Anatomical and Functional Predictions of Blindsight Capabilities in Patients With Lateral Hemianopsia

Anatomical and Functional Predictions of Blindsight Capabilities in Post-Stroke Patients With Homonymous Hemianopia (PRE-SIGHT)

Homonymous lateral hemianopia (HLH) is characterized by loss of vision in half the visual field, and is the most common neurovisual disorder following stroke.

Numerous behavioral and neuroanatomical studies have focused on the phenomenon of blindsight, corresponding to patients' unconscious residual visual capacities in the blind hemifield. Cohort studies of patients have highlighted different types of blindsight, and a low occurrence of the phenomenon initially described: (1) type 1 blindsight (≈12%), unconscious visual abilities; (2) type 2 blindsight, visual abilities associated with sensations in the blind field (≈18%); (3) blindsense, sensations in the blind field without visual abilities (≈30%); and (4) no blindsight (≈40%). The heterogeneity of these blindsight abilities in the HLH population is closely related to patients' neuroanatomical and functional profiles.

In particular, resting-state functional imaging (r-fMRI) and default mode network analysis have highlighted a significant correlation between the degree of inter-hemispheric connection (between the healthy and injured hemispheres) and the rate of spontaneous visual field recovery. To our knowledge, this degree of functional connectivity has not yet been studied in relation to blindsight abilities. However, this functional MRI measurement tool represents a potential predictive factor for patients' residual performance in their blindsight field, in order to assess the level of visuo-cognitive impairment and, ultimately, to adapt care.

Inclusion Criteria:

• Subjects aged 18 and over
• with homonymous visual field amputation sequelae of a retrochiasmatic lesion of vascular origin (stroke), including the occipital region (primary visual cortex, optic radiations, associated occipital areas)
• Requires follow-up brain MRI as part of treatment
• Able to perform experimental tasks on computer
• Express consent to participate in the study
• Member or beneficiary of a social security scheme

Exclusion Criteria:

• Severe neuropsychological disorders (language, memory, attention, vigilance, reasoning)
• Severe ophthalmological disorders or visual acuity below 3/10 prior to stroke
• Progressive ophthalmological disorders (cataract or glaucoma) likely to bias measurements
• Major psychiatric or behavioral disorders making care impossible
• Patient benefiting from a legal protection measure
• Pregnant or breast-feeding women (declarative information)