Khayla Santiago¹ (), Chunyue Teng¹; ¹Lawrence University

Successful goal-directed behavior requires the delicate balance between managing task-relevant information stored in working memory and the continuous processing of incoming sensory input. It remains unclear whether we can concurrently attend to both external sensory inputs and internal representations, or if the focus of attention oscillates between the two sources of information. To test this, we assessed fluctuations in performance during a task that requires simultaneous engagement of working memory and perceptual processing. Participants were instructed to maintain a specific orientation in mind while also observing another orientation patch on the screen. After a variable inter-stimulus-interval (ISI), they were prompted to compare a test probe against either the memorized orientation (memory comparison condition) or the visually monitored orientation (perceptual comparison). Critically, we manipulated the duration of the ISI: 500-1500 ms with a 20 ms step, resulting in a total of 50 ISIs. Response time (RT) and accuracy were analyzed separately for each task. Visual inspection of the time courses revealed notable fluctuations in both RT and accuracy. We performed Fast Fourier transform of the data to extract spectral power and phase angle across different frequencies. Statistical significance was examined through a non-parametric resampling procedure by permutating the RTs and hit/misses across all ISIs. The analysis identified increased power within the theta and low-alpha frequencies (3, 6, and 8 Hz) for both the perceptual and memory tasks. Importantly, the two representations fluctuated at different phase angles at those identified frequencies, indicating a distinct rhythmic alternation in attentional sampling between internal and external visual representations. Together, these results demonstrate the rhythmic nature of attentional shifts between internal and external visual representations, and further highlight the functional relevance of neural oscillations in supporting concurrent visual perception and working memory functions.