RESUMEN
Individuals interpret themselves as causal agents when executing an action to achieve an outcome, even when action and outcome are independent. How can illusion of control be managed? Once established, does it decay? This study aimed to analyze the effects of valence, probability of the outcome [p(O)] and probability of the actions performed by the participant [p(A)], on the magnitude of judgments of control and corresponding associative measures (including Rescorla-Wagner's, Probabilistic Contrast, and Cheng's Power Probabilistic Contrast models). A traffic light was presented on a computer screen to 81 participants who tried to control the green or red lights by pressing the spacebar, after instructions describing a productive or a preventive scenario. There were 4 blocks of 50 trials under all of 4 different p(O)s in random order (0.10, 0.30, 0.70, and 0.90). Judgments were assessed in a bidimensional scale. The 2 × 4 × 4 mixed experimental design was analyzed through General Linear Models, including factor group (between-subject valence), and block and p(O) (within subjects). There was a small effect of group and a large and direct effect of p(O) on judgments. Illusion was reported by 66% of the sample and was positive in the productive group. The oscillation of p(O) produced stronger illusions; decreasing p(O)s produced nil or negative illusions. Only Rescorla-Wagner's could model causality properly. The reasons why p(A) and the other models could not generate significant results are discussed. The results help to comprehend the importance of keeping moderate illusions in productive and preventive scenarios.
Asunto(s)
Ilusiones/fisiología , Ilusiones/psicología , Juicio/fisiología , Tiempo de Reacción/fisiología , Autocontrol/psicología , Adolescente , Adulto , Brasil , Femenino , Humanos , Masculino , Modelos Estadísticos , Autoinforme , Adulto JovenRESUMEN
The body ownership induced by the rubber hand illusion (RHI) has been related to a neural network involving a frontal-parietal circuit. Previous functional neuroimaging studies have demonstrated neural activation in the parietal area relative to the multisensory integration processing and to the recalibration of the felt position of body while a ventral premotor cortex activation has been linked to bodily self-attribution during the RHI. Our study aimed to investigate the effects of transcranial direct current stimulation (tDCS) on the posterior parietal cortex (PPC) or on the premotor cortex (PMv) during RHI to address the specific roles of these two brain areas in the illusion. 156 young adult participants (21.2 ± 3.13 years old; all right-handed) were enrolled for this between-subjects design experiment. Participants received anodal, cathodal and sham tDCS in three different sessions on the right PPC or right PMv and experienced visual-tactile stimulation from the brushes touching the rubber hand and their own left hand in synchronous or asynchronous manner. The RHI was quantified by the (1) onset time for the feeling of body ownership of the rubber hand, (2) proprioceptive drift, and (3) questionnaire about the intensity of the illusion as reported by the participant. All subjects felt the RHI during the synchronous condition. However, we found that the illusion onset time can be modulated by the anodal tDCS condition on the PPC: anodal tDCS decreased the illusion onset time and the subjective experience of body ownership. These findings suggest that the parietal area plays a crucial role in the speed of visual and tactile multisensory integration in the RHI and introduce tDCS as technique that can accelerate the time to integrate an artificial body part and increased the perception of body ownership.
Asunto(s)
Imagen Corporal , Ilusiones/fisiología , Lóbulo Parietal/fisiología , Percepción del Tacto/fisiología , Estimulación Transcraneal de Corriente Directa/métodos , Percepción Visual/fisiología , Adolescente , Adulto , Electrodos , Femenino , Humanos , Masculino , Estimulación Luminosa , Propiocepción/fisiología , Tacto/fisiología , Adulto JovenRESUMEN
Spinal cord injuries disrupt bidirectional communication between the patient's brain and body. Here, we demonstrate a new approach for reproducing lower limb somatosensory feedback in paraplegics by remapping missing leg/foot tactile sensations onto the skin of patients' forearms. A portable haptic display was tested in eight patients in a setup where the lower limbs were simulated using immersive virtual reality (VR). For six out of eight patients, the haptic display induced the realistic illusion of walking on three different types of floor surfaces: beach sand, a paved street or grass. Additionally, patients experienced the movements of the virtual legs during the swing phase or the sensation of the foot rolling on the floor while walking. Relying solely on this tactile feedback, patients reported the position of the avatar leg during virtual walking. Crossmodal interference between vision of the virtual legs and tactile feedback revealed that patients assimilated the virtual lower limbs as if they were their own legs. We propose that the addition of tactile feedback to neuroprosthetic devices is essential to restore a full lower limb perceptual experience in spinal cord injury (SCI) patients, and will ultimately, lead to a higher rate of prosthetic acceptance/use and a better level of motor proficiency.
Asunto(s)
Ilusiones/fisiología , Pierna/fisiología , Paraplejía/fisiopatología , Percepción/fisiología , Tacto/fisiología , Adulto , Encéfalo/fisiopatología , Retroalimentación , Femenino , Pisos y Cubiertas de Piso , Pie/fisiopatología , Humanos , Masculino , Traumatismos de la Médula Espinal/fisiopatología , Traumatismos de la Médula Espinal/rehabilitación , Propiedades de Superficie , Interfaz Usuario-Computador , Caminata/fisiologíaRESUMEN
In this work we report an illusion of proximity of a sound source created by a sonic crystal placed between the source and a listener. This effect seems, at first, paradoxical to naïve listeners since the sonic crystal is an obstacle formed by almost densely packed cylindrical scatterers. Even when the singular acoustical properties of these periodic composite materials have been studied extensively (including band gaps, deaf bands, negative refraction, and birrefringence), the possible perceptual effects remain unexplored. The illusion reported here is studied through acoustical measurements and a psychophysical experiment. The results of the acoustical measurements showed that, for a certain frequency range and region in space where the focusing phenomenon takes place, the sonic crystal induces substantial increases in binaural intensity, direct-to-reverberant energy ratio and interaural cross-correlation values, all cues involved in the auditory perception of distance. Consistently, the results of the psychophysical experiment revealed that the presence of the sonic crystal between the sound source and the listener produces a significant reduction of the perceived relative distance to the sound source.
Asunto(s)
Estimulación Acústica , Percepción Auditiva/fisiología , Cabeza/fisiología , Ilusiones/fisiología , Localización de Sonidos/fisiología , Percepción de Distancia , Humanos , Masculino , PsicoacústicaRESUMEN
The neurobiology of reaching has been extensively studied in human and non-human primates. However, the mechanisms that allow a subject to decide-without engaging in explicit action-whether an object is reachable are not fully understood. Some studies conclude that decisions near the reach limit depend on motor simulations of the reaching movement. Others have shown that the body schema plays a role in explicit and implicit distance estimation, especially after motor practice with a tool. In this study we evaluate the causal role of multisensory body representations in the perception of reachable space. We reasoned that if body schema is used to estimate reach, an illusion of the finger size induced by proprioceptive stimulation should propagate to the perception of reaching distances. To test this hypothesis we induced a proprioceptive illusion of extension or shrinkage of the right index finger while participants judged a series of LEDs as reachable or non-reachable without actual movement. Our results show that reach distance estimation depends on the illusory perceived size of the finger: illusory elongation produced a shift of reaching distance away from the body whereas illusory shrinkage produced the opposite effect. Combining these results with previous findings, we suggest that deciding if a target is reachable requires an integration of body inputs in high order multisensory parietal areas that engage in movement simulations through connections with frontal premotor areas.
Asunto(s)
Ilusiones/fisiología , Movimiento/fisiología , Propiocepción/fisiología , Desempeño Psicomotor/fisiología , Percepción Visual/fisiología , Adulto , Imagen Corporal , Femenino , Humanos , Juicio/fisiología , Masculino , Adulto JovenRESUMEN
The aim of this study was to investigate the adaptive process in the coupling between visual information and body sway in children postural control. Twenty-seven children from 4-, 8- and 12-year-olds and ten adults stood upright inside of a moving room. In the first 2 min, the room was moved continuously at frequency of 0.2 Hz, velocity of 0.6 cm/s and amplitude of 0.5 cm. In the minute subsequent the room was moved with velocity of 3.5 and amplitude of 3.2 and in the last 2 min with velocity of 0.6 cm/s and amplitude of 0.5 cm. Gain, phase, SFSA and transient gain were used to examine the relationship between sensory information and body sway. The results showed that children and adults were capable to adapt to the changes of visual stimulus, downweighting the visual information influences when the room's amplitude/velocity increased. However, the young children did not show calibrated response to the 12-year-old children and adults level, being more influenced by the visual stimulus.
Asunto(s)
Adaptación Fisiológica/fisiología , Envejecimiento/fisiología , Señales (Psicología) , Equilibrio Postural/fisiología , Postura/fisiología , Sensación/fisiología , Adulto , Factores de Edad , Niño , Preescolar , Ambiente , Femenino , Humanos , Ilusiones/fisiología , Masculino , Percepción de Movimiento/fisiología , Plasticidad Neuronal/fisiología , Pruebas Neuropsicológicas , Percepción/fisiología , Estimulación Luminosa , Percepción Visual/fisiología , Adulto JovenRESUMEN
A briefly presented target shape can be made invisible by the subsequent presentation of a mask that replaces the target. While varying the target-mask interval in order to investigate perception near the consciousness threshold, we discovered a novel visual illusion. At some intervals, the target is clearly visible, but its location is misperceived. By manipulating the mask's size and target's position, we demonstrate that the perceived target location is always displaced to the boundary of a virtual surface defined by the mask contours. Thus, mutual exclusion of surfaces appears as a cause of masking.
Asunto(s)
Estado de Conciencia/fisiología , Ilusiones/fisiología , Percepción Visual/fisiología , Humanos , Umbral Sensorial/fisiologíaRESUMEN
UNLABELLED: Perceptual visual filling-in of toxoplasmic retinochoroiditis chronic scotomas was studied in 13 patients. Although there is deficit of visual inputs, patients with such chronic lesions perceive the region in the visual field uninterrupted. Targets were programmed to appear just outside the edge of the retinal lesion, and healthy retinal areas in the same eye. The results showed no significant difference in perceptual filling-in latencies (P>0.05). CONCLUSIONS: (i) neural mechanisms of filling-in at the blind spot are probably involved explaining this perceptual phenomenon; (ii) any neuronal changes occurring at the edge of the lesion only affected filling-in within the scotoma area.
Asunto(s)
Coriorretinitis/fisiopatología , Escotoma/fisiopatología , Toxoplasmosis Ocular/fisiopatología , Percepción Visual/fisiología , Adaptación Fisiológica/fisiología , Adolescente , Adulto , Anciano , Animales , Coriorretinitis/diagnóstico , Coriorretinitis/parasitología , Coroides/parasitología , Coroides/patología , Coroides/fisiopatología , Femenino , Humanos , Ilusiones/fisiología , Masculino , Persona de Mediana Edad , Examen Neurológico , Estimulación Luminosa , Tiempo de Reacción/fisiología , Retina/parasitología , Retina/patología , Retina/fisiopatología , Escotoma/diagnóstico , Escotoma/etiología , Toxoplasma , Toxoplasmosis Ocular/diagnóstico , Visión Ocular/fisiología , Corteza Visual/fisiologíaRESUMEN
Visual illusions are formed by differences between the perception of one figure and its real physical characteristics. The Müller-Lyer illusion is the best known and most studied geometric illusion, consisting in the subject's judgment between two parallel lines that have the same size, one flanked with outward-pointing arrowheads, and the other with inward-pointing arrowheads. These arrowheads act as inductors that make the lines to be perceived as having different sizes, inward-pointing stimuli being estimated as longer. This study aimed to investigate the Müller-Lyer illusion in capuchin monkeys (Cebus apella), a New World primate not yet investigated for this illusion. For this purpose, stimuli were presented on a touch screen monitor. Ten adult subjects (five females and five males) were used. Before the tests, they were trained to discriminate between two physically different lines with and without arrowheads. The longer lines were always the positive (rewarded) stimuli. Regarding the Müller-Lyer Illusion test, all monkeys, unrespective of gender, demonstrated susceptibility to the illusion, by choosing preferentially the line with inward-pointing arrowheads. In order to determine the degree of the illusion, a point of subjective equality test (PSE) was performed. The PSE without arrowheads values were lower than the PSE with arrowheads. Thus, it was demonstrated that capuchin monkeys were susceptible to the Müller-Lyer illusion, once the perception of the lines' size was influenced by the presence of the arrowheads and by their orientation.
Asunto(s)
Cebus/fisiología , Discriminación en Psicología/fisiología , Ilusiones/fisiología , Juicio/fisiología , Animales , Conducta Animal , Femenino , Masculino , Reconocimiento Visual de Modelos/fisiología , Estimulación Luminosa/métodosRESUMEN
BACKGROUND: Aging is characterized by a decline in the postural control performance, which is based on a coherent and stable coupling between sensory information and motor action. Therefore, changes in postural control in elderlies can be related to changes in this coupling. In addition, it has been observed that physical activity seems to improve postural control performance in elderlies. These improvements can be due to changes in the coupling between sensory information and motor action related to postural control. OBJECTIVE: The purpose of this study was to verify the coupling between visual information and body sway in active and sedentary elderlies. METHODS: Sixteen sedentary elderlies (SE), 16 active elderlies (AE) and 16 young adults (YA) were asked to stand upright inside a moving room in two experimental conditions: (1) discrete movement and (2) continuous movement of the room. RESULTS: In the continuous condition, the results showed that the coupling between the movement of the room and body sway was stronger and more stable for SE and AE compared to YA. In the discrete condition, SE showed larger body displacement compared to AE and YA. CONCLUSIONS: SE have more difficulty to discriminate and to integrate sensory information than AE and YA indicating that physical activity may improve sensory integration.
Asunto(s)
Ejercicio Físico/fisiología , Equilibrio Postural , Adulto , Factores de Edad , Anciano , Análisis de Varianza , Humanos , Ilusiones/fisiología , Persona de Mediana Edad , Desempeño Psicomotor/fisiologíaRESUMEN
The Hermann grid illusion (HGI), elicited by a grid displayed as either horizontal-vertical (HV) or oblique (45 degrees ) configuration, was measured as the luminance necessary to cancel the illusory spots at the grid intersections. Overall, the HGI produced by the oblique grid was about one-third of that produced by the HV grid. The observers exhibited different sensitivities to the HGI orientation, and seemed to perceive the illusion in two manners: with moderate anisotropy (reduction of about 20%, three subjects) or large anisotropy (90% reduction, four subjects). The quantitative reduction of the HGI elicited by the oblique pattern tested and its reduction to almost zero in some subjects, constitute a benchmark for any model aimed at explaining the HGI on psychophysical grounds.
Asunto(s)
Señales (Psicología) , Ilusiones/fisiología , Orientación/fisiología , Reconocimiento Visual de Modelos/fisiología , Percepción Espacial/fisiología , Campos Visuales/fisiología , Adolescente , Adulto , Anisotropía , Sensibilidad de Contraste/fisiología , Femenino , Humanos , Iluminación , Masculino , Modelos Neurológicos , Variaciones Dependientes del Observador , Estimulación LuminosaRESUMEN
Esta comunicación trata de romper el esquema dicotómico que separa como entes aislados los diferentes síntomas en una totalidad biológica. Esta separación sirve a los fines didácticos, pero es un artificio en la visión de conjunto. Ilusiones, sueños, fobias, son distintos matices de una misma pulsión mórbida, en la dinámica de la totalidad (AU)
Asunto(s)
Humanos , Ilusiones/fisiología , Delirio/clasificación , Alucinaciones/clasificaciónRESUMEN
Esta comunicación trata de romper el esquema dicotómico que separa como entes aislados los diferentes síntomas en una totalidad biológica. Esta separación sirve a los fines didácticos, pero es un artificio en la visión de conjunto. Ilusiones, sueños, fobias, son distintos matices de una misma pulsión mórbida, en la dinámica de la totalidad