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J C Eccles

Publications and source records attributed to J C Eccles.

At least 19 recordsLinked to original sources
PubMed1992

Quantum aspects of brain activity and the role of consciousness.

The relationship of brain activity to conscious intentions is considered on the basis of the functional microstructure of the cerebral cortex. Each incoming nerve impulse causes the emission of transmitter molecules by the process of exocytosis. Since exocytosis is a quantal phenomenon of the presynaptic vesicular grid with a probability much less than 1, we present a quantum mechanical model for it based on a tunneling process of the trigger mechanism. Consciousness manifests itself in mental intentions. The consequent voluntary actions become effective by momentary increases of the probability of vesicular emission in the thousands of synapses on each pyramidal cell by quantal selection.

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PubMed1992

Evolution of consciousness.

The hypothesis of the origin of consciousness is built upon the unique properties of the mammalian neocortex. The apical dendrites of the pyramidal cells bundle together as they ascend to lamina I to form neural receptor units of approximately 100 apical dendrites plus branches receiving hundreds of thousands of excitatory synapses, the collective assemblage being called a dendron. It is proposed that the whole world of consciousness, the mental world, is microgranular, with mental units called psychons, and that in mind-brain interaction one psychon is linked to one dendron through quantum physics. The hypothesis is that in mammalian evolution dendrons evolved for more effective integration of the increased complexity of sensory inputs. These evolved dendrons had the capacity for interacting with psychons that came to exist, so forming the mental world and giving the mammal conscious experiences. In Darwinian evolution, consciousness would have occurred initially some 200 million years ago in relation to the primitive cerebral cortices of evolving mammals. It would give global experiences of a surrounding world for guiding behavior beyond what is given by the unconscious operation of sensory cortical areas per se. So conscious experiences would give mammals evolutionary advantage over the reptiles, which lack a neocortex giving consciousness. The Wulst of the avian brain needs further investigation to discover how it could give birds the consciousness that they seem to have.

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PubMed1986

Do mental events cause neural events analogously to the probability fields of quantum mechanics?

If non-material mental events, such as the intention to carry out an action, are to have an effective action on neural events in the brain, it has to be at the most subtle and plastic level of these events. In the first stage of our enquiry an introduction to conventional synaptic theory leads on to an account of the manner of operation of the ultimate synaptic units. These units are the synaptic boutons that, when excited by an all-or-nothing nerve impulse, deliver the total contents of a single synaptic vesicle, not regularly, but probabilistically. This quantal emission of the synaptic transmitter molecules (about 5000-10 000) is the elementary unit of the transmission process from one neuron to another. In the second stage this refined physiological analysis leads on to an account of the ultrastructure of the synapse, which gives clues as to the manner of its unitary probabilistic operation. The essential feature is that the effective structure of each bouton is a paracrystalline presynaptic vesicular grid with about 50 vesicles, which acts probabilistically in vesicular (quantal) release. In the third stage it is considered how a non-material mental event, such as an intention to move, could influence the subtle probabilistic operations of synaptic boutons. On the biological side, attention is focused on the paracrystalline presynaptic vesicular grids as the targets for non-material mental events. On the physical side, attention is focused on the probabilistic fields of quantum mechanics which carry neither mass nor energy, but which nevertheless can exert effective action at microsites. The new light on the mind-brain problem came from the hypothesis that the non-material mental events, the 'World 2' of Popper, relate to the neural events of the brain (the 'World 1' of matter and energy) by actions in conformity with quantum theory. This hypothesis that mental events act on probabilistic synaptic events in a manner analogous to the probability fields of quantum mechanics seems to open up an immense field of scientific investigation both in quantum physics and in neuroscience.

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PubMed1979

Synaptic plasticity.

Synaptic plasticity is manifested by long-lasting changes in synaptic potency. Increased potency is of special importance in relation to the neural basis of memory. Even mild repetitive stimulation evokes large and prolonged potentiations of hippocampal synapses, as is revealed by electrical recording either in vivo or in vitro. More importantly there is a matching hypertrophy of the synaptic spines on the dendrites of hippocampal granule cells, as is shown by most convincing electronmicrographs. The increase is to about 40% some 2 h after a mild stimulation (900 impulses) and there was relatively little decline by 23 h. There is brief reference to the metabolic processes that could be involved in this plastic response.

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PubMed1976

Medial reticular and perihypoglossal neurons projecting to cerebellum.

Almost 10% of neurons in the medial reticular nucleus or adjacent thereto were invaded antidromically in response to stimulation of the fastigial and interpositus nuclei. The fraction was 77/835 for the bulbar and caudal pontine levels, but 0/167 for rostral pontine levels. The mahority, 49, of the neurons projecting to the cerebellum were superficially located in the region of the perihypoglossal nucleus, but 23 were scattered through the medial reticular nucleus, being 2.5-5.0 mm below the bulbopontine dorsum. Both classes of cerebellopetal neurons had a similar range of antidromic latencies, usually from 0.8 to 2.0 ms, but some were ober 3 ms. Both classes responded to volleys from limb nerves and inputs from cutaneous mechanoreceptors, with ranges of excitatory and inhibitory latencies that were similar to those for other medial reticular neurons. It is conjectured that the axonal projection is primarily to the cerebellar cortex and that the branches to the nuclei are often slender, hence the long antidromic latencies; 31 of 59 neurons tested projected to cerebellar nuclei on both sides, often with a considerable latency differential. Rarely, there were also axonal branches projecting up the central tegmental tract. The experimental findings are in very good accord with the anatomical descriptions of Brodal and associates (4, 5, 8, 19). It is suggested that the paramedian reticular and the perihypoglossal nuclei may provide a background excitatory input to the interpositus nuclei.

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PubMed1976

Topographic studies on medial reticular nucleus.

Several distinct classes of neurons have been identified in the medial reticular nucleus of the medulla and pons and in proximity thereto. Neurons projecting down the spinal cord comprised the principal class with two subclasses according as the neurons did or did not receive monosynaptic inputs from the fastigial nuclei of the cerebellum. Two other classes were recognized accordings as they projected to the cerebellum or rostrally to the mesencephalon. Topographic planar maps giving the location of these neurons have been constructed by exploring the nucleus with series of microelectrode tracks in parasagittal or in transverse planes. The different classes of neurons were not arranged in large discrete nuclei. In part they appeared to be randomly distributed, but many colonies of one or another class of neurons could be recognized with 3-11 neurons in zones with dimensions of a millimeter or so. Because of the limitations of sampling by microelectrode tracks at spacings of 0.5 mm, single colonies might have an actual population of 100 or more. Many of the class of neurons projecting to the cerebellum were in the region of the perihypoglossal nucleus. However, almost as many were located deep in the medial reticular nucleus. None was found at the pontine level. Reticulospinal neurons with fast axonal conduction velocities tended to be located dorsally to those with slow velocities. Correlation with the findings of Ito et al. leads to the conjecture that the neurons with fast axons are excitatory, while those with slow axons are primary inhibitory neurons. There is a brief reference to the problems raised by the admixture of the various neuronal classes, there being discrete colonies immersed in a scattered arrangement of all classes.

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