Neural mechanisms of perceptual stability in magnitude perception
Magnitude dimensions such as space, time, and numerosity represent fundamental aspects of the external world. A correct perception of these dimensions is needed to understand the spatial properties of the environment and navigate through it, its temporal structure, cause-effect relations, and duration of events, and the number of objects that are present in the visual scene. As magnitude dimensions share similar properties and are often intertwined in the perceptual environment, they are thought to share a similar neural mechanism called the generalized magnitude system. However, while object and events in the space surrounding us usually appear as stable, embedded in a seamless stream of perception, neuronal activity is usually very noisy, and biological sensors like the eye are unstable due to continuous movements. Visual magnitude representation is thus subject to the noisiness of neuronal processing. How does the brain achieve such a remarkable stability despite the noisy nature of its complex machinery? The goal of this proposal is to investigate the brain processes ensuring the stability and continuity of visual magnitude information, using psychophysical, electroencephalography (EEG), and brain stimulation techniques (TMS). Recent studies suggest that to achieve perceptual stability and continuity the brain integrates visual information over time, giving rise to perceptual biases known as serial dependence. While serial dependence has been linked to stability and investigated across several domains, little is known about how magnitude information is stabilized and whether a generalized stability mechanism exists. By taking an interdisciplinary approach, NeSt thus aims to address these issues from a novel perspective and shed new light on the mechanisms ensuring continuity and stability of spatial, temporal, and numerical information.