Neural Control Mechanisms Research Articles

Intracerebroventricular infusion of neuropeptide Y increases glucose dependent-insulinotropic peptide secretion in the fasting conscious dog

The rapid increase of incretins glucose-dependent insulinotropic peptide (GIP) and glucagon like peptide-1 (GLP-1), within 5–15 min, after food ingestion, suggests that a neural mechanism might be involved in the regulation of their secretion. The aim of this study is to determine whether intracerebroventricular (i.c.v) administration of neuropeptide Y (NPY), a widely distributed neurotransmmiter, can mediate this neural regulation of GIP secretion after food consumption. Six healthy mongrel dogs were utilized for this study. A prototype epicranial apparatus was placed surgically, allowing easy and exact localization of the third ventricle for infusions or sampling. Simultaneous blood sampling was obtained from cannulation of a hind limb vein. Plasma insulin, and GIP concentrations were measured after i.c.v infusion of 5, 10 and 25 μg of NPY dissolved in 0.5 ml of artificial cerebrospinal fluid (a CSF). The secretion of GIP and insulin were increased after the injection of NPY in a different pattern. Our data indicate that NPY might be involved in a possible neural control mechanism of GIP secretion after food consumption.

Hand preference and skilled hand performance among individuals with successful rightward conversions of the writing hand

Searleman and Porac (2001) studied lateral preference patterns among successfully switched left-hand writers, left-hand writers with no switch pressure history, and left-hand writers who did not switch when pressured. They concluded that left-handers who successfully shift to right-hand writing are following an inherent right-sided lateralisation pattern that they already possess. Searleman and Porac suggested that the neural mechanisms that control lateralisation in the successfully switched individuals are systematically different from those of other groups of left-handers. I examined patterns of skilled and less-skilled hand preference and skilled hand performance in a sample of 394 adults (ages 18–94 years). The sample contained successfully switched left-hand writers, left-handers pressured to shift who remained left-hand writers, left-handers who did not experience shift pressures, and right-handers. Both skilled hand preference and skilled hand performance were shifted towards the right side in successfully switched left-hand writers. This group also displayed mixed patterns of hand preference and skilled hand performance in that they were not as right-sided as “natural” right-handers nor were they as left-sided as the two left-hand writing groups, which did not differ from each other. The experience of being pressured to switch to right-hand writing was not sufficient to shift lateralisation patterns; the pressures must be experienced in the context of an underlying neural control mechanism that is amenable to change as a result of these external influences.

System identification of muscle–joint interactions of the cat hind limb during locomotion

Neurophysiological experiments in walking cats have shown that a number of neural control mechanisms are involved in regulating the movements of the hind legs during locomotion. It is experimentally hard to isolate individual mechanisms without disrupting the natural walking pattern and we therefore introduce a different approach where we use a model to identify what control is necessary to maintain stability in the musculo-skeletal system. We developed a computer simulation model of the cat hind legs in which the movements of each leg are produced by eight limb muscles whose activations follow a centrally generated pattern with no proprioceptive feedback. All linear transfer functions, from each muscle activation to each joint angle, were identified using the response of the joint angle to an impulse in the muscle activation at 65 postures of the leg covering the entire step cycle. We analyzed the sensitivity and stability of each muscle action on the joint angles by studying the gain and pole plots of these transfer functions. We found that the actions of most of the hindlimb muscles display inherent stability during stepping, even without the involvement of any proprioceptive feedback mechanisms, and that those musculo-skeletal systems are acting in a critically damped manner, enabling them to react quickly without unnecessary oscillations. We also found that during the late swing, the activity of the posterior biceps/semitendinosus (PB/ST) muscles causes the joints to be unstable. In addition, vastus lateralis (VL), tibialis anterior (TA) and sartorius (SAT) muscle-joint systems were found to be unstable during the late stance phase, and we conclude that those muscles require neuronal feedback to maintain stable stepping, especially during late swing and late stance phases. Moreover, we could see a clear distinction in the pole distribution (along the step cycle) for the systems related to the ankle joint from that of the other two joints, hip or knee. A similar pattern, i.e., a pattern in which the poles were scattered over the s-plane with no clear clustering according to the phase of the leg position, could be seen in the systems related to soleus (SOL) and TA muscles which would indicate that these muscles depend on neural control mechanisms, which may involve supraspinal structures, over the whole step cycle.

Effects of external loads on balance control during upright stance: Experimental results and model-based predictions

The purpose of this study was to identify the effects of external loads on balance control during upright stance, and to examine the ability of a new balance control model to predict these effects. External loads were applied to 12 young, healthy participants, and effects on balance control were characterized by center-of-pressure (COP) based measures. Several loading conditions were studied, involving combinations of load mass (10% and 20% of individual body mass) and height (at or 15% of stature above the whole-body COM). A balance control model based on an optimal control strategy was used to predict COP time series. It was assumed that a given individual would adopt the same neural optimal control mechanisms, identified in a no-load condition, under diverse external loading conditions. With the application of external loads, COP mean velocity in the anterior–posterior direction and RMS distance in the medial–lateral direction increased 8.1% and 10.4%, respectively. Predicted COP mean velocity and RMS distance in the anterior–posterior direction also increased with external loading, by 11.1% and 2.9%, respectively. Both experimental COP data and model-based predictions provided the same general conclusion, that application of larger external loads and loads more superior to the whole body center of mass lead to less effective postural control and perhaps a greater risk of loss of balance or falls. Thus, it can be concluded that the assumption about consistency in control mechanisms was partially supported, and it is the mechanical changes induced by external loads that primarily affect balance control.

Neuromusculoskeletal Torque-Generation Process Has a Large Destabilizing Effect on the Control Mechanism of Quiet Standing

The delay of the sensory-motor feedback loop is a destabilizing factor within the neural control mechanism of quiet standing. The purposes of this study were 1) to experimentally identify the neuromusculoskeletal torque-generation process during standing posture and 2) to investigate the effect of the delay induced by this system on the control mechanism of balance during quiet standing. Ten healthy adults participated in this study. The ankle torque, ankle angle, and electromyograms from the right lower leg muscles were measured. A ground-fixed support device was used to support the subject at his/her knees, without changing the natural ankle angle during quiet standing. Each subject was asked to mimic the ankle torque fluctuation by exerting voluntary ankle extension while keeping the supported standing posture. Using the rectified soleus electromyogram as the input and the ankle torque as the output, a critically damped, second-order system (twitch contraction time of 0.152 +/- 0.027 s) successfully described the dynamics of the torque-generation process. According to the performed Bode analysis, the phase delay induced by this torque-generation process in the frequency region of spontaneous body sway during quiet standing was considerably large, corresponding to an effective time delay of about 200 to 380 ms. We compared the stability of the balance control system with and without the torque-generation process and demonstrated that a much smaller number of gain combinations can stabilize the model with the torque-generation process than without it. We concluded that the phase delay induced by the torque-generation process is a more destabilizing factor in the control mechanism of quiet standing than previously assumed, which restricts the control strategies that can stabilize the entire system.

Differential Neural Activation for Updating Rule versus Stimulus Information in Working Memory

Establishing what information is actively maintained in working memory (WM) and how it is represented and controlled is essential to understanding how such information guides future behavior. WM has traditionally been investigated in terms of the maintenance of stimulus-specific information, such as locations or words. More recently, investigators have emphasized the importance of rules that establish relationships between those stimuli and the pending response. The current study used a mental arithmetic task with fMRI to test whether updating of numbers (i.e., stimuli) and updating of mathematical operations (i.e., rules) in WM relies on the same neural system. Results indicate that, while a common network is activated by both types of updating, rule updating preferentially activates prefrontal cortex while number updating preferentially activates parietal cortex. The results suggest that both numbers and rules are maintained in WM but that they are different types of information that are controlled independently.

Commentary on Viewpoint: The human cutaneous circulation as a model of generalized microvascular function

VIEWPOINTCommentary on Viewpoint: The human cutaneous circulation as a model of generalized microvascular functionJian CuiJian CuiPublished Online:01 Jul 2008https://doi.org/10.1152/japplphysiol.90323.2008MoreSectionsPDF (26 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat to the editor: Because of the advantages of skin-specific methodologies (i.e., combining skin laser-Doppler with iontophoresis or intradermal microdialysis), Holowatz and colleagues (1) suggest that studies of cutaneous vascular beds can provide information regarding generalized vascular function in healthy and diseased individuals. However, as Holowatz and colleagues stated in the Viewpoint, blood flow in vivo is an integrated response by multiple mechanisms. In cutaneous vascular bed, these mechanisms include thermoregulatory (skin and core temperatures) and nonthermoregulatory reflexes (blood pressure control, etc.) (2). Because the physiological function and the control mechanisms of cutaneous vessels are different from other vascular beds (e.g., muscle, coronary, and renal), skin blood flow responses to stimuli can be totally different from responses seen in these other vascular beds. For example, heat stress at rest induces pronounced cutaneous vasodilation, but causes significant vasoconstriction in the splanchnic and renal circulations (3). It is well known that the neural control mechanisms of skin blood flow are different from those for muscle vascular beds (5). Moreover, the effects of some diseases (e.g., heart failure) on the controls of cutaneous vessels are different from the other beds (e.g., muscle) (4). Thus, without validation, the results obtained from the study of cutaneous vascular beds will provide only questionable insight into the effects of a pathological condition on a noncutaneous vascular bed.REFERENCES1 Holowatz LA, Thompson-Torgerson CS, Kenney WL. Viewpoint: The human cutaneous circulation as a model of generalized microvascular function. J Appl Physiol; doi:10.1152/japplphysiol.00858.2007.Link | ISI | Google Scholar2 Johnson JM, Proppe DW. Cardiovascular adjustments to heat stress. In: Handbook of Physiology: Environmental Physiology. Bethesda, MD: Am Physiol Soc, 1996, p. 215–243.Google Scholar3 Rowell LB. Human cardiovascular adjustments to exercise and thermal stress. Physiol Rev 54: 75–159, 1974.Link | ISI | Google Scholar4 Silber DH, Sutliff G, Yang QX, Smith MB, Sinoway LI, Leuenberger UA. Altered mechanisms of sympathetic activation during rhythmic forearm exercise in heart failure. J Appl Physiol 84: 1551–1559, 1998.Link | ISI | Google Scholar5 Vallbo AB, Hagbarth KE, Torebjork HE, Wallin BG. Somatosensory, proprioceptive, and sympathetic activity in human peripheral nerves. Physiol Rev 59: 919–957, 1979.Link | ISI | Google ScholarAUTHOR NOTESAddress for reprint requests and other correspondence: J. Cui, Penn State Heart and Vascular Institute, The Pennsylvania State Univ. College of Medicine, The Milton S. Hershey Medical Center, Hershey, PA 17033 (e-mail: [email protected]) Download PDF Previous Back to Top Next FiguresReferencesRelatedInformationCited ByDo peripheral and/or central chemoreflexes influence skin blood flow in humans?24 October 2014 | Physiological Reports, Vol. 2, No. 10 More from this issue > Volume 105Issue 1July 2008Pages 386-386 Copyright & PermissionsCopyright © 2008 the American Physiological Societyhttps://doi.org/10.1152/japplphysiol.90323.2008PubMed18641228History Published online 1 July 2008 Published in print 1 July 2008 Metrics

Structured control from self-organizing arm movements

Introduction The organization of unconstrained arm movements in humans appears to be determined essentially by the biophysical properties of the limb [1], which, however, might imply as well that the underlying neural control mechanisms are perfectly adapted to controlled system. The stiffness of the arm with respect to perturbing forces [2] is caused by an active process that cannot be inferred from the biomechanics of the arm alone, and may thus reveal information about the underlying neural control mechanisms. We approach the problem by analyzing experimental measurements of stiffness in human subjects and by simulations of emergent control of a model of the human arm.

Sexual Dimorphism in the Hoverfly Motion Vision Pathway

Many insects perform high-speed aerial maneuvers in which they navigate through visually complex surrounds. Among insects, hoverflies stand out, with males switching from stationary hovering to high-speed pursuit at extreme angular velocities [1]. In dipterans, 50-60 large interneurons -- the lobula-plate tangential cells (LPTCs) -- detect changes in optic flow experienced during flight [2-5]. It has been predicted that large LPTC receptive fields are a requirement of accurate "matched filters" of optic flow [6]. Whereas many fly taxa have three horizontal system (HS) LPTC neurons in each hemisphere, hoverflies have four [7], possibly reflecting the more sophisticated flight behavior. We here show that the most dorsal hoverfly neuron (HS north [HSN]) is sexually dimorphic, with the male receptive field substantially smaller than in females or in either sex of blowflies. The (hoverfly-specific) HSN equatorial (HSNE) is, however, sexually isomorphic. Using complex optic flow, we show that HSN, despite its smaller receptive field, codes yaw velocity as well as HSNE. Responses to a target moving against a plain or textured background suggest that the male HSN could potentially play a role in target pursuit under some conditions.

Autonomic neural control mechanisms and the release of adrenal steroids after hypoglycaemia in man.

The changes in blood glucose, plasma potassium, plasma renin activity, aldosterone, cortisol, corticosterone and ACTH were measured in 11 normal subjects, 6 tetraplegic subjects (pre-ganglionic sympathectomy) and 6 tetraplegic subjects given atropine (sympathectomy with cholinergic blockade), in response to acute insulin-induced hypoglycaemia. After hypoglycaemia, blood glucose recovery was impaired only in the tetraplegic group given atropine in whom ACTH secretion was delayed and the peak cortisol and corticosterone concentrations were lower compared with the other groups. Plasma renin activity rose both in the normal and the tetraplegic subjects; the aldosterone rise and the fall in potassium were similar in all three groups. Aldosterone release after hypoglycaemia appears to occur independently of stimulation of the sympatho-adrenal system and cholinergic blockade, and may result from activation of the renin-angiotensin system, rather than from ACTH stimulation. Activation of ACTH secretion in response to hypoglycaemia may involve a cholinergic mechanism at the hypothalamic level, with a consequent reduction in the increments of plasma cortisol and corticosterone after atropine administration.

Force coordination in static manipulation: Discerning the contribution of muscle synergies and cutaneous afferents

Both an elaborate coordination of the hand grip force (G; normal component of force acting at the digits-object contact area) and load force (L; tangential component), and the role of cutaneous afferents in G-L coordination have been well documented in a variety of manipulation tasks. However, our recent studies revealed that G-L coordination deteriorates when L consecutively changes direction (bidirectional tasks; e.g., when vigorously shaking objects or using tools). The aim of the study was to distinguish between the possible role of the synergy of hand grip and arm muscles (exerting G and L, respectively) and the role of cutaneous afferent input in the observed phenomenon. Subjects (N=14) exerted sinusoidal L pattern in vertical direction against an externally fixed device in trials that gradually changed from uni- to fully bidirectional. In addition, a manipulation of an external arm support decoupled L measured by the device (and, therefore, recorded by the cutaneous receptors) from the action of arm muscles exerting L. The results revealed that switching from uni- to bidirectional tasks, no matter how low and brief L exertion was in the opposite direction, was associated with an abrupt decrease in G-L coordination. This coordination remained unaffected by the manipulation of external support. The first result corroborates our previous conclusion that the force coordination in uni- and bidirectional manipulation tasks could be based on partly different neural control mechanisms. However, the second finding suggests that the studied control mechanisms could depend more on the cutaneous afferent input, rather than on the synergy of the muscles exerting G and L.

Reduction of neuromuscular redundancy for postural force generation using an intrinsic stability criterion

Postural control requires the coordination of multiple muscles to achieve both endpoint force production and postural stability. Multiple muscle activation patterns can produce the required force for standing, but the mechanical stability associated with any given pattern may vary, and has implications for the degree of delayed neural feedback necessary for postural stability. We hypothesized that muscular redundancy is reduced when muscle activation patterns are chosen with respect to intrinsic musculoskeletal stability as well as endpoint force production. We used a three-dimensional musculoskeletal model of the cat hindlimb with 31 muscles to determine the possible contributions of intrinsic muscle properties to limb stability during isometric force generation. Using dynamic stability analysis we demonstrate that within the large set of activation patterns that satisfy the force requirement for posture, only a reduced subset produce a mechanically stable limb configuration. Greater stability in the frontal-plane suggests that neural control mechanisms are more highly active for sagittal-plane and for ankle joint control. Even when the limb was unstable, the time-constants of instability were sufficiently great to allow long-latency neural feedback mechanisms to intervene, which may be preferential for movements requiring maneuverability versus stability. Local joint stiffness of muscles was determined by the stabilizing or destabilizing effects of moment-arm versus joint angle relationships. By preferentially activating muscles with high local stiffness, muscle activation patterns with feedforward stabilizing properties could be selected. Such a strategy may increase intrinsic postural stability without co-contraction, and may be useful criteria in the force-sharing problem.

A model for control of breathing in mammals: Coupling neural dynamics to peripheral gas exchange and transport

A new model for aspects of the control of respiration in mammals has been developed. The model integrates a reduced representation of the brainstem respiratory neural controller together with peripheral gas exchange and transport mechanisms. The neural controller consists of two components. One component represents the inspiratory oscillator in the pre-Bötzinger complex (pre-BötC) incorporating biophysical mechanisms for rhythm generation. The other component represents the ventral respiratory group (VRG), which is driven by the pre-BötC for generation of inspiratory (pre)motor output. The neural model was coupled to simplified models of the lungs incorporating oxygen and carbon dioxide transport. The simplified representation of the brainstem neural circuitry has regulation of both frequency and amplitude of respiration and is done in response to partial pressures of oxygen and carbon dioxide in the blood using proportional (P) and proportional plus integral (PI) controllers. We have studied the coupled system under open and closed loop control. We show that two breathing regimes can exist in the model. In one regime an increase in the inspiratory frequency is accompanied by an increase in amplitude. In the second regime an increase in frequency is accompanied by a decrease in amplitude. The dynamic response of the model to changes in the concentration of inspired O 2 or inspired CO 2 was compared qualitatively with experimental data reported in the physiological literature. We show that the dynamic response with a PI-controller fits the experimental data better but suggests that when high levels of CO 2 are inspired the respiratory system cannot reach steady state. Our model also predicts that there could be two possible mechanisms for apnea appearance when 100% O 2 is inspired following a period of 5% inspired O 2 . This paper represents a novel attempt to link neural control and gas transport mechanisms, highlights important issues in amplitude and frequency control and sets the stage for more complete neurophysiological control models.

On the influence of negative affect on the neural mechanisms of cognitive control: an event-related fMRI study

On the influence of negative affect on the neural mechanisms of cognitive control: an event-related fMRI study

Force coordination in static manipulation tasks: effects of the change in direction and handedness

A number of studies have demonstrated high coordination of the hand grip force (GF; normal component of force acting at the digits-object contact area) and load force (LF; tangential component) in a variety of manipulation tasks. The aim of the study was to explore the mainly neglected effect of the change in LF direction and the effect of handedness on GF and LF coordination in bimanual manipulation task. Subjects (N = 14) exerted a bimanual sinusoidal LF pattern against externally fixed handles in trials that gradually changed from unidirectional (LF exerted only in one direction) to fully bidirectional (equal LF peaks in two opposite directions). Despite the gradual change of LF, unidirectional trials demonstrated high indices of force coordination, while in all bidirectional trials, no matter how low and brief LF exertion was in the opposite direction, all indices of GF and LF coordination deteriorated to a considerably lower level. The non-dominant hand demonstrated both a higher directional accuracy of exerting LF and higher GF modulation than the dominant one. We concluded that manipulation tasks performed in a single and two alternating directions may be based on partly distinctive neural control mechanisms, as well as that a switching of muscle synergies required in bidirectional tasks could play a role in the observed phenomenon. Regarding the effect of hand dominance, the recorded advantage of the non-dominant hand could be considered as an addition to the current views of the non-dominant arm/hemisphere specialization in controlling limb position.

The autonomic nervous system regulates gastric ghrelin secretion in rats

Plasma ghrelin levels are responsive to short- and long-term nutrient fluctuation, but the mechanisms of its regulation are largely unknown. To explore the role of the autonomic nervous system in the regulation of ghrelin secretion, we measured plasma ghrelin levels after administration of cholinergic and adrenergic agents in rats under normally fed and 48-h fasting conditions. To assess the short- and long-term effects of vagotomy on ghrelin secretion, plasma ghrelin levels and stomach ghrelin levels and gene expressions were measured in rats subjected to fed or fasting. Additionally, we investigated whether plasma ghrelin levels were affected by the anorexigenic gastrointestinal peptides cholecystokinin and somatostatin. In the pharmacological study, plasma ghrelin levels were increased by a muscarinic agonist, an α-adrenergic antagonist, and a β-adrenergic agonist, and decreased by a muscarinic antagonist and an α-adrenergic agonist. Vagotomy inhibited ghrelin secretion acutely, but promoted ghrelin release from the stomach at later time points. Stomach ghrelin mRNA levels were unchanged after fasting, but were significantly upregulated in vagotomized rats. The change of plasma ghrelin levels in nutrient fluctuation was independent of the endogenous effects of cholecystokinin and somatostatin. This study demonstrates that stomach ghrelin secretion is modulated by both the cholinergic and adrenergic arms of the autonomic nervous system. The dissociation between the short- and long-term effects of vagotomy on plasma ghrelin level indicates that an additional neural control mechanism might be involved in the regulation of ghrelin secretion.

Heart rate turbulence and variability in patients with ventricular arrhythmias

Background:To evaluate the changes in autonomic neural control mechanisms before malignant ventricular arrhythmias, we measured heart rate variability (HRV) and heart rate turbulence (HRT) in patients with ventricular tachycardia or fibrillation (Group I; n=6), non sustained ventricular tachycardia (Group II; n=32), frequent premature ventricular beats (Group III; n=26) and with ICD implantation (Group IV; n=11).Methods:Time domain parameters of HRV and turbulence onset (TO) and slope (TS) were calculated on 24 hour Holter recordings. Normal values were: SDNN > 70 msec for HRV, TO <0% and TS >2.5 msec/RR-I for HRT.Results:Whereas SDNN was within normal range and similar in all study groups, HRT parameters were significantly different in patients who experienced VT/VF during Holter recording. Abnormal TO and/or TS were present in 100% of Group I patients and only in about 50% of Group II and IV. On the contrary, normal HRT parameters were present in 40–70% of Group II, III and IV patients and none of Group I.Conclusions:These data suggest that HRT analysis is more suitable than HRV to detect those transient alterations in autonomic control mechanisms that are likely to play a major trigger role in the genesis of malignant cardiac arrhythmias.

Brain activation during the Stroop task in adolescents with severe substance and conduct problems: A pilot study

Background Although many neuroimaging studies have examined changes in brain function in adults with substance use disorders, far fewer have examined adolescents. This study investigated patterns of brain activation in adolescents with severe substance and conduct problems (SCP) compared to controls. Methods Functional magnetic resonance imaging (fMRI) at 1.5 Tesla assessed brain activation in 12 adolescent males with SCP, ranging in age from 14 to 18, and 12 controls similar in age, gender, and neighborhood while performing the attentionally demanding Stroop task. Results Even though the adolescents with SCP performed as well as the controls, they activated a more extensive set of brain structures for incongruent (e.g., “red” in blue ink) versus congruent (e.g. “red” in red ink) trials. These regions included parahippocampal regions bilaterally, posterior regions involved in language-related processing, right-sided medial prefrontal areas, and subcortical regions including the thalamus and caudate. Conclusion These preliminary results suggest that the neural mechanisms of attentional control in youth with SCP differ from youth without such problems. This difficulty may prevent SCP youth from ignoring salient but distracting information in the environment, such as drug-related information.

Analysis of transcriptional regulation underlying central neural control mechanisms in acute hypertension

Analysis of transcriptional regulation underlying central neural control mechanisms in acute hypertension

人の視覚運動制御系の振舞いに基づく倒立振子系のむだ時間補償制御

An image-based inverted pendulum control system with a large time delay of camera has some analogies with human stick balancing control. Cabrera and his group pointed out that time delays and state-dependent fluctuations play an essential role in neural control mechanism. In this paper, we investigate some properties of the time delays and the fluctuations using our new model which is consistent with the actual inverted pendulum control system. For noise free case, a sufficient condition for the stability of our time-delayed control system is derived.