Attention modulation of complex motion patterns in human visual cortex

Abstract

When we are moving through the environment, our visual system exposes to a barrage of motion information about the objects around us as well as our own heading. Processing such an amount of incoming sensory data is beyond the power of the available processing resources. Thus, our visual system is provided with several mechanisms to select the most relevant information. Selective visual attention is one key solution to filter out the incoming visual information based on their relevance for the behavior. Visual attention emphasizes the representation of the behaviorally significant stimuli by dedicating the limited visual processing resources to them at the expense of the irrelevant information. Visual motion information is getting processed in a hierarchy of visual areas termed as the “dorsal stream”, which starts in primary visual cortex (area V1) and ends in parietal lobe. Among the visual areas in the dorsal stream, middle temporal area (MT) and medial superior temporal area (MST) have the key role in visual motion processing for their preponderance of motion-sensitive neurons. In this PhD dissertation, I studied the influence of attention on processing of complex motion information in human visual system. I used so called “spiral motion” patterns as the probe stimuli to simulate complex motion patterns. In the second chapter, I investigated the neuronal correlates of attention in response to “spiral” stimuli using functional magnetic resonance imaging (fMRI). I assessed the tuning as well as the influence of attention on such a hypothetical tuning to spiral motions in MT and MST areas in the dorsal stream of the human visual cortex, in addition to examining the influence of attention on the hemodynamic responses to spiral motion patterns. In the third chapter, I investigated the behavioral correlates of graded attention in discriminating spiral motions in a human psychophysics study.