| Recent research has blurred the lines between the neural mechanisms driving the cognitive control of perceptual attention and of short-term memory (STM), respectively. The control of attention alternates between tonic maintenance of attention to a location, object, or other item and shifts from one item to another. Attention shifting is mediated by parietal cortex in combination with frontal regions (e.g., frontal eye fields; FEF). However, the very same regions of the brain are often implicated in the control of STM. Perceptual attention research often focuses on parietal findings, while STM research often emphasizes frontal mechanisms. This may in part be due to the fact that STM consists of opposing forces of stability (required for maintenance) and flexibility (shifting and updating), and much of the neurophysiological STM research focuses on the stability side of the equation---how information is maintained in STM, especially via action of the dorsolateral prefrontal cortex (DLPFC).;Recent evidence has been reported concerning shifts of attention within STM (i.e., changes to the priority of continuously maintained STM contents), making the role of parietal cortex more apparent. Studies by Nobre and colleagues (e.g., Nobre et al, 2004), Nee and Jonides (2009), Montojo and Courtney (2008), Chiu and Yantis (2009), Esterman et al. (2009), and Tamber-Rosenau et al. (in revision) have demonstrated parietal as well as frontal mechanisms of control for shifts of selection, attention, or priority within multiple modalities of STM, including visuospatial, phonological, and rule STM. In this dissertation, I explore the psychological and neural bases of attention and STM, and attempt to explain the shared neural machinery behind their control. New research is presented that compares multiple acts on the flexibility side of the equation---shifts of selection and updates of content in STM---in order to further our understanding of the neural mechanisms of cognitive control. |
