The perceived world is not a mere copy of the real world, but a result of active processing by the brain. One of the most puzzling abilities of the visual system is size constancy: an object is perceived as having the same size even though its image on the retina varies continuously with viewing distance. This research aims to use psychophysical and neuroimaging techniques to investigate how perceived size is represented in the brain when viewing distance changes.
Afterimage formation, traditionally attributed to retinal stimulation, also depends on post-retinal factors. Interestingly, there are conditions under which
observers are not aware of an inducer stimulus, yet report visible afterimages. The goal of this research is to study the neural correlates of negative afterimages and perceptual awareness by integrating psychophysics and fMRI.
Extracting the meaning of a visual scene is critical to interact successfully with the external world. Previous research has shown that individuals with autism see the ‘trees before the forest’; their visual processing is more sensitive to details than global elements. Previous research has also shown that patients with schizophrenia exhibit deficits in early visual processing, perceptual organization, and facial emotion recognition. The goal of this research is to examine the effects of schizotypal and autistic-like personality traits, as measured by questionnaires, on visual perception. Testing participants from non-clinical populations with different degrees of schizotypal and autistic-like traits will allows us to make important inferences on how the cognitive operations underlying global processing might be affected in autism and schizophrenia.
It is generally accepted that, while the ventral stream (from occipital to temporal cortex) is more susceptible to visual illusions and familiar size, the dorsal stream (from occipital to parietal cortex) is typically resistant to visual illusions. A possible account for this dissociation could be the existence of two separate visual thresholds: one for perception and one for action. There is evidence that vision-for-action (mediated by the dorsal stream) has faster access to visual information than vision-for-perception (mediated by the ventral stream). This study examines the effects of different exposure durations to a visual illusion and the availability of depth cues (e.g. vergence) on perception and goal-directed hand movements.
An accurate evaluation of visual functions is still missing in ophthalmic clinic especially when selective lesions of either parvocellular (small-cell body) or magnocellular (large-cell body) visual pathways are involved. The purpose of this research is to assess and monitor impairments or improvements of magno and parvo visual pathways in patients with visual field defects by combining psychophysics and fMRI.