Topic: Effects of perceptual learning on functional MRI estimates of visual crowding in eccentric vision

Speaker: Dr. Mark W. Greenlee (Institute of Psychology, University of Regensburg, Germany)

Time: 2024/03/05 (Tue) 10:00-12:00

Location: 802 Meeting room, Research and Teaching Building, SH Campus, Taipei Medical University

Abstract:

We rely on central, foveal vision for tasks that require high spatial resolution like reading and face identification. However, eccentric vision is also important for providing spatial context forplanning our next eye, head and body movements. One of the limitations of eccentric vision is related to visual crowding, where flanking stimuli interfere with target identification. In my talk, I will present the results of a series of experiments that aim to investigate the impact of perceptual learning on visual crowding. Participants underwent functional MRI measurements before and after behavioral training on a visual crowding task, where the relative orientation of the opening (gap position: up/down, left/right) in a Landolt-C optotype had to be discriminated in the presence of flanking ring stimuli. Following training, the crowding zone shrinks, leading to an improvement in visual performance in the gap detection task. Estimates of population receptive field (pRF) sizes at and near the trained location decreased significantly (p=0.005). The most pronounced effects of training were found in ventral V2 at eccentricities corresponding to the trained location. In contrast, no significant changes in pRF estimates were found in primary visual cortex (area V1). These findings suggest that practice on a crowding task can lead to a reduction of pRF sizes in trained visual cortex, particularly in V2, highlighting the existence of a form of plasticity and adaptability in the adult visual system induced by prolonged training. Possible applications in low-vision rehabilitation in patients with central vision loss will be discussed.