Visual perceptual skill learning after long-term blindness: The reason of the laborious work
Park, Soon Young
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Visual perception is a process starting with the arrival of light information in our eyes and retina, followed by several steps in various brain areas along the pathway of visual information processing. During this process sensation becomes perception. Perception, however, only exists if the observer has a meaningful representation, which is built up from the moment we have visual experiences. Unlike normal visual development in infants, the process of learning visual perceptual skills turned out to be surprisingly laborious and frustrating when long-term blindness patients gained the possibility to perceive visual information after an operation. These patients were diagnosed with congenitally impaired ophthalmologic conditions and were operated at a much later stage in their life. Similar visual deprivation conditions were known using animal experiments in which animals were raised under visual deprivation conditions. The conclusion from the animal experiments was that lack of proper visual experience during the ‘critical period’ diminishes visual cortical development and subsequent learning process permanently. This critical period was considered the very reason that later visual learning efforts were seen as a fruitless enterprise. Despite the major skepticism towards later learning, visual rehabilitation in some case studies showed improvements. This reflects the possibility of visual learning at a later stage in life, and therefore other factors initiating the learning process seem to exist. Recent studies support this view. In this thesis, existing patient reports are analyzed and the potential influential factors will be discussed.