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1 On concentrated photoreceptors Consider the question of why we must move our eyes across a line of text in order
 

Summary: 1 On concentrated photoreceptors
Consider the question of why we must move our eyes across a line of text in order
to read it. Generally, an entire line, paragraph, or even page fits comfortably
inside our visual field, yet we laboriously move our eyes around in order to collect
enough information to recognize the individual visual symbols of language. This
behavior can be explained by the high concentration of cone photoreceptors in
the center of our visual field (see Figure 1.1). The central 5o
of visual angle
(about two thumbnails wide at arm's length) surprisingly account for roughly
half of the cortical representation of the visual input in the brain, and thus it
is only in this small area that highly selective character recognition is possible.
In fact, uneven visual acuity is a pattern preserved across many branches of
life from insects [4] to fish [2, 1] to birds [8] to mammals [7] (see Figure 1.2).
Interestingly, it confers a fitness advantage independently of the size of the brain
of the animal. To understand why this is at a basic level, suppose we have two
regions in the retina A and B that map corresponding parts of the visual world
wA and wB which on average contain information content a and b1
, and that
they will receive computational resource allocation (e.g. photoreceptor density)
x and y respectively, according to the genetics of the animal. Generally, we

  

Source: Adolphs, Ralph - Psychology and Neuroscience, California Institute of Technology

 

Collections: Biology and Medicine