Brains of Sand T TDE Differential Engine - technical overview
Figure T.1
The TDE (a recursive acronym of TDE Differential Engine) is a Turing Equivalent Machine (TEM) whose infinitely long magnetic recording tape has been realised as a finite circular wheel. While the TM has a Princeton architecture*, with data and code sharing the same memory space, the TDE has a Harvard architecture, with separate data store (the T-lobe) and instruction set (the F-lobe). The TDE is shown in figure T.1 (left). Turing Machine is shown in figure T.1 (right).
The TDE relies upon the theory of schizolinguistics^. Also called linguistic schismatics, this theory claims that the separation of syntax from semantics is a necessary precursor to the proper understanding of both cognition and linguistics. Schizolinguistics permits the precise specification of both semantics (symbolic/representational state) and syntax (transitions between semantic states).
Representational stasis is modelled by a finite succession of semantic states, in which each successor state depends only on its predecessor state. This idea of semantics is simulated by a synchronous ROM-based automaton known as a Moore machine. Representational change, or syntax consists of asynchronous transitions between semantic states, in which each subsequent state depends on BOTH its preceding state AND the next symbol in the input string. This type of computation is simulated by another ROM-based automaton known as a Mealy machine. Moore machines and Mealy machines are the logical duals or complements of one another. They are a familiar feature of electronic logic circuit designs, but are almost never encountered in biology. This kind of fundamental similarity between brains and computers is one of the TDE model's most interesting features. Another interesting TDE feature is its functional similarity to an epicyclic gear system**, driven by an equivalent central pinion gear, the L-lobe, which models the drive-state differentials at any given level (eg metabolic drives from hypothalamus at TDE level#3 ). The torques are transferred from the three carrier pinions, which are equivalent to the F-, T- and P-lobes, to the ring gear, representing the environment (not labelled).
^the same lexical derivation as schizophrenia :-a split mind
* Note Turing's choice in dividing the tape into erasable (read-write) and fixed (read-only) squares. This is similar but not identical to the division of memory between data and instructions. It can therefore be argued that the TM has an intermediate architecture type. The point is moot.
**the reader's attention is drawn to O'Brien & Opie's use of Fodor's term 'special sciences' used to describe multiply realisable mechanisms.
Figure T.2
Figure T.2 (duplicated from another section) depicts three of the four TDE levels. These are-
level#3 -> cogno-linguistic
level#2 -> spatio-temporal,
level#1 -> sensorimotor
level#0 -> neuroendocrine
Levels 0 through 2 are shared by humans and animals. The evolution of Level 3 is what makes us uniquely human. Figure T.3 below depicts some of the structures and functions at GLOBAL level 3.
Figure T.3
