Gödel, Escher, Bach An Eternal Golden Braid by Douglas R. Hofstadter

(a) Complex cell (area 17)

Stimulus; Response Stimulus; Response

Strong Zero

Weak Strong

~zem Strong

Zero ~Stmng

(b) Hypercomplex cell

(area 19)

Stimulus; Response

bzem

[!]weak

[:tJstmng

[jJweak

(c)

Ultrasuperhyper-

complex cell

(area 1729)

Stimulus; Response

~ Strong

~j.

({~~ i

Strong

~

~Medium

I ~~ I Weak

Zero dzem 88 zem

FIGURE 67. Responses to patterns by certain sample neurons.

(a) This edge-detecting neuron looks for vertical edges with light on the left and

dark on the right. The first column shows how the orientation of an edge is

relevant to this neuron. The second column shows how the position of the edge

within the field is irrelevant, for this particular neuron.

(b) Showing how a hypercomplex cell responds more selectively: here, only when

the descending tongue is in the middle of the field.

(c) The responses of a hypothetical "grandmother cell" to various random

stimuli; the reader may enjoy pondering how an "octopus cell" would respond to

the same stimuli.

"symbol" might emerge from "signal", the trail gets lost-a tantalizingly

unfinished story. We will return to this story shortly, however, and try to fill

in some of it.

Earlier I mentioned the coarse-grained isomorphism between all

human brains which exists on a large anatomical scale, and the very fine-

grained, neural-level isomorphism which exists between earthworm brains.

It is quite interesting that there is also an isomorphism between the visual

processing apparatus of cat, monkey, and human, the "grain" of which is

somewhere between coarse and fine. Here is how that isomorphism works.

First of all, all three species have "dedicated" areas of cortex at the back of

their brains where visual processing is done: the visual cortex. Secondly, in

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