higher-order cognitive functions. A major challenge for WM is interference from distracting stimuli during retention. When distractors are predictable, the brain may engage proactive mechanisms to protect memory representations. Whether these mechanisms differ depending on whether the anticipated distractor is in the same or different modality from the to-be-remembered items remains unclear. EEG theta oscillations (3.5–7.5 Hz) are associated with encoding and maintenance, while alpha oscillations (8–14 Hz) with cortical inhibition of irrelevant input. This thesis investigates theta and alpha activity during a visual WM task with anticipated visual or acoustic distractors. EEG (64 channels) was recorded from 22 participants who memorized visually presented consonants, maintained them across two retention intervals separated by a distractor phase, and responded to a probe. Distractors were consonants presented visually or acoustically, and their timing and modality could be anticipated by participants. EEG data were analyzed at scalp and cortical source levels to compare oscillatory activity during encoding and pre-distractor retention. Both conditions showed typical WM-related patterns: posterior alpha suppression during encoding, parieto-occipital alpha synchronization during retention, and sustained frontal theta synchronization. Visual distractors elicited stronger posterior theta synchronization during encoding and retention, and stronger occipital alpha synchronization during retention, suggesting greater effort to maintain visual representations and protect them from within-modal interference. Acoustic distractors were associated with broader parieto-frontal alpha and theta activity, indicating wider attentional-control networks for cross-modal inhibition. These findings suggest that WM protection relies on shared and specific oscillatory responses tuned to expected interference.