Influence of high-level visual processes on saccadic eye movements

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Research over the past 50 years has demonstrated that the primate cerebral cortex contains more than 30 specialised visual areas. An important principle that has emerged from research in the visual system is the anatomical segregation of cortical areas involved in specific functional aspects of visual processing. The visual system seems to be organised into at least two separate pathways that both originate in the primary visual cortex. A dorsal pathway projects through the parietal cortex whereas a ventral pathway projects through the temporal cortex.  According to an influential model, the two systems are assumed to act independently. The dorsal action stream provides flexible control of phylogenetic old subcortical visuomotor modules for the generation of motor acts, while the ventral "perception" stream provides the rich and detailed representation of the visual world required for cognitive operations. Although this hypothesis has been supported by numerous psychophysical and neuropsychological studies, several recent findings suggest that the visual streams may interact more often than expected from this model. The strongest evidence for an interaction of the two visual streams has come from studies that have demonstrated that faces act as potent targets for movements of the eyes and that the gaze direction of a subject can influence the motor preparation of the eye movements. This is surprising as the temporal lobe is involved in high-level visual processing, including the processing of faces, whereas areas in the frontal lobe, parietal lobe and midbrain are involved the generation of fast eye movements. In this research project, we will investigate the neural mechanisms that lead to the effects of faces on eye movements.