Investigating mechanisms of spatial and temporal selective visual attention

Selective attention in vision undoubtedly uses many different types of mechanisms to achieve better processing of behaviorally relevant visual information. The present dissertation inspects two such possible mechanisms. The first proposed mechanism is through selective spatial attention. We proposed that “attentional control” regions of the brain send selective attention signals that relate to the differential attentional modulation measured in visual cortex, corresponding to the attended and ignored sides of visual space. We find, surprisingly, that the BOLD signal of attentional control regions do not appear to code for selective spatial attention in this manner. fMRI signals therefore appear to prioritize general arousal effects of attention more so than the types of attentional control signals that frontoparietal regions send to early visual cortex. The second proposed mechanism is through sampling visual information through time. It is hypothesized that intrinsic neural oscillations represent inhibitory waves of cortical processing ability, in which subjects are more or less able to detect visual stimuli depending on the phase of α oscillations in the brain. We used a paradigm involving visual entrainment; this paradigm has been used in the past to support the “pulsed inhibition of α” hypothesis. We find that the behavioral effects of this paradigm cannot strongly be supported by the pulsed inhibition of α because the neural effects of visual entrainment are transient and do not carry over into the target period