Detecting Blindsight in Clinical Settings: A Preliminary Case Series Investigation

Aims: After occipital damage, hemianopic patients may respond to targets presented in their non-responsive hemifield even if they are unaware of their presence. This phenomenon, called blindsight, is probably mediated by an extrastriate route and can be revealed by forced-choice response paradigms. Since blindsight can help patients avoid obstacles and prevent collisions, and can be trained, identifying blindsight subjects within the clinical setting deserves consideration. This preliminary investigation assesses the effectiveness of a simple and fast procedure devised on purpose in four well-studied hemianopic patients. Study Design: Case-series. Place and Duration of Study: University of Turin, Dept of Ophthalmology, between February 2023 and July 2024. Methodology: Flickering sinusoidal gratings (temporal frequency: 10 Hz) were briefly presented in the blind hemifield above or below the horizontal meridian. Fixation was strictly monitored. Subjects had to report, according to a 2AFC (Alternative-Forced Choice) temporal paradigm, in which interval the stimulus was presented. Results: A proportion of correct responses significantly above chance was recorded in subject DC (60.94%, c2 = 6.08, p: .013) with selective deafferentiation of the striate cortex whereas the performance of the other patients, with more extensive damage, was at a chance level. Conclusion: In line with the literature, blindsight depends on the extent of the cerebral injury. This simple and fast procedure (examination time: approximately 20 minutes) seems promising for selecting, within the clinical setting, patients who should be further investigated for blindsight. Within a translational framework, the aim is to customize and optimize rehabilitation programs aimed at increasing the unconscious detection rate in the blind region and, hopefully, switching unconscious detection into aware perception.