ULTIMATE COMPUTING - Quantum Consciousness Studies

From Brain to Cytoskeleton 67
... Why have I chosen to quantize in nervous impulses ... If we think
(of the brain) in terms of its ultimate particles, one might split this at
the level of the atoms or one might split this at the level of the
neurons and so on. The question is at what level can one split the
behavior so as to define a set of units in terms of which to work
And obviously the nervous impulse at the level of the neuron is a
fairly nice unit for working ... . But what I’m looking for is
something that will perform a logical task. I’d like a thing that has a
grain and I’d like to take that grain as my unit.
The grain which would explain information processing within all eukaryotic
systems is the dynamic activity of subunits within cytoskeletal proteins.
McCulloch, Pitts and others had guessed that information was coded in the pattern
and sequence of nerve impulses somewhat like Morse code in telegraph lines.
However, Adrian showed in 1947 that the frequency of firing in a nerve cell is a
quantitative measure of the intensity of the stimulus. When skin is pressed, the
stronger the pressure applied to the skin, the higher the frequency and the better
maintained the firing of the cell. Frequency coding appears limited to information
about the intensity of a stimulus and impulses in a given cell appear identical with
those in other nerve cells. The significance and meaning are quite specific for
each cell; for example skin sensory neurons indicate that a particular part of the
skin has been pressed. Although there appears to be no reason why a great deal of
information could not be conveyed by any predetermined signal including a code
made up of different frequencies, the frequency or pattern of discharges do not
appear to stand on their own as qualitative information. Following this
recognition, the meaning of a signal became attributed to origins and destinations
of the nerve fibers which convey it: “connectionism.” The importance of
connections is exemplified by sensations of light produced by nonvisual
stimulation of the eyeball, or the phantom limb phenomenon in which an amputee
may have sensation of a limb long since removed. In each case, mental
representation is determined by the location of stimulation.
McCulloch and Pitts elaborated their model by adding a term which included
the possibility that a firing decision might depend on inputs of times more remote
than the synaptic delay period (dendritic memory) and by considering circular
neural networks: closed pathways with logical feedback and reverberation. Thus
pulse logic evolved into connectionism and neural networks as media of neural
information representation.
4.3.3 Connectionism and Neural Networks
The form and structure of neurons and the observation of neuroanatomy was
made available to optical microscopy by Italian anatomist Camillo Golgi in 1875.
He found a method by which, seemingly at random, a very few neurons in a brain
region became stained in their entirety, with all their branches becoming evident.
The cytoplasm of selected neurons take up a brightly colored stain and are thus
exposed against the tangled morass of less visible cells. Golgi’s contemporary,
Spaniard Santiago Ramon y Cajal (1955) used the Golgi stain to investigate
nearly every part of mammalian nervous systems. His neuroanatomy texts are still
classic and he resolved the question of whether nerves were separate entities like
all other cells, or part of a continual network. He also demonstrated that the
complex connections among neurons are not random, but highly selective and
specific.
Subsequent generations of neuroanatomists and neuroembryologists
including Roger Sperry (1969, 1980) have emphasized the