The main problem of eye movement control following central vision loss is that saccades lead to the foveation of peripheral saccade targets. While this is normally adaptive, bringing peripheral points of interest in full view, it is obviously maladaptive after central vision loss, requiring corrective saccades to bring the point of interest into view at a preferred retinal location (PRL) bordering the area of vision loss. What would be more adaptive in this case is to re-reference the saccade target location to an extrafoveal PRL. It is important to note that PRL-use is not the same as saccadic re-referencing to the PRL. In fact, SR has been found to develop only slowly - over months - in clinical populations suffering from foveal vison loss (von Noorden & Mackensen, 1962; White & Bedell, 1990; Whittaker, Cummings, & Swieson, 1991). However, recent experiments with central scotoma simulation (Barraza-Bernal et al., 2017; Kwon et al., 2013; Walsh and Liu, 2014; Liu and Kwon, 2016) have demonstrated ways to induce SR over hours rather than months, as reported in the patient studies. While these reports have shown the feasibility of successful SR training with simulated scotomata, they still leave many open questions, as outlined in the work program. Moreover, it took up to 25 hours of training for the fixations with the PRL to become comparably accurate as with the fovea (Kwon et al., 2013), so even a significant reduction of training hours with improved training techniques would be a considerable progress, making future training programs for patients more feasible. Furthermore, the usefulness of SR-training in AMD-patients (instead of study participants with simulated scotomata) still needs to be established.
Because of the slow spontaneous development of saccadic rereferencing and its importance for efficient visual search (including memory-driven search guidance), the main aim of this proposal is the development of an efficient method to train the fast and durable establishment of saccadic re-referencing (SR) to a PRL in the presence of foveal vision loss and to test effects on memory-guided search in the contextual cueing paradigm as well as its transfer to another important task - reading.