Theta-band spectral centroid shifts during visual working memory

Abstract

Objective Theta oscillations (4–8 Hz) are known to be involved in visual working memory (WM), but little is known about the role of the speed and the dynamics of the dominant individual theta frequency (ITF) in visual WM. This study investigates shifts in theta-band spectral centroid and theta spectral power across visual WM stages, alongside neighboring frequency bands (delta and alpha), and their relationship with performance. Methods EEG data were recorded from thirty-six healthy adults performing a color change detection task. Results Time–frequency analyses showed that theta power increased during the encoding and response stage compared to the retention stage ( p < .001). The theta-band spectral centroid accelerated from encoding to response ( p < .012). A similar pattern was observed in the delta band, but not in the alpha band. Shifts in theta-band spectral centroid or theta power between stages did not correlate with performance ( p > .05). Conclusions Our findings show that centroid frequencies are not stable across working memory stages, but vary between encoding, retention, and response. This pattern was observed not only in the theta band but also in neighboring frequency bands, suggesting that these effects are not limited to theta activity, but reflect broader low-frequency dynamics. Significance These results indicate stage-related changes in power and centroid frequency during WM, extending beyond theta-band activity.