>NATURE NEWS UPDATE
>Tuesday 21 March 2000
>Does not compute
>Old people tend to have worse eyesight. But, as Audie Leventhal and
>co-workers, of the University of Utah, have discovered, this isn't
>necessarily because they have worse eyes. It could be because their brains'
>image-analysis software has gone awry.
>A brain region called the 'primary visual cortex' pieces together nerve
>impulses from the eyes into a basic picture of the world, which it passes on
>to other bits of the brain that give meaning to what we see.
>The primary visual cortex employs specialists to get the job done. Some nerve
>cells, for example, are particularly sensitive to vertical lines, while
>others respond to horizontal lines. This is called 'orientation bias', and
>allows the brain to assess the shape of objects. Other neurons act as motion
>detectors, firing in response to objects moving left, or right, say, due to
>their 'direction bias'.
This is disturbing; it suggests that ordinary brains get worse as
they get older. It's not that they stay fine and the body they
run gets worse.
Robin Hanson firstname.lastname@example.org http://hanson.gmu.edu
Asst. Prof. Economics, George Mason University
MSN 1D3, Carow Hall, Fairfax VA 22030
703-993-2326 FAX: 703-993-2323
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