Reply to: The dorsal and ventral streams are both visual

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The dorsal and ventral streams are both visual pathways that carry signals formed from visual stimuli through the brain for processing. However, they function differently in how they process visual information and what perception they facilitate.

The dorsal (or occipitoparietal) pathway carries signals from the occipital cortex to the parietal cortex while gathering/analyzing information related to space, motion, and time. This pathway is known as the “where” pathway because it aids in spatial awareness, locating stimuli in someone’s field, and processing motion. On the other hand, the ventral (or occipitotemporal) stream is known as the “what” pathway. As the name suggests, this pathway carries signals from the occipital cortex to the temporal lobe. Along that path, the brain processes the “what” of the visual information, such as color, shape, depth, light, etc. and matches that information with visual memories and cognition in the temporal lobe so the person can reach recognition. This includes facial recognition, object recognition, color recognition, and more. This pathway sometimes carries information further to the frontal lobe where significance and meaning are accessed and the perception changes from subconscious to conscious. In short, the major differences in processing between these two pathways are what aspects of visual information is perceived and recognized (Visual pathways, 2009).

An injury or damage to the dorsal stream leads to disorders affecting spatial awareness, visual attention defects, and issues with hand-eye coordination. An example of this impacting daily functioning and the inability to reach about and grab a spoon off of the table. This person would still be able to recognize that the object is a spoon and understand that it should be used to eat their cereal. If this person incurred an injury to the ventral pathway, resulting in agnosia, they would not be able to label the object as a spoon. This would be an example of associative agnosia resulting from damage to the ventral pathway where a person can see the object and knows its appropriate use but cannot say what the object is (Visual pathways, 2009).

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