Attention samples features in working memory rhythmically

Attention samples perceptually available stimuli at a theta rhythm (3-6 Hz). When participants split their attention between several locations or non-spatial features, target detection is facilitated rhythmically and in alternation between those locations/features (Fiebelkorn & Kastner, 2019,Mo et al., 2019; Re et al., 2019). Recently, it has been demonstrated that these rhythmic attentional processes also extend to internal, object-based representations in a spatial visual working memory paradigm (Peters et al., 2018). Importantly these findings indicate that similar attentional mechanisms are engaged for visually available and internally stored item representations. In this study we aimed to show that attention to non-spatial features in visual working memory displays similar rhythmic patterns. Participant's encoded two sequentially presented objects of different colors at fixation. A subsequent retro-cue directed attention to one of these items and predicted the color of the probe with 75% cue validity. We probed the current focus of internal feature-based attention by presenting valid (same color as cued VWM item) or invalidly cued (different color) probes at several densely sampled SOA's. RT time-series of valid and invalid probes fluctuated at a frequency of 4 Hz in an anti-phasic pattern, indicating that encoded features of VWM items were sampled in alternation. Our findings suggest that attention towards external and internal stimuli might be utilizing similar, rhythmic neural mechanisms. This has potential implications for the temporal dynamics of multi-object VWM maintenance, multi-object visual search and might help understand the binding problem for VWM representations.