ULTIMATE COMPUTING - Quantum Consciousness Studies

From Brain to Cytoskeleton 71
preconceived classifications. As in all parallel processing systems, output of the
individual processors must be reconciled if they are not identical. Lateral
communicating networks between Darwin and Wallace resolve conflicting output
and form an associative memory. Because they operate on an unchanging
connectionist network, Darwin and Wallace are considered “selectionist.” Similar
recognition automata may be operating in dynamic cytoskeletal networks within
neurons.
4.3.4 Distributedness
Neuroanatomical appreciation of synaptic structure gave credence to
connectionist theory, and permitted Hebb to extend the theory of synaptically
regulated, discretely assembled neural nets to memory and behavior in humans.
However, the only experimental data came from 30 years of work by Karl
Lashley (1929, 1950) who had shown that memory and perception appear to be
distributed throughout the brain. Lashley’s quest was the site of representation—
the “engram”—of information, memory and learned behavior in the brains of
laboratory animals.
Lashley’s experiments in search of the engram consisted of ablation of
specific parts of animal brains with careful testing for retention of habits learned
before the ablation, ability to relearn, and ability to learn new tasks. The overall
conclusion was that memory function is disturbed in proportion to the amount of
cortex destroyed, irrespective of which part of the cortex had been removed. As
far as learning, Lashley felt that all parts of the cortex were equipotent except for
the specific sensory receiving areas involved in that particular learning modality.
Lashley’s findings were a disappointment to connectionists and engendered a
bleak, hopeless outlook. In his famous life’s work, In Search of the Engram,
Lashley (1950) wrote that after 30 years of searching for the location of the
engram in the brain he was convinced that “learning is just not possible.
Nevertheless, in spite of all the evidence against it, learning does sometimes
occur.” Lashley rallied from despair to propose an alternative to localized storage
of memory traces attached to spatially fixed reflex pathways. Agreeing that recall
involves reactivating a previous pattern of neuronal excitation, he insisted that the
pattern representing any one memory could be evoked not just in one specific set
of neurons, but in many sets, in many places, and perhaps anywhere in regions of
the brain having to do with memory function. This distribution of information in
memory was explained by Lashley as excitatory patterns in cortex related to the
spread of interference patterns on the surface of a liquid disturbed at several
points at once. (His theory of interference patterns later inspired comparisons
between the brain, storage of information and laser holography).
Lashley (1929):
Nerve impulses are transmitted ... through definite intercellular
connections, yet all behavior seems to be determined by masses of
excitation ... within general fields of activity without regard to
particular nerve cells. It is the pattern and not the element that
counts.
Hebb (1949) commented:
Lashley has concluded that a learned discrimination is not based on
the excitation of any particular nerve cells. It is supposed to be
determined solely by the pattern or shape of the sensory excitation ...
this suggests that the ‘nmemonic trace’, the neural change that is
induced by experience and constitutes memory, is not a change of