178 HOW THE BRAIN MAKES POTENTIAL
you can nevertheless read: all examples of structure pulled into corre-
sponding attractors for verifi cation and further pro cessing.
Th at, of course, depends on the system (from eye to brain) having
assimilated and stored those structural par ameters. Th is is the impor tant
point. Th e system cannot rely on fi xed pro cessing rules as if working with
recurring stimuli. Th at would not work with the usual fuzzy, ambiguous
inputs like those from the point- light walker. Instead, the visual system
must abstract the relational par ameters from previous experience with
similar objects (like real people walking). Th e par ameters in the attrac-
tor basin serve as a kind of grammar from which to generate a reliable
prediction from the unreliable inputs. As with speech, it is through the
grammar that novel, or imperfect, inputs can be interpreted and from
which novel responses can be created.
Th is is, in princi ple, the same kind of grammar used in cell functions
and in development and physiology. But in the ner vous system, there are
vast numbers of cells with vast numbers of modifi able interconnections.
Each neuron may receive inputs from thousands of others, and also send
signals to thousands of others through its axon branches, some nearby,
others at possibly great distance. Statistical patterns of great depth can be
abstracted (learned) and permanently updated to provide predictability
in changeable environments.
THE BRAIN PRO CESSES STRUCTURE, NOT ELE MENTSTh at the brain is most interested in such statistical structure rather than
trigger features has been suspected for some time. In the nineteenth
century, physicist and physician Hermann von Helmholtz described the
visual experiences of patients who had gained sight for the fi rst time aft er
operations for congenital cataracts. One patient was surprised that a coin,
which is round, should so drastically change its shape when it is rotated
(becoming elliptical in projection). Another found it seemingly impos-
sible that a picture of his father’s face, the size of which he knew from
touch, could fi t into a small locket.
Th at vision in par tic u lar, and the brain in general, are not interested
in stable features, images, or other ele ments is suggested in another, rather
This content downloaded from 139.184.14.159 on Tue, 17 Oct 2017 13:54:00 UTChttp://www.ebook3000.com