ULTIMATE COMPUTING - Quantum Consciousness Studies

From Brain to Cytoskeleton 65
digital substrates (switches or gates in a computer) may be overlooking an
important dimension available for the organization of intelligence.
4.3.1 Integration—Sherrington’s Reflex Centers
Processing the dynamic excitatory and inhibitory patterns of activity within
masses of neurons (“reflex centers”) was described as “integration” by the famed
neuroscientist C. S. Sherrington during the 1930’s.
The brain is continually faced with the task of making decisions on the basis
of information about the outside world provided by sensory end-organs and
information stored in memory. At any one instant, incoming signals from diverse
sources in the periphery excite the brain. The mechanisms by which the various
types of information are taken into account and assigned priorities is called
“integration” which is carried out at all levels of brain organization. In a global
example of integration, an animal confronted by danger integrates input towards a
binary output decision: “fight or flight.” Our higher centers continually receive
information arising in a great variety of sources on the surface of the body and in
the internal organs. A typical central neuron faces a task similar to that of the
brain as a whole. It is a target of converging excitatory and inhibitory signals that
it transforms (“integrates”) into its own impulses. The general principles of
integration were discovered in the early 20th century by Sherrington (1933, 1947)
who recorded tension in skeletal muscle by the stretch reflex before electrical
recording from individual cells was possible. Integration appears to occur at all
levels of nervous systems and among various types of organisms: crustacean, fish,
and mammals. Sherrington proposed and cited evidence for integration by groups
of neurons which he termed neural masses or reflex centers and suggested that
they correlated with anatomically identifiable “nuclei.”
A nucleus is a compact region of gray matter of relatively homogeneous
neural architecture and recognizable boundaries which contains a high density of
neuronal cell bodies and synapses. (White matter connotes a high density of
cable-like axon fibers.) A reflex center is an assembly of neurons performing a
specific function. A nucleus is purely morphological or structural while a center is
functional. Nuclei may coincide with centers, but often do not (Freeman, 1972).
The concept of neural centers may convey an erroneous impression of
anatomically specific function, but remains as a vestigial reference to
Sherrington’s concept of the nervous system and now denotes groups of neurons
whose destruction leads to loss of specific function and/or the stimulation of
which evoke a certain behavioral or physiological function. Brain functions are
clearly not divided among centers in the same way as the work of a large
organization or factory is divided among its various offices and workshops. The
relation between anatomic regions devoted to specific functions, and the brainwide
distribution of information is perplexing and complicated. For example, the
satiety center is located in the hypothalamus; if this general region is stimulated in
an animal having a meal, the animal will stop eating as though it has had enough.
If the same structure is destroyed, the animal eats too much and gets fat as though
it is never satisfied. Thus clearly the satiety center neurons are essentially related
to evoking the sensation of fullness or satiety. Feeding behavior, however, is
regulated by a much wider range of many neuronal circuits in different regions.
The satiety center integrates multiple inputs to a binary output: eat or don’t eat.
Body representations such as motor and sensory homunculi and other concrete
evidence of anatomical localization of neuronal function may also integrate wide
sources of distributed input to representations of anatomical sensation and action.
Anatomical hardware such as satiety centers, motor and sensory homunculi