scholarly journals Logistics in the Brain as Non-synaptic Interactions

2021 ◽  
Vol 28 (2) ◽  
pp. 71-80
Author(s):  
Hiromu Monai
Keyword(s):  
Synaptic Interactions ◽  
The Brain

THE MODELLING OF CHEMICAL MODULATION IN NEURAL NETWORKS

1992 ◽  
Vol 03 (supp01) ◽  
pp. 149-161
Author(s):  
A.C.C. Coolen ◽  
A.J. Noest ◽  
G.B. de Vries
Keyword(s):  
Neural Networks ◽  
System Size ◽  
Learning Stage ◽  
Ising Spin ◽  
Specific Subset ◽  
Synaptic Interactions ◽  
Mode Of Operation ◽  
Collective Processes ◽  
Chemical Modulation ◽  
The Brain

We analyse the effect of chemical neuro-modulation on collective processes in Ising spin neural networks with separable Hebbian type synaptic interactions. Neuro-modulation is taken into account in the most simple way: a modulator-specific subset of neurons is prevented from transmitting signals. However, the presence of neuro-modulators is taken into account also during the learning stage, which leads to non-symmetric interaction matrices. We derive (in the limit of an infinite system size) the macroscopic laws that determine the system’s evolution in time on the level of order parameters. These laws are very transparant and show that, within the proposed framework, one can understand the functioning of neuro-modulators as follows: their role is to choose from the repertoire of learned behaviour a particular mode of operation. By considering specific examples of learning stages we indicate how neuro-modulation might be used by the brain as an extra degree of freedom for (a) performing selective pattern reconstruction, (b) controlling the reproduction speed of stored pattern sequences or (c) for choosing a particular path from a set of partially overlapping stored trajectories through state space (at points where the trajectories separate).

scholarly journals The brain matters: effects of descending signals on motor control

2012 ◽  
Vol 107 (10) ◽  
pp. 2730-2741 ◽  
Author(s):  
Olivia J. Mullins ◽  
W. Otto Friesen
Keyword(s):  
Nerve Cord ◽  
Motor Output ◽  
Swimming Activity ◽  
Neuronal Circuit ◽  
Numerous Species ◽  
Physiological Conditions ◽  
Synaptic Interactions ◽  
Hirudo Verbana ◽  
Episode Duration ◽  
The Brain

The ability of nerve cords and spinal cords to exhibit fictive rhythmic locomotion in the absence of the brain is well-documented in numerous species. Although the brain is important for modulating the fictive motor output, it is broadly assumed that the functional properties of neuronal circuits identified in simplified preparations are conserved with the brain attached. We tested this assumption by examining the properties of a novel interneuron recently identified in the leech ( Hirudo verbana) nerve cord. This neuron, cell E21, initiates and drives stereotyped fictive swimming activity in preparations of the isolated leech nerve cord deprived of the head brain. We report that, contrary to expectation, the motor output generated when cell E21 is stimulated in preparations with the brain attached is highly variable. Swim frequency and episode duration are increased in some of these preparations and decreased in others. Cell E21 controls swimming, in part, via excitatory synaptic interactions with cells 204, previously identified gating neurons that reliably initiate and strongly enhance leech swimming activity when the brain is absent. We found that in preparations with the brain present, the magnitude of the synaptic interaction from cell E21 to cell 204 is reduced by 50% and that cell 204-evoked responses also were highly variable. Intriguingly, most of this variability disappeared in semi-intact preparations. We conclude that neuronal circuit properties identified in reduced preparations might be fundamentally altered from those that occur in more physiological conditions.

Distributed processing by visual interneurons of crayfish brain. I. Response characteristics and synaptic interactions

1980 ◽  
Vol 43 (3) ◽  
pp. 729-740 ◽  
Author(s):  
H. L. Wood ◽  
R. M. Glantz
Keyword(s):  
Information Transfer ◽  
Time Lag ◽  
Higher Order ◽  
Integration Time ◽  
Visual Responses ◽  
Functional Connections ◽  
Synaptic Potentials ◽  
Synaptic Interactions ◽  
Descending Interneurons ◽  
The Brain

1. The visual responses and synaptic interactions of a small population of crayfish interneurons are described. 2. The discharge of optic nerve sustaining fibers (tonic on-cells) appears in the brain prior to the onset of the light-evoked discharge of any of the higher order, descending visual interneurons. Direct depolarization of impaled sustaining fibers elicits impulse responses in a large number of descending interneurons. These results indicate that the sustaining fibers provide the visual input to higher order interneurons. 3. Four classes of descending interneurons can be distinguished. All arise in the brain and have axons in the circumesophageal connectives. The response forms vary from tonic to phasic. Two classes of tonic cells are distinguished by response latency and two classes of phasic neurons are distinguished by the rate of response adaptation. The phasic neurons exhibit the most rapid habituation, the largest receptive fields, and the most potent nonvisual inputs. 4. Synaptic interactions are studied by cross-correlation of impulse trains and direct observation of synaptic potentials. About 84% of the cells examined reveal evidence of functional connections to other descending visual interneurons. 5. Cross-correlograms derived from impulses of parallel interneurons exhibit a mean time lage to peak of 6.6 +/- 2.8 ms (SD). The measured delay from EPSP onset to spike onset is 6.0 +/- 4.0 ms. Thus a substantial proportion of the correlogram's time lag to peak is associated with postsynaptic integration time. 6. Direct depolarization of impaled tonic on-cells elicits impulse activity at a fixed delay in other descending interneurons. 7. Synaptic potentials in descending visual interneurons are correlated 1:1 with axon spikes of other descending interneurons. 8. A third of the 80 interactions examined were reciprocal and many cells were implicated in multiple interactions. 9. The results suggest that the descending visual interneurons are organized in a complex network, which can cordinate the discharge of various subpopulations of the ensemble. It is proposed that the coordination of impulses in parallel interneurons may be a mechanism for coding and information transfer in the crayfish nervous system.

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