Figure - available from: Frontiers in Human Neuroscience
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Panel (A) depicts the mirror visual feedback (MVF) scenario. Participants were required to watch the mirror so that they felt as if the hand in the mirror reflection was the hidden hand behind the mirror. An experimenter sitting at the opposite side of the desk (not shown) presented a foam pad to each hand of the participant through the rectangular window of the partition. Panel (B) shows the sensor of the electromagnetic tracker used to measure finger movements. The sensor was attached to the fingertip of the third finger of both hands using surgical tape. No tape was attached to the finger pad. The transmitter of the device was placed behind the partition such that it remained hidden from the participant. Panel (C) indicates the coordinates for the finger movements.
Source publication
Several studies have demonstrated that observation of a dummy or mirror-reflected hand being stroked or moving at the same time as the hidden hand evokes a feeling that the dummy hand is one’s own, such as the rubber hand illusion (RHI) and mirror visual feedback (MVF). Under these conditions, participants also report sensing the tactile stimulatio...
Citations
... These studies investigate discriminative touch and touch imagery [29,30], roughness recognition classification [6,31,32], and tactile pleasantness in response to different textures or touch types [12,33,34]. Most studies examine active touch after eliminating the visual stimuli since it may have a major impact in haptic perception [35]. However, tactile perception in combination with visual stimuli has also been explored. ...
Touch sensation is a key modality that allows humans to understand and interact with their environment. More often than not, touch sensation depends on vision to accumulate and validate the received information. The ability to distinguish between materials and surfaces through active touch consists of a complex of neurophysiological operations. To unveil the functionality of these operations, neuroimaging and neurophysiological research tools are employed, with electroencephalography being the most used. In this paper, we attempt to distinguish between brain states when touching different natural textures (smooth, rough, and liquid). Recordings were obtained with a commercially available EEG wearable device. Time and frequency-based features were extracted, transformed with PCA decomposition, and an ensemble classifier combining Random Forest, Support Vector Machine, and Neural Network was utilized. High accuracy scores of 79.64% for the four-class problem and 89.34% for the three-class problem (Null-Rough-Water) were accordingly achieved. Thus, the methodology's robustness indicates its ability to classify different brain states under haptic stimuli.
... Further research in cognitive psychology suggests that the information observed through vision can simulate the sense of touch. This is a phenomenon known as the visual-tactile mirror mechanism (Keysers et al., 2004;Katsuyama et al., 2018;Zazio et al., 2019). Accordingly, touch visualization theory suggests that observing another person being touched, seeing an object being touched, or even any visual touch (such as a tree branch beating against a window glass) can lead to the activation of the tactile nervous system involved in the individual somatosensation (Ebisch et al., 2008;Tholen et al., 2020). ...
Introduction
There is a common phenomenon of tactile missing in online retail. How to realize consumer tactile compensation is a consensus problem in the field of e-commerce. More and more marketeers and scholars convey their ideas via visual display, but few researches have focused on the tactile compensatory effect of visual language.
Methods
Study 1 collected data from nearly 13,000 online purchases to analyze the impact of haptic cues on sales in real online shopping platforms; Study 2 used a experimental research method to design three experimental groups: hand haptic cue group vs. Object haptic cue group vs. control group (N = 165) to investigate whether the main effect of haptic cues and the dual mediating effect of mental simulation held. Study 3 also adopted a simulated experimental research approach to design a two-factor group: 2 (haptic cue: hand vs. object) × 2 (product type: tactile functional product vs. tactile experiential product) (N = 198). To further explore whether the moderating effect of product type holds based on Study 2.
Results
Therefore, based on the visualization theory and mental simulation theory, and through a second-hand data experiment and two simulated experiments, this study confirmed that visual language did have a compensation effect on tactile missing specifically. Haptic cues in metaphorical visual language can actively compensate for consumers’ tactile loss, thus affecting the purchase intention. Mental simulation plays a mediating role in the tactile compensation effect. Product type has a moderating effect, and the use of hand (object) haptic cues in metaphorical visual language in tactile functional products (tactile experiential products) can lead to a more active purchase intention.
Discussion
This study not only enriches the theoretical research on the tactile compensation effect of visual language, but also provides valuable management enlightenment for e-commerce enterprises to improve the effectiveness of online product display and online sensory marketing strategies.
... The overarching focus is whether Mirror Therapy improves mobility, lack of focus on pain, everyday activity effectiveness, and awareness of the impaired range of view after a glass cut injury. Mirror treatment has recently gained popularity, with claims of a rising number of PLP patients showing "significant benefit" [5] p. 2. The approach, also referred to as mirrored visual feedback (MVF), has proven beneficial in various conditions, including brain stroke and complicated localized pain syndrome [6]. Because mirror therapy depends on visual inputs, it is attainable, and some forms of stimuli, such as aural feedback, could help with motor skills in the wrist and hands. ...
... This specular superimposition has been used to "resurrect" a phantom limb in patients following upper-limb amputation and, in some patients, to relieve pain in the phantom limb (Ramachandran et al., 1995;Ramachandran and Rogers-Ramachandran, 1996). Parasagittal mirrors have also been used to: manipulate the visually perceived distance between participants' hands (Gallace and Spence, 2005); assess the influence of vision on proprioception (Holmes et al., 2006); investigate visual enhancement of touch (Ro et al., 2004;Longo et al., 2008a); compare tactile illusions in amputees' phantom limbs and healthy individuals' intact but untouched limbs (Giummarra et al., 2010); explore relationships between the illusion of ownership, proprioceptive drift, estimates of the hardness of a foam pad, and skin temperature on the hands (Sadibolova and Longo, 2014;Medina et al., 2015;Katsuyama et al., 2018;Crivelli et al., 2021). ...
When I see my face in a mirror, its apparent position (behind the glass) is not one that my own face could be in. I accept the face I see as my own because I have an implicit understanding of how mirrors work. The situation is different if I look at the reflection of my right hand in a parasagittal mirror (parallel to body midline) when my left hand is hidden behind the mirror. It is as if I were looking through a window at my own left hand. The experience of body ownership has been investigated using rubber hand illusion (RHI) paradigms, and several studies have demonstrated ownership of a rubber hand viewed in a frontal mirror. Our “proof of concept” study was the first to combine use of a parasagittal mirror and synchronous stroking of both a prosthetic hand (viewed in the mirror) and the participant’s hand, with a manipulation of distance between the hands. The strength of the RHI elicited by our parasagittal-mirror paradigm depended not on physical distance between the hands (30, 45, or 60 cm) but on apparent distance between the prosthetic hand (viewed in the mirror) and the participant’s hand. This apparent distance was reduced to zero when the prosthetic hand and participant’s hand were arranged symmetrically (e.g., 30 cm in front of and behind the mirror). Thus, the parasagittal-mirror paradigm may provide a distinctive way to assess whether competition for ownership depends on spatial separation between the prosthetic hand and the participant’s hand.
... According to graded motor imagery, MVF is recognized as a visual induced motor imagery, which may contain components of motor and sensory experiences (Moseley, 2006;Voisin et al., 2011). As a type of visual induced imagery, MVF could generate referred sensations, where sensory stimulus evoked from one hand is referred to as the contralateral one behind the mirror (Ramachandran et al., 1995;Takasugi et al., 2011;Katsuyama et al., 2018). Therefore, we speculated that the vibrotactile sensory stimulus itself and the strengthened proprioceptive feedback could be referred to the dominant side via MVF and contribute to enhance embodiment. ...
As one determinant of the efficacy of mirror visual feedback (MVF) in neurorehabilitation, the embodiment perception needs to be sustainable and enhanced. This study explored integrating vibrotactile stimulation into MVF to promote the embodiment perception and provide evidence of the potential mechanism of MVF. In the experiment, the participants were instructed to keep their dominant hand still (static side), while open and close their non-dominant hand (active side) and concentrate on the image of the hand movement in the mirror. They were asked to tap the pedal with the foot of the active side once the embodiment perception is generated. A vibrotactile stimulator was attached on the hand of the active side, and three conditions were investigated: no vibration (NV), continuous vibration (CV), and intermittent vibration (IV). The effects were analyzed on both objective data, including latency time (LT) and electroencephalogram (EEG) signals, and subjective data, including embodiment questionnaire (EQ). Results of LT and EQ suggested a stronger subjective sense of embodiment under the condition of CV and IV, comparing with NV. No significant difference was found between CV and IV. EEG analysis showed that in the hemisphere of the static side, the desynchronization of CV and IV around the central-frontal region (C3 and F3) in the alpha band (8–13 Hz) was significantly prominent compared to NV, and in the hemisphere of the active side, the desynchronization of three conditions was similar. The network analysis of EEG data indicated that there was no significant difference in the efficiency of neural communication under the three conditions. These results demonstrated that MVF combined with vibrotactile stimulation could strengthen the embodiment perception with increases in motor cortical activation, which indicated an evidence-based protocol of MVF to facilitate the recovery of patients with stroke.
... These studies employed virtual reality techniques to experimentally manipulate the visual and haptic stimuli. In our previous study (Katsuyama et al., 2018), we attempted to examine the effect of visual information on hardness perception by active touch under a more natural condition. For this purpose, we used a mirror visual feedback (MVF) paradigm, in which the reflection of the hand appears to be the hand hidden behind the mirror. ...
... Many studies have demonstrated that tactile illusions, including the rubber hand illusion, referred sensation, and MVF, are accompanied by illusory ownership toward the fake hands (Botvinick and Cohen, 1998;Ehrsson et al., 2004;Tsakiris et al., 2006;Bertamini et al., 2011;Bekrater-Bodmann et al., 2014). In particular, when the dummy and hidden hands are moving simultaneously, participants also experience the sensation that the dummy hand is moved by their own will; this is known as the sense of agency (Sanchez-Vives et al., 2010;Kalckert and Ehrsson, 2012;Jenkinson and Preston, 2015;Katsuyama et al., 2018). Therefore, we also investigated whether participants experienced the sense of hand ownership of the image of the hand in the mirror during the hardness estimation task with MVF. ...
... Participants touched the pad with both hands synchronously and asynchronously in the SYNC and ASYNC conditions, respectively, while observing the mirror reflection of the left hand. The results were consistent with our previous behavioral study (Katsuyama et al., 2018): the perceived hardness significantly increased as the hardness of the pad in the mirror reflection increased in the SYNC condition and remained constant in the ASYNC condition (Supplementary Figure 1). This result indicated that the visual modulation of hardness perception was induced even while the participant was lying in the MR scanner. ...
Recent studies have revealed that hardness perception is determined by visual information along with the haptic input. This study investigated the cortical regions involved in hardness perception modulated by visual information using functional magnetic resonance imaging (fMRI) and multivoxel pattern analysis (MVPA). Twenty-two healthy participants were enrolled. They were required to place their left and right hands at the front and back, respectively, of a mirror attached to a platform placed above them while lying in a magnetic resonance scanner. In conditions SFT, MED, and HRD, one of three polyurethane foam pads of varying hardness (soft, medium, and hard, respectively) was presented to the left hand in a given trial, while only the medium pad was presented to the right hand in all trials. MED was defined as the control condition, because the visual and haptic information was congruent. During the scan, the participants were required to push the pad with the both hands while observing the reflection of the left hand and estimate the hardness of the pad perceived by the right (hidden) hand based on magnitude estimation. Behavioral results showed that the perceived hardness was significantly biased toward softer or harder in >73% of the trials in conditions SFT and HRD; we designated these trials as visually modulated (SFTvm and HRDvm, respectively). The accuracy map was calculated individually for each of the pair-wise comparisons of (SFTvm vs. MED), (HRDvm vs. MED), and (SFTvm vs. HRDvm) by a searchlight MVPA, and the cortical regions encoding the perceived hardness with visual modulation were identified by conjunction of the three accuracy maps in group analysis. The cluster was observed in the right sensory motor cortex, left anterior intraparietal sulcus (aIPS), bilateral parietal operculum (PO), and occipito-temporal cortex (OTC). Together with previous findings on such cortical regions, we conclude that the visual information of finger movements processed in the OTC may be integrated with haptic input in the left aIPS, and the subjective hardness perceived by the right hand with visual modulation may be processed in the cortical network between the left PO and aIPS.
Mirror therapy (MT) is a treatment for improving motor function after stroke. Video therapy (VT) training combines observation and imitation of video clips, and it has been used to conduct efficient occupational therapy. We sought to determine the effects of MT and VT on tool-use with healthy young adults. We assigned participants to three different training groups in which they used their non-dominant left hands to move a ball with chopsticks: (a) a self-paced MT group ( N = 14), (b) an MT group who moved the ball while looking at the mirror image of the right hand with a sound cue (4-second intervals) ( N = 12), and (c) a group who imitated a video demonstration (4-second intervals) ( N = 13). The ball-moving time was significantly reduced after training in all three groups: MT group ( p < .001), MT-R group ( p = .010), and VT group ( p = .014), but the video group showed significantly greater relative improvements in motion variability ( p = .030) and object prediction ( p = .008).We concluded that MT was as effective as VT in improving movement speed, but, with these healthy young adults, MT was less effective than VT in learning speed control or hand pre-shaping to refine task movements for tool use.
Haptic illusions provide unique insights into how we model our bodies separate from our environment. Popular illusions like the rubber-hand illusion and mirror-box illusion have demonstrated that we can adapt the internal representations of our limbs in response to visuo-haptic conflicts. In this manuscript, we extend this knowledge by investigating to what extent, if any, we also augment our external representations of the environment and its action on our bodies in response to visuo-haptic conflicts. Utilizing a mirror and a robotic brushstroking platform, we create a novel illusory paradigm that presents a visuo-haptic conflict using congruent and incongruent tactile stimuli applied to participants' fingers. Overall, we observed that participants perceived an illusory tactile sensation on their visually occluded finger when seeing a visual stimulus that was inconsistent with the actual tactile stimulus provided. We also found residual effects of the illusion after the conflict was removed. These findings highlight how our need to maintain a coherent internal representation of our body extends to our model of our environment.
Past studies have examined embodiment in the rubber hand illusion, using principal components analysis (PCA) to identify factors from questionnaire responses during synchronous and asynchronous stroking. To better understand the phenomenology of embodiment, we used PCA in the mirror box illusion to examine performance across conditions that varied in movement synchrony to examine multisensory integration and movement type to vary the amount of multisensory congruence. We found three dissociable components in all conditions: embodiment, deafference and attentiveness. We also examined how these embodiment ratings varied across the four conditions. As hypothesized, embodiment ratings were highest for synchronous movement, with feelings of deafference highest for asynchronous movement. Furthermore, there was a movement by timing interaction, such that sliding resulted in greater differences in synchronous versus asynchronous ratings than tapping. These results suggest that embodiment or deafference can be changed as a function of the amount of multisensory congruence.
