link: information flow
THE PROBLEM OF CONTINUITY OF INFORMATION IN THE BRAIN:
theme: Information flow in the brain involves the propagation of nerve impulses along the neurons and their transmission across the synapses in a series of molecular events described in the 'synaptic theory of transmission of impulses'.
The continuity of information in the brain is a function of stimuli which are intense ..strong enough to produce nerve impulses of sufficient intensity to ensure their transmission across the synaptic clefts and their propagation along connecting neurons. This is of particular significance to learning theory... 'brain-based learning'. intrinsic motivation enhances synaptic transmission and thus enhances learning. Learning is a function of 'synapse modification'.
THE PROBLEM OF INFORMATION FLOW The term 'information flow' refers to the propagation of electrical signals or 'nerve impulses' along nerve cells or 'neurons' and their transmission across the interconnnections or 'synapses'. The mechanism of transmission is a problem for brain research or 'neuroscience'.
AT THE TIME OF FREUD (1856-1939) IT WAS BELIEVED THAT INFORMATION FLOW WAS PURELY ELECTRICAL The transmission of impulses from one cell to another is so fast that for a long time it was believed to be a purely electrical phenomenon. The problem was to explain the apparent continuity of information in the brain or 'information flow'.
It was Spanish anatomist Santiago Ramon y Cajal who had set out to understand the workings of the brain by analysing its functional architecture or 'wiring diagram'. Cajal pictured the brain as a continuous net or 'syncytium' of nerve cells or 'neurons' connected to each other by hypothetical junctions or bridges of protoplasm. The hypothetical protoplasmic bridges 'explained' the problem of apparently unimpeded flow of information in the brain. Up until the 1940s the problem of information flow was approached in terms of analysis of the neuron because it was believed to be simply a function of the generation and propagation of nerve impulses along the neurons i.e. 'neural processes'.
"Freud saw the nervous system as a syncytium of cells connected to each other by 'protoplasmic bridges' - a concept that solved the problem of continuity, since, in it, the flow of information was unimpeded." (J. Allan Hobson, The Dreaming Brain. New York: Basic Books, 1977, 97.)
Freud's most significant contribution to psychology was his discovery of the unconscious motivations of human behaviour i.e. 'intrinsic motivation' and his work on neurotic development or 'neurosis'. When he set out to establish his 'scientific psychology' he was unaware that information is transmitted along the neuron in the form of 'electrochemical pulses' or 'signals' i.e. 'nerve impulse'.
INVESTIGATIONS WITH THE ELECTRON MICROSCOPE REVEAL GAPS BETWEEN THE NEURONS Since the 1940s technology of the 'electron microscope' has made it possible to study individual neurons and to magnify them enough to 'see' how they are connected. There is no evidence of 'protoplasmic bridges' connecting neurons to each other. Instead there are gaps which separate them. Discovery of the gaps has produced a picture of the brain as a network of single and separate neurons which propagate nerve impulses travelling at varying rates. The problem for neuroscience has been to provide an explanation for information flow along successive neurons when there are gaps which separate them.
THE GAPS ARE COMPONENTS OF THE 'SYNAPSE' The gaps are components of the intimate contact points of connection between interconnecting neurons - the 'synapses'. The synapse is a structure which is specialized for the transmission of impulses from one neuron to the next. There are more than a thousand billion of them in the brain. The structure of the synapse can be described in terms of three main components: the 'synaptic knob', the 'subsynaptic membrane' and the 'synaptic cleft'. Synaptic knobs or 'axon terminals' are derived from the multiple axon branches resulting from the bifurcation of the axon at many points along its length. The subsynaptic membrane is the limiting membrane of the synaptic knob. And the synaptic cleft is the gap between the subsynaptic membrane and the 'postsynaptic membrane' of the connnecting neuron.
The synaptic cleft measures twenty nanometers in width or two one thousandths of a millimeter (0.000002mm).
THE SYNAPSE PLAYS A CRITICAL ROLE IN INFORMATION FLOW The discovery of the synaptic cleft modified the picture of the brain as a syncitium of neurons. Each of the millions of single neurons in the brain has a separate biological existence. The separate neurons are connected to each other by way of more than a thousand billion synapses to form the various nervecircuits or 'neural pathways'. Neural pathways can be altered with the creation of new synapses and with the strengthening or weakening of existing synapses in a process of 'synapse modification'. Synapse modification is the biological basis for the process of forming neural networks or 'learning'. Learning involves the generation of nerve impulses at the synapse, their propagation at definite rates along the axons of neurons and their transmission across the synaptic clefts.
The function of the synaptic cleft is explained in a working hypothesis known as the 'synaptic theory of transmission of impulses'.
SYNAPTIC THEORY OF TRANSMISSION OF IMPULSES The new working hypothesis provides an explanation for the problem of information flow from one neuron to the next when there are gaps which separate them. It explains the mechanism involved in the transformation of neural information as it travels from one neuron to a connecting neuron across the synaptic cleft. The hypothesis is known as the 'junctional mechanism', the 'two process mechanism', the 'junctional two process mechanism' and the 'synaptic theory of transmission'. According to the synaptic theory, nerve impulses are transmitted from one neuron to another as follows: nerve impulses arrive at the synapse at varying intensities. If they are sufficiently intense they trigger the release of specialized molecules contained in small vesicles in the synaptic knob - 'neural transmitter molecules' or 'neurotransmitters'. The neurotransmitters are released through the synaptic membrane of the synaptic knob - the presynaptic membrane - and propagated across the synaptic cleft. When they reach post synaptic membrane of the neighbouring neuron they attach to protein receptor molecules i.e. 'binding sites'. The binding sites are specialized for the attraction and binding of neurotransmitter molecules. The binding of neurotransmitter molecules to the receptor molecule forms a 'transmitter-receptor complex'. The formation of the transmitter-receptor complex triggers a change in the membrane permeability of the connecting neuron. The binding is excitatory if it produces movement of electrically charged ions which results in the depolarization of the membrane and generation of a new nerve impulse i.e. 'excitatory binding'. The binding is inhibitory if it produces movement of electrically charged ions which results in the further polarization of the membrane and the failure to generate a new nerve impulse i.e. 'inhibitory binding'. Nerve impulses are transmitted across the synaptic clefts only if excitatory binding exceeds inhibitory binding.
As a result of excitatory binding, existing synaptic connections are strengthened and new ones are created... leading to reinforcement of existing neural pathways and the creation of new ones.
IMPLICATIONS FOR EDUCATION The molecular events at the synapse and synapse modification - the strengthening of existing synapses and the creation of new ones - becomes the focal point of investigation into the process of continuity of information flow in the physiological process of 'learning'. Learning is a natural function of modification and creation of neural pathways. Facilitation of natural learning - 'brain based learning' - by way of brain compatible methods of teaching - 'thematic teaching' is conducive to the brain's optimal functioning i.e.'optimalearning'. Optimalearning involves the psychological value of the individual's capacity for creativity and productivity or 'work'. Education which involves meaningful work engages t or 'self-actualisation'. Education for self-actualisation of the human potential for self-fulfillment... 'holistic education'.
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