Visual and Oculomotor Integration: Representations and Temporal Mechanisms

The visual system recruits the oculomotor system to enhance processing at a particular location of interest with the use of saccadic eye movements. This involves the transfer of visual information from the visual system to the oculomotor system so that the correct location or object may be fixated at the expense of all othersa process called target selection. However, the relative extent of visual processing between the visual and oculomotor systems to facilitate this process is disputed. Here, this question is examined by specifically investigating the extent of oculomotor processing prior to a saccade. First, the nature of object representations in the ventral stream of the visual system is examined to gain insight into how complex visual representations are encoded. Next, target selection was examined in a visual context requiring extremely complex visual computations in order to select the correct stimulus. Last, the temporal factors that affect oculomotor target selection were examined. This research demonstrated that objects of considerable complexity elicit similar perceptual behaviours as do simple visual features. This elucidates that there are very robust modes of encoding object representations, which generalize to objects of varying complexity and familiarity. Furthermore, when these same complex visual representations were utilized on a target selection task (visual search), there was evidence of oculomotor competition between them. Given the complexity of these stimuli and the limitations of oculomotor visual processing, it was reasoned that the visual system performed these computations, as observed in the previous experiment, and the results of this computation were output to the oculomotor system. Finally, an analysis of the target selection time course suggested that the oculomotor competition observed previously is likely due to cortical top-down input, further elucidating the role of the visual system in mediating oculomotor target selection.