scholarly journals Voluntary suppression of neck reflexes during passive head-on-trunk rotations - reflex gain control vs. proprioceptive feedback

2021 ◽  
Author(s):  
Dimitri Anastasopoulos ◽  
Lysandros Anastasopoulos ◽  
Thomas Mergner
Keyword(s):  
Muscle Relaxation ◽  
Sensory Information ◽  
Gain Control ◽  
Normal Subjects ◽  
Underlying Mechanism ◽  
Quantitative Model ◽  
Proprioceptive Reflexes ◽  
Reflex Gain ◽  
Initial Resistance ◽  
Continuous Feedback

Normal subjects can completely eliminate resistance upon imposed head-on-trunk rotations when they are asked to relax. It is not, however, clear how neck reflexes to stretch can be voluntarily suppressed. Reflexive responses might be modified by adjusting the gain of the reflex loop through descending control. Theoretically, necessary corrections upon interfering disturbances during coordinated motor performace requiring the interplay of relaxation/activation may be missing if muscle relaxation is taking place exclusively by this mechanism. It has been alternatively proposed, that sensory information from the periphery may be allowed to "neutralize" neck reflexes if it is fed back with opposite sign to the structures driving the reflexes. Six healthy subjects were asked to relax while subjected to head-on-trunk rotations generated by a head motor. After any initial resistance had completely subsided, the head was unexpectedly exposed to "ramp-and-hold" perturbations of up to 2○ amplitude and 0.7 s duration. Resistance to stretch consistently reappeared thereupon suggesting that stretch reflex gain had not been set to zero during the previously achieved complete relaxation. Resistance to perturbations under these circumstaces was compared to the forces generated when the same "ramp-and-hold" displacements were delivered unpredictably to the head held stationary. A quantitative model of neck proprioceptive reflexes suppression has been thus constructed. Gain scheduling or "motor set" cannot sufficiently account for the voluntary reflex suppression during slow passive head rotations. Instead, we propose as underlying mechanism the "neutralization" of the controlling servo by means of continuous feedback tracking displacement and force signals from the periphery.

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.

Attentional Recruitment of Inter-Areal Recurrent Networks for Selective Gain Control

2002 ◽  
Vol 14 (7) ◽  
pp. 1669-1689 ◽  
Author(s):  
Richard H. R. Hahnloser ◽  
Rodney J. Douglas ◽  
Klaus Hepp
Keyword(s):  
Receptive Field ◽  
Network Architecture ◽  
Receptive Fields ◽  
Sensory Information ◽  
Gain Control ◽  
External Noise ◽  
Stimulus Selection ◽  
Low Contrast ◽  
Winner Take All ◽  
Higher Visual Areas

There is strong anatomical and physiological evidence that neurons with large receptive fields located in higher visual areas are recurrently connected to neurons with smaller receptive fields in lower areas. We have previously described a minimal neuronal network architecture in which top-down attentional signals to large receptive field neurons can bias and selectively read out the bottom-up sensory information to small receptive field neurons (Hahnloser, Douglas, Mahowald, & Hepp, 1999). Here we study an enhanced model, where the role of attention is to recruit specific inter-areal feedback loops (e.g., drive neurons above firing threshold). We first illustrate the operation of recruitment on a simple example of visual stimulus selection. In the subsequent analysis, we find that attentional recruitment operates by dynamical modulation of signal amplification and response multistability. In particular, we find that attentional stimulus selection necessitates increased recruitment when the stimulus to be selected is of small contrast and of small distance away from distractor stimuli. The selectability of a low-contrast stimulus is dependent on the gain of attentional effects; for example, low-contrast stimuli can be selected only when attention enhances neural responses. However, the dependence of attentional selection on stimulus-distractor distance is not contingent on whether attention enhances or suppresses responses. The computational implications of attentional recruitment are that cortical circuits can behave as winner-take-all mechanisms of variable strength and can achieve close to optimal signal discrimination in the presence of external noise.

scholarly journals A confirmation bias in perceptual decision-making due to hierarchical approximate inference

2018 ◽  
Author(s):  
Richard D. Lange ◽  
Ankani Chattoraj ◽  
Jeffrey M. Beck ◽  
Jacob L. Yates ◽  
Ralf M. Haefner
Keyword(s):  
Model Comparison ◽  
Empirical Studies ◽  
Temporal Integration ◽  
Sensory Information ◽  
Quantitative Model ◽  
Perceptual Decision Making ◽  
Sensory Evidence ◽  
Hierarchical Nature ◽  
Integration Strategies ◽  
The Brain

AbstractHuman decisions are known to be systematically biased. A prominent example of such a bias occurs when integrating a sequence of sensory evidence over time. Previous empirical studies differ in the nature of the bias they observe, ranging from favoring early evidence (primacy), to favoring late evidence (recency). Here, we present a unifying framework that explains these biases and makes novel psychophysical and neurophysiological predictions. By explicitly modeling both the approximate and the hierarchical nature of inference in the brain, we show that temporal biases depend on the balance between “sensory information” and “category information” in the stimulus. Finally, we present new data from a human psychophysics task that confirms a critical prediction of our framework showing that effective temporal integration strategies can be robustly changed within each subject, and that allows us to exclude alternate explanations through quantitative model comparison.

scholarly journals Effect of interglomerular inhibitory networks on olfactory bulb odor representations

2020 ◽  
Author(s):  
Daniel Zavitz ◽  
Isaac A. Youngstrom ◽  
Alla Borisyuk ◽  
Matt Wachowiak
Keyword(s):  
Experimental Data ◽  
Olfactory Bulb ◽  
Computational Model ◽  
Lateral Inhibition ◽  
Sensory Input ◽  
Sensory Information ◽  
Gain Control ◽  
Innervation Patterns ◽  
Cell Networks ◽  
Inhibitory Networks

AbstractLateral inhibition is a fundamental feature of circuits that process sensory information. In the mammalian olfactory system, inhibitory interneurons called short axon cells comprise the first network mediating lateral inhibition between glomeruli, the functional units of early olfactory coding and processing. The connectivity of this network and its impact on odor representations is not well understood. To explore this question, we constructed a computational model of the interglomerular inhibitory network using detailed characterizations of short axon cell morphologies taken from mouse olfactory bulb. We then examined how this network transformed glomerular patterns of odorant-evoked sensory input (taken from previously-published datasets) as a function of the selectivity of interglomerular inhibition. We examined three connectivity schemes: selective (each glomerulus connects to few others with heterogeneous strength), nonselective (glomeruli connect to most others with heterogenous strength) or global (glomeruli connect to all others with equal strength). We found that both selective and nonselective interglomerular networks could mediate heterogeneous patterns of inhibition across glomeruli when driven by realistic sensory input patterns, but that global inhibitory networks were unable to produce input-output transformations that matched experimental data and were poor mediators of intensity-dependent gain control. We further found that networks whose interglomerular connectivity was tuned by sensory input profile decorrelated odor representations more effectively. These results suggest that, despite their multiglomerular innervation patterns, short axon cells are capable of mediating odorant-specific patterns of inhibition between glomeruli that could, theoretically, be tuned by experience or evolution to optimize discrimination of particular odorants.Significance StatementLateral inhibition is a key feature of circuitry in many sensory systems including vision, audition, and olfaction. We investigate how lateral inhibitory networks mediated by short axon cells in the mouse olfactory bulb might shape odor representations as a function of their interglomerular connectivity. Using a computational model of interglomerular connectivity derived from experimental data, we find that short axon cell networks, despite their broad innervation patterns, can mediate heterogeneous patterns of inhibition across glomeruli, and that the canonical model of global inhibition does not generate experimentally observed responses to stimuli. In addition, inhibitory connections tuned by input statistics yield enhanced decorrelation of similar input patterns. These results elucidate how the organization of inhibition between neural elements may affect computations.

scholarly journals Deficits in Prediction Ability Trigger Asymmetries in Behavior and Internal Representation

2020 ◽  
Vol 11 ◽  
Author(s):  
Anja Philippsen ◽  
Yukie Nagai
Keyword(s):  
Developmental Disorders ◽  
Computational Models ◽  
Predictive Coding ◽  
Sensory Information ◽  
Internal Representation ◽  
Human Perception ◽  
Underlying Mechanism ◽  
Autism Spectrum ◽  
Prediction Ability ◽  
And Behavior

Predictive coding is an emerging theoretical framework for explaining human perception and behavior. The proposed underlying mechanism is that signals encoding sensory information are integrated with signals representing the brain's prior prediction. Imbalance or aberrant precision of the two signals has been suggested as a potential cause for developmental disorders. Computational models may help to understand how such aberrant tendencies in prediction affect development and behavior. In this study, we used a computational approach to test the hypothesis that parametric modifications of prediction ability generate a spectrum of network representations that might reflect the spectrum from typical development to potential disorders. Specifically, we trained recurrent neural networks to draw simple figure trajectories, and found that altering reliance on sensory and prior signals during learning affected the networks' performance and the emergent internal representation. Specifically, both overly strong or weak reliance on predictions impaired network representations, but drawing performance did not always reflect this impairment. Thus, aberrant predictive coding causes asymmetries in behavioral output and internal representations. We discuss the findings in the context of autism spectrum disorder, where we hypothesize that too weak or too strong a reliance on predictions may be the cause of the large diversity of symptoms associated with this disorder.

scholarly journals Sensory-Marketing-Evaluation of E-Commerce Websites with Artificial Intelligence

2021 ◽  
Author(s):  
Kevin Hamacher ◽  
◽  
Rüdiger Buchkremer ◽  
Keyword(s):  
Artificial Intelligence ◽  
Natural Language ◽  
Language Processing ◽  
Sensory Information ◽  
Quantitative Model ◽  
Automatic Machine ◽  
Language Generation ◽  
Sensory Marketing ◽  
Digital Environments ◽  
Media Types

Multisensory consumer engagement on e-commerce websites is technically limited to visual, acoustic, and written elements. Consumers communicate, buy, and share products and services via digital environments in which sensory information is limited. To improve consumers' online sensory experience, media types and the content need to be quantitatively assessed and adapted. This project aims to develop a quantitative model, an Online Sensory Marketing Index (OSMI), which assesses ecommerce websites in multisensory communication quality. The OSMI will be supported by an automatic procedure that is based on artificial intelligence. Content of texts, images, and videos is evaluated by natural language processing (NLP), natural language generation (NLG) as well as automatic machine learning (AutoML) procedures. Multiple e-commerce websites from various industries are examined.

Eye-head coordination in darkness: Formulation and testing of a mathematical model

2003 ◽  
Vol 13 (2-3) ◽  
pp. 79-91
Author(s):  
Stefano Ramat ◽  
Roberto Schmid ◽  
Daniela Zambarbieri
Keyword(s):  
Mathematical Model ◽  
Vestibular System ◽  
Sensory Information ◽  
Head Rotation ◽  
Normal Subjects ◽  
Head Movements ◽  
Vestibular Nystagmus ◽  
Ocular Reflex ◽  
Head Displacement ◽  
Vestibulo Ocular Reflex

Passive head rotation in darkness produces vestibular nystagmus, consisting of slow and quick phases. The vestibulo-ocular reflex produces the slow phases, in the compensatory direction, while the fast phases, in the same direction as head rotation, are of saccadic origin. We have investigated how the saccadic components of the ocular motor responses evoked by active head rotation in darkness are generated, assuming the only available sensory information is that provided by the vestibular system. We recorded the eye and head movements of nine normal subjects during active head rotation in darkness. Subjects were instructed to rotate their heads in a sinusoidal-like manner and to focus their attention on producing a smooth head rotation. We found that the desired eye position signal provided to the saccadic mechanism by the vestibular system may be modeled as a linear combination of head velocity and head displacement information. Here we present a mathematical model for the generation of both the slow and quick phases of vestibular nystagmus based on our findings. Simulations of this model accurately fit experimental data recorded from subjects.

Effect of Vasopressin on Bronchial Reactivity to Histamine

1989 ◽  
Vol 77 (5) ◽  
pp. 467-471
Author(s):  
Alan J. Knox ◽  
John R. Britton ◽  
Anne E. Tattersfield
Keyword(s):  
Salt Intake ◽  
Plasma Concentrations ◽  
Normal Subjects ◽  
Underlying Mechanism ◽  
Forced Expiratory Volume ◽  
Bronchial Reactivity ◽  
Dietary Salt ◽  
Double Blind ◽  
Dietary Salt Intake ◽  
Significant Difference

1. Recent evidence suggests that a high salt diet increases bronchial reactivity, but the underlying mechanism is unclear. 2. To determine whether alterations in circulating vasopressin might be responsible, we have studied the effect of an infusion of vasopressin on the airways of six normal and eight asthmatic subjects measuring the response as expiratory flow at 30% of vital capacity (V̇30P) in the normal subjects and as forced expiratory volume in 1s (FEV1) in the asthmatic subjects, in a double-blind, placebo-controlled, cross-over study. 3. Vasopressin, given as an infusion at a rate of 2 i.u./h for 1 h, followed by 4 i.u./h for a further hour, produced plasma concentrations of 12.8 and 17 ng/l, respectively, compared with 2.0 and 2.0 ng/l on placebo. 4. Airway reactivity to histamine was measured after 1 and 2 h as the provocative doses of histamine causing a 40% reduction in V̇30P (PD40V̇30P) in the normal subjects and a 20% reduction in FEV1 (PD20FEV1) in the asthmatic subjects. 5. There was a small increase in PD40V̇30P after both vasopressin and placebo in normal subjects (refractoriness) but no change in PD20FEV1 in the asthmatic subjects. 6. There was no significant difference between vasopressin and placebo in V̇30P or PD40 V̇30P over the 2 h after the drug in the normal subjects or in FEV1 or PD20FEV1 over the 2 h after the drug in the asthmatic subjects. 7. We conclude that alterations in circulating vasopressin are unlikely to be responsible for the increase in bronchial reactivity when dietary salt intake is increased.

Cerebellar control of postural scaling and central set in stance

1994 ◽  
Vol 72 (2) ◽  
pp. 479-493 ◽  
Author(s):  
F. B. Horak ◽  
H. C. Diener
Keyword(s):  
Sensory Information ◽  
Normal Subjects ◽  
Anterior Lobe ◽  
Rate Of Change ◽  
Response Magnitude ◽  
Body Sway ◽  
Magnitude Scaling ◽  
Postural Responses ◽  
Surface Displacements ◽  
Central Set

1. The effects of cerebellar deficits in humans on scaling the magnitude of automatic postural responses based on sensory feedback and on predictive central set was investigated. Electromyographic (EMG) and surface reactive torques were compared in patients with anterior lobe cerebellar disorders and in normal healthy adults exposed to blocks of four velocities and five amplitudes of surface translations during stance. Correlations between the earliest postural responses (integrated EMG and initial rate of change of torque) and translation velocity provided a measure of postural magnitude scaling using sensory information from the current displacement. Correlations of responses with translation amplitude provided a measure of scaling dependent on predictive central set based on sequential experience with previous like displacements because the earliest postural responses occurred before completion of the displacements and because scaling to displacement amplitude disappeared when amplitudes were randomized in normal subjects. 2. Responses of cerebellar patients to forward body sway induced by backward surface displacements were hypermetric, that is, surface-reactive torque responses were two to three times larger than normal with longer muscle bursts resulting in overshooting of initial posture. Despite this postural hypermetria, the absolute and relative latencies of agonist muscle bursts at the ankle, knee, and hip were normal in cerebellar patients. 3. Although they were hypermetric, the earliest postural responses of cerebellar patients were scaled normally to platform displacement velocities using somatosensory feedback. Cerebellar patients, however, were unable to scale initial postural response magnitude to expected displacement amplitudes based on prior experience using central set. Randomization of displacement amplitudes eliminated the set effect of amplitude on initial responses in normal subjects, but responses to randomized and blocked trials were not different in cerebellar patients. 4. Cerebellar patients compensated for hypermetric responses and lack of anticipatory scaling of earliest gastrocnemius activity by scaling large, reciprocally activated tibialis and quadriceps antagonist activity with the displacement velocity and amplitude. Correlations between these antagonist EMG integrals and displacement amplitudes were preserved when amplitudes were randomized, suggesting that feedback-dependent and not set-dependent mechanisms were responsible for scaling of antagonists by cerebellar patients. Antagonist compensation for initial hypermetric responses also could be induced in normals when they overresponded to unexpectedly small amplitudes of surface displacements. 5. The major effects of anterior lobe cerebellar damage on human postural responses involves impairment of response magnitude based on predictive central set and not on use of velocity feedback or on the temporal synergic organization of multijoint postural coordination.(ABSTRACT TRUNCATED AT 400 WORDS)

Do Amplitude-Sensitive Hearing Protectors Improve Detectability of Vehicle Backup Alarms in Noise?

1995 ◽  
Vol 39 (15) ◽  
pp. 994-998 ◽  
Author(s):  
John G. Casali ◽  
Willliam H. Wright
Keyword(s):  
Noise Exposure ◽  
Gain Control ◽  
Warning Signal ◽  
Normal Subjects ◽  
Exposure Dose ◽  
Low Noise ◽  
Separate Analysis ◽  
Similar Frequency ◽  
Protection Devices ◽  
Band Limited

Signal detection thresholds to a vehicle backup alarm were determined for audiometrically-normal subjects under broadband (pink) noise at 75, 85, and 95 dBA. The objective was to compare detection performance achieved under two contemporary amplitude-sensitive hearing protection devices (HPDs), an electronic Peltor T7-SR earmuff and a passive, orifice-type E-A-R Ultra 9000 earmuff, against detection achieved under the conventional (non-amplitude-sensitive) counterparts to these muffs, a Peltor H7A and an E-A-R 2000. Amplitude-sensitive HPDs are intended to provide better hearing in low noise levels either through band-limited amplification of outside sounds (electronic Peltor muff), or through reduced attenuation via passage of low-intensity sounds (E-A-R 9000). However, for the noise conditions and common warning signal tested, the amplitude-sensitive HPDs produced no statistically-significant advantage in masked signal threshold compared to the conventional muffs. Therefore, it cannot be concluded that these amplitude-sensitive muffs will improve aural detection of important workplace sounds of similar frequency content to the backup alarm evaluated herein. A separate analysis comparing the dBA levels experienced under the Peltor electronic muff with the circuit on and off indicated that the subjects’ gain control setting did not significantly increase the noise exposure dose over amplifier-off conditions.

Sign in / Sign up

Export Citation Format

Share Document