Attention and perceived stability across eye movements

The purpose of this research is to investigate the role of attention in maintaining spatial continuity across eye movements. The eyes move several times each second, and with each eye movement, the entire visual array moves across the retina. When driving, for instance, we may shift our direction of gaze from the rearview mirror to the gear shift, causing the entire windscreen to shift from the lower visual field to the upper visual field. Yet we do not seem to lose track of the visual scene as a whole, and in particular we seem to have little difficulty maintaining the focus of our attention on the locations where important information (such as oncoming traffic) will appear. Indeed, the shift across the retina of the entire visual scene has surprisingly little impact on our subjective sense of space and continuity, despite the fact that when the eyes move, all the neurons in visual cortex suddenly begin receiving information from a new location in space. Visual mechanisms must exist that assist us in maintaining accurate representations of relative space over changes in their retinal positions. One candidate is known as saccadic remapping: namely, cells in some visual cortex regions have been demonstrated to respond to the visual array as though it were already in the retinal locations that it will be in when the impending eye movement is completed. The source of this signal seems to be, at least in part, the eye movement system itself. Saccadic remapping has been suggested to underlie our subjective sense of continuity by providing a continuous representation of visual space over eye movements, though not much is known about how much it actually contributes to visual experience in human observers. This project will investigate the nature of spatial stability over eye movements, specifically assessing whether selective visual attention is a fundamental component of the process. Specific questions that will be addressed are: to what extent do eye movements disrupt spatial attention to peripheral locations? To what extent does attending to specific objects in the environment determine whether their spatial information will be preserved across an eye movement? To what extent do we rely on stable environmental information to keep track of objects when they move on our retina? Behavioural research on healthy observers and patients with brain damage will be used to address these questions. The answers will shed light on the fundamental mechanisms underlying the continuity of conscious visual experience.

Eye movements shift the visual array across the retinae, causing each neuron in visual cortex to suddenly begin receiving information from a new location in the world. The ability to maintain a stable representation of objects in the world across these disruptions in their retinal positions has been attributed to saccadic remapping, a mechanism through which information from the oculomotor system about an upcoming movement is used to stabilize visual information in expected post-saccadic coordinates. The goal of the proposed research is to test the hypothesis that attention plays a critical role in the maintenance of spatial information over eye movements. The first series of experiments will systematically map the locus of spatial attention by first drawing it to a specific location and then presenting probes before, during, and after an eye movement. The prediction is that attention will shift to the expected retinotopic location of the target just before the eyes shift. The relative contribution of environmental cues in guiding attention will be explored as well. In the second part, the degree to which directed attention is necessary for spatial positions to be maintained across an eye movement will be measured using a dual-task approach. Finally, the role of awareness in maintaining spatial representations across eye movements will be explored by collecting reports of the experience when objects are brought in and out of the blind field of patients with hemianopia due to damage to visual cortex. The results will establish the role of attention in remapping and have important implications for current theories of perceptual stability across eye movements.

The primary impact of the proposed research will be an increased understanding of fundamental aspects of human experience, namely, vision, eye movements, and attention. The stable and continuous perception of our surroundings and the ability to keep track of objects in our surroundings is a critical aspect of human experience and to understand it is intrinsically valuable. The fundamental nature of this research means that the beneficiaries, in the short term, will be other researchers, of two varieties: first, researchers who can integrate the results of this research with other discoveries at various levels of analysis to construct a complete and functional understanding of the human brain; second, researchers endeavoring to apply the results to address immediate problems and challenges, such as remediation of disordered processes underlying impaired visual and attentional functioning, human-error accident prevention, and more effective user-interface design. The proposed work will benefit both groups by addressing a specific and novel hypothesis about the nature of perceptual continuity and the relationship between eye movements and attention. The opportunity to benefit from this work will be achieved by publishing the work in high-impact journals and pursuing other less conventional opportunities to communicate the results, such as news media (for example, my most recent results on the topic were reported in Discover Magazine), and also through networking, both within the university (for example, remediation programmes for blind patients being developed within my own department) and outside the university (for example, with companies seeking to develop more effective human-operated devices). The reputation of the United Kingdom as a leading country for fundamental research, and as a center for cutting-edge discoveries in brain and cognitive sciences, will be upheld by the advances made in the proposed research. The appearance of this work in top journals will attract more world-class researchers to work at institutions within the UK and further advance the scientific community here.