ROSS ASHBY - The Cybernetic Brain - page 137

in the brain is presumably a quantity which varies continuously, up or down.
Insanity, in contrast, appears to be dichotomous—one is either mad or not.
How then can a continuous cause give rise to a discontinuous effect? “What
is not always appreciated is that the conditions under which instability ap-
pears are often sharply bounded and critical even in a system in which every
part varies continuously. . . Every dynamic system is potentially explosive . . . .
These facts are true universally. . . . They are necessarily true of the brain”
(1954, 115-16). And Ashby had, in fact, addressed this topic mathematically
in a 1947 paper (Ashby 1947). There he considered a complex system con-
sisting of interlinked autocatalytic chemical reactions of three substances,
with rates assumed to be controlled by the presence of some enzyme, and
he showed by numerical computation that there was an important threshold
in enzyme concentration. Below that threshold, the concentration of one of
the reacting chemicals would inevitably fall to zero; above the threshold, the
concentration would rise to unity. This mathematical result, then, showed
in general how discontinuous effects can emerge from continuous causes,
and, more specifically, it shed more light on the possible go of ECT—how
the outpouring of steroids might conceivably flip the patient's brain into a
nonpathological state. 43
The other suggestion was more directly cybernetic. Ashby supposed that
when the essential variables exceed their limits in the brain they open a chan-
nel to signals from a random source, which in turn pass into the cortex and
initiate homeostat-like reconfigurations there (fig. 4.11). Both the source and
the channel were supposed to be real anatomical structures (1954, 120): “ V
[the random source] could be small, perhaps even of molecular size. It won't
be found until specially looked for. The channel U [carrying the random signal
to the cortex], however, must be quite large. . . . One thinks naturally of a tract
like the mammillo-thalamic . . . [and] of the peri-ventricular fibres . . . but
these matters are not yet settled; they offer an exceptional opportunity to any
worker who likes relating the functional and the anatomical.” And, having hy-
pothesized this cybernetic channel U , Ashby was in a position to describe the
pathologies that might be associated with it. If it was unable to carry sufficient
information, the brain would be unable to change and learn from its mistakes,
while if it carried too much, the brain would be continually experimenting
and would never reach equilibrium—conditions which Ashby associated with
melancholia and mania, respectively. Here then, he came back to the idea that
he had unsuccessfully explored in the 1930s—that there exists an identifiable
organic basis for the various forms of mental pathology—but now at a much
greater level of specificity. Instead of examining gross features of brains in