Balali M R, Hosseini M, Khanboloki M, Mohammadi M, Khorshidvand A M, Taghi Joghataei M. Pathways Mediating Blindsight After V1 Injury: A Systematic Review of Human and Monkey Studies. BCN 2025; 16 (3) :533-550
URL:
http://bcn.iums.ac.ir/article-1-3057-en.html
1- Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran.
2- Department of Anatomy, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran.
Abstract:
Introduction: Although damage to the visual area (V1) leads to visual impairment, some patients retain the ability to process visual information unconsciously, a phenomenon known as blindsight. This study aims to systematically review and compare the proposed neural pathways mediating blindsight in humans and monkeys, providing a structured framework for future investigations in this field.
Methods: This is a systematic review of related articles retrieved from online databases. Following the screening process, we employed the JBI critical appraisal checklist as well as the SYRCLE tool to assess the risk of bias in human and animal studies. We selected 25 articles focusing on the mediating pathways of blindsight.
Results: In humans, the pathways from the lateral geniculate nucleus (LGN) to V5, from the superior colliculus (SC) to higher brain areas, and to the remaining segments of V1 are crucial. The pathway that connects the SC, pulvinar, and amygdala is essential for processing emotional visual information. Studies conducted on monkeys emphasized the importance of the SC-pulvinar pathway and the connections between the LGN and extrastriate visual areas for developing blindsight.
Conclusion: Rather than a single consistent pathway, blindsight appears to involve multiple parallel routes whose engagement depends on factors such as lesion extent, individual neuroanatomy, and time since injury. Future studies should explore the therapeutic potential of these pathways by integrating.
Full-Text [PDF 927 kb]
● LGN to MT pathways are key for motion detection in blindsight.
● The SC-pulvinar-amygdala pathway is vital for affective blindsight.
● Individual neuroplasticity shapes blindsight pathway activation.
● Animal studies have reinforced the roles of the SC-pulvinar and LGN in residual vision.
● Personalized rehabilitation strategies can enhance recovery from blindsight.
Plain Language Summary
This study explores how some people can still "see" in certain ways even after significant damage to their primary visual area (V1) in the brain, a condition known as “blindsight.” Blindsight allows individuals to respond to visual cues without conscious awareness, such as identifying movement or emotional expressions, even though they may report seeing nothing. This review study gathered and analyzed results from 25 studies on humans and monkeys to understand the brain pathways that help enable blindsight. We identified key pathways, including connections from the lateral geniculate nucleus (LGN) to another area involved in motion processing, as well as from the superior colliculus (SC) to regions that aid in recognizing emotions. Each pathway plays a role in providing different aspects of unconscious visual abilities. We also found that blindsight abilities can vary depending on individual differences in brain adaptability, the exact location and extent of the injury, and the time elapsed since the injury occurred. Understanding these pathways is crucial for designing better personalized rehabilitation programs for individuals with visual impairments. By knowing which pathways can potentially compensate for lost vision, therapists may be able to train other parts of the brain to improve visual responses even when conscious sight is impaired. This research helps explain how the brain adapts to injury and highlights the remarkable ways it can find alternative routes to process vision, offering hope for those affected by vision loss.
Type of Study:
Review |
Subject:
Behavioral Neuroscience Received: 2024/10/16 | Accepted: 2024/11/19 | Published: 2025/05/1