Anodal transcranial direct current stimulation over the posterior parietal cortex reduces the onset time to the rubber hand illusion and increases the body ownership.

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.

Ilusão da mão de borracha induzida por estímulos controlados por equipamento eletrônico / Rubber hand illusion induced by electronic equipment­controlled stimuli / Ilusión de la mano de goma inducida por estímulos controlados por los equipos electrónicos

A indução da ilusão da mão de borracha (IMB) é tipicamente realizada por pincéis de forma manual. Nesse sentido, elaboramos um equipamento eletrônico com intuito de aumentar a precisão dos estímulos táteis na IMB. Objetivo: verificar a eficácia de um equipamento eletrônico para indução da IMB. Método: participaram do estudo 51 participantes, com idades entre 11 e 59 anos divididos em quatro grupos. Para coleta de dados utilizamos próteses de mãos e o equipamento eletrônico desenvolvido. A intensidade da IMB foi avaliada por um questionário subjetivo contendo 13 perguntas classificadas entre concordância ou discordância sobre as sensações percebidas do paradigma. Resultados: encontramos efeitos significativos em todas as perguntas de incorporação da mão de borracha. Conclusão: o equipamento eletrônico mostrou‑se eficaz na velocidade, sincronia e precisão da movimentação dos pincéis, com indução robusta do paradigma da IMB. Sugere‑se a utilização desse equipamento em experimentação científica do paradigma da IMB.

The induction of rubber hand illusion (RHI) is typically manually performed by brushes. In this direction, we developed an electronic device in order to increase the accuracy of tactile stimuli in RHI. Objective: To determine the effectiveness of an electronic and programmable apparatus developed for induction of RHI. Method: The study included 51 participants, age (11 and 59 years) distributed in four groups. For data collection we used the prosthetic hands and the personaly developed electronic equipment. The intensity of RHI was assessed using a subjective questionnaire containing 13 questions ranked in agreement or disagreement on the sensations perceived paradigm. Results: We found significant effects on all questions about incorporation of the rubber hand. Conclusion: The electronic equipment was effective in speed, timing and accuracy of movement of brushes and displayed the robust induction of RHI. Hence, we propose the use of such eletronic equipment in the RHI paradigm in scientific studies.

La inducción de la ilusión de la mano de goma (IMG) se realiza normalmente manualmente mediante cepillos. De este modo, hemos elaborado un dispositivo electrónico con el fin de aumentar la precisión de los estímulos táctiles en IMG. Objetivo: determinar la eficacia de un aparato electrónico y programable desarrollado para la inducción de IMG. Método: el estudio incluyó a 51 participantes, entre 11 y 59 años, divididos en cuatro grupos. Para la obtención de datos se utilizaron prótesis de mano y equipos electrónicos desarrollados. Para evaluar la intensidad de la inducción la IMG, se utilizó un cuestionario subjetivo que contiene 13 preguntas sobre la sensación ilusoria de incorporación de la mano. Resultados: un efecto significativo de las preguntas sobre la sensación ilusoria de incorporación de la mano de goma fue observado. Conclusión: el equipo electrónico fue eficaz en la velocidad, el tiempo y la precisión de movimiento de los cepillos con la inducción robusta de la IMG. Sugerimos el uso de estos equipos en el paradigma de la IMG experimentación científica.

Relación entre el fenómeno de la ilusión de la mano falsa y variables personales / Relationship between the rubber hand illusion phenomenon and personal variables

El fenómeno de la ilusión de la mano falsa (IMF) se ha propuesto como un diseño que permite discriminar procesos perceptuales a partir de entradas sensoriales multimodales. Se han reportado varias modificaciones y variables que podrían afectar la generación del fenómeno. Este estudio se planteó bajo un diseño descriptivo-correlacional del fenómeno. Se realizó el procedimiento en jóvenes (16-48 años M = 20.86 años, DE = 4.4) colombianos para replicar el fenómeno de IMF. Los sujetos se dividieron al azar en dos grupos que diferían en el tipo de estimulación (sincrónica y desincronizada). La identificación de la IMF se realizó mediante la escala reportada en múltiples estudios, mostrando que en algunas variables como la estimulación se presentaba una diferencia en el reporte de IMF (P2. X² = 5.856: p < 0.05; P3. X² = 6.655: p <0.01 y P7(X² = 4.764: p < 0.05). Otras variables como sexo y dominancia manual mostraron algunas diferencias. La escala presenta una consistencia interna aceptable (α = 0.8). Los resultados de la IMF son similares a algunos estudios pero con puntuaciones menores que en los estudios iniciales, la diferencia en cuanto al género en tareas perceptuales podría explicar gran parte de los resultados.

The Rubber Hand Illusion (RHI) has been proposed as a design which allows to discriminate perceptual processes based on multimodal sensory inputs. Several modifications and variables have been reported that could affect the generation of the phenomenon. This study was conducted using a descriptive correlational design of this phenomenon. The procedure was conducted with young Colombian individuals (16-48 years-M = 20.86 years, SD = 4.4), seeking to replicate the RHI. The subjects were randomly divided into two groups that differed in type of stimulation (synchronised and unsynchronised). Identification of the RHI was performed using the scale reported in multiple studies, showing that the RHI report had differences in some variables such as stimulation (P2. X² = 5.856: p <.05; P3. X² = 6.655: p <.01 y P7 (X² = 4.764: p <.05). Other variables, such as gender and handedness, also showed some differences. The scale has an acceptable internal consistency ( X= 0.8). The results of the RHI are similar to some studies, but with lower scores than in the initial studies. The difference in gender in perceptual tasks could explain most of the results.

Exploring the subjective experience of the "rubber hand" illusion.

Despite the fact that the rubber hand illusion (RHI) is an experimental paradigm that has been widely used in the last 14 years to investigate different aspects of the sense of bodily self, very few studies have sought to investigate the subjective nature of the experience that the RHI evokes. The present study investigates the phenomenology of the RHI through a specific elicitation method. More particularly, this study aims at assessing whether the conditions usually used as control in the RHI have an impact in the sense of body ownership and at determining whether there are different stages in the emergence of the illusion. The results indicate that far from being "all or nothing," the illusion induced by the RHI protocol involves nuances in the type of perceptual changes that it creates. These perceptual changes affect not only the participants' perception of the rubber hand but also the perception of their real hand. In addition, perceptual effects may vary greatly between participants and, importantly, they evolve over time.