Retinotopic Maps

From: Saha, Sanna (
Date: Wed May 22 1996 - 21:35:14 BST

Q. 57 What is a Retinotopic map?

In brain anatomy and imaging there are parts of the brain that are
analog copies of the shadow, cast by objects on the retina. They are
shadows of shadows. Whenever an object casts a shadow on the retina, it
casts a shadow on higher retinotopic areas, as well as keeping its
shape. However, the brain image does not look like the mental image or
the original object. This image mapping is known as 'retinotopic
mapping', which is point-for-point copies of the topography of the

An example is the somatosensory (skin) humunculus, which is analogus
exactly to the retinotopic map. It is a point-for-point map of your
skin surface copied to higher levels of your brain, preserving the
local topography and connectivity.

Retinotopic mapping occurs due to the principle by which stimuli, that
are adjacent to each other in the visual world are processed by
adjacent sets of neurons at the higher levels of the visual system; in
this way the spatial pattern of light and dark arriving at the retina
is preserved. PET imaging has been utilised to identify retinotopic
areas, that are active during imaging.

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