Wikipedia - Top-down and bottom-up in neuroscience and psychology

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    • Published: 05-25-2014 04:09 pm
      Updated: 05-25-2014 04:09 pm
    • http://en.m.wikipedia.org/wiki/Top-down_and_bottom-up_design#Neuroscience_and_psychology

      These terms are also employed in neuroscience, cognitive neuroscience and cognitive psychology to discuss the flow of information in processing.[4] Typically sensory input is considered "down", and higher cognitive processes, which have more information from other sources, are considered "up". A bottom-up process is characterized by an absence of higher level direction in sensory processing, whereas a top-down process is characterized by a high level of direction of sensory processing by more cognition, such as goals or targets (Beiderman, 19).[3]According to Psychology notes written by Dr. Charles Ramskov, a Psychology professor at De Anza College, Rock, Neiser, and Gregory claim that top-down approach involves perception that is an active and constructive process.[5] Additionally, it is an approach not directly given by stimulus input, but is the result of stimulus, internal hypotheses, and expectation interactions. According to Theoretical Synthesis, "when a stimulus is presented short and clarity is uncertain that gives a vague stimulus, perception becomes a top-down approach."[6]Conversely, Psychology defines bottom-up processing as an approach wherein there is a progression from the individual elements to the whole. According to Ramskov, one proponent of bottom-up approach, Gibson, claims that it is a process that includes visual perception that needs information available from proximal stimulus produced by the distal stimulus.[7] Theoretical Synthesis also claims that bottom-up processing occurs "when a stimulus is presented long and clearly enough."[6]Cognitively speaking, certain cognitive processes, such as fast reactions or quick visual identification, are considered bottom-up processes because they rely primarily on sensory information, whereas processes such as motor control and directed attention are considered top-down because they are goal directed. Neurologically speaking, some areas of the brain, such as area V1 mostly have bottom-up connections.[6] Other areas, such as the fusiform gyrus have inputs from higher brain areas and are considered to have top-down influence.[8]The study of visual attention provides an example. If your attention is drawn to a flower in a field, it may be because the color or shape of the flower are visually salient. The information that caused you to attend to the flower came to you in a bottom-up fashion—your attention was not contingent upon knowledge of the flower; the outside stimulus was sufficient on its own. Contrast this situation with one in which you are looking for a flower. You have a representation of what you are looking for. When you see the object you are looking for, it is salient. This is an example of the use of top-down information.In cognitive terms, two thinking approaches are distinguished. "Top-down" (or "big chunk") is stereotypically the visionary, or the person who sees the larger picture and overview. Such people focus on the big picture and from that derive the details to support it. "Bottom-up" (or "small chunk") cognition is akin to focusing on the detail primarily, rather than the landscape. The expression "seeing the wood for the trees" references the two styles of cognition.[9]
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