Assessing the Neural Correlates, Sources and Consequences of the Attentional Rhythm

Evidence suggests that even when sustained at a single location, spatial attention waxes and wanes over time. These fluctuations are cyclic, lasting about 125-200 ms (i.e., ~4-8 Hz), and are characterized by alternating periods of focused attention to a single location together with exploratory periods during which attention is prone to switching to a new source of stimulation. Despite an increasing interest in this temporal property of spatial attention, multiple aspects of rhythmic attentional sampling remain to be explored. In this dissertation, I introduce and examine three unexplored areas related to this topic. The first area, addressed in Experiment 1, concerns the potential neural oscillatory signatures of attentional rhythmicity. Precisely, it assesses the role of a well-established oscillatory correlate of selective attention, alpha band power, in rhythmic switching of attention over time. The second area focuses on the neural sources controlling rhythmic attentional sampling. More specifically, the goal of Experiment 2 is to establish causal evidence for the involvement of an important attentional hub in generating the attentional rhythm using transcranial magnetic stimulation. Finally, the last area examines the consequences of attentional rhythmicity on the encoding and storage of information in working memory. In particular, Experiment 3 provides evidence that rhythmic changes in spatial attention affect the quality with which information is encoded into working memory. Finally, Experiment 4 assesses whether attention rhythmically cycles between items stored in WM in a manner similar to the cycling observed when attention is directed to the external world. In summary, the work included in this dissertation makes an important contribution to extending our understating of the attentional rhythm and introduces multiple avenues for further research necessary in this area