Blindsight.Evidence of Blindsight - Essay Example

? Blindsight Introduction Blindsight is a situation where patients with damage in the primary visual cortex of the brain have the ability to tell where an object is although they cannot see it. The ability to see is a connection between the mind and the visual field of an individual (Carlson, 2010). Patients in this condition are blind in one side of their visual field, which happens due to destruction of the striate cortex or the V1 or the primary visual field (Collins, 2010). Researchers in neuroscience show evidences of blindsight with studies showing that patients have an ability to guess visual stimulus aspects like location or movements even when consciously unaware of the stimuli. This ability is called blindsight 1. The patients also show to have ability to perceive change in movement within the blind area. This type of perception is called Type 2 blindsight. The essay that follows discusses the evidence for blindsight and how evolving research techniques avail information of neural processes involved in blindsight. Evidence of Blindsight Research has proved the existence of blindsight. A research team from Japan with Prof. Tadashi Isa and Dr. Masatoshi Yoshida as leaders form the Institute of Physiological Sciences brings a compelling evidence of blindsight. According to National Institute for Physiological Sciences (NIPS), the team found that blindsight occurs because information bypasses the primary visual cortex. The researchers used Japanese monkeys that had one side of their primary visual cortex damaged, and recorded their eye movements. The team engaged the monkeys in eye training task for 2-3 months, which enabled the monkeys to move their eyes correspondingly to the direction of an object even in their affected visual filed side. The monkeys’ brains gained ability to feel the presence of an object without even having to see it. At the end of the training, the monkey’s eye movements seemed almost normal. To investigate eye movement, the researchers compared how the monkeys’ eye moves to targets in their affected visual field with eye movements to dark targets in the normal visual field. They found that both states were difficult to see (NIPS, 2008). Form this observation, the researchers derived two differences of the affected from the normal visual fields; first, the monkeys had straight trajectory of the eye movements, and secondly, they had short time response of their eye movement. According to the research, the difference was a result of the damage of eye movement control and mind’s decision making, but not entirely due to vision. Thus; the conclusion arrived by the research shows that the monkeys’ eye movement after the primary visual cortex damage were a mediation of qualitatively different vision supported by alternative brain circuits bypassing the primary visual cortex. According to Dr. Yoshida, the finding helps implement a new strategy that aims at rehabilitating those patients with damaged primary visual cortex (NIPS, 2008). The process will train patients to activate alternative brain circuits to see the unseen. A similar training would help people with this condition to know the location of an object without having to see it. Another research conducted by Tony Ro at New York City College shows that training can help a damaged or injured brain to see again. Tony Ro, according to National Science Foundation (NSF) points that blindsight shows useful clues on brain structure (O'Brien & Baime, 2012). There are a number of brain areas that work with processing visual information, but without awareness of the visual fields. The other parts of the brain receive visual inputs from the eyes but do not consciously access the inputs (O'Brien & Baime, 2012). Tony Ro’s research develops a clear vision of how other parts of the brain, apart from the visual cortex respond to visual stimuli. The research recreates an artificial blindsight to a volunteer by having a powerful magnetic pulse shot into their visual cortex. The magnetic pulse brings disability to the volunteer’s visual cortex and becomes blind shortly and rapidly. The research takes place in a small booth with the volunteer seated in front and instructed to directly look at a computer. Tony puts a around device at the back of the volunteer’s head. Clicks of two seconds apart are set in the booth where each click is a magnetic pulse disrupting the visual cortex activity of the volunteer causing blindness. As the pulse blind the volunteer, a diamond or square shape flashes on to the computer screen in front of him. Tony says that 60 to around 100 percent of the time, test subjects give a correct image report (O'Brien & Baime, 2012). Tony observes other parts of the brain to see what happens to them at the instance when the volunteer is blinded and a shaped flashed on the screen. As the blindness continues to wear off right away with no lasting effects, there is a likelihood of a lot of alternative visual pathways going into the brain from an individual’s eyes to process information at unconscious levels. This research shows the processes that happen in the mind when visual information is sent to the brain from the visual cortex and the alternative pathways it follows to reach the brain when there is damage on the visual cortex. The researcher believes that understanding and mapping the alternative pathways can make a good move in finding alternative rehabilitation on blindsight disorder. Naturally when people approach objects, they easily avoid the obstruction they bring. Studies have suggested that the ability to avoid the obstacle relies on mechanisms in the dorsal visual stream in the posterior parietal cortex (Christopher, Craig & Melvyn, 2009). This research sought answer the question of where the visual inputs of the mechanism come from by providing evidence that the mechanisms can operate in real-time without primary visual cortex (V1) inputs. The research conducted an experiment that showed that a patient with a dense visual field resulting from damage to V1 showed sensitivity to position of unseen static objects placed in their blind side. Avoiding stationary objects needs a complex interplay between incoming visual information, which shows the location of the information and the visual system that controls the execution of the reach (Christopher, Craig & Melvyn, 2009). Previous studies argue that there two separate but interacting visual processing streams within the brain that mediate vision for action and perception. A visual pathway extending from the primary visual cortex (V1) to the superior parietal lobe is taken as significant for controlling visually based actions like reaching and eye movements. On the other hand, visual pathway extending from primary visual cortex to an inferior temporal cortex is significant in object recognition and conscious visual perception. Damaged dorsal stream largely affects the ability of people with neurological disorder to avoid objects in their way according to previous studies. The studies have also shown no effect on object avoidance from damaged ventral stream. This shows that patients with damaged dorsal stream who can recognize objects have difficult in recognizing the position of the obstacle while reaching them. This contrasts people with damaged ventral stream who can avoid obstacles although they do not have ability to recognize the obstacle (Christopher, Craig & Melvyn, 2009). This shows that pathways mediating obstacle avoidance differ with those that enable object recognition. Neurological patients can avoid obstacles even with completely impaired visual awareness. For quite some time, people have known that there exist multiple pathways through which visual information reaches the brain cortex. Some of these pathways bypass the primary visual cortex and project to visual areas. Existence of these alternative visual pathways have been used to explain blindsight where patients who lose conscious vision due to v1 lesion have the ability to respond to visual information subjected into their blind field (Christopher, Craig & Melvyn, 2009). Patients with complete blindness from damaged primary visual cortex have ability to avoid obstacles while walking although they cannot recognize the obstacles. During walking, individuals can self-generate motion cues and optic flow, which lead them to avoid obstacles in their reach. Studies show that patients with damages on primary visual cortex retain motion cues sensitivity though they may not be aware of the movement itself. Previous research suggests effect of dorsal stream on obstacle avoidance even absence of visual awareness however; the visual inputs that help avoid obstacles are unknown. Conclusion Blindsight is an evident occurrence that affects many people in the world. Previous studies proved blindsight existence, and new or current studies still prove its existence. However, these studies have differed in some ways in that the forces driving patients to be able to avoid obstacles in their way or recognize their position vary. The researches have shown that there exist processes associated with blindsight. There is a close connection in psychological emotions brought by the patient’s mind and the primary visual cortex. As the essay discusses, people with damaged visual cortex can, with the help of the mind recognize position of an object as well as others recognizing the object. Patients with damaged V1 have a striking sensitivity to position of static objects placed on their blind side. They have ability to code the position of the obstacles despite inability to recognize their presence (Christopher, Craig & Melvyn, 2009). Although it took long for the reach trajectories in the patient’s blind side to show clear separation, they became different by the end of the reach. While the patient remains sensitive to the obstacle’s position in their blind side, the longer time taken to show spatial separation may be as a result of the inability of the patient to perceive the object. The second experiment conducted by this research showed that sensitivity to obstacles in people with damaged V1 is abolished after a 2 seconds delay. It is consistent with pervious demonstrations that introduction of a short delay before one can reach an object severely disrupt visual stream performance in people with V1 damage. Researchers have shown difference on effect of delay on sensitivity on the object. The research by Tony Ro shows no interruption on images on the computer screen when the volunteer goes shortly blind because other processes in the mind still hold the image (O'Brien & Baime, 2012). The research by Christopher and colleagues however shows disruption on sensitivity when delayed for 2 seconds (Christopher, Craig & Melvyn, 2009). In summary, the researches show that there are neurological processes that associate with blindsight, which help people perform certain activities in life even in damaged visual cortexes. References Baime, J & O'Brien, M. (2012). Seeing Beyond the Visual Cortex: National Science Foundation Retrieved on October 19, 2013, from www.nsf.gov/news/special_reports/science_nation/blindsight.jsp Carlson, N. R. (2010). Physiology of behavior. Boston: Allyn & Bacon. Christopher L. S, Craig S. C & Melvyn A. G. (2009). “Real-time” obstacle avoidance in the absence of primary visual cortex. Retrieved on October 19, 2013, from http://www.pnas.org/content/106/37/15996.full Collins, G. (2010). Blindsight: Seeing without knowing it. Retrieved on October 19, 2013, from http://blogs.scientificamerican.com/observations/2010/04/22/blindsight-seeing-without-knowing-it/ NIPS. (2008. Blindsight: How brain sees what you do not see. Retrieved on October 19, 2013, from http://phys.org/news143222136.html Read More