RESUMEN
88 undergraduates (44 men, 44 women) participated in an experiment to examine whether the cutaneous sensation of having the cheeks lifted would cause a feeling of happiness. Two types of paired adhesive bandages connected with rubber bands were prepared and used either to raise or lower the cheeks. While the bandages were applied, the participants rated their feelings. The results showed that 50 participants felt happiness when their cheeks were lifted, statistically significant compared to the 27 who felt sadness. They confirmed the hypothesis that people may feel happy when their cheeks are lifted upward.
Asunto(s)
Mejilla/fisiología , Emociones/fisiología , Expresión Facial , Retroalimentación/fisiología , Felicidad , Sonrisa/fisiología , Adulto , Afecto/fisiología , Músculos Faciales/fisiología , Femenino , Humanos , Masculino , Proyectos de Investigación , Estudiantes/estadística & datos numéricosRESUMEN
Previous studies have demonstrated that varied practice (involving several versions of a skill) has advantage over constant practice (involving only one version of a skill) in learning a motor skill. However, the support for variable practice mainly came from studies using discrete motor skills. Therefore, the purpose of the study was to assess if variable practice was more effective than constant practice for the purpose of learning a continuous and real-life motor skill: wheelchair propulsion. A total of 36 able-bodied undergraduate students participated in this study. There were two constant-practice groups. One group practiced wheelchair propulsion on a roller system with a single speed, 30% of the maximum speed (30%-only group), and one group practiced using 55% of the maximum speed (55%-only group). One variable-practice group (variable group) practiced the propulsion with two different speeds, 30 and 55% of the maximum speed. In addition to retention tests, two transfer tests (i.e., tests on 40 and 70% of the maximum speeds) were performed by the three groups after the 10 weeks of training. The results were mixed. The variable-practice group produced significantly fewer absolute errors on both transfer tests than the 30%-only group. However, when compared to the 55%-only group, the variable-practice group only produced significantly fewer absolute errors on the transfer test at 70% speed, but not at 40% speed.
Asunto(s)
Aprendizaje/fisiología , Destreza Motora/fisiología , Práctica Psicológica , Transferencia de Experiencia en Psicología/fisiología , Silla de Ruedas/estadística & datos numéricos , Aceleración , Adulto , Retroalimentación/fisiología , Femenino , Humanos , Masculino , Instrucciones Programadas como Asunto , Retención en Psicología/fisiologíaRESUMEN
In motor control, prediction of future events is vital for overcoming sensory-motor processing delays and facilitating rapid and accurate responses in a dynamic environment. In human ocular pursuit this is so pervasive that prediction of future target motion cannot easily be eliminated by randomizing stimulus parameters. We investigated the prediction of temporally randomized events during pursuit of alternating constant-velocity (ramp) stimuli in which the timing of direction changes varied unpredictably over a given range. Responses were not reactive; instead, smooth eye velocity began to decelerate in anticipation of each target reversal. In the first experiment, using a continuous-motion stimulus, we found that the time at which this occurred was relatively constant regardless of ramp duration, but increased as mean ramp duration of the range increased. Regression analysis revealed a quantitative association between deceleration timing and the previous two or three ramp durations in a trial, suggesting that recent stimulus history was used to create a running average of anticipatory timing. In the second experiment, we used discrete motion stimuli, with intervening periods of fixation, which allowed both target velocity and reversal timing to be varied, thereby decoupling ramp duration and displacement. This enabled us to confirm that the timing of anticipatory deceleration was based on the history of timing, rather than displacement, within the stimulus. We conclude that this strategy is used to minimize error amid temporal uncertainty, while simultaneously overcoming inherent delays in visuomotor processing.
Asunto(s)
Retroalimentación/fisiología , Fijación Ocular/fisiología , Percepción de Movimiento/fisiología , Tiempo de Reacción/fisiología , Adulto , Aprendizaje Discriminativo/fisiología , Femenino , Humanos , Masculino , Dinámicas no Lineales , Estimulación Luminosa/métodos , Valor Predictivo de las Pruebas , Psicofísica , Análisis de Regresión , Factores de Tiempo , Adulto JovenRESUMEN
Two rhesus monkeys were trained to move a cursor using neural activity recorded with silicon arrays of 96 microelectrodes implanted in the primary motor cortex. We have developed a method to extract movement information from the recorded single and multi-unit activity in the absence of spike sorting. By setting a single threshold across all channels and fitting the resultant events with a spline tuning function, a control signal was extracted from this population using a Bayesian particle-filter extraction algorithm. The animals achieved high-quality control comparable to the performance of decoding schemes based on sorted spikes. Our results suggest that even the simplest signal processing is sufficient for high-quality neuroprosthetic control.
Asunto(s)
Potenciales de Acción/fisiología , Algoritmos , Encéfalo/fisiología , Electroencefalografía/métodos , Potenciales Evocados Motores/fisiología , Retroalimentación/fisiología , Movimiento/fisiología , Interfaz Usuario-Computador , Animales , Macaca mulatta , MasculinoRESUMEN
Single neurons in several brain areas intervening between sensation and action signal the accumulation of sensory evidence favoring a particular behavioral response. Two new studies show that these same neurons encode decision confidence and that decision makers continue to process relevant sensory information even after a choice has been made.
Asunto(s)
Toma de Decisiones/fisiología , Juicio/fisiología , Aprendizaje/fisiología , Tiempo de Reacción/fisiología , Animales , Retroalimentación/fisiología , Humanos , RecompensaRESUMEN
Leptin-stimulated Stat3 activation in proopiomelanocortin (POMC)-expressing neurons of the hypothalamus plays an important role in maintenance of energy homeostasis. While Stat3 activation in POMC neurons is required for POMC expression, the role of elevated basal Stat3 activation as present in the development of obesity has not been directly addressed. Here, we have generated and characterized mice expressing a constitutively active version of Stat3 (Stat3-C) in POMC neurons (Stat3-C(POMC) mice). On normal chow diet, these animals develop obesity as a result of hyperphagia and decreased POMC expression accompanied by central leptin and insulin resistance. This unexpected finding coincides with POMC-cell-specific, Stat3-mediated upregulation of SOCS3 expression inhibiting both leptin and insulin signaling as insulin-stimulated PIP(3) (phosphatidylinositol-3,4,5 triphosphate) formation and protein kinase B (AKT) activation in POMC neurons as well as with the fact that insulin's ability to hyperpolarize POMC neurons is largely reduced in POMC cells of Stat3-C(POMC) mice. These data indicate that constitutive Stat3 activation is not sufficient to promote POMC expression but requires simultaneous PI3K (phosphoinositide 3-kinase)-dependent release of FOXO1 repression. In contrast, upon exposure to a high-fat diet, food intake and body weight were unaltered in Stat3-C(POMC) mice compared with control mice. Taken together, these experiments directly demonstrate that enhanced basal Stat3 activation in POMC neurons as present in control mice upon high-fat feeding contributes to the development of hypothalamic leptin and insulin resistance.
Asunto(s)
Insulina/metabolismo , Leptina/metabolismo , Proteínas de la Membrana/metabolismo , Inhibición Neural/fisiología , Neuronas/fisiología , Obesidad/fisiopatología , Proopiomelanocortina/metabolismo , Proteína Relacionada con Agouti/genética , Proteína Relacionada con Agouti/metabolismo , Animales , Composición Corporal/genética , Peso Corporal/genética , Modelos Animales de Enfermedad , Ingestión de Alimentos/genética , Ensayo de Cambio de Movilidad Electroforética , Ensayo de Inmunoadsorción Enzimática/métodos , Retroalimentación/fisiología , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/genética , Prueba de Tolerancia a la Glucosa , Proteínas Fluorescentes Verdes/genética , Hipotálamo/patología , Técnicas In Vitro , Resistencia a la Insulina/genética , Factor Inhibidor de Leucemia/farmacología , Proteínas de la Membrana/genética , Ratones , Ratones Transgénicos , Inhibición Neural/efectos de los fármacos , Inhibición Neural/genética , Neuropéptido Y/genética , Neuropéptido Y/metabolismo , Obesidad/genética , Obesidad/metabolismo , Técnicas de Placa-Clamp/métodos , Fosfatidilinositol 3-Quinasas/metabolismo , Transducción de Señal/genética , Proteína 3 Supresora de la Señalización de Citocinas , Proteínas Supresoras de la Señalización de Citocinas/genética , Proteínas Supresoras de la Señalización de Citocinas/metabolismo , TransfecciónRESUMEN
Adenosine 1 receptors (A1AR) in the kidney are expressed in the vasculature and the tubular system. Pharmacological inhibition or global genetic deletion of A1AR causes marked reductions or abolishment of tubuloglomerular feedback (TGF) responses. To assess the function of vascular A1AR in TGF, we generated transgenic mouse lines in which A1AR expression in smooth muscle was augmented by placing A1AR under the control of a 5.38-kb fragment of the rat smooth muscle alpha-actin promoter and first intron (12). Two founder lines with highest expression in the kidney [353 +/- 42 and 575 +/- 43% compared with the wild type (WT)] were used in the experiments. Enhanced expression of A1AR at the expected site in these lines was confirmed by augmented constrictor responses of isolated afferent arterioles to administration of the A1AR agonist N6-cyclohexyladenosine. Maximum TGF responses (0-30 nl/min flow step) were increased from 8.4 +/- 0.9 mmHg in WT (n = 21) to 14.2 +/- 0.7 mmHg in A1AR-transgene (tg) 4 (n = 22; P < 0.0001), and to 12.6 +/- 1.2 mmHg in A1AR-tg7 (n = 12; P < 0.02). Stepwise changes in perfusion flow caused greater numerical TGF responses in A1AR-tg than WT in all flow ranges with differences reaching levels of significance in the intermediate flow ranges of 7.5-10 and 10-15 nl/min. Proximal-distal single-nephron glomerular filtration rate (SNGFR) differences (free-flow micropuncture) were also increased in A1AR-tg, averaging 6.25 +/- 1.5 nl/min compared with 2.6 +/- 0.51 nl/min in WT (P = 0.034). Basal plasma renin concentrations as well as the suppression of renin secretion after volume expansion were similar in A1AR-tg and WT mice, suggesting lack of transgene expression in juxtaglomerular cells. These data indicate that A1AR expression in vascular smooth muscle cells is a critical component for TGF signaling and that changes in renal vascular A1AR expression may determine the magnitude of TGF responses.
Asunto(s)
Vasos Sanguíneos/metabolismo , Retroalimentación/fisiología , Glomérulos Renales/metabolismo , Receptor de Adenosina A1/biosíntesis , Agonistas del Receptor de Adenosina A1 , Animales , Arteriolas/citología , Arteriolas/metabolismo , Presión Sanguínea/fisiología , ADN Complementario/biosíntesis , ADN Complementario/genética , Tasa de Filtración Glomerular , Riñón/patología , Glomérulos Renales/patología , Ratones , Ratones Transgénicos , Músculo Liso Vascular/citología , Músculo Liso Vascular/metabolismo , Concentración Osmolar , ARN Mensajero/biosíntesis , ARN Mensajero/genética , Ratas , Receptor de Adenosina A1/genética , Renina/sangre , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de Señal/fisiología , Factor de Crecimiento Transformador alfa/fisiologíaRESUMEN
The aim of this study is to employ feedback control loops to provide a stable forward dynamics simulation of human movement under repeated position constraint conditions in the environment, particularly during stair climbing. A ten-degrees-of-freedom skeletal model containing 18 Hill-type musculotendon actuators per leg was employed to simulate the model in the sagittal plane. The postural tracking and obstacle avoidance were provided by the proportional-integral-derivative controller according to the modulation of the time rate change of the joint kinematics. The stability of the model was maintained by controlling the velocity of the body's centre of mass according to the desired centre of pressure during locomotion. The parameters of the proposed controller were determined by employing the iterative feedback tuning approach to minimize tracking errors during forward dynamics simulation. Simultaneously, an inverse-dynamics-based optimization was employed to compute a set of desired musculotendon forces in the closed-loop simulation to resolve muscle redundancy. Quantitative comparisons of the simulation results with the experimental measurements and the reference muscles' activities illustrate the accuracy and efficiency of the proposed method during the stable ascending simulation.
Asunto(s)
Marcha/fisiología , Articulaciones/fisiología , Pierna/fisiología , Locomoción/fisiología , Modelos Biológicos , Contracción Muscular/fisiología , Músculo Esquelético/inervación , Simulación por Computador , Retroalimentación/fisiología , Humanos , Músculo Esquelético/fisiología , Valores de ReferenciaRESUMEN
CD4(+)CD25(+)Foxp3(+) natural regulatory T cells (T reg cells) maintain self-tolerance and suppress autoimmune diseases such as type 1 diabetes and inflammatory bowel disease (IBD). In addition to their effects on T cells, T reg cells are essential for maintaining normal numbers of dendritic cells (DCs): when T reg cells are depleted, there is a compensatory Flt3-dependent increase in DCs. However, little is known about how T reg cell homeostasis is maintained in vivo. We demonstrate the existence of a feedback regulatory loop between DCs and T reg cells. We find that loss of DCs leads to a loss of T reg cells, and that the remaining T reg cells exhibit decreased Foxp3 expression. The DC-dependent loss in T reg cells leads to an increase in the number of T cells producing inflammatory cytokines, such as interferon gamma and interleukin 17. Conversely, increasing the number of DCs leads to increased T reg cell division and accumulation by a mechanism that requires major histocompatibility complex II expression on DCs. The increase in T reg cells induced by DC expansion is sufficient to prevent type 1 autoimmune diabetes and IBD, which suggests that interference with this feedback loop will create new opportunities for immune-based therapies.
Asunto(s)
Células Dendríticas/fisiología , Diabetes Mellitus Tipo 1/inmunología , Retroalimentación/fisiología , Homeostasis/fisiología , Enfermedades Inflamatorias del Intestino/inmunología , Linfocitos T Reguladores/fisiología , Animales , Anticuerpos Monoclonales , Proliferación Celular , Citocinas/metabolismo , Células Dendríticas/metabolismo , Diabetes Mellitus Tipo 1/metabolismo , Citometría de Flujo , Factores de Transcripción Forkhead/metabolismo , Genes MHC Clase II/genética , Enfermedades Inflamatorias del Intestino/metabolismo , Ratones , Ratones Endogámicos NOD , Ratones Transgénicos , Análisis de Regresión , Linfocitos T Reguladores/metabolismoRESUMEN
Feedforward neural networks such as multilayer perceptrons (MLP) and recurrent neural networks are widely used for pattern classification, nonlinear function approximation, density estimation and time series prediction. A large number of neurons are usually required to perform these tasks accurately, which makes the MLPs less attractive for computational implementations on resource constrained hardware platforms. This paper highlights the benefits of feedforward and recurrent forms of a compact neural architecture called generalized neuron (GN). This paper demonstrates that GN and recurrent GN (RGN) can perform good classification, nonlinear function approximation, density estimation and chaotic time series prediction. Due to two aggregation functions and two activation functions, GN exhibits resilience to the nonlinearities of complex problems. Particle swarm optimization (PSO) is proposed as the training algorithm for GN and RGN. Due to a small number of trainable parameters, GN and RGN require less memory and computational resources. Thus, these structures are attractive choices for fast implementations on resource constrained hardware platforms.
Asunto(s)
Retroalimentación/fisiología , Modelos Neurológicos , Redes Neurales de la Computación , Neuronas/fisiología , Algoritmos , Animales , Simulación por Computador , Humanos , Almacenamiento y Recuperación de la Información , Aprendizaje/fisiología , Dinámicas no Lineales , Valor Predictivo de las Pruebas , Procesamiento de Señales Asistido por Computador , Factores de TiempoRESUMEN
The ability of the human hand to perform complex sensorimotor tasks such as tactile exploration and grasping is based on 1. exact encoding of somatosensory information by cutaneous mechanoreceptors, 2. elaborated processing of afferent signals in somatosensory relay stations and cortex fields, 3. rapid and effective interaction of sensory feedback with motor programs, and 4. different modes of sensory control, which can be switched over.
Asunto(s)
Mano/fisiología , Procesos Mentales , Neurofisiología , Sensación/fisiología , Vías Aferentes/fisiología , Electrofisiología , Retroalimentación/fisiología , Mano/inervación , Humanos , Mecanorreceptores/fisiología , Desempeño Psicomotor/fisiologíaRESUMEN
We examine the potential to treat unstable ventilatory control (seen in periodic breathing, Cheyne-Stokes respiration, and central sleep apnea) with carefully controlled dynamic administration of supplementary CO(2), aiming to reduce ventilatory oscillations with minimum increment in mean CO(2). We used a standard mathematical model to explore the consequences of phasic CO(2) administration, with different timing and dosing algorithms. We found an optimal time window within the ventilation cycle (covering approximately 1/6 of the cycle) during which CO(2) delivery reduces ventilatory fluctuations by >95%. Outside that time, therapy is dramatically less effective: indeed, for more than two-thirds of the cycle, therapy increases ventilatory fluctuations >30%. Efficiency of stabilizing ventilation improved when the algorithm gave a graded increase in CO(2) dose (by controlling its duration or concentration) for more severe periodic breathing. Combining gradations of duration and concentration further increased efficiency of therapy by 22%. The (undesirable) increment in mean end-tidal CO(2) caused was 300 times smaller with dynamic therapy than with static therapy, to achieve the same degree of ventilatory stabilization (0.0005 vs. 0.1710 kPa). The increase in average ventilation was also much smaller with dynamic than static therapy (0.005 vs. 2.015 l/min). We conclude that, if administered dynamically, dramatically smaller quantities of CO(2) could be used to reduce periodic breathing, with minimal adverse effects. Algorithms adjusting both duration and concentration in real time would achieve this most efficiently. If developed clinically as a therapy for periodic breathing, this would minimize excess acidosis, hyperventilation, and sympathetic overactivation, compared with static treatment.
Asunto(s)
Dióxido de Carbono/uso terapéutico , Respiración/efectos de los fármacos , Algoritmos , Dióxido de Carbono/administración & dosificación , Respiración de Cheyne-Stokes/fisiopatología , Retroalimentación/fisiología , Análisis de Fourier , Humanos , Modelos Estadísticos , Alveolos Pulmonares/fisiología , Receptores de Superficie Celular/fisiología , Factores de TiempoRESUMEN
Children with autism spectrum disorder (ASD) have deficits in motor control, imitation and social function. Does a dysfunction in the neural basis of representing internal models of action contribute to these problems? We measured patterns of generalization as children learned to control a novel tool and found that the autistic brain built a stronger than normal association between self-generated motor commands and proprioceptive feedback; furthermore, the greater the reliance on proprioception, the greater the child's impairments in social function and imitation.
Asunto(s)
Trastorno Autístico/fisiopatología , Encéfalo/fisiopatología , Trastornos del Movimiento/fisiopatología , Movimiento/fisiología , Desempeño Psicomotor/fisiología , Trastorno de la Conducta Social/fisiopatología , Trastorno Autístico/complicaciones , Trastorno Autístico/psicología , Niño , Evaluación de la Discapacidad , Retroalimentación/fisiología , Femenino , Humanos , Conducta Imitativa/fisiología , Aprendizaje/fisiología , Masculino , Modelos Neurológicos , Destreza Motora/fisiología , Trastornos del Movimiento/etiología , Trastornos del Movimiento/psicología , Propiocepción/fisiología , Trastorno de la Conducta Social/etiología , Trastorno de la Conducta Social/psicologíaRESUMEN
Discrete wavelet analysis is used to resolve the center of pressure time series data into several timescale components, providing new insights into postural control. Healthy young and elderly participants stood quietly with their eyes open or closed and either performed a secondary task or stood quietly. Without vision, both younger and older participants had reduced energy in the long timescales, supporting the concept that vision is used to control low frequency postural sway. Furthermore, energy was increased at timescales corresponding to closed-loop (somatosensory and vestibular) and open-loop mechanisms, consistent with the idea of a shift from visual control to other control mechanisms. However, a relatively greater increase was observed for older adults. With a secondary task a similar pattern was observed-increased energy at the short and moderate timescales, decreased energy at long timescales. The possibility of a common strategy-at the timescale level-in response to postural perturbations is considered.
Asunto(s)
Retroalimentación/fisiología , Movimiento/fisiología , Postura/fisiología , Desempeño Psicomotor/fisiología , Percepción del Tiempo/fisiología , Adulto , Anciano , Envejecimiento/fisiología , Relojes Biológicos/fisiología , Fenómenos Biomecánicos/fisiología , Femenino , Análisis de Fourier , Humanos , Masculino , Pruebas Neuropsicológicas , Propiocepción/fisiología , Procesamiento de Señales Asistido por Computador , Factores de Tiempo , Transductores de Presión , Vestíbulo del Laberinto/fisiología , Percepción Visual/fisiología , Adulto JovenRESUMEN
Neural coupling of proximal and distal upper limb segments may have functional implications in the recovery of hemiparesis after stroke. The goal of the present study was to investigate whether the stretch reflex response magnitude of spastic finger flexor muscles poststroke is influenced by sensory input from the shoulder and the elbow and whether reflex coupling of muscles throughout the upper limb is altered in spastic stroke survivors. Through imposed extension of the metacarpophalangeal (MCP) joints, stretch of the relaxed finger flexors of the four fingers was imposed in 10 relaxed stroke subjects under different conditions of proximal sensory input, namely static arm posture (3 different shoulder/elbow postures) and electrical stimulation (surface stimulation of biceps brachii or triceps brachii, or none). Fast (300 degrees/s) imposed stretch elicited stretch reflex flexion torque at the MCP joints and reflex electromyographic (EMG) activity in flexor digitorum superficialis. Both measures were greatest in an arm posture of 90 degrees of elbow flexion and neutral shoulder position. Biceps stimulation resulted in greater MCP stretch reflex flexion torque. Fast imposed stretch also elicited reflex EMG activity in nonstretched heteronymous upper limb muscles, both proximal and distal. These results suggest that in the spastic hemiparetic upper limb poststroke, sensorimotor coupling of proximal and distal upper limb segments is involved in both the increased stretch reflex response of the finger flexors and an increased reflex coupling of heteronymous muscles. Both phenomena may be mediated through changes poststroke in the spinal reflex circuits and/or in the descending influence of supraspinal pathways.
Asunto(s)
Retroalimentación/fisiología , Dedos/patología , Músculo Esquelético/fisiopatología , Reflejo de Estiramiento/fisiología , Accidente Cerebrovascular/patología , Extremidad Superior/fisiopatología , Adulto , Anciano , Análisis de Varianza , Fenómenos Biomecánicos , Electromiografía/métodos , Femenino , Humanos , Masculino , Articulación Metacarpofalángica/fisiopatología , Persona de Mediana Edad , Postura/fisiología , TorqueRESUMEN
Humans use their arms to engage in a wide variety of motor tasks during everyday life. However, little is known about the statistics of these natural arm movements. Studies of the sensory system have shown that the statistics of sensory inputs are key to determining sensory processing. We hypothesized that the statistics of natural everyday movements may, in a similar way, influence motor performance as measured in laboratory-based tasks. We developed a portable motion-tracking system that could be worn by subjects as they went about their daily routine outside of a laboratory setting. We found that the well-documented symmetry bias is reflected in the relative incidence of movements made during everyday tasks. Specifically, symmetric and antisymmetric movements are predominant at low frequencies, whereas only symmetric movements are predominant at high frequencies. Moreover, the statistics of natural movements, that is, their relative incidence, correlated with subjects' performance on a laboratory-based phase-tracking task. These results provide a link between natural movement statistics and motor performance and confirm that the symmetry bias documented in laboratory studies is a natural feature of human movement.
Asunto(s)
Retroalimentación/fisiología , Modelos Estadísticos , Movimiento/fisiología , Desempeño Psicomotor/fisiología , Rango del Movimiento Articular/fisiología , Brazo/fisiología , Codo/inervación , Humanos , MasculinoRESUMEN
The sensory signals that drive movement planning arrive in a variety of 'reference frames', and integrating or comparing them requires sensory transformations. We propose a model in which the statistical properties of sensory signals and their transformations determine how these signals are used. This model incorporates the patterns of gaze-dependent errors that we found in our human psychophysics experiment when the sensory signals available for reach planning were varied. These results challenge the widely held ideas that error patterns directly reflect the reference frame of the underlying neural representation and that it is preferable to use a single common reference frame for movement planning. We found that gaze-dependent error patterns, often cited as evidence for retinotopic reach planning, can be explained by a transformation bias and are not exclusively linked to retinotopic representations. Furthermore, the presence of multiple reference frames allows for optimal use of available sensory information and explains task-dependent reweighting of sensory signals.