Thesis title: The Effects of Selective Attention on Time-Course of Visual Maintenance: Implication for Phenomenal Consciousness
This thesis aims to contribute to a better understanding of the role of selective attention at early stages of visual processing and maintenance, associated with phenomenal consciousness. A common procedure is used in three experiments, i.e. a change detection paradigm based on Landman et al. (2003). Selective attention is manipulated by assigning the items with different colors coding for different priority to be selected (i.e. high, equal, low). Early and late retro-cues tested different memory stage within sensory store, i.e. iconic memory (< 0.5 sec) and fragile-VSTM (> 0.5 sec). The Experiment 1 (Chapter 2) show that attentional bias has different effects between high (80%) and low priority (20%) items at longer delays (i.e. 600 and 1,200 ms from stimulus offset). The Experiment 2 (Chapter 3) show that the bias is related to suppressive mechanisms, evidenced by increasing difference between low priority and the equal priority items (baseline condition; 50-50%). The Experiment 3 (Chapter 3) excluded the occurrence of feedforward mechanisms in selection. Finally, the neural simulations with an updated version of ViSA (Simione et al., 2012; Chapter 4) confirmed that our results fit well within the theoretical framework of this multistage neural model of selective attention and visual consciousness. General Discussion considers implication relevant for theories of consciousness and attention such as Theory of Attention and Consciousness (Raffone et al., 2014), Global Neuronal Workspace Theory (Dehaene et al., 1998) and Recurrent Processing Theory (Lamme, 2004, 2006).