ISBN
978-3-00-037458-6
Monograph by Dr. rer. nat. Andreas Heinrich Malczan
We summarize our findings and understandings in this section.
We define the circular linkage of hippocampus, amygdala and septal cores as the elementary limbic oscillation circuit or the inner Papez Circuit.
We define the circular linkage of hippocampus, corpus mamillare, nucleus anterior thalami and gyrus cinguli as the Papez Circuit.
Depending on species, the limbic system consists of between thousands and hundreds of thousands of elementary oscillation circuits that are mostly more or less independent of each other, each single one of which is an active memory for a signal of its own.
A tetanic oscillation interrupted intermittently at short intervals with a low-frequency envelope curve of between 4 and 8 Hertz is generated in each elementary limbic oscillation circuit.
All action potentials exerting an action on each granule cell are subjected to a time lag during transmission along the cell’s unmyelinated axon – the mossy fibers. Echo neurons tap these mossy fibers to produce an echo of the input that is time-lagged as a result of the difference in transmission time. These primary echoes from each mossy fiber are collected and pooled by an integration neuron belonging to the mossy fiber into a higher-frequency echo and transmitted to a recycling neuron in the lateral amygdala, from which they are fed back to the granule cell that originally generated them as output, and also to the cortical neurons responsible for emitting the original signals.
The dead time phases of the neurons prevent damage from an increase in firing rate of the continuous oscillation.
Excitatory projection of this input oscillation to the septum and negative feedback from the septum to the hippocampus creates intervals in this continuous oscillation enabling the neurons to reactivate. The duration of these intervals corresponds to the time taken by the action potential to travel from the hippocampus to the septum and back.
An input signal in the hippocampus is kept alive and temporarily stored in the elementary limbic oscillation circuit in the form of a timed, titanic oscillation.
Some of the weaker neighboring signals are suppressed by blockade of neighboring receptors by GABAergic interneurons.
Signals can be deleted by interruption of the oscillation by means of prolonged inhibitory signals onto the recycling neuron in the lateral amygdala responsible for the oscillation. An alternative pathway is excitation of GABAergic interneurons in the hippocampus that will enable them to block the hippocampal pyramidal cells.
A further option is to submit the relevant GABAergic projection neurons in the septum to prolonged excitation, thereby causing these to block the hippocampal pyramidal cells and terminate signal rotation.
Signals from cores with time-dependent activity-control capability enable time-driven interruption of signal rotation, e.g. after prey has escaped.
An inactive signal in the hippocampus can be activated by external stimuli and signal rotation initiated by excitation of any one of the neurons in the signal loop. The start location can be either the hippocampus or the central amygdala.
Sustained excitatory input into the central amygdala is switched over to the inhibitory transmitter GABA to block the signal neurons allotted to it in the lateral amygdala and stop oscillation of the signals belonging to it.
The output of the elementary hippocampal oscillation circuit can exit this circuit at various points, either via the hippocampus in the form of primary echo signals from the CA3 pyramidal cells, or as a secondary echo from the CA1 pyramidal cells via the hippocampus, and also via the amygdala or the septum.
(End of Theorem 3.1)
Although the limbic system includes not only hippocampus, amygdala and septal
cores, but also nucleus accumbens, area tegmentalis ventralis
and ventral pallidum, it will for reasons connected with system theory be the
three first-mentioned organs that will be reviewed in Part 4 of this monograph.
Part 4 will demonstrate that evolution allotted a series of tasks to the basal ganglia, including the parts of these located in the limbic system. Evolution was so successful in concealing the nature of these tasks that it has as yet been impossible to decipher them. In the opinion of the author of this monograph, the most important of these tasks was digitalization of cortical output to enable binary processing of signals within the cerebral system. Should it prove possible to prove this, there is no doubt that the existing theoretic difference between present-day computers and vertebrate brain will be joined by a common feature, namely, binary signal processing in both systems.
ISBN 978-3-00-037458-6
Monograph by Dr. rer. nat. Andreas Heinrich Malczan