Dipartimento di Psicologia

Descrizione del progetto

Injury to cortical visual areas leads to the loss of visual experience in the contralesional hemifield (hemianopia). Nonetheless, implicit visual functioning may be retained in hemianopic patients (HP), even in the absence of visual awareness.
For instance, they may implicitly detect or discriminate the emotional content of the visual signals (affective blindsight, AB) and integrate unseen visual stimuli with auditory information (crossmodal blindsight, CB). The present project investigates which neuronal structures and pathways can sustain unconscious perception of visual signals in the absence of V1 or a damage of the neural pathway feeding V1 and whether a training of residual visual abilities can induce a restoration of normal conscious vision in the blind field of hemianopic patients.
Indeed, a strong debate exists about the existence of either one single pathway sustaining both unconscious and conscious perception, or of different pathways that diverge at early processing stages. The former position envisages a difference in the threshold/mechanisms of activation within the same neural system, whereas the latter postulates two or more separate pathways; one (Retina-SC-Pulvinar-Parietal cortex, i.e. retina-colliculo-dorsal pathway, RCDP) for unconscious perception and a different one for conscious perception (Retina-LGN-Occipital pathway, RLOP). By combing multiple approaches from cognitive neuroscience, including psychophysics, lesion, transcranial magnetic stimulation (TMS), electrophysiological measures (EEG), functional magnetic resonance imaging (fMRI) and tractography (DTI), our aim is to formally test these models, in order to assess:
1. the role of SC and Pulv in unconscious visual perception of emotion, in the absence of any cortical feedback,
2. the role of RCDP in the crossmodal blindsight,
3. whether it is possible to find conditions in which the neural activity along the dorsal stream (RCDP) can generate visual awareness and
4. the emergence of conscious vision from the various forms of unconscious visual capacities, i.e. whether multisensory training of the residual visual abilities can induce a restoration of normal conscious vision in the blind field of hemianopic patients.
The studies will involve both brain damaged patients lacking visual awareness and healthy participants. Critically, the present program also involves computational model studies, aiming to articulate our interpretation of the behavioral data and provide a reliable and coherent explanation of the mechanisms underlying residual visual abilities in hemianopic patients and the restoration of visual abilities in the blind field after multisensory training. We believe that there is an extraordinary theoretical, computational, as well clinical advantage in combining basic science, rehabilitation studies and computational modeling in the field of vision.

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