Abstract
We take for granted that when we open our eyes we experience a rich and complex scene, extending over a wide field of view, an experience described by William James as a stream of visual consciousness. But what we see is the result of integration of incoming information over time and space. Recently scientists have discovered interactions also between foveal and peripheral visual information, using different methodologies. Here we bring together the study of some phenomena originally described as illusions (Uniformity illusion; Honeycomb illusion) with accurate psychophysical measurements of sensitivity to visual form in the periphery, and we study clinical cases of patients with central vision deficits. Central vision is critical for shape perception, and contributes also to the analysis of shape information in the periphery. One situation is when extrapolation and filling-in processes lead to properties from the centre to be perceived as extending in the periphery. We study systematically the conditions of continuity between regions that allow such extrapolation. We predict that information about discontinuity between regions will modulate their interaction. This is tested in a series of experiments (PD1) for 2D shapes and in a second series (BO2) for solid shapes and illumination. Besides having an immediate effect on peripheral appearance, foveal stimulation has also longer-lasting effects on visual processing, e.g., by modulating peripheral adaptation. One way to evidence these changes is to measure after-effects, which has been done for orientation. We extend this approach to more complex properties such as numerosity. So far, we have described how we investigate phenomenal appearance, and sensitivity (the ability to correct identify shapes). In another set of studies, we examine the conditions under which the illusory nature of peripheral appearance affects perceptual confidence (BO2), i.e., to what extent we feel confident in what we see. In the final part (PD3) we address the plasticity mechanisms that allow the foveal visual cortex to process peripheral input after longand short-term deprivation. We do this by using Transcranial Magnetic Stimulation (TMS) in both patients with macular degeneration (MD), who lack foveal vision, and in healthy observers temporarily deprived of foveal input using a gaze-contingent display. When the foveal cortex is deprived of normal input, it may start to respond to peripheral stimuli. Furthermore, we test whether perceptual learning can alter the peripheral representation in the foveal cortex both in MD patients and in healthy observers. Overall, we propose an integrated research program, which elucidates how central and peripheral vision interact over a range of stimulus complexities (from simple 2D gratings to complex 3D shapes), representation levels (from detection to appearance and to confidence) and time frames (from immediate interactions to adaptation and to long-term plasticity).
Dettagli del progetto
Responsabile scientifico: Matteo Valsecchi
Strutture Unibo coinvolte:
Dipartimento di Psicologia "Renzo Canestrari"
Coordinatore:
Università degli Studi di PADOVA(Italy)
Contributo totale Unibo: Euro (EUR) 78.174,00
Durata del progetto in mesi: 24
Data di inizio
05/10/2023
Data di fine:
28/02/2026
