Modulations of spatial processing through attentional load

Spatial processing is implemented by selective attention mechanisms and allows us to effectively deal with the broad flow of visual information in a seemingly effortless and highly efficient way. Yet, spatial processing efficiency seems to be influenced by levels of attentional load. The common thread weaving through the diverse contributions that will be presented in this thesis is a detailed investigation into load-induced spatial processing modulations. To do that we adopted a multitasking approach, grounded on the hypothesis that different tasks, despite their distinct nature and specific demands, are characterized by the common use of relatively unspecific yet limited attentional resources. Therefore, when the attentional load increases, for example because of dual-tasking, performance may be impacted. Firstly, we investigated load-induced spatial processing modulations in the damaged cognitive system. Specifically, we tested the impact of attentional load upon spatial processing in an ultra-chronic right hemisphere damaged patient. Despite his ceiling performance in classic paper and pencil test, he showed biases toward the ipsilesional space when attentional load was increased. As, understanding the performance of the "baseline system" is essential for assessing the extent of impairment in patients, we also investigated load-induced spatial processing modulations in healthy adults. In this case we employed different versions of a rather complex dual-task paradigm, involving the presentation of stimuli capable of eliciting an audiovisual integration illusion (i.e., sound-induced flash illusion). Although participants showed increased illusion rates when attentional load was increased, there were no differences between left- and right-sided stimuli. Finally, we investigated neural correlates of load-induced spatial processing modulations in healthy adults. Specifically, we employed a dual-task paradigm identical to the one used in the previous study and recorded electroencephalography during resting-state and while the participants were completing the task. Analysing resting-state data, we have uncovered significant correlations between task performance and intrinsic functional connectivity networks related to auditory and visual processing, as well as the allocation of attentional resources in space. Additionally, analysing Event-Related Potentials, we have identified N1, N2, and P3 modulations associated with the presentation of stimuli eliciting the sound-induced flash illusion during different levels of attentional load, with N1 modulations differing depending on the side of the stimuli.