Mechanisms for generating temporal filters in the electrosensory system

1999 ◽  
Vol 202 (10) ◽  
pp. 1281-1289 ◽  
Author(s):  
G.J. Rose ◽  
E.S. Fortune
Keyword(s):  
Nervous System ◽  
Discharge Rate ◽  
Temporal Structure ◽  
Sensory Information ◽  
Gain Control ◽  
Membrane Properties ◽  
Control Mechanisms ◽  
Temporal Features ◽  
Level Of Activity ◽  
The Central Nervous System

Temporal patterns of sensory information are important cues in behaviors ranging from spatial analyses to communication. Neural representations of the temporal structure of sensory signals include fluctuations in the discharge rate of neurons over time (peripheral nervous system) and the differential level of activity in neurons tuned to particular temporal features (temporal filters in the central nervous system). This paper presents our current understanding of the mechanisms responsible for the transformations between these representations in electric fish of the genus Eigenmannia. The roles of passive and active membrane properties of neurons, and frequency-dependent gain-control mechanisms are discussed.

Grasp stability during manipulative actions

1994 ◽  
Vol 72 (5) ◽  
pp. 511-524 ◽  
Author(s):  
Roland S. Johansson ◽  
Kelly J. Cole
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Precision Grip ◽  
Sensory Information ◽  
Parameter Control ◽  
Control Mechanisms ◽  
Control Processes ◽  
Grasp Stability ◽  
The Central Nervous System ◽  
Fingertip Forces

The control of adequate contact forces between the skin and an object (grasp stability) is examined for two classes of prehensile actions that employ a precision grip: lifting objects that are "passive" (subject only to inertial forces and gravity) and preventing "active" objects from moving. For manipulating either passive or active objects the relevant fingertip forces are determined by at least two control processes. "Anticipatory parameter control" is a feedforward controller that specifies the values for motor command parameters on the basis of predictions of critical characteristics, such as object weight and skin–object friction, and initial condition information. Through vision, for instance, common objects can be identified in terms of the fingertip forces necessary for a successful lift according to previous experiences. After contact with the object, sensory information representing discrete mechanical events at the fingertips can (i) automatically modify the motor commands, (ii) update sensorimotor memories supporting the anticipatory parameter control policy, (iii) inform the central nervous system about completion of the goal for each action phase, and (iv) trigger commands for the task's sequential phases. Hence, the central nervous system monitors specific, more or less expected peripheral sensory events to produce control signals that are appropriate for the task at its current phase. The control is based on neural modelling of the entire dynamics of the control process that predicts the appropriate output for several steps ahead. This "discrete-event, sensor-driven control" is distinguished from feedback or other continuous regulation. Using these two control processes, slips are avoided at each digit by independent control mechanisms that specify commands and process sensory information on a local, digit-specific basis. This scheme obviates explicit coordination of the digits and is employed when independent nervous systems lift objects. The force coordination across digits is an emergent property of the local control mechanisms operating over the same time span.Key words: precision grip, hand, grasp stability, grasp force, tactile afferents.

scholarly journals Reduced motoneuron excitability in a rat model of sepsis

2013 ◽  
Vol 109 (7) ◽  
pp. 1775-1781 ◽  
Author(s):  
Paul Nardelli ◽  
Jaffar Khan ◽  
Randall Powers ◽  
Tim C. Cope ◽  
Mark M. Rich
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Intensive Care ◽  
Motor Unit ◽  
Action Potentials ◽  
Cecal Ligation ◽  
Membrane Properties ◽  
Whole Body ◽  
Repetitive Firing ◽  
The Central Nervous System

Many critically ill patients in intensive care units suffer from an infection-induced whole body inflammatory state known as sepsis, which causes severe weakness in patients who survive. The mechanisms by which sepsis triggers intensive care unit-acquired weakness (ICUAW) remain unclear. Currently, research into ICUAW is focused on dysfunction of the peripheral nervous system. During electromyographic studies of patients with ICUAW, we noticed that recruitment was limited to few motor units, which fired at low rates. The reduction in motor unit rate modulation suggested that functional impairment within the central nervous system contributes to ICUAW. To understand better the mechanism underlying reduced firing motor unit firing rates, we moved to the rat cecal ligation and puncture model of sepsis. In isoflurane-anesthetized rats, we studied the response of spinal motoneurons to injected current to determine their capacity for initiating and firing action potentials repetitively. Properties of single action potentials and passive membrane properties of motoneurons from septic rats were normal, suggesting excitability was normal. However, motoneurons exhibited striking dysfunction during repetitive firing. The sustained firing that underlies normal motor unit activity and smooth force generation was slower, more erratic, and often intermittent in septic rats. Our data are the first to suggest that reduced excitability of neurons within the central nervous system may contribute to ICUAW.

Cardiovascular and respiratory control mechanisms during exercise: an integrated view

1991 ◽  
Vol 160 (1) ◽  
pp. 309-340
Author(s):  
D. L. Turner
Keyword(s):  
Nervous System ◽  
Neural Coding ◽  
Phase 1 ◽  
Sensory Information ◽  
Respiratory Control ◽  
Motor Command ◽  
The Body ◽  
Control Mechanisms ◽  
Parasympathetic Nerves ◽  
Sites Of Action

Exercise can impose an immense stress upon many physiological systems throughout the body. In order that exercise performance may be optimally maintained, it is essential that a profound and complex series of responses is coordinated and controlled. The primary site for coordination is the central nervous system, whereas control mechanisms (both feedback loops and feedforward activation) involve complex sensory information, often in the form of neural coding but also in the form of blood-borne chemical signals, a number of levels of peripheral and central integration and, finally, the efferent branches of the nervous system coursing via sympathetic and parasympathetic nerves to target sites of action. The neurohumoral control of the cardiorespiratory responses to exercise has received intense attention for over two decades and some particularly important steps forward in its understanding have occurred within the last 10 years. The initial fast increase (phase 1) in cardiovascular and ventilatory flow parameters are brought about by neurally mediated muscle mechanoreceptor feedback reflexes and a feedforward ‘central motor command’. The blood pressure operating point is also raised by a combination of these two neural mechanisms. Fine control of the matching of cardiac output to ventilation may occur by means of a feedforward ventilatory control of cardiac origin. During the slower phase of adjustment (phase 2), the neurally mediated mechanisms are augmented by a cohort of humorally mediated feedback reflexes involving muscle and vascular chemoreceptors as well as being supported by central neural reverberation.(ABSTRACT TRUNCATED AT 250 WORDS)

Are There Parallel Channels in the Vestibular Nerve?

Physiology ◽  
1998 ◽  
Vol 13 (4) ◽  
pp. 194-201 ◽  
Author(s):  
Ellengene H. Peterson
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Sensory Information ◽  
Primary Afferents ◽  
Vestibular Nerve ◽  
Functional Roles ◽  
The Central Nervous System ◽  
Parallel Channels

A popular concept in neurobiology is that sensory information is transmitted to the central nervous system over parallel channels of neurons that play different functional roles. But alternative organizing schemes are possible, and it is useful to ask whether some other framework might better account for the diversity of vestibular primary afferents.

Insights into the neural control of eccentric contractions

2014 ◽  
Vol 116 (11) ◽  
pp. 1418-1425 ◽  
Author(s):  
Jacques Duchateau ◽  
Stéphane Baudry
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Neural Control ◽  
Current Knowledge ◽  
Discharge Rate ◽  
Voluntary Activation ◽  
Eccentric Contractions ◽  
Future Research ◽  
Neural Activation ◽  
The Central Nervous System

The purpose of this brief review is to examine our current knowledge of the neural control of eccentric contractions. The review focuses on three main issues. The first issue considers the ability of individuals to activate muscles maximally during eccentric contractions. Most studies indicate that, regardless of the experimental approach (surface EMG amplitude, twitch superimposition, and motor unit recordings), it is usually more difficult to achieve full activation of a muscle by voluntary command during eccentric contractions than during concentric and isometric contractions. The second issue is related to the specificity of the control strategy used by the central nervous system during submaximal eccentric contractions. This part underscores that although the central nervous system appears to employ a single size-related strategy to activate motoneurons during the different types of contractions, the discharge rate of motor units is less during eccentric contractions across different loading conditions. The last issue addresses the mechanisms that produce this specific neural activation. This section indicates that neural adjustments at both supraspinal and spinal levels contribute to the specific modulation of voluntary activation during eccentric contractions. Although the available information on the control of eccentric contractions has increased during the last two decades, this review indicates that the exact mechanisms underlying the unique neural modulation observed in this type of contraction at spinal and supraspinal levels remains unknown and their understanding represents, therefore, a major challenge for future research on this topic.

Neurology Update: “Recent Developments in the Understanding of the Nervous System”

1980 ◽  
Vol 47 (2) ◽  
pp. 61-66
Author(s):  
M. Jean Gillespie
Keyword(s):  
Nervous System ◽  
Motor Response ◽  
Neural Mechanisms ◽  
Membrane Properties ◽  
Excitable Cells ◽  
Sensory Inputs ◽  
New Methods ◽  
Nucleus Plus ◽  
Recent Developments ◽  
The Central Nervous System

Neural Mechanisms of Sensori-Motor Integration New methods of investigation have enlarged understanding of the mechanisms underlying activity in the nervous system. Excitable cells transmit impulses by means of their special membrane properties and excitation is transmitted from cell to cell across specialized sites called synapses. In the nuclei of the central nervous system there are many small neurons that have no axon or only very short axons and dendrites. These are referred to as interneurons and the chemical transmitters they release may be excitatory or inhibitory to the cells with which they synapse. Cells with axons ending in a nucleus and cells with dendrites in the nucleus plus the interneurons which may intervene between the input of the message by an axon reaching the nucleus and its transmission onwards, form networks of cells that act as micro-circuits, affecting the nature of the neural signal. Control of transmission by these networks is the means by which sensory and motor impulses may be modified, enhanced, suppressed or facilitated. The integration of many sensory inputs, and the feedback during movement modulate and shape the motor response. An understanding of the mechanisms of inhibition and facilitation becomes increasingly important for therapists who use techniques based on “sensori-motor integration“.

scholarly journals Representation of uncertainty in macaque visual cortex

2019 ◽  
Author(s):  
Olivier J. Hénaff ◽  
Zoe M. Boundy-Singer ◽  
Kristof Meding ◽  
Corey M. Ziemba ◽  
Robbe L. T. Goris
Keyword(s):  
Visual Cortex ◽  
Neural Circuits ◽  
Sensory Information ◽  
Gain Control ◽  
Response Strength ◽  
Control Mechanisms ◽  
Stimulus Uncertainty ◽  
Population Activity ◽  
Stimulus Features ◽  
Do So

Uncertainty is intrinsic to perception. Neural circuits which process sensory information must therefore also represent the reliability of this information. How they do so is a topic of debate. We propose a view of visual cortex in which average neural response strength encodes stimulus features, while cross-neuron variability in response gain encodes the uncertainty of these features. To test our theory, we studied spiking activity of neurons in macaque V1 and V2 elicited by repeated presentations of stimuli whose uncertainty was manipulated in distinct ways. We show that gain variability of individual neurons is tuned to stimulus uncertainty, that this tuning is invariant to the source of uncertainty, and that it is specific to the features encoded by these neurons. We demonstrate that this behavior naturally arises from known gain-control mechanisms, and derive how downstream circuits can jointly decode stimulus features and their uncertainty from sensory population activity.

scholarly journals Adaptive Encoding of Coordinating Information in the Crayfish Central Nervous System

2018 ◽  
Author(s):  
Anna C. Schneider ◽  
Felix Blumenthal ◽  
Carmen R. Smarandache-Wellmann
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Sensory Information ◽  
Excitation Level ◽  
Electrophysiological Properties ◽  
Body Segments ◽  
Adaptive Encoding ◽  
The Central Nervous System ◽  
Activity State ◽  
A Chain

AbstractLocomotion is essential for an animal’s 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.One 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.Here, we demonstrate that the system’s 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 ganglion’s 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 network’s influence. This balancing may be one feature to adapt the limited spike range to the system’s current activity state.

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