Biology subjects

Smarandache-Wellmann, C. R.

Publications and source records attributed to Smarandache-Wellmann, C. R..

2 recordsLinked to original sources

bioRxiv2022

Unmasking hidden changes in intrinsic properties in neurons that coordinate oscillatory networks

2.Neurons utilize gain control to efficiently encode shifting inputs with maximum sensitivity. While gain control is present in a multitude of neurons, research on the underlying mechanisms is still sparse. We focused on one coordinating neuron (ASCE) in the crayfish swimmeret system that is both necessary and sufficient to coordinate distributed motor circuits. This neuron encodes properties of the motor activity in its home ganglion and sends the information as burst of spikes to its anterior target ganglia. Previous research has shown that ASCE encodes the strength of the motor activity by its spike number, and that the range of the number of spikes per burst adapts to the average motor activity. In turn, the motor activity can be activated and modulated via cholinergic pathways. We explored ASCEs response to changing levels of motor system excitation, which was induced with cholinergic agonists, both when the neuron was part of the full swimmeret systems circuit and when it was isolated from the network. The cholinergic agonist carbachol directly depolarized ASCEs membrane potential via nicotinic receptors when the neuron was isolated. In the intact circuit, ASCEs membrane potential did not change but its input resistance decreased. This indicated an additional indirect action of carbachol, presumably via presynaptic central pattern generating neurons at the core of each motor circuit. The balance of direct and indirect effects could allow ASCE to match its spiking range to the systems excitation level. 1. Summary statementA balance of direct and indirect cholinergic effects precisely controls the membrane potential, and therefore the gain, of a neuron that is involved in the coordination of distributed motor circuits.

neuroscience↗

bioRxiv2018

Adaptive Encoding of Coordinating Information in the Crayfish Central Nervous System

Locomotion is essential for an animals survival. This behavior can range from directional changes to adapting the motor force to the conditions of its surroundings. Even if speed and force of movement are changing, the relative coordination between the limbs or body segments has to stay stable in order to provide the necessary thrust. The coordinating information necessary for this task is not always conveyed by sensory pathways. Adaptation is well studied in sensory neurons, but only few studies have addressed if and how coordinating information changes in cases where a local circuit within the central nervous system is responsible for the coordination between body segments at different locomotor activity states.\n\nOne system that does not depend on sensory information to coordinate a chain of coupled oscillators is the swimmeret system of crayfish. Here, the coordination of four coupled CPGs is controlled by central Coordinating Neurons. Cycle by cycle, the Coordinating Neurons encode information about the activity state of their home ganglion as burst of spikes, and send it as corollary discharge to the neighboring ganglia. Activity states, or excitation levels, are variable in both the living animal and isolated nervous system; yet the amount of coordinating spikes per burst is limited.\n\nHere, we demonstrate that the systems excitation level tunes the encoding properties of the Coordinating Neurons. Their ability to adapt to excitation level, and thus encode relative changes in their home ganglions activity states, is mediated by a balancing mechanism. Manipulation of cholinergic pathways directly affected the coordinating neurons electrophysiological properties. Yet, these changes were counteracted by the networks influence. This balancing may be one feature to adapt the limited spike range to the systems current activity state.

neuroscience↗