Topic proposal for visual extinction.
The topic of visual extinction will be covered by Aaron Fishman, Marissa Hone and Matthew Warman. Tentatively, the following subtopics will be covered: Characteristics, causes/ Signs & Symptoms, Pathophysiology, Diagnosis, Prevention, Management/Treatment, Prognosis, Epidemiology, History, Society and Cultural, Background, and Research.
Visual extinction is a neurological disorder characterized by severe impairment in identifying two or more visual stimuli displayed briefly at the same time. Patients having this condition can successfully identify single objects presented to them briefly. In case of multiple stimuli patients either fail to identify some of the objects or even do not detect them at all.
Visual extinction is caused by unilateral brain damage (Rorden). Symptoms involve the inability to see two objects simultaneously. Sufferers fail to see objects related to the side of the brain that was damaged during the trauma (the ipsilesional side).
Diagnosis is achieved by flashing lights simultaneously in different parts of the field of vision, both right and left. The patent is then asked to report which lights are visible. From this information, a diagnosis of visual extinction can be attained.
The only real treatment for visual extinction is through rehabilitation and exercise of the left hemisphere. One paper notes that simply telling a patient to work on his visual field is not enough, that more proactive approaches must be taken and a number of tools are available the help a patient work on his or her visual field. The same paper says that scanning rows of bright lights is one such approach and that there are many other techniques available with various rates of success.
Visual extinction is most often caused by lesions in the parietal lobe and occasionally by lesions in the frontal or thalamic regions. Usually problems occur in the right hemisphere. Visual extinction, just as other kinds of visual neglect, is often caused by a stroke. Treatments can sometimes improve function, though the damage can never truly be repaired and the problems are never completely cured, only mitigated.
As visual extinction is usually the result of a stroke, there is no way to transmit this disorder to other people. Researchers began studying visual extinction in great depth in the 1990s.
This condition does not inhibit patients from social interaction. In fact, most people would not be able to distinguish a visual extinction patient from a non-visual extinction patient in passing. Detrimental social aspects may be repercussions of the stroke, which caused the visual extinction, but not from the visual extinction condition alone.
Work Distribution: The work for this project has been divided into three broad categories; one of us will be assigned to each of the categories. Matt will take background of the disease: Characteristics, causes/ Signs & Symptoms, Pathophysiology, Diagnosis. Aaron will take the impacts of the disease: Prevention, Management/Treatment, Prognosis, Epidemiology. Marissa will take the social impacts, along with history and future work on this disorder: History, Society and Cultural, Background, Research. In the end, we will of course all review each part and the whole finished project, but for gathering data and writing up information, these subsections will be effective.
References:
(MH) Pavlovskaya, Marina, Dov Sagi, Nachum Soroker, Haim Ring. Visual Extinction and Cortical Connectivity in Human Vision. Cognitive Brain Research, Volume 6, Issue 2, October 1997, Pages 159-162
(MH) Rafal, Robert D., and Patrik O. Vuillemumier. A Systematic Study of Visual Extinction: Between and within-field deficits of attention in hemispatial neglect. Brain. 24 January 2000, Pages 1263-1279
Bailey, Maggie, M Jane Riddoch, and Peter Crome. "Treatment of Visual Neglect in Elderly Patients With Stroke: A Single-Subject Series Using Either a Scanning and Cueing Strategy or a Left-Limb Activation Strategy." Physical Therapy 82.8 (2002): 782-797.
"Neuroexam.com - Vision (CN II)." neuroexam.com - An interactive online guide to the neurologic examination. 30 Sep. 2009 <http://www.neuroexam.com/content.php?p=18>.
Geeraerts, S, C Lafosse, E Vandenbussche, and K Verfaillie. "A psychophysical study of visual extinction: ipsilesional distractor interference with contralesional orientation thresholds in visual hemineglect patients." Neuropsychologia 43.4 (2005): 530-541.
Rorden, C, L Jelsone, S Simon-Dack, LL Baylis, and GC Baylis. "Visual extinction: The effect of temporal and spatial bias.." Neuropsychologia 47.2 (2009): 321-329.