別紙41 (課程博士(英文))Date of submission (month day, year)

January 8小,2021

DePιlrtment of conlPⅡter
Stud引ltlD Nunlber

Pplicant's nanle

D121823
SupeTvisors

Science Ⅲld EΠ即Πeenng

Michiteru Kitazaki

ShigekiNakauchi

Ryota Kondo

Abst"ad (Doctor)
Title ofThesis

Investigating a mini11〕al condition to induce i11Usm'y body ownership using vil'tuah'eality

Approx.80o wm'ds
Hulnans have a desire to have an ideal body.1t seems that we want to change 0山 Self・image orSelf・consciousness by chan部Πg tl)eir own body. HoweV引', it has not been understood ho、v to change theSelf・image.1 assumed that tl)e self・image could be updated by accumulating a temporary change of bodily
Self・consciousness. To investigate u〕is issue, it iS 打1'stly required to investigate how {o change bodily
Self・consciousness. sevel'al studies have shown that we can change our body u〕rough iⅡUsory body

OwnerS11ip i11duced by visual・tactile and visual・motor synchronizations. A recent invisible body study hasShown that stroking an 引npty space with a brush and stroking the subject's body at d]e salne time produce

body o、vnel'ship in an empty space. This finding S1唱gests a minimal condition for body ownership inVisual・tactile synchronization. However, a minimal condition in d〕e visual・mot01' synchronization is sti11

Undear.1t is one of tl〕e most fundamentalissues to identify minimal conditions for the body o、Nnel、shipbecause we can dlange our bodily self‑consciousness based on those minimal conditions. TherefoTe, theaim of this tl〕esis was to investigate a minimal condition to hlduce i11Usory body ownership byVisual・mot0↑ Synd11'onization.

Study l ahned to test whether the i11Usory o、vnership of an invisible body could be induced by u〕emetl〕od of visual・motor synchl'onicity and if the i11Usory invisible body could be experi引〕ced in 介ont of
the obsel'V飢' similal' to the fU11・body ownersl〕ip i11Usion. participants observed left and rigl]t whHe gloves
and socks in 介ont of them, at a distance of 2 1n, in a virtual room through a 11ead・mounted display. TheWhite σ10ves and socks wel'e synchronized with the observers' actions.111tl〕e experiments,、Ne tested theeffect of synd〕ronization, and compared this to a whole・body avatal', as measul'ing self‑10caHzation dl、ift.

Xve observed that visual hands and feet were S11fficient to induce i11Usory body o、vnel'ship, and tl]is effectWas as strong as using a whole・body avatar. The iⅡUsory o、Nnel'ship 、vas also supp01'ted by a S11ift ofProprioceptive self・10calization.

Study n aimed to develop a met110d to separate the body o、vn引'ship of fUⅡ・body from tl)at of bodyParts. S引'ambled stilnulithat disrupt tl〕e spatial relationsl)ip by randolnizing u〕e positions of body parts

from the originavnonnal body part lay011t stimulus was developed to induce only body part ownershゆ. wefound that participants felt as if the space between t11e gloves and socks 、vas their bodies only in tl〕enonna11ayout condition. They felt as if the gloves or socks were part of their bodies in both normal andScrambled conditions, but tlw feeling was strong引' in t11e nonna11ayout condition than in the scl'ambled
body condition.
Study 111 aimed to investigate 、vhether 、ve can have i11Usory ownershゆ of the invisible body with anelongated ann by presenting only hands and feet with modifying the position ofthe hands. As a result, theiⅡUsory body o、Nnersl〕ip to the body with a long aml was induced to an invisible body by synchronizing
Only gloves and socks with participants' movement. Learning of the invisible long ann gl'aduaⅡy changed

the reaching behavior to use tl〕e long aml more fl'equently t11an t11e nonnal al'm. Thus, the body scheme

Could be changed by changing the posjtion of the hand by maintaining t11e spatia11'elationsl〕ip of bodyPal'ts and visual・motm' synchronicity in t11e same directions between tl)e virt1旧l body and the actual body.

Study lv ailned to see 、vhether a re・association of the different body parts is induced by visual・motorSyncl〕rony in healthy adults. we focused on the re‑association of the real right t1川mb with a vil'tua11eft
ann because although the right thulnb and the left ann a↑e different in size and laterality, the dil'ecti01〕s of
their movements are similar.＼Ne found t11at partiCゆants felt as if tl〕eir right ulumb had become the leftanη and i11Usory body o、vnership ofthe vil'tua11eft aml was induced more in ule visual・motor syncl〕1'onous
Condition than h〕 the asynd]1'onous one.

To sulnmarize minimal conditions to induce body ownership by ule visual・motm' method, U)e fUⅡ・body
Hlusion needs a spatial relationship and the synchl'onous movement ofthe l〕ands and feet, while the body
Part ownership needs the synchl'onous movement of the body parts in motion dil、ections and angles. TheSize, sylnmetry, or laterality does not have to be identical bet、veen u〕e actual body and the virtual body.1t
has been proved thatthe body scheme can be changed by maintaining the minimal condition by modifying
Other parameters. TI]e final goalis to update the self・image by accumulatjng temporary changes in bodily
Self‑consciousness, and our findings should contribute to developing a method to change our bodily
Self‑consciousness.