Genes, Brains, and Human Potential The Science and Ideology of Intelligence

172 HOW THE BRAIN MAKES POTENTIAL

or inhibiting signals and so permitting enormous plasticity of the nerve

networks in the brain. Advanced systems have millions of cells connect-

ing with thousands of others through billions of connections. A stagger-

ing depth of statistical structure can now be captured for predictability

and be hav ior.

All this creates much to discuss, but for illustration, in this chapter, I

concentrate on vision as in a fairly general vertebrate brain. Most of what

it reveals can be extended to other sense modes and to more general brain

functions.

VISUAL GENIUSES

Th e visual system, in nearly all visually unimpaired individuals, pres ents
a good example of the information sent to the brain and what the brain
is interested in. Clearly some hard work has to be done there because, like
any intelligent system, much has to be deduced from rapidly changing,
incomplete information. Th e information deduced in the “mind’s eye” is
much richer ( orders of magnitude richer) than that actually immediately
presented to the physical eye. In vision, in par tic u lar, sensory inputs are
in constant fl ux, complex, noisy, and full of ambiguity. So what exactly is
the work, and how is it achieved?
Again a simple mechanical metaphor— this time the camera— has
sometimes passed as the popu lar model of vision. In that model, the light-
sensitive cells in the ret ina, in large numbers at the back of the eye, each
picks up a tiny part of that image as tiny light spots, like pixels. Aft er fur-
ther pro cessing, the whole snapshot is passed on, as an electrochemical
discharge, down the optic nerve to the brain (this is sensation, or sensory
reception). Th e brain reassociates these features, through a series of lin-
ear convergences into an image of the original object (this is perception).
Th is image can than be handed over to “higher” centers in the brain for
recognizing, classifying, memorizing, thinking, action planning, con-
structing a motor program, and so on (this is cognition).
And that is how we make sense of real ity: a pro cess of simply rebuild-
ing the sensory image.

This content downloaded from 139.184.14.159 on Tue, 17 Oct 2017 13:54:00 UTC

http://www.ebook3000.com