Artificial Consciousness/Neural Correlates/Synaptic Models/Tentative Comprehensive Model
A Tentative Comprehensive Synapse Model edit
A Synapse is a Chemo-Electric connection between neurons, although some purely electrical connections may be found in the early stages of development, these are thought to be attempts to keep the neurons involved from learning before their development is sufficiently advanced. Learning in a Neuron, is controlled by the synapse partially through the leverage associated with the number of ion channels that amplify the signal or inhibit it, and partially through protein tags that are sequestered in active synapses and thus indicate which synapses are more likely to be candidates for other types of learning such as conversion to long term memory.
Synapses sequester two types of tags, Ephemeral tags, which are an indication to the membrane replacement mechanism, to increase the number of ion channels in the sensitive patch of the synapse but are not replaced during membrane replacement, and Survivable tags, which are replaced during membrane replacement, and so, are not allowed to degrade as quickly as free proteins, and can act as guides to long-term processes such as the conversion to long-term memory by the production of new synapses and fibrils to connect the neurons.
The primary difference between these two types of protein tags, is a feedback connection caused by a chemical produced only during the firing of the presynaptic buds of the neuron, and pumped back into the body of the neuron where it influences protein production. Without this signal, the survivable tags would not be produced, and only ephemeral tags would be available to be sequestered.
Some synapses such as the S synapse and the NMDA synapse trigger other functions within the cell, including chemical cascades that result in the conversion of short term memories into long-term memories by the growth of new connections between cells.
Of interest is the role of Calcium in Habitutation a mechanism that causes neurons that fire too often to gradually lose their firing strength, possibly because the calcium in the presynaptic bud is used up by its role in attaching vessicles of Neuro-Transmitter to the cellular membrane, or maybe because propagation of the signal along the axon requires calcium ion channels to pump calcium out of the axon, reducing the supply of calcium and thus reducing the propagation of the signal down the axon fiber as supplies dwindle. It is interesting to note that Facilitation, the recovery from Habituation is virtually instantaneous once calcium ion channels start pumping calcium back into the cell. A role of facilitation in deciding which memories survive long enough to impinge on attention, might be indicated. It is also noteworthy that both the NMDA and S synapse are Calcium ion channels pumping calcium into the cell, and thus Facilitating the output of the neuron. The linking of Facilitation to long-term memory development might be interesting.