The neurophysiology of intersensory selective attention and task switching

The neurophysiology of intersensory selective attention and taskswitching by Jeremy William Murphy Advisors: John J. Foxe, Ph.D. and Sophie Molholm Ph.D. Our ability to selectively attend to certain aspects of the world and ignore others is fundamental to our day-to-day lives. The need for selective attention stems from capacity limitations inherent in our perceptual and cognitive processing architecture. Because not every elemental piece of our environment can be fully processed in parallel, the nervous system must prioritize processing. This prioritization is generally referred to as selective attention. Meanwhile, we are faced with a world that is constantly in flux, such that we have to frequently shift our attention from one piece of the environment to another and from one task to another. This process is generally referred to as task-switching. Neural oscillations in the alpha band (~8-14 Hz) have been shown to index the distribution of selective attention, and there is increasing evidence that oscillations in this band are in fact utilized by the nervous system to suppress distracting, task-irrelevant information. In order to elaborate on what is known of the function of alpha oscillations as well as current models of both intersensory selective attention and task switching, I investigated the dynamics of alpha amplitude modulations within the context of intersenory selective attention and task switching in neurologically typical young adults. Participants were alternately cued to attend to v either the visual or auditory aspect of a compound audio-visual stimulus while high-density electroencephalography was recorded. It is typically found that alpha power increases over parieto-occipital cortices when attention is directed away from the visual modality and to the auditory modality. I report evidence that alpha oscillations play a role in task-switching (e.g., when switching from attending the visual task versus repeating this task), specifically as biasing signals, that may operate to re-weight competition among two tasks-sets. I further investigated the development of these same processes in school-aged children and adolescents. While exhibiting typical patterns of alpha modulations relevant to selective attention, Young school-aged children (8-12 years), compared to older participants, did not demonstrate specific task switching modulation of alpha oscillations, suggesting that this process does not fully develop until late adolescence. Finally, children and adolescents on the autism spectrum failed altogether to exhibit differentiation of alpha power between attend-visual and attend-auditory conditions—an effect present in age and IQ matched controls—suggesting that ASD individuals may have a deficit in the overall top-down deployment of alpha oscillatory biasing signals. This could result in an inability to ignore distracting information in the environment, leading to an overwhelming, disordered experience of the world, resulting in profound effects on the both social interaction and cognitive development. Altogether, these findings add to growing evidence that alpha oscillations serve as domain general biasing signals and are integral to our flexible goal-oriented behavior. Furthermore, the flexible use of these biasing signals in selective attention and task switching develops over a protracted period, and appears to be aberrant in autism spectrum disorder.