Fig. 2

Reactivation of an inter-postsynaptic functional LINK that induces the formation of units of internal sensation. An action potential arriving at presynaptic terminal A activates synapse A–B and reactivates inter-postsynaptic functional LINK between postsynapses B and D. When postsynapse D is activated in the absence of arrival of activity from its presynapse (not shown), a semblance of arrival of activity from its presynapse occurs. The sensory equivalent of the semblance (sensory hallucinations) can be extrapolated from examining the packets of minimum sensory stimuli capable of stimulating postsynapse D. The sensory identity of the semblance of activity occurring at postsynapse D consists of inputs from neuron Y. Neuron Y is normally activated by inputs from a set of lower order neurons {X}. Continuing this extrapolation towards the sensory level identifies a set of sensory receptors {SR}. {a}, {b} and {c} are subsets of {SR} and are capable of independently activating postsynapse D. Hypothetical packets of sensory stimuli activating sensory receptor sets {a}, {b} and {c} are called semblions 1, 2 and 3 respectively. Activation of postsynapse D through inter-postsynaptic functional LINK B–D by the cue stimulus can lead to the virtual internal sensation of semblions either 1, or 2, or 3 or their integral or their overlapping region. Cue stimulus-induced activation of postsynapse D reaches the soma of its neuron Z. If neuron Z already receives baseline summated EPSP short of one EPSP to trigger an action potential, then the additional EPSP arriving through inter-postsynaptic functional LINK B–D and through postsynapse D can add to the sub-threshold EPSP and fire neuron Z, resulting in latter’s concurrent activation during the formation of internal sensation (Figure modified from Vadakkan 2010)