Intracellular and extracellular electrophysiology of nigral dopaminergic neurons—1. Identification and characterization

Most rhythmic behaviors are produced by a specialized ensemble of neurons found in the central nervous system. These central pattern generators (CPGs) have become a cornerstone of neuronal circuit analysis. Studying simple invertebrate nervous systems may reveal the interactions of the neurons involved in the production of rhythmic motor output. There has recently been progress in this area, but due to certain intrinsic features of CPGs it is unlikely that present techniques will ever yield a complete understanding of any but the simplest of them. The chief impediment seems to be our inability to identify and characterize the total interneuronal pool making up a CPG. In addition, our general analytic strategy relies on a descriptive, reductionist approach, with no analytical constructs beyond phenomenological modeling. Detailed descriptive data are usually not of sufficient depth for specific model testing, giving rise instead to ad hoc explanations of mechanisms which usually turn out to be incorrect. Because they make too many assumptions, modeling studies have not added much to our understanding of CPCs; this is due not so much to inadequate simulations as to the poor quality and incomplete nature of the data provided by experimentalists.A basic strategy that would provide sufficient information for neural modeling would include: (1) identifying and characterizing each element in the CPG network; (2) specifying the synaptic connectivity between the elements; and (3) analyzing nonlinear synaptic properties and interactions by means of the connectivity matrix. Limitations based on our present technical capabilities are also discussed.

Are central pattern generators understandable

Intracellular and extracellular electrophysiology of nigral dopaminergic neurons—3. Evidence for electrotonic coupling

Centrally programmed feeding in helisoma: Identification and characteristics of an electrically coupled premotor neuron network

Sprouting and functional regeneration of an identified neuron in helisoma

Burst generation by electrically coupled network in the snail helisoma: analysis using computer simulation.

This paper deals with a quantitative analysis of a network of electrically coupled neurons (cyberchrons) in the snail Helisoma trivolvis. This network produces regular bursts of activity which drive the motoneurons controlling the feeding musculature. Analysis of the time constants and Bode plots obtained from current injection leads to the development of an equivalent model circuit describing the functional relationships of the individual neuronal elements. The equivalent model is used to demonstrate compensation of the frequency response of an individual neuron by the effective loading of the rest of the network. However, the current observed in a postsynaptic neuron is intergrated across the long cell time constant resulting in increased temporal and spatial summation. This frequency compensation and long duration of the postsynaptic response are both believed to be instrumental in the maintenance of a high frequency burst. This model will act as a framework on which active properties such as burst form, timing, and termination can be tested.

Analysis of a Network of Electrically Coupled Neurons Producing Rhythmic Activity in the Snail Helisoma Trivolvis

Chloride-bicarbonate exchange in the urinary bladder of the turtle. Independence from sodium ion

Necessary conditions are derived for optimality of a control in a differential process with an isoperimetric constraint that is not necessarily differentiable. It is found that the gradient of the functional describing the isoperimetric constraint can be replaced by its Gateaux differential. The techniques of mathematical programming and the Dubovitskii-Milyutin theorem are employed. The necessary conditions derived are in the form of an adjoint differential equation and a pointwise maximal condition.

Optimal control problems with non-differentiable isoperimetric constraints

The purpose of this investigation is to study the effect that the amortisseur winding has on the stability of an alternator when it is driven by an engine. The simulation of the system was done with the use of an analogue computer. The effect of each amorlisseur winding was studied separately and together. This type of information is not available and the control engineer needs these results when analysing certain complex systems. In order to arrive at system equations, the alternator is treated as a many-winding transformer, and the equations are obtained from the transformer equipment circuit. A transformation due to Blondel was applied to these system equations which in effect causes the demodulation of the frequency of the alternator. Then, on the analogue computer, only variations of amplitude and not the individual frequency had to be simulated. This study revealed that the amorlisseur windings could be treated as feedback compensation to the prime mover, and this paper presents the development of a...

Earl D. Eyman

Papers

Burst generation by electrically coupled network in the snail helisoma: analysis using computer simulation.

Analysis of a Network of Electrically Coupled Neurons Producing Rhythmic Activity in the Snail Helisoma Trivolvis

Chloride-bicarbonate exchange in the urinary bladder of the turtle. Independence from sodium ion

Optimal control problems with non-differentiable isoperimetric constraints

Analogue Computer Study of some Fundamental Control Relations Involving Alternators and Diesel Engines