Vision for perception and vision for action: Difference between revisions

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{{Short description|Types of visual processing in the brain}}

{{More citations needed|date=July 2007}}

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== Visual Processing in the Brain ==

Visual stimuli have been known to process through the brain via two streams: the [[dorsal stream]] and the [[ventral stream]]. The dorsal pathway is commonly referred to as the ‘where’ system; this allows the processing of ___location, distance, position, and motion. This pathway spreads from the [[primary visual cortex]] dorsally to the [[parietal lobe]]. Information then feeds into the [[motor cortex]] of the [[frontal lobe]]. The second pathway, the ventral stream, processes information relating to shape, size, objects, orientation, and text. This is commonly known as the ‘what’ system. Visual stimuli in this system process ventrally from the primary visual cortex to the [[medial temporal lobe]]. In childhood development, vision for action and vision for perception develop at different rates, provingsupporting the hypothesis of two distinct, linear streams for visual processing. This acknowledges the potential of having two, independent streams.

The above hypothesis has recently been challenged by a new and more parsimonious hypothesis with regard to evolution. The two streams must work hand-in-hand while processing visual information. Neuroanatomical and function neuroimaging studies have proven multiple visual maps that exist in the [[posterior brain]], regarding at least 40 distinct regions. A single part of the outside world controls visual processing, and then particular areas are recognized in which single cells react to specific stimuli, such as faces. This hypothesis, one that indicates a more network-like model, is becoming more and more accepted among researchers. The pathway model mentioned above now experiences many conflicts. It has been discovered experimentally that there is more than just one way to process actions. For example, three distinct processing routes could exist dorsally, one for grasping, another for reaching, and yet a third for awareness of personal actions. No longer can just one dorsal stream be accounted for with regard to processing vision for action. The previous hypothesis also states that there is a clear hierarchy in which processing of visual stimuli goes from least complex to most complex in a linear fashion. However, [[lesions]] at one end should therefore have the same effect on the opposite end, and this cannot be observed experimentally. This further proves the integration of the two streams and many visual processes operating in parallel, involving multiple ventral and dorsal streams in a patchwork-type model.