錯覚現場を足場に構想する, のリコンストラクション

T_ADS + 新建築社｜レクチャーシリーズ@東大駒場

錯覚現象を足場に構想する, ＜からだ＞のリコンストラクション名古屋市立大学芸術工学研究科　小鷹研理

2015.8.28Body-image reconstruction based on the principle of the body ownership illusionGraduate school of Design and Architecture, Nagoya-City University

KENRI [email protected]

mailto:[email protected]

T_ADS + 新建築社｜レクチャーシリーズ@東大駒場Body-image reconstruction

kenrikodaka laboratory

body image reconstruction

T_ADS + 新建築社｜レクチャーシリーズ　2015.8.30

Cognitive psychology / Human neuroscience

Virtual reality / Human computer interaction?


Your body-image is not stable as you might believe.

The body ownership is artificially generated based on the multi-sensory correlation mechanism.

CONTENTS

#exercise <experience body-image confusion>

#exercise <experience proprioceptive drift>

Application: Finger extension / Rubber hand pointer


Virtual reality / Human computer interaction

T_ADS + 新建築社｜レクチャーシリーズ@東大駒場Body-image reconstructionYour body-image is not stable as you believe.

Perception system

Physical world

Imagined body

Physical body


http://luaxan.deviantart.com/art/Anorexia-paint-5-61713488

Physical world

Physical body

Imagined body

Perception system

Anorexia


Imagined body

Physical world

Physical body

Perception system

Phantom Limb


Physical world

Physical body

Perception system

Out of body experience

Imagined body


Physical world

Physical body

Perception system


Imagined body

笹岡貴史, 乾敏郎, 「視点取得機能に関わる脳内基盤の検討：fMRI研究」認知心理学会第12回大会, 2014

Right angular gyrus

Blanke, O., Ortigue, S., Landis, T., & Seeck, M. (2002). Stimulating illusory own-body perceptions. Nature, 419(6904), 269‒70. doi:10.1038/419269a


Third person perspective


Physical world

Physical body

Perception system


Imagined body


Stroke of insight

https://www.ted.com/talks/jill_bolte_taylor_s_powerful_stroke_of_insight


La La Land…

I could no longer clearly discern the physical boundaries of where I began and where I ended. I sensed the composition of my being is that of a fluid rather than that of a solid. I no longer perceived myself as a whole object separate from everything. Instead, I now blended in with the space and flow around me. (p. 42)

http://personalityspirituality.net/2010/04/13/dr-jill-bolte-taylor-the-neuroscientist-who-had-a-stroke-and-discovered-nirvana/

https://www.ted.com/talks/jill_bolte_taylor_s_powerful_stroke_of_insight


Imagined body

Physical body and imagined body are deeply connected each other, while the imagined body can transform or change its essential characteristic in a special situation.

It is particularly important to understand that our familiar body-image might be one of many probable options !!

Physical world

Physical body

Perception system


Easy exercises to find that

your body-image is not always stable as

you believe.


Hong et al. Hand-reversal illusion

FIGURE 1 | Hand and finger postures. (A) Example of the hand and fingerposture for the Hand-Reversal Illusion (left) and a naturally folded handposture (right). (B) Hand and finger postures with the ball in Experiment 3.

such as interweaving fingers (Zampini et al., 2005; Haggard et al.,2006; Riemer et al., 2010; Overvliet et al., 2011) and crossinghands (Benedetti, 1985; Yamamoto and Kitazawa, 2001; Heedet al., 2012), can affect tactile localization on the fingers andhands. The effect of the configuration of fingers and hands onlocalization and identification of touch has been observed bothwith (Haggard et al., 2006) and without (Riemer et al., 2010;Overvliet et al., 2011) visual information, indicating that visualinformation may not be the main source of confusion. Instead,these studies suggest that the effect of unnatural body configura-tion on localization of touch is due to the conflict between thesomatotopic body coordinate and the external spatial coordinate.For example, when two hands are crossed-folded (see Figure 1A,left), the right hand belongs to the right side of the body in termsof somatotopic coordinates but is located on the left side in termsof external spatial coordinates. According to a somato-perceptualinformation processing model (Longo et al., 2010), the spatiallocation of the finger within the body schema should be firstidentified, which is achieved based on somatotopic organization,and then transformed to an external spatial representation to exe-cute a finger movement. This remapping of the representationof the body part to the external spatial representation is impor-tant for performing goal-directed movements such as reachingand pointing (Sarlegna et al., 2009), since such actions requirelocalization of both the target object and the hands in the externalthree-dimensional space.

In the current study, we were specifically interested in whichof three factors might cause the hand-reversal illusion. One pos-sibility, as was originally proposed by Van Riper (1935), is thatpotentially confusing visual information in the crossed-handsposition leads to slower response times (RTs) and more errors.Another possibility is that unnatural hand configuration itself(switch between left and right body part) impairs a person’s abil-ity to localize the touched digit or to make the relevant motoraction in response to that touch due to greater confusabilitybetween left and right hands. Lastly, the impairment may be due

to the mismatch between the somatotopic body representationand the external spatial representation (Longo et al., 2010), assuggested by previous research on tactile localization (Haggardet al., 2006; Riemer et al., 2010; Overvliet et al., 2011). We con-ducted three experiments to distinguish between these possibleaccounts.

In our experiments, we re-evaluated the illusion by obtainingreaction time measurements because, in the original study, sub-jects might have relied on a strategy of responding more slowlyto minimize making errors. If potentially confusing visual infor-mation is not the main cause of the illusion, we should be ableto observe evidence of the illusion that is slower responses withcross-folded hands, even when conflicting visual input is elimi-nated. We used only tactile cues (tapping the designated finger)to directly compare the results from different visual conditions(i.e., with vs. without input). In the second experiment, we exam-ined whether RT delays in the crossed-hands configuration wasattributable to left-right confusions during response selection, bytesting fingers from only one hand. Moving the finger that wastouched requires localization of the tactile input, response selec-tion of the finger to move, and execution of the movement. RTdelays might occur at any of these processing stages. By testingonly a single hand in Experiment 2, we minimized the potentialfor left-right confusion between the hands at the stage of bothidentification and response selection. If delays in RT are stillobserved in the crossed-hands position, such a result would indi-cate that the impairment is unlikely to reflect confusion at thesestages. In the third experiment, we determined whether RT delaysin the crossed-hands configuration might simply be due to theunnatural posture of the hands and fingers, by testing only onehand. Note that both hands were used for cross-folding but fin-gers from only one hand were tested in the second experiment. Ifconfusability of the left and right hands is the primary cause of RTdelays in the crossed-hands configuration, then no impairmentshould occur when only a single hand makes a similar unnaturalconfiguration.

MATERIALS AND METHODSPARTICIPANTSTwenty healthy adult volunteers with normal or corrected-to-normal vision participated in the experiments. Each participanttook part in two of the three experiments. All participantsprovided informed consent to participate in the study, whichwas approved by the Vanderbilt University Institutional ReviewBoard.

PROCEDUREFor the experiment, the participant sat between two desksthat each supported a MacBook Pro 13” computer used forvideo recording (PhotoBooth software) the participant’s handsfrom both sides. The participant wore latex gloves, and eachof the index and middle fingers were marked with a uniquecolor band for experimental coding (Figure 1). This experi-ment focused on the index and middle fingers exclusively, as itproved more difficult to move the third or fourth digits indepen-dently, especially when the hands were positioned in the reversedconfiguration.

Frontiers in Integrative Neuroscience www.frontiersin.org September 2012 | Volume 6 | Article 83 | 2

Hong, S. W., Xu, L., Kang, M.-S., & Tong, F. (2012). The hand-reversal illusion revisited. Frontiers in Integrative Neuroscience, 6, 83. doi:10.3389/fnint.2012.00083


2015.1.17-31, Biccafe, Gifu


2015.1.17-31, Biccafe, Gifu2015.1.17-31, Biccafe, Gifu


2015.1.17-31, Biccafe, Gifu

And, this drawing is inspired by this old-fashioned play. This is a poster picture from the exhibition of my laboratory, which took place last January, entitled “your body image is now turning into a battlefield”. You may think this drawing is similar to this posture. But, in fact, this new construction consists of four hands. It is just 2 people, making this complex posture. Specifically, it is a result of combining this posture with another. I think this drawing gives us a fairy odd feeling, just by looking at it. It will become stronger when you become a part of the four hands. This odd feeling seems similar to the feeling that the boundary between you and I is gradually becoming unclear. I recommend you to try to make this posture with your girlfriend or boyfriend when you go home.


#Exercise

“An invisible man climbing a fence”




CONTENTS







Imagined body

Physical body

How do we regard our physical body as our own?

The body ownership is artificially generated.


Physical body



body image


What consistently happens around your body? （thought experiment）

When you move your hand, you can see that hand move.

When you see your hand touched, you feel a tactile

sensation in that hand.

When you knock on a door, you hear a hitting sound from

where you knock.

visionmotion

vision tactile

tactile auditory



When you move your hand, visionmotion

vision tactile

tactile auditory

tactile tactile

When you touch an object you only feel you touch something.

When you touch your body, you also feel you are touched by something.

tactile tactile


visionmotion

Body is the place where somatic sensations are correlated one after

another or correlated with other special sensations (like a visual or audible one).

Such a multi-sensory correlation mechanism can create a sense of

owning “it” as your body.


vision tactile

tactile auditory

tactile tactilebody ownership

T_ADS + 新建築社｜レクチャーシリーズ@東大駒場Body-image reconstructionThe body ownership is artificially generated.

multi-sensory correlation

It is done by extracting an object involving a multi-sensory correlation with somatic sensations.

Physical body

body image



Anatomic similarity is not a hard requirement for body ownership.

vs.



Artificial body

Physical body


vision

motion

tactile

auditory


How can the artificial body deprive body ownership of the physical body ?

？


Artificial body

Physical body


vision

motion

tactile

auditory




Physical body


vision

motion

tactile

auditory

Artificial body




Physical body


vision

motion

tactile

auditory

Artificial body


Mask, and

Correlation


Proximity,


Physical body

Artificial



Principle 1 (Proximity) Placing the artificial body close to the physical body. Principle 2 (Mask) Hiding the physical body from sight. Principle 3 (Correlation) Correlating multiple sensations between the physical body and the artificial body.

body ownership illusion (BOI)


Physical body

Artificial body



Principle 1 (Proximity) Placing the artificial body close to the physical body. Principle 2 (Mask) Hiding the physical body from sight. Principle 3 (Correlation) Correlating multiple sensations between the physical body and the artificial body.



Rubber Hand Illusion

Full body illusion

Rubber hand illusion（1998 -）Moving rubber hand illusion（2009 -）

Full body illusion（2011 -）Barbie doll illusion（2012）


Self-touch illusion（2005 -）


Body swapping（2008）

・・・

・・・


Rubber hand illusion

出典, 別冊日経サイエンス知覚は幻, p12


vision

tactile Physical body

Artificial body



Full body illusion







・・・

・・・


Kalckert and Ehrsson Ownership and agency in self-recognition

only), promoted ownership. The authors reported similar levelsof proprioceptive drift in the three conditions when synchronousstimulation was compared with the asynchronous control con-ditions. In this design, agency was always present in the contextof ownership; in other words, no condition with agency withoutownership was included. Therefore, it was not possible to test fordouble dissociation between ownership and agency or to examinepossible differences between agency over one’s limbs and externalobjects.

In the present study, we introduce a version of the rubber handillusion in which participants “move” the index finger of a physi-cal (wooden) model hand by moving their own index finger anddescribe how this paradigm results in a strong illusion of owner-ship, quantified by both subjective and objective measures. In thefirst series of experiments (Experiments 1 and 2), we manipulatedthe relative timing of visual and somatic feedback. As synchronyis known to play crucial roles in both the sense of ownership andthe sense of agency, we hypothesized that asynchronous sensoryfeedback would effectively eliminate both ownership and agencyand thereby serve as a control condition.

In a second series of experiments (Experiments 3 and 4), wetested the hypothesis that ownership and agency represent dif-ferent processes and can therefore be dissociated. To this end,the mode of movement generation (active versus passive) andthe position of the model hand with respect to the participant’sbody (anatomically congruent versus incongruent positions) weremanipulated in a 2 × 2 factorial design. Our prediction was thatpassive movements would eliminate agency but have no influenceon ownership, whereas an anatomically incongruent hand pos-ture would eliminate ownership but leave agency intact. In thecontext of the last prediction, we reasoned that because agencycan be experienced during tool use and object-directed actions,it should also be maintained when moving a finger that does notfeel like a part of one’s body. Our results support our hypothesesand provide evidence of a (double) dissociation between owner-ship and agency. Furthermore, our factorial design allowed us todirectly compare the agency sensed over an owned limb (bodyagency) with the agency sensed over an external object (externalagency). Our results suggest that agency over a part of one’s bodyis more vivid and more tightly linked with ownership than agencyover an external object. This finding provides preliminary sup-port that body agency and external agency may involve differentprocesses.

MATERIALS AND METHODSSUBJECTSA total of 104 healthy, experimentally naïve participants weretested in four separate experiments. Experiment 1 included 20participants (nine males, mean age 24.5 years, SD ± 4.4). In Exper-iment 2, another 20 participants were tested (eight males, meanage 30.5 years, SD ± 12.6). The third and fourth experiments eachinvolved testing 32 participants (Experiment 3: 15 males, mean age24.8 years, SD ± 5.8; Experiment 4:14 males, mean age 27.2 years,SD ± 8.1). No volunteers participated in more than one experi-ment. All participants provided written informed consent priorto participation. The study methodology was approved by theRegional Ethical Review Board of Stockholm (www.epn.se).

APPARATUS AND PROCEDURESParticipants sat at a table and put their right hand into a woodenbox (see Figure 1; dimensions 35 cm × 25 cm × 12 cm) placed30 cm in front of them. The participant sat comfortably in thisposition, with the right hand and arm outstretched so that the tipof the index finger was approximately 50 cm from the shoulder. Alife-sized wooden model of a human hand was placed above thebox. The model hand measured 20 cm in length (from the end ofthe wrist to the tip of the middle finger) and was covered witha latex glove. Subjects wore identical latex gloves on their righthands. A plastic finger cap was placed on the tip of the index fin-ger, which was mechanically connected to the index finger of themodel hand above the box by a thin wooden rod installed througha small hole in the box. A blanket was placed over the participant’sright shoulder to cover the space between the model hand and theparticipant and to create a visual scenery for the participant thatthe model hand was the participant’s own outstretched hand (seeFigure 1).

Prior to the experiments, the participants were asked to readwritten instructions that introduced them to the procedure. Theparticipants’ task was to tap their right index finger in a semi-regular rhythm at approximately 1 Hz. In the passive condition,however, participants were instructed only to relax their fingers(see Experiments 3 and 4 below for further details). A strictlyregular rhythm was avoided because such perfectly regular visuo-somatic correlations were considered to produce weaker illusionsthan more irregular patterns (based on anecdotal observations).Thus, in the present experiment, participants were instructed atrandom intervals to occasionally execute a quick “double tap”instead of a single tap. Participants were briefly trained beforethe experiment to perform the tapping in the requested manner,using a metronome for pacing. The metronome was not presentduring the experimental trials. During the experiments, the par-ticipants were instructed to look at the model hand and focus onthe moving model finger.

The experimenter sat opposite the participant and moved themodel hand in the asynchronous and passive conditions (seebelow). The experimenter’s arm was hidden under a cover so

FIGURE 1 | (A) The setup used to induce the moving rubber hand illusion.The participant placed his right hand wearing a latex glove into the box. Awooden model hand wearing an identical latex glove was placed on top ofthe box. A blanket covered the space from the participant’s right shoulderto the right wrist of the model hand. The index fingers of the participant’shand and the model hand were mechanically connected by a rod attachedto two small plastic rings on the index fingers. (B) The proprioceptive driftmeasure. With eyes closed, the participants indicated where they felt theirright index finger was located by moving their left index finger to thecorresponding location on the board.

Frontiers in Human Neuroscience www.frontiersin.org March 2012 | Volume 6 | Article 40 | 3


Moving rubber hand illusionKalckert, A., & Ehrsson, H. H. (2012). Moving a Rubber Hand that Feels Like Your Own: A Dissociation of

Ownership and Agency. Frontiers in Human Neuroscience, 6(March), 40. doi:10.3389/fnhum.2012.00040


Physical body

Artificial bodyvision

motion


vision

motionPhysical body

Artificial body



Full body illusion







・・・

・・・


Full body illusion


Physical body

Artificial body

vimeo.com/78514476

Salomon, R., Lim, M., Pfeiffer, C., Gassert, R., & Blanke, O. (2013). Full body illusion is associated with widespread skin temperature reduction. Frontiers in Behavioral Neuroscience, 7, 65. doi:10.3389/fnbeh.2013.00065

http://vimeo.com/78514476


Full body illusion


Physical body

Artificial body

vimeo.com/78514476

Salomon, R., Lim, M., Pfeiffer, C., Gassert, R., & Blanke, O. (2013). Full body illusion is associated with widespread skin temperature reduction.

Frontiers in Behavioral Neuroscience, 7, 65. doi:10.3389/fnbeh.2013.00065

http://vimeo.com/78514476


Cooling of a specific body part caused by the illusory ownership


G. Lorimer Moseley, Nick Olthof, Annemeike Venema, Sanneke Don, Marijke Wijers, Alberto Gallace, and Charles Spence, Psychologically induced cooling of a specific body part caused by the illusory ownership of an artificial counterpart, PNAS 2008 105 (35) 13169-13173


G. Lorimer Moseley, Nick Olthof, Annemeike Venema, Sanneke Don, Marijke Wijers, Alberto Gallace, and Charles Spence, Psychologically induced cooling of a specific body part caused by the illusory ownership of an artificial counterpart, PNAS 2008 105 (35) 13169-13173

Cooling of a specific body part caused by the illusory ownership


body ownership illusion

affects or is affected by

skin temperatureheartbeat

immune system


Proprioception is distorted during BOI












sense of body locationproprioception


M. Botvinick, J. Cohen, “Rubber Hands ‘feel’ touch that eyes see”, Nature, 391, p.756 (1998)

Where do you feel your hand is located ?


proprioceptive drift












Moving rubber hand illusion


Kalckert, A., & Ehrsson, H. H. (2012). Moving a Rubber Hand that Feels Like Your Own: A Dissociation of Ownership and Agency. Frontiers in Human Neuroscience, 6(March), 40. doi:10.3389/fnhum.2012.00040


looking down (n = 5) at the virtual body located below them(i.e., incongruent with their physical perspective: Down-group,n = 11). Selected experiences of the Down-group participantsduring the synchronous and asynchronous body conditions arelisted in Table 1B. In summary, whereas several participantsfelt as if they were looking upward at the virtual body ‘‘abovethem’’ (Up-group), the remaining participants had the impressionthat they were looking down at the virtual body ‘‘below them’’(Down-group). This was found despite somatosensory, motor,and cognitive cues from our participants about their body posi-tion (they were lying on their back, facing upward, and werehead-constrained in the headcoil; Figure 1E; Supplemental Infor-mation). Based on these findings, we carried out data analysisconsidering each group of participants. This led to a 2 3 2 3 2factorial design with Perspective (up; down) as in-betweenfactor, and Object (body; no-body) and Stroking (synchronous;asynchronous) as within factors that were applied to the analysisof self-location, self-identification, and the fMRI data.

Robotically-Induced Changes in Self-Locationand Self-IdentificationStatistical analysis of RTs in theMBD task showed that self-loca-tion depended on Object, Stroking, and Perspective [significantthree-way interaction; F(1,20) = 4.4; p < 0.05]. Post hoc compar-isons showed that in the body conditions, the participants of theUp-group (participants experiencing themselves to be lookingupward at the visually presented body) estimated self-locationas higher (longer RTs) during the synchronous (1071 ms)comparedwith the asynchronous stroking (991ms; p < 0.01; Fig-ure 2A). The opposite pattern was found in the Down-group(participants experiencing that they were looking downward atthe visually presented body): lower self-location and shorter

RTs during the synchronous stroking (1047 ms) with respect tothe asynchronous stroking while viewing the body (1138 ms;p < 0.03; Figure 2B). No significant differences were foundbetween synchronous and asynchronous stroking in the controlconditions in both groups (all p > 0.2; see Figures 2A and 2B).Notably, RTs in the body conditions are modulated, withineach group, as a function of stroking and the experienced direc-tion of the first-person perspective. Thus, self-location changesfor the Up-group were characterized by a generally lower self-location that was further modulated by stroking in the upwarddirection (toward the seen virtual body), whereas self-locationchanges for the Down-group were characterized by a generallyhigher self-location that was further modulated by stroking inthe downward direction (toward the seen virtual body) (see Fig-ure 2). For other effects see Supplemental Information.Our questionnaire results showed that predictable changes in

self-identification and illusory touch, depending on the factorsObject and Stroking, can be induced using robotic stroking inthe fMRI environment. As predicted, and in accordance withprevious work (Ehrsson, 2007; Lenggenhager et al., 2007,2009), statistical analysis of the questionnaires (SupplementalInformation) showed that, regardless of Perspective, responsesto Q3 (‘‘How strong was the feeling that the body you saw wasyou?’’) indicated stronger self-identification [F(4,80) = 13.5;p<0.01]with the virtual bodyduring synchronous (4.1) thanasyn-chronous stroking (2.3), and that responses to Q5 (‘‘How strongwas the feeling that the touch you felt was located where yousaw the stroking?’’) indicated stronger illusory touch [F(4,80) =13.5; p < 0.001] during the synchronous (8.1) than the asynchro-nous stroking (2.8; Figure 3; Supplemental Information).To summarize these findings, participants from the Up-group

experienced themselves to be looking up at the body above

Figure 2. Self-Location ManipulationGraphic representation of the experimentally induced changes in self-location and perspective in the Up- and Down-group. The position of the human bodies

represents the experienced position as indicated by the self-location task (mental ball dropping). The labels on the trousers indicate the experimental conditions.

The direction of the experienced first-person perspective (asmeasured through questionnaires) is represented by the direction of the feet and nose, as well as the

black arrows (pointing upward or downward). In both perspective groups, the body/synchronous condition leads to a drift in self-location toward the virtual body,

but in opposite directions depending on the experienced perspective.

(A) Thus, participants that had the impression of looking upward at the virtual body (Up-group) had increased response times (RTs) in the MBD task during the

synchronous as compared to the asynchronous stroking condition (represented by a blue line), indicating an elevation of self-location.

(B) Participants that had the impression of looking downward at the virtual body from an elevated perspective (Down-group) had decreased RTs in the MBD task

during the synchronous as compared to the asynchronous stroking condition (represented by a blue line) indicating a lowering of self-location. The drift in

self-location occurred in the direction of the experienced perspective (black arrows). RTs for the MBD task are plotted for each group as a function of the factors

Object and Stroking. Orange bars represent the synchronous stroking conditions and the red bars the asynchronous stroking conditions. Asterisks indicate

significant differences. Error bars indicate standard error. Note the differences between synchronous and asynchronous stroking conditions only in the body

conditions (not in the control conditions) and in opposite directions between Up- and Down-group. The MR-scanner is depicted only for illustration purposes

(participants were not asked to estimate the position of the scanner bed).

Neuron

Temporo-Parietal Junction Encodes Self-Location

366 Neuron 70, 363–374, April 28, 2011 ª2011 Elsevier Inc.

looking down (n = 5) at the virtual body located below them(i.e., incongruent with their physical perspective: Down-group,n = 11). Selected experiences of the Down-group participantsduring the synchronous and asynchronous body conditions arelisted in Table 1B. In summary, whereas several participantsfelt as if they were looking upward at the virtual body ‘‘abovethem’’ (Up-group), the remaining participants had the impressionthat they were looking down at the virtual body ‘‘below them’’(Down-group). This was found despite somatosensory, motor,and cognitive cues from our participants about their body posi-tion (they were lying on their back, facing upward, and werehead-constrained in the headcoil; Figure 1E; Supplemental Infor-mation). Based on these findings, we carried out data analysisconsidering each group of participants. This led to a 2 3 2 3 2factorial design with Perspective (up; down) as in-betweenfactor, and Object (body; no-body) and Stroking (synchronous;asynchronous) as within factors that were applied to the analysisof self-location, self-identification, and the fMRI data.

Robotically-Induced Changes in Self-Locationand Self-IdentificationStatistical analysis of RTs in theMBD task showed that self-loca-tion depended on Object, Stroking, and Perspective [significantthree-way interaction; F(1,20) = 4.4; p < 0.05]. Post hoc compar-isons showed that in the body conditions, the participants of theUp-group (participants experiencing themselves to be lookingupward at the visually presented body) estimated self-locationas higher (longer RTs) during the synchronous (1071 ms)comparedwith the asynchronous stroking (991ms; p < 0.01; Fig-ure 2A). The opposite pattern was found in the Down-group(participants experiencing that they were looking downward atthe visually presented body): lower self-location and shorter

RTs during the synchronous stroking (1047 ms) with respect tothe asynchronous stroking while viewing the body (1138 ms;p < 0.03; Figure 2B). No significant differences were foundbetween synchronous and asynchronous stroking in the controlconditions in both groups (all p > 0.2; see Figures 2A and 2B).Notably, RTs in the body conditions are modulated, withineach group, as a function of stroking and the experienced direc-tion of the first-person perspective. Thus, self-location changesfor the Up-group were characterized by a generally lower self-location that was further modulated by stroking in the upwarddirection (toward the seen virtual body), whereas self-locationchanges for the Down-group were characterized by a generallyhigher self-location that was further modulated by stroking inthe downward direction (toward the seen virtual body) (see Fig-ure 2). For other effects see Supplemental Information.Our questionnaire results showed that predictable changes in

self-identification and illusory touch, depending on the factorsObject and Stroking, can be induced using robotic stroking inthe fMRI environment. As predicted, and in accordance withprevious work (Ehrsson, 2007; Lenggenhager et al., 2007,2009), statistical analysis of the questionnaires (SupplementalInformation) showed that, regardless of Perspective, responsesto Q3 (‘‘How strong was the feeling that the body you saw wasyou?’’) indicated stronger self-identification [F(4,80) = 13.5;p<0.01]with the virtual bodyduring synchronous (4.1) thanasyn-chronous stroking (2.3), and that responses to Q5 (‘‘How strongwas the feeling that the touch you felt was located where yousaw the stroking?’’) indicated stronger illusory touch [F(4,80) =13.5; p < 0.001] during the synchronous (8.1) than the asynchro-nous stroking (2.8; Figure 3; Supplemental Information).To summarize these findings, participants from the Up-group

experienced themselves to be looking up at the body above

Figure 2. Self-Location ManipulationGraphic representation of the experimentally induced changes in self-location and perspective in the Up- and Down-group. The position of the human bodies

represents the experienced position as indicated by the self-location task (mental ball dropping). The labels on the trousers indicate the experimental conditions.

The direction of the experienced first-person perspective (asmeasured through questionnaires) is represented by the direction of the feet and nose, as well as the

black arrows (pointing upward or downward). In both perspective groups, the body/synchronous condition leads to a drift in self-location toward the virtual body,

but in opposite directions depending on the experienced perspective.

(A) Thus, participants that had the impression of looking upward at the virtual body (Up-group) had increased response times (RTs) in the MBD task during the

synchronous as compared to the asynchronous stroking condition (represented by a blue line), indicating an elevation of self-location.

(B) Participants that had the impression of looking downward at the virtual body from an elevated perspective (Down-group) had decreased RTs in the MBD task

during the synchronous as compared to the asynchronous stroking condition (represented by a blue line) indicating a lowering of self-location. The drift in

self-location occurred in the direction of the experienced perspective (black arrows). RTs for the MBD task are plotted for each group as a function of the factors

Object and Stroking. Orange bars represent the synchronous stroking conditions and the red bars the asynchronous stroking conditions. Asterisks indicate

significant differences. Error bars indicate standard error. Note the differences between synchronous and asynchronous stroking conditions only in the body

conditions (not in the control conditions) and in opposite directions between Up- and Down-group. The MR-scanner is depicted only for illustration purposes

(participants were not asked to estimate the position of the scanner bed).

Neuron

Temporo-Parietal Junction Encodes Self-Location

366 Neuron 70, 363–374, April 28, 2011 ª2011 Elsevier Inc.

Resp

onse

Tim

e (m

s)

SYNC

ASYNC

SYNC

ASYNC

mental ball dropping task

Stimulation Pattern

The participants are asked to imagine to drop a ball from the current imagined position and to report a time when the boll lands on the ground.


Ionta, S., Heydrich, L., Lenggenhager, B., Mouthon, M., Fornari, E., Chapuis, D., … Blanke, O. (2011). Multisensory mechanisms in temporo-parietal cortex support self-location and first-person perspective. Neuron, 70(2), 363‒74. doi:10.1016/j.neuron.2011.03.009


Shadow is my hand (Kanazawa and Kodaka, 2015-)

T_ADS + 新建築社｜レクチャーシリーズ@東大駒場Body-image reconstructionMoving rubber hand

Shadow attracts the physical hand upwards.

Please move your hand upward until where you think your hand hits the top screen.



Full body illusion







・・・

・・・


Self-touch illusion (Ehrsson, 2005)

that it touched the rubber hand and simultaneously touched the partic-ipant’s right hand, synchronizing the touches as exactly as possible. Thisstimulation elicits the illusion that one is touching one’s own hand.

Asynchronous. As in the previous condition, the experimenter movedthe participant’s left finger so that it touched the rubber hand andtouched the participant’s right hand. However, the touches on the twohands were alternated (i.e., they were asynchronous). Typically, thisstimulation did not elicit the illusion of self-touch during pilot testing.Instead, the participants felt both that they are touching an externalobject and that someone else is touching their right hand.

Incongruent. The experimenter moved the participants left index fin-ger so that it touched the brush and simultaneously touched the partici-pant’s right hand, synchronizing touches. Because the texture of thebrush was very different compared with the rubber hand and the partic-ipant’s own hand, no illusion of self-touch was typically elicited.

Rest. The participants lay at rest with their eyes closed and the righthand in a relaxed position without touching the rubber hand.

The movements of the participant’s left index finger were small andbrisk with a mean frequency of 1 Hz. Likewise, touches to the partici-pant’s right hand were applied with a mean frequency of 1 Hz. The timingof the touches was irregular (i.e., not isochronous) because pilot experi-ments had shown that this caused a more vivid illusion than regulartapping (Armel and Ramachandran, 2003). The experimenter listened toa metronome, which provided a base frequency of 1 Hz, and then variedthe interval between the touches from 0.5 to 1.5 s in a pseudorandommanner. Only the experimenter could hear the metronome. Two smallpotentiometers attached on the participant’s left index finger and theexperimenter’s right index finger registered the number of touches andthe amplitude of the movements. Importantly, the number of move-ments of the left index finger and the number of touches on the righthand were identical in all conditions. Likewise, the amplitude of thepassive left-finger movements was matched.

Each condition lasted 42 s. To indicate the onset of the illusion in theillusion condition, the participants were instructed to press a key padwith the left foot in a relaxed manner when they first started to feel theillusion that the hand they were touching was their own. When theypressed the key, they heard a brief tone in the earphones to match thetone presented in the other conditions (see below). The reported onset ofthe illusion was 9.7 ! 5.3 s (mean ! SD across participants; mean withinparticipant SD was 3.8 s) after the beginning of the trial, ensuring anaverage of over 32 s of stimulation per trial. In the asynchronous andincongruent conditions, the participants were required to make a keypress with their foot when they heard the tone. Thus, the foot responsewas matched in all three conditions. The timing of the presentation ofthese tones was yoked to the recorded times of the key response duringthe preceding illusion condition (Cogent 2000 software; WellcomeDepartment of Imaging Neuroscience, London, UK). After havingmade the key-press response, participants were instructed to relaxcompletely in all conditions. Analyses of the functional-imaging datawere performed during the period after the participants indicated thatthey felt illusion in the illusion condition, and during the period afterthe key press in the asynchronous and incongruent conditions. It isnoteworthy that, during these periods, the participants relaxed andperformed no active task.

After the scanning procedures, when participants were outside thescanner, they completed the rubber-hand questionnaire describing theillusion statement (“touching own hand”) (see Fig. 3D). The participantswere asked to rate the average sensation across the whole experiment foreach of the three stimulation conditions.

Acquisition and analysis of functional-imaging dataThe functional imaging was conducted with a Siemens Allegra 3.0 Tscanner (Siemens, Erlangen, Germany) to acquire gradient echo, T2*-weighted echo-planar images with blood oxygenation level-dependentcontrast (BOLD) (Kwong et al., 1992; Ogawa et al., 1992) as an index oflocal increases in synaptic activity (Logothetis et al., 2001). The imageparameters used were as follows: matrix size, 64 " 64; voxel size, 3 " 3mm; echo time, 40 ms, and repetition time, 2600 ms. A functional imagevolume comprised 40 contiguous horizontal slices of 2.5 mm thickness(with a 1.25 mm interslice gap), which ensured that the whole brain waswithin the field of view. Four experimental runs, each lasting 13 min,were performed for each participant. For each of these runs, we collected302 image volumes, with one volume being collected every 2.6 s. Thethree stimulation conditions were repeated four times in each run in apseudorandomized order. Each condition lasted for 42 s. Rest conditions(20 s long) were performed before and after each stimulation condition.A high-resolution, T1-weighted structural image was also collected at theend of the experiment [using a modified driven equilibrium Fouriertransform sequence (Ugurbil et al., 1993) with optimized parameters asdescribed by Deichmann et al. (2004)].

The fMRI data were analyzed using the Statistical Parametric Map-ping software (SPM2) (http://www.fil.ion.ucl.ac.uk/spm/; WellcomeDepartment of Imaging Neuroscience, London, UK) (Friston et al.,2004). The images were realigned to correct for head movements,

Figure 1. The somatic rubber-hand illusion. The experimenter moved each participant’s leftindex finger so that it touched the right rubber hand on the knuckle of the index finger, and atthe same time, the experimenter touched the participant’s right index finger on the knuckle,synchronizing the touches on the two hands as closely as possible. Tapping movements wereapplied to the two hands at 1 Hz, which, after a period of #10 s, elicited an illusion that theparticipants were touching their own hand (illusion). The illusion was not elicited in the controlconditions when asynchronous touches were applied (asynchronous), or if the participantswere touching a brush rather than the rubber hand (incongruent). The top panel illustrates thesetup with a sitting participant, as used in our initial psychophysical experiment. The bottompanel shows the setup used in the brain-scanning experiment. In the brain scan experiments(bottom), a small brush was attached to the lateral side of the rubber hand to be used in theincongruent control condition.

10566 • J. Neurosci., November 9, 2005 • 25(45):10564 –10573 Ehrsson et al. • Neural Correlates of Somatic Rubber-Hand Illusion

Ehrsson, H. H., Holmes, N. P., & Passingham, R. E. (2005). Touching a rubber hand: feeling of body ownership is associated with activity in multisensory brain areas. The Journal of Neuroscience : The Official Journal of

the Society for Neuroscience, 25(45), 10564‒73. doi:10.1523/JNEUROSCI.0800-05.2005


Ehrsson, H. H., Holmes, N. P., & Passingham, R. E. (2005). Touching a rubber hand: feeling of body ownership is associated with activity in multisensory brain areas. The Journal of Neuroscience : The Official Journal of

the Society for Neuroscience, 25(45), 10564‒73. doi:10.1523/JNEUROSCI.0800-05.2005

Uncrossed

Active

(Resting onsurface)

ROS

Crossedrubber finger

receptive finger

100 mm

vibration motor

acrylic stand

vibration motor

vibration motor+force sensitive resistor


Self-touch illusion assistance

We made an apparatus for inducing the self-touch illusion without any assistant.

Uncrossed

Active

(Resting onsurface)

ROS

Crossedrubber finger

receptive finger

100 mm

vibration motor

acrylic stand

vibration motor




self-touch assistance


administrating finger

receptive finger

Proprioceptive drift is stronger for the administrating hand than for the receptive hand.



ORIGINAL RESEARCH ARTICLEpublished: 17 June 2014

doi: 10.3389/fnhum.2014.00422

Crossed hands strengthen and diversify proprioceptivedrift in the self-touch illusionKenri Kodaka* and Yuki IshiharaGraduate School of Design and Architecture, Nagoya City University, Nagoya, Japan

Edited by:Burkhard Pleger, Max PlanckInstitute for Human Cognitive andBrain Sciences, Germany

Reviewed by:Michael Schaefer, UniversityMagdeburg, GermanyChristopher Gundlach, Max PlanckInstitute for Human Cognitive andBrain Sciences, Germany

*Correspondence:Kenri Kodaka, Graduate School ofDesign and Architecture, NagoyaCity University, 2-1-10, Kita-Chikusa,Chikusa-ku, Nagoya, 464-0083,Japane-mail: [email protected]

In the self-touch illusion (STI), some can feel that both hands are touching each othereven when they are separated actually. This is achieved by giving synchronized touches toboth hands. Because the STI involves both hands (an administrating hand and a receptivehand) of a single person, two types of proprioceptive drifts (PDs) simultaneously occur insuch a way that both hands are attracted to each other. It is known that the PD distanceis generally larger for the administrating hand than for the receptive hand when the twohands are uncrossed. However, it remains unclear why such an asymmetrical relationshipis observed universally. In this study, we conducted two types of experiment to inducethe STI. The first experiment involved four conditions combining a factor of “whetherthe hands are uncrossed or crossed” and a factor of “whether the administrating handis resting or active on the surface,” with the receptive (left) hand located at the body’smidline. The result demonstrated that crossing hands and resting on surface (ROS)induced the STI. Specifically, crossing hands enhanced the amount of PD distance by morethan two or three times. Moreover, it is interesting that strong PD with dominance of thereceptive hand, which did not appear in the uncrossed condition, was observed frequently.The second experiment collected seven “illusion-sensitive” participants from the firstexperiment, all of whom had a strong tendency to feel the self-touch, and examined theeffect of the location of the body midline on the PD when hands are crossed with theadministrating hand ROS. The result demonstrated that the dominant hand on the PDcompletely differed among participants, but was relatively stable over the midline positionand time in the same person. We also found that a small number of participants exhibitedquite a different pattern of the PD in the identical posture. On the basis of the results, weanalyze in detail how the dominant hand on the PD is determined in the STI.

Keywords: self-touch illusion, proprioceptive drift, multi-sensory integration, body image, cognitive dissonance

1. INTRODUCTIONThe self-touch illusion (STI), involving a proprioceptive senseand a sense of touch, was originally reported by Ehrsson et al.(2005). They originally named the STI the “somatic rubber handillusion” because it has been sometimes regarded as a variation ofthe rubber hand illusion (RHI). Although some people exhibit astriking STI, far fewer studies have explored the STI than the RHI.In the RHI (reported first by Botvinick and Cohen, 1998), onefeels as if one has a prosthetic hand as a part of one’s body whenan experimenter simultaneously strokes one’s occluded hand andthe prosthetic hand in one’s sight (placed near the occluded handin the same direction), where each stroked location is identicalanatomically. The RHI integrates a proprioceptive sense, a senseof touch and a vision into a single physical event in such a waythat the vision information is strongly weighted among the threetypes of senses. The best proof for this is that the proprioceptivesense for the occluded hand moves toward the prosthetic hand insight by a specific distance during the illusion. This phenomenonhas been called proprioceptive drift (PD). Several studies havedemonstrated that the PD positively correlates with an agreement

rating score on a questionnaire ownership statement like “I felt asif the rubber hand was my own hand” (e.g., Longo et al., 2008;Lopez et al., 2010; Kalckert and Ehrsson, 2012). It is instructive toconfirm that the other hand (lacking the experimenter’s stroke)plays no role whatsoever in inducing the RHI.

The participant’s vision is thus essentially involved in the RHI,whereas the STI is induced with the participant’s eyes blinded.A process of one hand’s being stroked by an experimenter inthe RHI also applies to the STI. In contrast, the stroke to theprosthetic hand in the RHI, which is non-sensical for a blindedperson, is replaced with a participant stroking the prosthetichand with the other hand. We call the stroked hand the “recep-tive hand” and the stroking hand the “administrating hand,”following the terminology of White et al. (2011). The strokewith the administrating hand should be simultaneous with thestroke on the receptive hand, and the two strokes should bein the same place anatomically. Therefore, the blinded partici-pant’s administrating hand’s movement has been generally guidedby the experimenter in inducing the STI (Ehrsson et al., 2005;White et al., 2011; Petkova et al., 2012; Aimola Davies et al.,

Frontiers in Human Neuroscience www.frontiersin.org June 2014 | Volume 8 | Article 422 | 1

HUMAN NEUROSCIENCE


ORIGINAL RESEARCH ARTICLEpublished: 17 June 2014

doi: 10.3389/fnhum.2014.00422

Crossed hands strengthen and diversify proprioceptivedrift in the self-touch illusionKenri Kodaka* and Yuki IshiharaGraduate School of Design and Architecture, Nagoya City University, Nagoya, Japan

Edited by:Burkhard Pleger, Max PlanckInstitute for Human Cognitive andBrain Sciences, Germany

Reviewed by:Michael Schaefer, UniversityMagdeburg, GermanyChristopher Gundlach, Max PlanckInstitute for Human Cognitive andBrain Sciences, Germany

*Correspondence:Kenri Kodaka, Graduate School ofDesign and Architecture, NagoyaCity University, 2-1-10, Kita-Chikusa,Chikusa-ku, Nagoya, 464-0083,Japane-mail: [email protected]

In the self-touch illusion (STI), some can feel that both hands are touching each othereven when they are separated actually. This is achieved by giving synchronized touches toboth hands. Because the STI involves both hands (an administrating hand and a receptivehand) of a single person, two types of proprioceptive drifts (PDs) simultaneously occur insuch a way that both hands are attracted to each other. It is known that the PD distanceis generally larger for the administrating hand than for the receptive hand when the twohands are uncrossed. However, it remains unclear why such an asymmetrical relationshipis observed universally. In this study, we conducted two types of experiment to inducethe STI. The first experiment involved four conditions combining a factor of “whetherthe hands are uncrossed or crossed” and a factor of “whether the administrating handis resting or active on the surface,” with the receptive (left) hand located at the body’smidline. The result demonstrated that crossing hands and resting on surface (ROS)induced the STI. Specifically, crossing hands enhanced the amount of PD distance by morethan two or three times. Moreover, it is interesting that strong PD with dominance of thereceptive hand, which did not appear in the uncrossed condition, was observed frequently.The second experiment collected seven “illusion-sensitive” participants from the firstexperiment, all of whom had a strong tendency to feel the self-touch, and examined theeffect of the location of the body midline on the PD when hands are crossed with theadministrating hand ROS. The result demonstrated that the dominant hand on the PDcompletely differed among participants, but was relatively stable over the midline positionand time in the same person. We also found that a small number of participants exhibitedquite a different pattern of the PD in the identical posture. On the basis of the results, weanalyze in detail how the dominant hand on the PD is determined in the STI.

Keywords: self-touch illusion, proprioceptive drift, multi-sensory integration, body image, cognitive dissonance

1. INTRODUCTIONThe self-touch illusion (STI), involving a proprioceptive senseand a sense of touch, was originally reported by Ehrsson et al.(2005). They originally named the STI the “somatic rubber handillusion” because it has been sometimes regarded as a variation ofthe rubber hand illusion (RHI). Although some people exhibit astriking STI, far fewer studies have explored the STI than the RHI.In the RHI (reported first by Botvinick and Cohen, 1998), onefeels as if one has a prosthetic hand as a part of one’s body whenan experimenter simultaneously strokes one’s occluded hand andthe prosthetic hand in one’s sight (placed near the occluded handin the same direction), where each stroked location is identicalanatomically. The RHI integrates a proprioceptive sense, a senseof touch and a vision into a single physical event in such a waythat the vision information is strongly weighted among the threetypes of senses. The best proof for this is that the proprioceptivesense for the occluded hand moves toward the prosthetic hand insight by a specific distance during the illusion. This phenomenonhas been called proprioceptive drift (PD). Several studies havedemonstrated that the PD positively correlates with an agreement

rating score on a questionnaire ownership statement like “I felt asif the rubber hand was my own hand” (e.g., Longo et al., 2008;Lopez et al., 2010; Kalckert and Ehrsson, 2012). It is instructive toconfirm that the other hand (lacking the experimenter’s stroke)plays no role whatsoever in inducing the RHI.

The participant’s vision is thus essentially involved in the RHI,whereas the STI is induced with the participant’s eyes blinded.A process of one hand’s being stroked by an experimenter inthe RHI also applies to the STI. In contrast, the stroke to theprosthetic hand in the RHI, which is non-sensical for a blindedperson, is replaced with a participant stroking the prosthetichand with the other hand. We call the stroked hand the “recep-tive hand” and the stroking hand the “administrating hand,”following the terminology of White et al. (2011). The strokewith the administrating hand should be simultaneous with thestroke on the receptive hand, and the two strokes should bein the same place anatomically. Therefore, the blinded partici-pant’s administrating hand’s movement has been generally guidedby the experimenter in inducing the STI (Ehrsson et al., 2005;White et al., 2011; Petkova et al., 2012; Aimola Davies et al.,


HUMAN NEUROSCIENCE

Kodaka and Ishihara Self-touch illusion with hands crossed

FIGURE 4 | Diagram for understanding new measures: attractivity anddirectivity. The attractivity indicates how strongly two fingers are attractedafter experiencing an illusion stage. The directivity measures the power

balance of the attraction, focusing on the difference between the two typesof proprioceptive drifts (PDs), whose sign is positive/negative if the PD of theadministrating hand is larger/smaller than that of the receptive hand.

A

C

B

FIGURE 5 | Results of attractivity, directivity, and agreement rating forfour types of hand postures (Uncrossed × Active, Uncrossed × ROS,Crossed × Active, Crossed × ROS) in Experiment I. Charts (A,B) depict anaverage of attractivity/directivity among 36 participants at every first or

second session. Chart (C) depicts an average of the questionnaire’sagreement rating for five statements among 36 participants, each of whichparticipated in two sessions for every posture. Error bars in all charts indicatestandard error.

× Active or Uncrossed × ROS, directivity had a moderatepositive correlation with attractivity, meaning that a strength-ened PD does not undermine the admin-dominant asymme-try (Spearman with n = 72, Uncrossed × Active: r = 0.238,

p < 0.03; Uncrossed × ROS: r = 0.314, p < 0.01). In contrast,there is no specific trend of the correlation in Crossed × Activeor Crossed × ROS in the entire group (Spearman with n = 72,Crossed × Active: r = −0.185, n.s.; Uncrossed ×ROS: r = 0.046,


Kodaka and Ishihara Self-touch illusion with hands crossed

FIGURE 4 | Diagram for understanding new measures: attractivity anddirectivity. The attractivity indicates how strongly two fingers are attractedafter experiencing an illusion stage. The directivity measures the power

balance of the attraction, focusing on the difference between the two typesof proprioceptive drifts (PDs), whose sign is positive/negative if the PD of theadministrating hand is larger/smaller than that of the receptive hand.

A

C

B

FIGURE 5 | Results of attractivity, directivity, and agreement rating forfour types of hand postures (Uncrossed × Active, Uncrossed × ROS,Crossed × Active, Crossed × ROS) in Experiment I. Charts (A,B) depict anaverage of attractivity/directivity among 36 participants at every first or

second session. Chart (C) depicts an average of the questionnaire’sagreement rating for five statements among 36 participants, each of whichparticipated in two sessions for every posture. Error bars in all charts indicatestandard error.

× Active or Uncrossed × ROS, directivity had a moderatepositive correlation with attractivity, meaning that a strength-ened PD does not undermine the admin-dominant asymme-try (Spearman with n = 72, Uncrossed × Active: r = 0.238,

p < 0.03; Uncrossed × ROS: r = 0.314, p < 0.01). In contrast,there is no specific trend of the correlation in Crossed × Activeor Crossed × ROS in the entire group (Spearman with n = 72,Crossed × Active: r = −0.185, n.s.; Uncrossed ×ROS: r = 0.046,


Results ＜手の交差が自己接触感覚誘起中のドリフトパターンに及ぼす効果＞2014.6.28-29　仙台国際会議場日本認知心理学会第12回大会

attractivity

*

**

(0,-1)

(0,1) (1,1)

(1,-1)(0,-1)

(0,1) (1,1)

(1,-1)

Uncrossed

(R LINEAR = 0.288, p<.01)2

2(R LINEAR = 0.429, p<.03)

Crossed

attractivity

dire

ctiv

ity

dire

ctiv

ity

ACTIVE

ROS (R LINEAR = 0.021, p=0.35)2

2(R LINEAR = -0.266, p=0.06)ACTIVE

ROS

A B

receptor-dominant drift

admin-dominant drift

Results ＜手の交差が自己接触感覚誘起中のドリフトパターンに及ぼす効果＞2014.6.28-29　仙台国際会議場日本認知心理学会第12回大会

attractivity

*

**

(0,-1)

(0,1) (1,1)

(1,-1)(0,-1)

(0,1) (1,1)

(1,-1)

Uncrossed

(R LINEAR = 0.288, p<.01)2

2(R LINEAR = 0.429, p<.03)

Crossed

attractivity

dire

ctiv

ity

dire

ctiv

ity

ACTIVE

ROS (R LINEAR = 0.021, p=0.35)2

2(R LINEAR = -0.266, p=0.06)ACTIVE

ROS

A B

admin-dominant drift

receptor-dominant drift


#Exercise

Experiencing the self-touch illusion in pairs.

“Jack unreachable hand”


#Exercise

Experience the proprioceptive drift

quickly with mirror

“hand teleportation”




CONTENTS






T_ADS + 新建築社｜レクチャーシリーズ@東大駒場Body-image reconstructionApplication

How does BOI contribute to

designing a virtual reality system ?


The body ownership is invented based on the multi-sensory correlation

Barbie doll IllusionEhrsson, H. H., Holmes, N. P., & Passingham, R. E. (2005). Touching a rubber hand: feeling of body ownership is associated with activity in multisensory brain areas. The Journal of Neuroscience : The Official Journal of the Society for Neuroscience, 25(45), 10564‒73. doi:10.1523/JNEUROSCI.0800-05.2005

https://www.youtube.com/watch?v=uhRbAjdEiGw/tv-shows/through-the-wormhole/videos/mysteries-of-the-subconscious.htm


The body ownership is invented based on the multi-sensory correlation mechanism.

Barbie doll IllusionEhrsson, H. H., Holmes, N. P., & Passingham, R. E. (2005). Touching a rubber hand: feeling of body ownership is associated with activity in multisensory brain areas. The Journal of Neuroscience : The Official Journal of the Society for Neuroscience, 25(45), 10564‒73. doi:10.1523/JNEUROSCI.0800-05.2005

https://www.youtube.com/watch?v=uhRbAjdEiGw/tv-shows/through-the-wormhole/videos/mysteries-of-the-subconscious.htm


BOI can move the imagined location of the body to where there is a correlated artificial body.

BOI can drastically change the characteristics of the original body.

Proprioceptive drift

Body transformation

How do BOI contribute to designing virtual reality system ?


Physical body

Proprioceptive drift

Artificial space

body image


Artificial space

Physical body

Proprioceptive driftBody transformation

programmable body

body image


Finger extending assistance (Mori and Kodaka, 2014-)

振動子

リニア・アクチュエータ

Arduino


Finger extending assistance

振動子


Arduino


in Exhibition


振動子


Arduino

Subject experiments showed giving correlated vibration is a requirement to induce a strong sense of extension and retraction, while the effect of a lack of a visual image was limited.

Finger extending assistance


Rubber hand pointer (Ishihara and Kodaka, 2013-)


The rubber hand pointer explores the creation of an alternative hand onto a 2D rectangle display. It moves on the display in sync with the hand movement, at the rear of the display.














vision

motion


④③


visionmotiontactile


④③



④③


visionmotiontactile



virtual skin



Many users experienced a tactile vibration, which occurred just at a point somewhere between thumb and index finger. In this sense, they felt as if two fingers were being united like a flipper.

virtual skin


CONCLUSION

(with rough script)


body reconstruction / architectural construction



Firstly, I think the principle of the body ownership illusion is an epoch-making invention because we got the first technique of intervening a personal body structure in human history. That is, we can dream brand-new structure of our body according to the principle of the body ownership illusion just like we plan the construction of new architecture freely.



We know the plan that won an architectural competition is not always constructed in the physical world. Sometimes it is called as “Unbuild”. We know It is mainly due to strong constraints in terms of the physical structure. Or it may be a matter of budget.



I think it is also applicable to the body-image reconstruction. We will not be able to accept all of the possible variations of the body-structure even when it satisfies the BOI principle. As the feasibility of the architectural construction depends on the physical constraints in real world, the feasibility of the body-image reconstruction depends on our perceptual constraints in our nervous system. That’s why I have attached great importance to exploring the field of human cognitive neuroscience.


Unique experience of “I”



There are many architectures in the real world. We can experience many beautiful constructions all over the world.

Similarly, there are also many bodies in the real world. We can experience seeing or touching various types of body appearances around me, in this room, or, all over the world.



On the other hand, when it comes to the body belonging to “I”, it is completely unique. The qualia of “my” body is completely different from that of others. It is applicable to all of the subjects.

I can see or touch many bodies around me, but I cannot experience their bodies as my belonging. Only I can experience as my belonging is my body.



I think it has been one of the biggest constraint around the subject. Probably, our body appearance or structure is strongly associated with our personality or how we view the world.

And this new technique based on the principle of the BOI has a potential of destroying this barrier and of extending our sensitivity to the world, which is the first in history.

In this sense, I think the project of the body-image reconstruction is significant.