Seeing the invisible: theory and evidence of blindsight
Aleci, C., Dutto, K. Discov Med 1, 149 (2024). https://doi.org/10.1007/s44337-024-00156-x
Purpose Since the fifties of the last century, a bulk of research demonstrated that unconscious visual functions may persist
in the blind hemifield after stroke, striate deafferentiation, or ablation. This experience is known as blindsight. Great
effort has been paid to clarify the mechanisms underlying this fascinating phenomenon: the characteristic dissociation
in performance between yes/no response design and alternative forced choice procedures, the relationship between
conscious and unconscious perception, the anatomo-functional substrates, and, last but not least, the implications within
the clinical setting. In this review, the theoretical and experimental evidence of blindsight are described.
Methods Bibliographic research was carried out on PubMed, Google Scholar and other resources supporting biomedical
literature, starting with the following keywords (isolated or in combination): blindsight, unconscious vision, hemianopia,
stroke, extrastriate pathway. The references in each selected paper were then analyzed. Overall almost 200 studies were
examined and approximately 150 of them were considered suitable for our purpose.
Results The main findings are reported and organized into two sections: “theory and evidence of blindsight” and “testing
blindsight”. According to the current theories, blindsight may be degraded conscious vision or it can rely on extrastriate
routes. It encompasses a large number of tasks such as grating, color, orientation detection and discrimination, contrast
sensitivity and implicit processing, and is believed to rely on retinal-extrastriate routes that bypass V1. Finally, blindsight
can be trained.
Conclusion Blindsight is worth being investigated in hemianopic patients suffering from stroke or striate deafferentiation
not only within a theoretical framework but also from a rehabilitative perspective.
Keywords Blindsight · Hemianopia · Stroke · Psychophysics · Extrastriate pathway · Unconscious vision
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