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The role of bodily
self‑consciousness in episodic
memory of naturalistic events:
an immersive virtual reality study
Sylvain Penaud
*, Delphine Yeh , Alexandre Gaston‑Bellegarde & Pascale Piolino
*
Recent studies suggest that the human body plays a critical role in episodic memory. Still, the precise
relationship between bodily self‑consciousness (BSC) and memory formation of specic events,
especially in real‑life contexts, remains a topic of ongoing research. The present study investigated the
relationship between BSC and episodic memory (EM) using immersive virtual reality (VR) technology.
Participants were immersed in an urban environment with naturalistic events, while their visuomotor
feedback was manipulated in three within‑subjects conditions: Synchronous, Asynchronous, and
No‑body. Our results show that asynchronous visuomotor feedback and not seeing one’s body,
compared to synchronous feedback, decrease the sense of self‑identication, self‑location and
agency, and sense of presence. Moreover, navigating in the Asynchronous condition had a detrimental
impact on incidental event memory, perceptual details, contextual association, subjective sense
of remembering, and memory consolidation. In contrast, participants in the No‑Body condition
were only impaired in egocentric spatial memory and the sense of remembering at ten‑day delay.
We discuss these ndings in relation to the role of bodily self‑representation in space during event
memory encoding. This study sheds light on the complex interplay between BSC, sense of presence,
and episodic memory processes, and strengthens the potential of embodiment and VR technology in
studying and enhancing human cognition.
Like every workday, you are sitting in a cafe enjoying your coee when suddenly the memory of a brief con-
versation that took place in the same cafe comes to mind. In addition to recalling objective details about the
conversation, yourself, and the other people involved, as well as contextual information about the specic place
and time the event occurred, this meaningful representation also includes subjective vivid perceptual details,
emotional states, and thoughts, all bound together in a rich multidimensional reexperience1–4. Hence, your
memory comes with a sense of self. Indeed, when we remember a personal event from our past, we not only
undergo the experience of being the protagonist of a conscious episode but also of being the subject in the
memory5. According to Tulving, this subjective experience linked to the memory of everyday eventsthat occurred
at particular times and places is a hallmark of episodic memory (EM), which is closely related to what researchers
refer to as episodic autobiographical memory6. It is supported by autonoetic consciousness (i.e., the ability to
remember previous events as a sense of self-recollection), a specic form of self-consciousness that allows one
to mentally travel in time and reexperience specic events from one’s past. Moreover, autonoetic consciousness
distinguishes EM from semantic memory, which is supported by noetic consciousness (i.e., the ability to know
facts without recollection)7.
e central role of the self in EM retrieval raises questions about the inuence of self-consciousness during
the process of initial encoding8,9. Numerous studies have explored the importance of cognitive self-referencing
in the process of encoding and retrieving episodic memories, which is commonly referred to as the self-refer-
ence eect10,11. Over the years, self-reference has been shown to enhance the recall of objective and subjective
information12, and to promote associative memory (i.e., feature binding)13. However, other dimensions of self-
hood have been overlooked. Indeed, it has been emphasized that experiences assume an “I” who is the subject of
the ongoing ow of events14,15. is minimal sense of self is characterized by the pre-reective feeling of being a
self in a body, dissociated from its environment and providing a sense of presence in the world16,17. Over recent
OPEN
Université Paris Cité, Laboratoire Mémoire, Cerveau & Cognition (LMC2 UR 7536), Institut de Psychologie, 71 Ave
Édouard Vaillant, 92100 Boulogne-Billancourt, France. *email: sylvain.penaud@u-paris.fr; pascale.piolino@u-paris.
fr
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decades, convergent ndings from psychology and neuroscience have demonstrated that this minimal sense of
self is exible, plastic, and depends upon multi-sensory integration processes that combine bodily signals18–20.
Research has consistently demonstrated that simultaneous visual and tactile or motor stimulation that is both
spatially and temporally congruent can trigger body illusions dened as an incorporation of an extra-corporeal
body part or even an entire body into the sense of bodily-self21,22. Central features of body self-consciousness
(BSC) encompass the sense of identication with one’s own body (i.e., self-identication), the sense of being
located in space and time (i.e., self-location), the feeling of having control over one’s own body (i.e., agency) and
the centeredness of experience around the body (i.e., rst-person perspective)23.
Proponents of the embodied approach of EM argue that bodily and sensorimotor information is integrated
into the memory trace and later reactivated to support memory retrieval24–26. Several recent theoretical frame-
works on memory and the self have also stressed the inuence of bodily processes and BSC on autonoetic con-
sciousness and mental time travel27–32. For example, Prebble, Addis and Tippett argued that episodic recollection
“requires the sensory-perceptual and internal aspects of the original experience to be encoded from a subjective,
egocentric perspective”27. us, according to these authors, BSC is a necessary precursor of higher order and
extended forms of selood. In addition, a growing amount of clinical evidence indicates that compromised
BSC is associated with impairments in EM, as observed in individuals with schizophrenia or depersonalization
disorders27,33.
Noteworthy, the rapid growth and broad accessibility of computer-based 3D technologies have enabled
researchers to make signicant progress in understanding memory and the self. Devices such as Virtual Reality
(VR) provide many advantages for evaluating EM34,35. VR is a computer-generated immersive technology that
enables users to interact with a simulated world in a three-dimensional space, providing a sense of presence or
“being there”36,37. It allows researchers to create self-involving experiences and simulate expansive and ecologi-
cally valid environments that better capture how cognition operates in real-world settings over various popula-
tions, including children, young adults, and healthy and pathological aging38–42. Moreover, VR allows for the
presentation of complex stimuli such as 3D objects and everyday-like scenes that provide the opportunity for
evaluating the multidimensional and associative nature of EM in naturalistic settings while maintaining a high
degree of experimental control43. Accordingly, it has been shown that assessments of EM using VR were more
reliably associated with daily memory complaints in healthy aging and pathological populations and were more
sensitive to memory impairments than standard neuropsychological tools. Furthermore, knowledge acquired
in VR is more easily transferable to the real world44. VR has also established itself as an embodied technology,
allowing us to assess the inuence of the body on cognition45. For example, the enactment eect—the nding that
actively navigating in a virtual environment enhances EM compared to passively observing—generally improves
factual, contextual, and associative memory and the sense of remembering46,47. In more recent times, scientic
research has used the aordances of VR technology to manipulate the synchrony of bodily signals, producing
a complete bodily illusion over a virtual avatar perceived from a rst-person perspective (1PP). is form of
bodily illusion has been employed to investigate the role of body self-consciousness in EM48–53 (see Table1).
For example, Bréchet and colleagues used a head-mounted display to immerse participants in a sequence
of virtual rooms in which a collection of everyday-life objects were organized. During the encoding phase of
the experiment, participants were instructed to explore each room freely. Half of the subjects experienced the
integration of their physical body in the virtual environment from a rst-person perspective, while the other half
did not have any visible body representation. en, participants were immersed again in the same rooms for a
retrieval session in which they underwent a surprise forced-choice recognition task immediately or one hour
aer the encoding session. e results indicated that participants recalled fewer objects when the participants’
physical bodies were not visible during encoding, but only with a 1-h delay49. Additionally, in a subsequent
neuroimaging investigation, the same group demonstrated that observing one’s own body during the process
of encoding was linked to a higher connectivity between the brain regions associated with BSC and EM51. e
authors conclude that the multisensory stimulations associated with the perception of one’s body in 1PP are
essential for memory encoding.
More recently, Tacikowski etal. (2020)52 asked pairs of friends to complete a personality-trait judgment task
serving as an incidental encoding. e HMD device was connected to two sets of cameras so that participants
could see either their own or the friend’s body in a supine position from a rst-person perspective. Depending
on the experimental condition, the seen body was stroked with a wooden stick either synchronously or asyn-
chronously to manipulate sense of body ownership. Next, participants were asked to complete a body-ownership
questionnaire and underwent an unattended recognition task. eir results showed that participants who received
Table 1. Summary of the methodology and main ndings of previous studies. Synch, synchronous;
Asynch, asynchronous; V-T, visuo-tactile.
Studies Stimuli Encoding Method Main ndings
Tuena etal.48 Virtual scenes Incidental High vs. Medium vs. Low embodiment High > Medium and Low embodiment for source and hit rate (immediate)
Bréchet etal.49,50 3D objects Incidental Body vs. No-Body Body > No-body in a delayed recognition task
Gauthier etal.51 3D objects Incidental Body vs. No-Body Body = No-body in a recognition task (immediate and delayed)
Tacikowski etal.52 Trait-adjectives Incidental Synch vs
Asynch V-T stimulation Synch > Asynch in a recognition task (immediate)
Iriye and Ehrsson53 Videoscenes Intentional Synch vs
Asynch V-T stimulation Synch > Asynch for details, reliving (immediate), vividness, emotional intensity,
and condence (one week delay)
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synchronous stroking during the incidental learning phase performed better in the recognition task. Moreover,
changes in memory performances during the recognition task were positively correlated with rating changes in
body ownership between the synchronous and asynchronous conditions52.
Lastly, Iriye and Ehrsson53 presented a series of videos using a head-mounted display that depicted realistic
everyday life scenarios. Each scenario consisted of a stereoscopic view of a mannequin’s body seen from a supine
position and aligned with the participant’s actual body. During the scenarios, participants observed a wooden
stick repeatedly stroking the mannequin at a regular pace, either synchronously or asynchronously. Subsequently,
participants were administered a cued recall test immediately and aer one week to assess memory accuracy
for both central and peripheral details. Participants also rated their memories on seven-point Likert scales for
reliving, emotional intensity, vividness, and condence in memory accuracy. e authors found that synchronous
stroking improved memory accuracy regardless of the time delay between the encoding and retrieval of informa-
tion. Additionally, analysis of subjective measures indicated that participants remembered the encoded event
with a stronger sense of reliving immediately aer the encoding session and with higher emotional intensity and
condence aer a one-week delay. Taken together, these ndings demonstrate that the sense of owning a virtual
body observed from a rst-person perspective during encoding has an impact on the encoding of both objective
and subjective elements of EM. Nevertheless, various issues remain to be addressed.
First, the studies mentioned above mostly used simple stimuli such as words or 3D objects or intentional
encoding instructions that do not account for EM complexity and multidimensionality in everyday life, thereby
deviating from its functioning in real-world situations. To date, only one study has used full embodiment and
incidental encoding of virtual scenes48. is study from our team compared the impact of high, medium, and low
levels of embodiment on source memory and hit rate. e results indicated that participants in the high embodi-
ment condition trended towards superior performance compared to those in the medium and low embodiment
conditions. However, the sense of embodiment was not measured in all conditions, which makes it challenging
to link memory performance to bodily self-consciousness. Additionally, the study’s sample size was small, and
the materials used (Kinect) did not allow for perfect real-time tracking of bodily movements. Second, the stud-
ies above used simplistic encoding material, whichdoes not enable the complete examination of the associative
component of EM54,55. e integration of spatial and temporal information encoding, along with associative
mechanisms that bind items and contextual information, is at the core of EM56. Interestingly, recent studies
have shown that BSC may inuence both spatial57 and temporal processing58, as well as their association in the
hippocampus59. erefore, assessing contextual information is crucial to understand better how BSC aects
EM. ird, the studies mentioned above focused exclusively on the impact of body ownership. However, other
studies on BSC and EM have demonstrated that spatial, including sense of self-location59 and perspective9, and
agentive components of BSC may also play a role in EM encoding. Moreover, changes in self-location may occur
even when participants are embodied in rst-person60. Hence, a comprehensive evaluation that encompasses
all aspects of somatic self-awareness is crucial for gaining a better comprehension of its function in EM and its
distinct constituents. Lastly, the literature reported mixed ndings regarding the eect of delay and used dierent
types of memory tests and experimental designs, which makes it dicult to compare them.
In this experiment, we sought to explore the role of BSC on EM in conditions close to its expression in daily
life, examining incidental memory of new events experienced in a naturalistic controlled environment. We were
especially interested in assessing complex EM traces by considering the objective and subjective components
(event details, contextual information, and sense of reexperiencing). We used HMD to embody participants in
a personalized avatar seen from a rst-person perspective and manipulated visuo-motor feedback to modulate
BSC. Visuomotor stimulation has been widely used to induce body-part and full-body illusions61,62. Like visuo-
tactile stimulation, visuomotor stimulation relies on the spatiotemporal congruence between the seen and the
felt movements. However, in contrast to visuo-tactile stimulation, visuomotor stimulation conveys a variety of
bodily signals that goes beyond the integration of mere visual and tactile information. It provides information
on how the relative position and orientation of the real and fake bodies change over time, allowing individuals to
track how the body moves in relation to the environment. Moreover, visuomotor signals bear signicant signals
for the self-other distinction and have been shown to produce stronger and more stable changes in BSC (for a
review, see Kilteni etal.63). Finally, visuomotor stimulation is more ecologically valid than visuo-tactile stimula-
tion, as it more closely resembles the way in which we typically experience the world.
us, using a within-subjects design, participants were immersed in a personalized avatar’s body, either
synchronized, desynchronized, or occluded from the participant’s view during their walk in the virtual environ-
ment. In light of the results mentioned above, we hypothesized rst that participants in the Asynchronous and
No-Body conditions would report lower self-identication, self-localization, agency, and sense of presence than
those in the Synchronous condition. Second, for the memory tests, we hypothesized that participants would
recall fewer events and less contextual information and report a weaker sense of remembering and associated
phenomenology in the Asynchronous and No-Body conditions compared to the Synchronous condition. Finally,
as our study is the rst to contrast Asynchronous and No-Body conditions directly, there is no clear evidence to
anticipate there would be any dierences between the two conditions for any of our measures. Similarly, we did
not have expectations regarding the interaction between BSC and recall’s delay.
Method
Participants
A total of 38 young adults (11 males; mean age: 22.11yo ± 4.77) were recruited for this experiment. Two partici-
pants were removed from the pool due to cybersickness issues, and two others as they did not attend the second
session. us, the nal number of participants was 34 (10 males; m: 22.11yo (4.75)). All participants had nor-
mal or corrected visual acuity, declared no history of neurological and psychopathological disorders, and were
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blind to the purpose of the experiment. Participants were recruited from the University of Paris-Cité and from
the Relais d’Information sur les Sciences de la Cognition (RISC). All participants signed informed consent and
received course credits or a 20€ voucher in exchange for their participation. All the experimental procedures
and methods were approved by the Ethical Research Committee of Paris-Cité University (N° IRB: 0012021-107)
and have been conducted in accordance with the Declaration of Helsinki.
Material
e virtual environment was built in our lab using Unity 2019.2.5f1 soware. e environment was designed to
immerse participants in a close-to-daily-life urban landscape with rich ambient sounds, animations, and scenes
displayed on an HTC Vive Pro headset equipped with headphones (stereoscopic). We further circumscribed three
paths of approximately equal length (~ 5min) at dierent locations in the virtual environment (Fig.1a). A bright
white line was visible on the ground to delineate all paths and indicate the route to follow. Each path included
12 short audiovisual animated scenes representing everyday-life events for a total of 36 scenes (Fig.1b–d). e
scenes depicted characters, animals, or objects engaged in daily-life situations (e.g., a street musician playing the
guitar, a trashcan on re, or a group of friends saying “Hello”) and were evenly distributed around the white line
so that as many events were on the le, right, or in front of the participants. Animations started when participants
entered a dened area around the events and were played only once. ree mirrors were also placed respectively at
one-third, halfway, and two-thirds along each path. e purpose of these mirrors was to maintain multi-sensory
stimulation as body illusion may decay over time64 (see Procedure below and Fig.2a). Virtual avatars were cre-
ated using Character Creator 3. Each avatar was personalized by means of a headshot sent by the participants a
few days before the experiment. is was meant to increase participants’ identication with virtual avatars. e
photo was matched (gender, age, skin color, haircut, hair color, and facial traits) on the avatar’s body using the
Character Creator 3 headshot functionality. Participants’ body movements were tracked in real-time by means of
ve HTC-Vive sensors installed on participants’ heads, hands, ankles, and waists, and two base stations installed
at the corners of the experimental room.
Figure1. Study paths and events—(a) Map of the three dierent paths used in the study (red, blue, and green;
the yellow path is for training). (b) Virtual event of a man playing the guitar. (c) Virtual event of a trashcan on
re. (d) Virtual event of a dog barking aggressively. (e) First-person view of the mirror. Participants are asked to
stop in front of each mirror and raise each of their limbs once. (f) First-person view of the cellphone. Images and
map were obtained in the MC2 Lab using UNITY v2019.2.5f1 soware.
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Behavioral data acquisition
Free recalls were registered using audio recording soware for later scoring. e recognition tasks were imple-
mented using Neuropsydia soware65 and presented on a 15.6″ laptop screen.
Procedure
e experiment comprised two sessions approximately ten days apart (m = 9.34; sd = 3.7; min = 4, max = 21)
(Fig.2).
Encoding session
Upon arrival, participants signed an informed consent form and were given the task instructions. Participants
were told that they would be immersed successively in three dierent parts of a city and that they should visit
each as if they were planning to live there (incidental encoding). ey were asked to pay careful attention to each
path and the events that might occur in it as we would question them on which district they preferred and why
at the end of the experiment. Next, participants were fully equipped with VR sensors, controllers, and headset.
Figure2. Experimental design—the experiment has a within-participant design. All sessions started with an
induction phase in front of a virtual mirror. In the No-Body condition, there was no reection of the participant
in the mirror (see induction phase). Next, participants were assigned to one of the paths in a counterbalanced
order. Aer each navigation, participants completed the body-illusion, presence, and cybersickness
questionnaires. is procedure was repeated for each experimental condition. Once all the navigation tasks
had been completed, participants were administered an unattended free recall and recognition task, both
immediately and 10days aer the encoding session. Figure and maps designed in the MC2 Lab using UNITY
v2019.2.5f1 soware.
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Training
Before starting the experimental navigation, participants were rst immersed in a training environment to famil-
iarize them with the virtual city and the controls. e training session took place in a dedicated path similar to,
but not overlapping with, the path used in the experimental condition. e training comprised three events not
used for the experimental conditions and one mirror. Mirrors were marked with a ashing panel, and participants
were asked to stop in front of each mirror to raise each of their limbs once, rst looking at their reection in the
mirror, then looking directly at their limbs to actualize embodiment (Fig.1e). Moreover, a virtual cellphone was
added in the right hand of the virtual avatar during the training session and experimental navigations (Fig.1f).
Participants were told they could freely use the cellphone to take pictures in the environment by pressing a trig-
ger placed behind the right controller. e purpose of the cellphone was to encourage participants to use their
virtual bodies to maintain multi-sensory stimulation throughout the navigation.
Experimental session
Once the participants had completed the training, they were immersed in a virtual empty room equipped with
a large virtual mirror from a rst-person perspective. Each participant successively underwent each of three
experimental conditions in a counterbalanced order (see Induction phase and Fig.2). In the Synchronous Ava-
tar condition, the movements of the virtual avatar were visible and fully synchronized with the participant’s
head, arms, legs, and waist movement. In the Asynchronous Avatar condition, the virtual avatar was visible,
but a 650ms delay was introduced between the participant and the avatar’s movements. is delay was chosen
because a pilot study revealed that shorter asynchrony (i.e., 500ms) failed to dierentiate synchronous from
asynchronous ratings on the body-illusion questionnaire. Finally, in the No Avatar condition, the virtual avatar’s
body was not visible from the participant’s view. Importantly, in the Asynchronous condition, a 650-ms delay was
also introduced between the participant’s movements and the cellphone, as well as between the trigger push and
the camera’s click sound. In the No-Body condition, the cellphone was fully synchronized with the participant’s
movements; thus, it was visible at the location of the (not visible) participant’s avatar hand.
Induction phase
e induction phase was designed to induce the body illusion over the virtual avatar depending on the experi-
mental condition before experimental navigation started. To this end, participants were immersed in a room
equipped with a large mirror. e induction started with a calibration procedure to ensure the correct position-
ing of the avatar relative to the participant’s body. Next, participants were instructed to slowly raise each of their
arms and legs ve times in front of the mirror, once looking at their reection in the mirror and then looking
directly at the avatar’s body. For the No-Body condition, participants were asked to raise each of their limbs ve
times as if they were seeing them in the mirror and then as if they were seeing them directly. us, the induction
phase was identical in all conditions except for body visibility and synchrony.
Navigation
Aer completing the induction phase, participants were immersed in the assigned virtual path. Every naviga-
tion started with a new calibration. Aer each navigation, the participant completed three short questionnaires
assessing body illusion, sense of presence, and level of cybersickness.
Questionnaires
e body-illusion questionnaire included ve statements and was adapted from various existing questionnaires
to accommodate ratings on visible and invisible virtual bodies53,66 (see Table2). Q1 (“I felt I had control over
the body under the virtual reality headset/my head”), Q2 (“I felt that the body under the virtual reality headset/
my head was my body”), and Q3 (“I had the feeling that I was located in the same place as the body under the
virtual reality headset/my head”) assessed the sense of self-identication with the avatar, sense of agency, and
sense of self-location, respectively. C1 (“I had the feeling that I couldn’t feel my body anymore”), and C2 (“I felt
as if I had two bodies”) were control statements assessing compliance and suggestibility. Participants were asked
to rate each statement on a 7-point Likert scale (−3 = Strongly Disagree, 0 = Neutral, 3 = Strongly Agree). Sense
of presence was measured using a short version of the Igroup Presence Questionnaire (IPQ)67, and cybersickness
using the French version of the Simulator Sickness Questionnaire68.
Table 2. Body-illusion questionnaire—Q1, Q2, and Q3 assess self-identication, self-location, and sense of
agency respectively. C1 and C2 are control questions.
Body illusion questionnaire
Sometimes during navigation…
Q1 I felt I had control over the body under the virtual reality headset/my head (Agency)
Q2 I felt that the body under the virtual reality headset/my head was my body (Self-identication)
Q3 I had the feeling that I was located in the same place as the body under the virtual reality headset/my head (Self-location)
C1 I had the feeling that I couldn’t feel my body anymore (Control)
C2 I felt as if I had two bodies (Control)
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Retrieval session
Once all three navigations were completed, participants underwent an unattended free recall and recognition
test. e free recall test lasted 20min and was adapted from a Virtual Reality EM questionnaire previously
validated by our team9. Participants were asked to recall as many events as possible in the allotted time while
being recorded for later scoring. To assess contextual egocentric spatial and temporal information, participants
were further asked to indicate if the events took place on their right, on their le, or in front of them (egocentric
spatial situation) and had to roughly tell if the event happened at the beginning, in the middle, or at the end of a
given district (temporal situation). Finally, they were asked to provide as many specic details as possible about
each event. Details could be visual or auditive perceptual details, characters’ actions, or details pertaining to the
background of the scene.
For the recognition task, the 36 old events were presented in a random order mixed up with 18 new events for
a total of 54 trials. is ratio has been chosen because it accommodates better e new events were like the old
events regarding the types of content and complexity and could have been used interchangeably with the events
used in the navigations (e.g., A man playing football, two peoples laughing out loud in the street). e stimuli
were presented on the center of a white 15.6″ laptop screen. Background information was removed from the
events to avoid contextual cues. For each event, participants had to indicate if it was seen before in one of the three
paths by clicking on the right mouse button. When the event was correctly recognized, participants were further
asked to indicate the source (condition of encoding) and their degree of remembering (i.e., reexperiencing) on a
continuous scale (0 = I don’t remember, I know; 100 = I fully remember)69, which is a more ne-grained measure
of remembering experienced events than the classic dichotomous Remember/Know paradigm7 used for simple
material such as words70. Finally, each event with a remember score > 50 was presented again in random order.
To assess egocentric spatial memory, the participants were asked to indicate if the event happened on their le,
right, or in front of them. For temporal memory, three events pertaining to the same path were presented on the
upper part of the screen and numbered randomly from 1 to 3. e participants had to choose the correct order
of appearance of the events among all six possible orders noted in the lower part of the screen (e.g., 2–3–1).
We only asked for contextual information on the correct recognized events to avoid participants deducing old
and new events based on the temporal order task: because all the events presented in a single trial were part of
the same path, participants could have deduced the old event based on this information. For source memory,
participants were asked to indicate whether the event pertained to the rst, second or third navigation. Lastly,
participants assessed each past event they had previously recognized and associated to a Remembering score
greater than 50 with respect to rst-person perspective, vividness, condence in memory, emotional intensity
and memory ownership using a series of Likert 0–100 scales.
Finally, the participants completed an unattended free recall and recognition test in the same way approxi-
mately ten days later.
Scoring
For the scoring of the free recall and the recognition tasks, all the measures were computed for each of three
conditions (Synchronous, Asynchronous and No-Body): one point was attributed for every correctly recognized
or recalled event (what), spatial egocentric (where), and temporal information (when). Specic details for each
event were scored up to a maximum of three points (one point per detail). is maximum was decided based
on a pilot study. Importantly, details had to be specic to the remembered event (e.g., reporting that characters
in a scene representing a meditating group were in a lotus position was not considered specic as it is com-
mon to most meditating situations, whereas saying that one character was wearing a white and green shirt was
considered specic). Each score was then normalized by dividing it by the maximum attainable score and was
expressed as a percentage to account for individual performances. For example, the “What” score of a partici-
pant was determined by dividing the count of correctly retrieved events by the highest attainable score (i.e., 12).
In contrast, the scores for “Where,” “When”, “Details” and “Source” were computed by dividing the number of
correct responses for each of these categories by the number of “What” responses for that particular condition.
For the recognition task, we further calculated a d-prime score by subtracting the Z score of the false-alarm rate
from the Z score of the hit rate to assess overall performance.
To assess the richness of contextual information, we calculated a total associative memory score that cor-
respond to the mean amount of information category per condition in the free recall task : 1 point was given for
each information category associated with What (i.e., where, when, and at least one specic detail) and summed
up for each event out of a maximum of 3 points. For example, a participant recalling an event with its spatial
egocentric location and in the correct temporal order would have an associative memory score of 2 points. If
the participant further recalled at least one specic detail, this raised the associative memory score to 3 points.
We then calculated the mean amount of information per condition and expressed this score as a proportion of
the maximum possible given the “What” responses.
Statistical analysis
We performed a mixed model analysis that included the within factors of Condition (Synch, Asynch, and No-
Body). We also examined the interaction between Condition and Delay (Immediate or Delayed) for the memory
tests by adding Delay as an additional within factor. Mixed models are well suited for repeated measure designs
as they enable dependencies in the data to be considered. Models were computed using the lmer function from
the lme4 package in R studio version 4.0.4. When data residuals were not normally distributed (as assessed by a
Shapiro–Wilk test), we used a robust version of the lmer function named rlmer using the robustlmm package71.
Estimates, condence intervals, and p-values for xed eects estimates were computed using a Wald t-distri-
bution approximation using the parameters function of the performance package72. Marginal and conditional
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R2 were computed following the method prescribed by Nakagawa and Schielzeth73. Pairwise comparisons and
adjusted means were obtained with the emmeans package, version 1.7.574. e alpha level was set at 0.05, and
p-values were adjusted for multiple comparisons using the Holm-Bonferroni correction. e “Results” section
presents signicant results only. Non-signicant results are accessible in the supplementary material (see Sup-
plementary Material).
Results
Control check for conditions
We rst checked for potential dierences in cybersickness and navigation between conditions. To assess dier-
ences in cybersickness, we tted a hierarchical mixed model on the main and the sub-scores of the Simulation
Sickness Questionnaire (SSQ) with Condition as a xed eect and subjects as a random intercept. Importantly,
none of our subjects exceeded the SSQ threshold for cybersickness. Our model revealed no signicant predic-
tor of condition on the oculomotor sub-type of the SSQ. For the nausea sub-type, our model indicated that the
Asynchronous (β = 0.62, SE = 0.25, CI(95%) = [0.14, 1.10], t = 2.52, p = 0.012) and No-Body conditions (β = 0.58,
SE = 0.25, CI(95%) = [0.10, 1.06], t = 2.37, p = 0.018) were signicant positive predictors of nausea score (η2c = 0.83,
η2m = 0.007). Pairwise comparisons showed that participants in the Asynchronous condition had a higher feeling
of nausea compared to those in the Synchronous condition (Masynch = 3.84, SE = 0.564, Msynch = 3.22, SE = 0.564,
β = −0.6172, SE = 0.245, p = 0.0356) and No-Body condition (Mnob = −3.80, SE = 0.564, β = −0.5807, SE = 0.245,
p = 0.0358). For the total cybersickness score, our model indicated that the Asynchronous (β = 0.95, SE = 0.46,
CI(95%) = [0.06, 1.85], t = 2.08, p = 0.037) and the No-Body conditions (β = 0.91, SE = 0.46, CI(95%) = [0.02, 1.81],
t = 2.00, p = 0.046) were signicant positive predictors of total cybersickness score (η2c = 0.83, η2m = 0.005).
However, pairwise comparisons did not indicate any signicant dierences between conditions (all p > 0.05).
Regarding the oculomotor subtype, neither being in the Asynchronous (β = −1.12, SE = 2.71, CI(95%) = [−6.46,
4.23], t = −0.41, p = 0.681) nor in the No-Body condition (β = -0.56, SE = 2.66, CI(95%) = [−5.81, 4.70], t = −0.21,
p = 0.835) were signicant predictors of oculomotor cybersickness.
To assess dierences in navigation duration between conditions, we tted the same model with navigation
duration as the dependent variable and SSQ nausea as a covariate to control for dierences in cybersickness.
Analysis of navigation duration showed that being in the Asynchronous condition was a positive predictor of
navigation duration (β = 0.79, SE = 0.30, CI(95%) = [0.53, 1.05], t = 5.99, p < 0.001; η2c = 0.81, η2m = 0.085). Pair-
wise comparisons showed that navigation duration was higher in Asynchronous compared to the Synchronous
(Msynch = 8.44, SE = 0. 273, Masynch = 9.23, SE = 0. 273; β = −0. 7941, SE = 0.133, p < 0.0001) and the No-Body con-
dition (Mnob = 8.44, SE = 0. 273; β = 0. 8385, SE = 0.131, p < 0.0001). erefore, we decided to add the navigation
duration and SSQ Nausea sub-scores as two covariates in all the subsequent models.
Body illusion
First, to ensure that our experimental manipulation worked as expected, we conducted an analysis of the body-
illusion questionnaire responses aer each navigation. To analyze the body-illusions score, we tted a model with
Condition as a xed eect and Subjects as a random intercept. Based on our previous results, we also included
Navigation Duration and SSQ Nausea sub-scores as covariates in the model. Analysis of sense of body self-
identication showed that being in the Asynchronous (β = −1.09, SE = 0.23, CI(95%) = [−1.54, -0.64], t(203) =
−4.74, p < 0.001) and No-Body conditions (β = −1.00, SE = 0.22, CI(95%) = [−1.44, −0.56], t(203) = −4.50,
p < 0.001) were negative predictors of sense of self-identication (η2c = 0.50, η2m = 0.08). Pairwise comparisons
showed that participants in the Asynchronous condition had a higher sense of self-identication score than
participants in the Synchronous condition (Masynch = −0.687, SE = 0.242, Msynch = 0.402, SE = 0.239, β = 1.0887,
SE = 0.230, p = 0.0001), and the No-Body condition (Mnob = −0.600, SE = 0.240, β = 1.0022, SE = 0.223, p = 0.0001).
Our model also indicated that the Asynchronous (β = −1.00, SE = 0.18, CI(95%) = [−1.34, −0.66], z = −5.69,
p < 0.001) and No-Body conditions (β = −1.12, SE = 0.17, CI(95%) = [−1.45, -0.80], z = −6.75, p < 0.001) were
negative predictors of sense of agency (η2c = 0.67, η2m = 0.20). Post hoc pairwise comparisons indicated that
participants in the Asynchronous condition had a lower sense of agency than participants in the Asynchronous
(Masynch = 1.075, SE = 0. 227, Msynch = 2.049, SE = 0.224, β = − 0.973, SE = 0.173, p < 0.0001) and in the No-Body
condition (Mnob = 0.953, SE = 0.223, β = −1.095, SE = 0.163, p < 0.0001). Similarly, being in the Asynchronous con-
dition (β = −0.65, SE = 0.19, CI(95%) = [−1.02, −0.28], t = −3.49, p < 0.001) and No-Body condition (β = −0.44,
SE = 0.18, CI(95%) = [−0.79, −0.09], t = −2.46, p < 0.014) were negative predictors of sense of self-location
(η2c = 0.67, η2m = 0.15). e pairwise comparison conrmed this result and indicated a lower sense of self-loca-
tion for Asynchronous compared to Synchronous conditions (Maynch = 0.831, SE = 0.257, Msynch = 1.481, SE = 0.255,
β = 0.650, SE = 0.187, p = 0.0015) as well as a lower score in the No-Body compared to the Synchronous condition
(Mnob = 1.039, SE = 0.255, β = 0.442, SE = 0.179, p = 0.0276) (Fig.3A–C).
Analysis of the control questions revealed that being in the Asynchronous condition was a negative predic-
tor of the feeling of having no body (β = −0.29, SE = 0.13, CI(95%) = [−0.55, −0.03], t = −2.18, p = 0.029) while
being in the No-Body condition was a positive predictor (β = 0.26, SE = 0.12, CI(95%) = [0.02, 0.50], t = 2.14,
p = 0.032) compared to the Synchronous condition (η2c = 0.88, η2m = 0.02). Pairwise comparisons showed a trend
toward a higher score in the Asynchronous compared to the Synchronous condition (Masynch = −0.798, SE = 0.336,
Msynch = − 0.510, SE = 0.335, β = 0.288, SE = 0.132, p = 0.0583) and the No-Body condition (Mnob = −0.247,
SE = 0.334, β = −0.263, SE = 0.123, p = 0.0583), and also indicated a lower score in the Asynchronous compared
to the No-Body condition (β = −0.551, SE = 0.131, p = 0.0001). For the Two-bodies question, our model indicated
that being in the Asynchronous condition was a positive predictor (β = 0.56, SE = 0.23, CI(95%) = [0.11, 1.01],
z = −2.45, p = 0.014; η2c = 0.58, η2m = 0.03). Pairwise comparisons conrmed this result and revealed a higher
score for the Asynchronous compared to the Synchronous condition (Maynch = 0.149, SE = 0.281, Msynch = −0.716,
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SE = 0.278, β = -0.566, SE = 0.222, p = 0.0211) (Fig.3D, E) and the No-Body condition (Mnob = -0.821, SE = 0.279,
β = −0.672, SE = 0.223, p = 0.0079).
Sense of presence
Next, to test for dierences in the sense of presence, we analyzed each subscore of the IPQ independently while
controlling for the nausea subscore and navigation duration. e mixed model analysis revealed that the Asyn-
chronous condition (β = −0.51, SE = 0.12, CI(95%) = [−0.75, − 0.27], t = − 3.54, p < 0.001) and the No-Body
condition (β = −0.27, SE = 0.12, CI(95%) = [−0.50, −0.04], t = −2.27, p < 0.001) were signicant negative pre-
dictors of the general sense of presence. (η2c = 0.80, η2m = 0.07). Pairwise comparisons indicated a lower sense
of general presence in the Asynchronous compared to the Synchronous condition (Msynch = 4.17, SE = 0.241,
Masynch = 3.66, SE = 0.242, β = 0.509, SE = 0.124, p = 0.0001), and in the No-Body compared to the Synchronous
condition (Mnob = 3.90, SE = 0.241, β = 0.267, SE = 0.118, p = 0.0469). Moreover, pairwise comparisons also indi-
cated a trend toward a lower sense of general presence in the Asynchronous compared to the No-Body condition
(β = -0.242, SE = 0.125, p = 0.0525). For the Spatial Presence subscore, our model revealed that being in the Asyn-
chronous condition was a negative predictor of spatial presence (β = −1.16, SE = 0.42, CI(95%) = [−2.00, −0.30],
t = −2.75, p = 0.006; η2c = 0.75, η2m = 0.06). Pairwise comparisons indicated that the sense of spatial presence
was lower in Asynchronous than the Synchronous condition (Msynch = 20.9, SE = 0.726, Masynch = 19.7, SE = 0.730,
β = 1.164, SE = 0.424, p = 0.0181). Our model indicated similar results for ecological validity (β = −1.24, SE = 0.40,
CI(95%) = [−2.03, −0.44], t(203) = −3.06, p = 0.003; η2c = 0.77, η2m = 0.04). Pairwise comparisons indicated a
lower sense of ecological validity in the Asynchronous compared to the Synchronous condition (Msynch = 11.02,
SE = 0.732, Masynch = 9.79, SE = 0.736, β = 1.235, SE = 0.404, p = 0.0078). Lastly, the Psychological Implication sub-
score did not indicate any signicant dierences between conditions (p > 0.05) (Fig.4).
Memory performances
To analyze memory performance, we tted a model with Condition and Delay as a xed eect and Subject as
a random eect. For this model, in addition to the SSQ Nausea and Navigation Duration, we added the inter-
session duration as a covariate, as it may vary substantially between participants.
Free recall
Our model indicated that being in the Asynchronous condition was a negative predictor of the number of
events (What) recalled (β = −9.99, SE = 4.07, CI5(95%) = [−18.03, −1.96], t(199) = −2.45, p = 0.015; η2c = 0.30;
η2m = 0.07). Pairwise comparisons indicated a lower score in the Asynchronous compared to the Synchronous
Figure3. Results of the Body illusion questionnaire.
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condition (Masynch = 40.5, SE = 2.63, Msynch = 49.9, SE = 2.60, β = 9.4, SE = 2.93, p = 0.0047). ere was no eect of
the delay or interaction (Fig.5A).
Regarding Egocentric Spatial and Temporal Situation memory, our model did not indicate any signicant pre-
dictor. However, being in the Asynchronous condition was also a negative predictor of specic details (β = −9.59,
SE = 3.44, CI5(95%) = [−16.32, −2.85], t = −2.79, p = 0.005; η2c = 0.39, η2m = 0.06). e pairwise comparison
indicated that, on average, participants recalled fewer specic details in the Asynchronous compared to the Syn-
chronous condition (Masynch = 27.5, SE = 2.48, Msynch = 36.1, SE = 2.45, β = 8.57, SE = 2.47, p = 0.0016). e model
did not indicate any other main eect or interaction (Fig.5B).
Analysis of the mean total associative memory score revealed that being in the Asynchronous condition was
a signicant negative predictor of the total associative memory score. (β = −3.49, SE = 1.66, CI5(95%) = [−6.76,
−0.23], t(198) = −2.11, p = 0.036; η2c = 0.39, η2m = 0.06). Pairwise comparisons indicated a lower association
score in the Asynchronous compared to the Synchronous condition (Masynch = 16.6, SE = 1.008, Msynch = 20.3,
SE = 0.995, β = 3.71, SE = 1.19, p = 0.0063). No other result was signicant, and no eect of delay or interaction
was found (Fig.5C).
Recognition
Regarding the hit score, being in the Asynchronous condition was a negative predictor (β = −6.94, SE = 2.95,
CI(95%) = [−12.71, −1.16], t = −2.35, p = 0.019; η2c = 0.42; η2m = 0.07). Pairwise comparisons further showed
a lower hit score in the Asynchronous compared to the Synchronous condition (Msynch = 85.8, SE = 2.16,
Masynch = 79.5, SE = 2.19, β = 6.274, SE = 2.12, p = 0.0094), and a lower hit score in the Asynchronous compared to
the No-Body condition (Mnob = 85.2, SE = 2.17, β = −5.662, SE = 2.14, p = 0.0163) (Fig.6A). Regarding false alarms,
our model indicated that recall aer a 10-day delay was a positive predictor of the false alarm rate (β = 4.85,
SE = 0.94, CI(95%) = [3.01, 6.69], t = −2.35, p < 0.001; η2c = 0.59; η2m = 0.18). Post hoc comparisons conrmed
this result and indicated a lower False Alarm percentage in the Immediate compared to the Delayed condition
(Mimm = 1.83, SE = 0.929, Mdel = −6.91, SE = 0.928, β = −5.08, SE = 0.543, p < 0.0001). To assess overall p erformance
in the recognition task, we calculated a d prime score based on the hit and false alarm scores. Our model indicated
that being in the Asynchronous condition (β = −0.41, SE = 0.22, CI(95%) = [−0.84, 0.02], t = −1.89, p = 0.059)
or Delayed recall (β = −0.44, SE = 0.21, CI(95%) = [−0.85, −0.03], t = −2.08, p = 0.037) was a negative predictor
of the d’ score (η2c = 0.63; η2m = 0.08). Post hoc comparisons indicated a trend toward a lower d’ score in the
Asynchronous compared to the Synchronous condition (Masynch = −0.126, SE = 0.215, Msynch = 0.247, SE = 0.214,
β = 0.3722, SE = 0.157, p = 0.0544), as well as a trend toward a lower score in the Asynchronous compared to the
No-Body condition (Mnob = 0.193, SE = 0.214, β = − 0.3188, SE = 0.159, p = 0.0897). Moreover, the d’ score was
higher in the Immediate, compared to the Delayed condition (Mimm = 0.30, SE = 0.204, Mdel = -0.09, SE = 0.204,
Figure4. Results of the Igroup presence questionnaire.
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β = −0.39, SE = 0.122, p = 0.0014) (Fig.6B). Our model did not reveal any eect of delay or interaction between
delay and condition.
Regarding contextual information, our model indicated that being in the No-Body condition was a nega-
tive predictor of egocentric spatial recall at 10days delay (β = −10.91, SE = 5.34, CI(95%) = [−21.44, −0.37],
t(199) = −2.04, p = 0.043) (η2c = 0.31; η2m = 0.09). Post hoc comparisons indicated a lower score in the No-Body
compared to the Synchronous condition (Mnob = 57.5, SE = 3.11, Msynch = 67.1, SE = 3.10, β = 9.631, SE = 3.79,
p = 0.0361) as well as a trend toward a lower score in the Asynchronous compared to the Synchronous condition
(Masynch = 59.3, SE = 3.13, β = 7.805, SE = 3.84, p = 0.0873) at 10days delay only (Fig.6C). Analysis of temporal
order and source recognition percentage did not reveal any signicant main eect or interaction (All p > 0.05; See
Supplementary TableS4). We did not nd any other eect of delay or interaction between delay and condition.
Lastly, we did not nd any signicant predictor regarding source condition (all p > 0.05) (Fig.6D).
For sense of remembering, our model showed that recall at 10days was a negative predictor of sense of
remembering (β = −8.08, SE = 2.65, CI(95%) = [−13.30, −2.86], t(199) = − 3.05, p = 0.003). Moreover, our
model revealed a signicant interaction between Condition and Delay such that being in the No-Body condi-
tion (β = −7.58, SE = 3.74, CI(95%) = [−14.97, −0.20], t(199) = −2.02, p = 0.044) was a negative predictor of
sense of remembering at 10days delay only (η2c = 0.64; η2m = 0.23). e post hoc test revealed that the sense
of remembering was lower for the No-Body compared to the Synchronous condition (Mnob = 63.5, SE = 2.66,
β = 8.137, Msynch = 71.6, SE = 2.66, SE = 2.66, p = 0.0078) and in the Asynchronous than in the Synchronous condi-
tion (Masynch = 65.2, SE = 2.68, β = 6.420, SE = 2.71, p = 0.0381), but only aer a 10-day delay (Fig.6E).
Lastly, we analyzed mean subjective ratings of the events associated with a sense of remembering. Our
model indicated that recall at 10days was a negative predictor of memory Vividness, Condence, Perspective,
and Emotional intensity. Post hoc tests indicated a higher score for Immediate compared to Delayed recall for
all measures (all p < 0.5, see Supplementary TableS4). No other eect of condition or interaction was found.
Discussion
e role of bodily self-consciousness (BSC) in episodic memory (EM) has been the subject of increasing inter-
est in recent years due to growing evidence suggesting that the body plays a crucial part in memory formation
and retrieval8,9. In this study, we aimed to investigate further the impact of BSC on the incidental encoding of
Figure5. Results of the What, specic details and total association score of the EM free recall.
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experienced specic events and its contribution to the objective, subjective, and associative components of EM
by using immersion in a naturalistic virtual environment. By manipulating visuomotor synchronicity and body
visibility to induce a body illusion over a personalized virtual avatar, participants navigated through a rich, mul-
timodal naturalistic virtual environment in which a series of ecological, close-to-daily-life events were arranged.
Our results revealed that synchronous visuo-motor stimulation positively enhances both objective and subjective
components of EM compared to the Asynchronous condition and, to a lesser extent, the No-Body condition. In
this discussion, we will rst explore how our manipulations aected BSC in the three conditions, then we will
focus on the comparison between Synchronous and Asynchronous conditions, followed by a discussion of the
No-Body condition.
BSC manipulation check and sense of presence
e results of our body-illusion questionnaire conform to our rst hypothesis as the participants reported a lower
sense of self-identication, a lower sense of agency, and a lower sense of being located within the avatar’s body
in the Asynchronous and No-Body conditions compared to the Synchronous condition. ese results conrm
that our manipulation worked as expected and show that manipulating visuo-motor feedback on a virtual avatar
eectively modulated all three components of BSC. Noteworthy, the self-identication score was positive only in
the Synchronous condition, suggesting that it was the only condition where participants experienced a positive
sense of identication with the virtual avatar. In contrast, sense of self-location and sense of agency scores were
positive in all three conditions. For the No-Body condition, the positive agency score may be attributed to the
presence of the virtual cellphone. e cellphone provided a minimal visual representation of the participants’
bodies in space, which may have helped them feel more embodied and experience a better sense of their actions.
Additionally, the cellphone was synchronized with the participants’ movements, which may have helped them
to feel more in control of their actions and to have a stronger sense of agency. For the Asynchronous condition,
we expected sense of agency scores to follow self-identication as a sense of agency is known to depend on the
comparison between the expected and actual multi-sensory consequences of motor commands, including their
temporal dynamics75. us, as the visual feedback delay increases, the sense of agency should be diminished
or abolished76. However, in our study, visuo-motor delay was kept constant, allowing participants to adjust to
the altered temporal gap between their actions and consequences, thereby increasing their sense of agency over
Figure6. Results of the recognition tests.
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time77. Of note, although body parts and trunk movements were desynchronized, head movements and naviga-
tion controls remained synchronized with participants’ actions, which may have inuenced participants while
judging feelings of control over the virtual avatar. Nevertheless, large dierences in questionnaire ratings between
conditions may reect various degrees of condence or vividness of the illusion. Together, these results support
the role of the multi-sensory integration of bodily signals for BSC and show that visuo-motor congruency may
inuence not only the sense of self-identication but also the sense of control and sense of self-location in space
over an avatar seen from the 1PP.
Turning to the sense of presence, participants in the Synchronous condition had a higher feeling of general
presence compared to the Asynchronous and No-Body conditions, as well as a higher sense of spatial presence
and ecological validity compared to the Asynchronous but not the No-body condition. General presence refers
to the subjective feeling of “being there” and measures the psychological immersion of the participants in the
virtual environment. It has been argued that looking down at one’s body is strong evidence of being present in a
given environment78. is result aligns with this claim and shows that multi-sensory congruency of body signals
and body visibility are both important for sense of presence. Spatial presence, in turn, relates to the feeling of
being physically present in a given environment78 and is tightly linked to body representation and the possibility
of acting upon the immediate environment. Interacting with the environment requires monitoring the position
of one’s body and eectors in relation to external objects79. Sense of body in space relies heavily on multi-sensory
integration processes that blend spatial information about body position from various modalities80. us, one
possible explanation for this result is that contrary to the No-Body condition, the discrepancy between visual
and proprioceptive information in the Asynchronous condition may have prevented correct monitoring of the
participant’s body in space due to ambiguous or conicting body representations and disrupted sensorimotor
coupling between the body, the self, and the world, leading to a lower sense of spatial presence and ecological
validity. In support of this, a detailed inspection of our body illusion questionnaire revealed that the feeling of
having no-body decreased from the No-Body to the Asynchronous condition. In contrast, participants in the
Asynchronous condition had a higher feeling of having two bodies and a lower feeling of being in the avatar’s
body. Another interpretation is that a lower sense of spatial presence and ecological validity results from higher
cybersickness in the Asynchronous condition. However, in this case, we would have expected a similar pattern
of results in the No-Body condition. Moreover, this result remains even when dierences in cybersickness were
controlled for.
Together, these results link the sense of bodily-self in space and a sense of presence. A strong sense of bodily
self in space, as produced by synchronous visuomotor feedback, is associated with higher immersion, as well
as a high psychological and physical sense of being “here” in the virtual environment. As sense of bodily-self
decreases, the sense of psychological implication decreases while the sense of spatial presence and ecological
validity remains. Lastly, a weak or conicting bodily-self representation impairs both the psychological and
physical sense of presence, as well as the participant’s feeling that the virtual environment is real. We will next
discuss the relevance of these results for EM encoding.
BSC and multifaceted episodic memory performance
e ndings of the present EM tests oer partial support for our original hypotheses. Our results indicate that
participants in the Asynchronous condition had a lower score on nearly all memory tests than those in the
Synchronous condition. However, participants in the No-Body condition showed only slight deterioration in
a few tests compared to those in the Synchronous condition. Consequently, our discussion will rst focus on
the dierences between the Synchronous and Asynchronous conditions before analyzing the results from the
No-Body condition separately.
e impact of Synchronous vs. Asynchronous condition
Concerning factual information, our results corroborate the ndings of previous studies. We found that par-
ticipants recalled fewer new events (i.e., specic scenes encountered during navigation) in the Asynchronous
condition, regardless of the delay interval, and across both free recall and recognition tasks. More specically,
it was demonstrated through a lower proportion of event recall in the free recall task, a lower hit rate and a
trend toward a lower d’ score in the recognition task, irrespective of the recall delay. is nding is consistent
with previous studies showing that asynchronous visuo-tactile stimulation diminishes memory performance
for factual information using words52, 3D objects49,50, and complex video scenes53, and extends this result to the
incidental encoding of ecological events in naturalistic settings.
In addition to these results, our study reports several novel ndings regarding the inuence of bodily self-
awareness on objective and subjective components of episodic memory.
First, we found that the free recall of events (What) was less oen associated with multifaceted informa-
tion(associativememoryscore), including contextual (Where, When) and specic details, in the Asynchronous
condition compared to the Synchronous condition, showing for the rst time that BSC may play a crucial role
in the richness of EM traces (multiple features association). In fact, the Asynchronous condition signicantly
reduced the number of specic details recalled regardless of retention duration compared to the Synchronous
condition. e present ndings replicate those of Iriye and Ehrsson53, who found that asynchronous visuo-tactile
stimulation during the encoding of an everyday-like scene decreased memory for central and peripheral details
of the scene. Here, we extend these results to encoding ecological events in a naturalistic virtual environment
in line with the view that the self-related bodily cues in the environment increase the event’s self-relevance of
an experienced scene. us, the interaction between the BSC system and the memory system may help bind
the various dimensions of experience into a well-integrated representation of the event in memory encoding,
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reinstatement, and long-term consolidation81,82. In support of this claim, Bréchet etal.50 found that seeing one’s
own body in a given environment retroactively strengthened memories of material encoded in this environment.
Concerning more specically spatial information, our results from the recognition tests indicated that fac-
tual information tended to be less frequently linked to egocentric spatial information aer a 10-day delay in the
Asynchronous than the Synchronous condition. Remarkably, being in the Asynchronous condition altered the
egocentric spatial reference frame57. According to the Scene Construction Hypothesis, reconstructing space is
essential to EM and mental time travel76. Previous studies have shown that manipulating BSC modulates space
perception, such as size estimation or depth perception. More recently, it has been demonstrated that changes
in BSC are also associated with decreased spatial memory and spatial navigation performances. For example,
Bergouignan and colleagues found that discrepancies between physical and seen body position during memory
encoding may disturb binding processes in the hippocampus and impair EM for spatial, temporal, and emo-
tional information59. It suggests that sense of bodily-self in space is essential for the EM of naturalistic events in
context. In another study, Moon etal.60 immersed participants in a large virtual empty space where participants
had to memorize the position of 3D objects while navigating freely. Notably, during the navigation, participants
could see the body of a virtual mannequin in a supine position matching their physical body being stroked either
synchronously or asynchronously. At retrieval, participants were again placed in the virtual environment and
asked to navigate to the previous position of the object memorized. ey demonstrated fewer distance errors
and shorter path navigations when the participants saw the avatar associated with synchronous sensorimotor
stimulation60.
Because of a ceiling eect, we failed to nd signicant dierences between our conditions for egocentric
spatial information in the free recall task. is means that when participants had to draw on internal resources
to recall an event, it was quasi-systematically associated with correct egocentric spatial information. Future
research could extend these investigations to dierent aspects of spatial information connected to EM, including
visuospatial and allocentric measures (e.g., location of events on a map). Otherwise, there was no signicant
eect of conditions regarding specically temporal information in the free recall and recognition tasks assessing
the temporal order of events. ese results depart from a recent study showing that BSC may modulate time
perception58. However, this study investigates time duration estimation rather than sequential event memory,
which was particularly dicult for our participants. Similar to spatial measurements, further studies could
examine dierent types of temporal information to better understand the role of BSC in the precision of EM
for temporal information83. Lastly, we found no dierence between conditions regarding source memory. Our
instructions directed participants’ attention to the environment (which route) rather than their bodies (which
condition). Consequently, it seems that none of our participants targeted visuo-motor changes as the primary
goal of the experiment, leading to poor remembering of the condition. Future studies should explore additional
measures to assess source information in greater detail.
Secondly, regarding the subjective dimensions of EM, we found that participants reported a higher sense
of remembering (i.e., autonoetic recollection) in the Synchronous compared to the Asynchronous condition at
delayed retrieval. Immediately aer the rst-person incidental encoding in VR, the sense of remembering was
similar, whatever the BSC condition, but with a retention delay, there was a lower decrease in memory phenom-
enology in the Synchronous condition. is result supports previous VR studies demonstrating a link between
body self-awareness and autonoetic consciousness for immediate and delayed recall51,53. For instance, Gauthier
and colleagues used functional neuroimaging to measure changes in connectivity aer encoding a virtual scene
composed of a series of objects. ey showed that post-encoding changes in connectivity strength between
cerebral regions associated with BSC and the medial temporal lobe region correlated with the participant’s
autonoetic recollection rating at one month delay only when the participant’s virtual body was visible during
encoding51. Iriye and Ehrsson found that synchronous visuo-tactile stimulation over a virtual body seen from
the rst-person perspective enhanced the sense of reliving immediately aer encoding and memory vividness,
condence, and emotional intensity at one week of delay53. However, their most recent study has not replicated
these ndings84. Regarding memory phenomenological scales, we did not reproduce all of Iriye and Ehrsson’s
results, as we only found a main eect of delay on the memory vividness, condence, emotional intensity, reliv-
ing, and rst-person perspective, but no eect of condition or interaction. One relevant explanation is that
compared to Iriye and Ehrsson, our phenomenological evaluation of event memory retrieval was only proposed
to participants with a remembering state attested by a score above 50 on the remembering scale. Consequently,
all the participants who completed the phenomenological scales had a high level of remembering, which may
have erased subtle dierences in memory phenomenology in our participants.
Altogether, the present results reinforce our prior research on the eect of self-awareness on EM of naturalistic
events using virtual reality9,47,85 and extend previous studies (see Table1) revealing that BSC plays a crucial role
in incidental encoding of naturalistic events supporting associative memory and autonoetic consciousness at
retrieval, thus the objective and subjective properties of EM. ese ndings suggest, for the rst time, that the
perception of one’s body in space may impact the level of detail in incidental memories of real-life events. e
result of this study provides support to the claim that the integrated properties of self-perception may extend
to the most basic form of bodily self-consciousness and improve the formation and retention of distinctive
memory traces.
e special case of the No-Body condition
In addition to Synchronous and Asynchronous conditions, we also investigated a condition where the virtual
body was removed from the participant’s rst-person view. To date, no studies have directly compared Synchro-
nous, Asynchronous, and No-Body conditions. Our results indicated that the No-Body condition is intermedi-
ate between the Synchronous and Asynchronous conditions. Specically, we found that memory performance
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was better in the No-Body condition than in the Asynchronous condition regarding hit rates in the recognition
task. Conversely, scores in the No-Body condition for egocentric spatial memory and sense of remembering
were lower than in the Synchronous condition when the recall was delayed. No further dierences were found
regarding the other scores.
Before delving deeper into the possible reasons for this nding, it is essential rst to discuss the nature of
our No-Body condition. When participants are immersed in a virtual environment without a visible body, they
must rely on proprioceptive and motor information to monitor the spatial position of their body. However, the
lack of visual feedback for sensorimotor information may constitute a surprise event for the brain that may lead
to a decrease in BSC. is is consistent with our data and ndings showing that asynchronous visuo-tactile and
visuomotor stimulation can reduce the sense of identication with one’s own body86. Additionally, proprioceptive
representations of the body in space are known to be less reliable than visual representation, which can further
impair cognitive operations that rely on BSC. Only a few studies have investigated the impact of synchronous
visuo-motor stimulation on memory performance compared to a No-Body condition49–51, but they have reported
inconsistent results. Bréchet etal.49,50 found that occluding participants’ bodies while encoding objects in a vir-
tual room decreased memory performance in a subsequent surprise recognition task. However, Gauthier etal.51
failed to replicate this result using a similar procedure. Moreover, as a subjective BSC measure was not assessed
in these studies, it is impossible to ensure that changes in memory performances were specically related to
changes in the sense of bodily self.
Nevertheless, a signicant dierence between our study and the studies cited above is to be noted. As men-
tioned above, participants in each condition, including the No-Body condition, were equipped with a virtual
cellphone placed in their right-hand during navigation. is procedure was chosen to motivate participants to
use their virtual bodies and to ensure the comparability of our experimental conditions. Although the avatar’s
body was occluded in the No-Body condition, the cellphone moved congruently and synchronously with the
participant’s physical hand. us, congruent spatial and temporal feedback from the cellphone may have been
sucient to help participants to build a more stable and accurate bodily-self representation in the No-Body
compared to the Asynchronous condition, as shown by their higher sense of spatial presence. Indeed, it has
been demonstrated that synchronous multi-sensory stimulation may elicit a sense of self-identication over an
invisible body66. Similarly, Kondo etal.87 found that the mere perception of spatially congruent but disconnected
hands and feet might suce to create a sense of self-identication, sense of agency, and sense of self-location
over the corresponding interpolated body. us, we suggest that minimal visuo-motor cues, as provided by the
spatially congruent position of the cellphone, may have been sucient for participants to form a weak but coher-
ent representation of the body in space that helped them to construct an organized and integrated memory trace
from encoding and in turn, helped them to form a coherent representation of the event in memory.
An alternative explanation is that the additional cognitive resources required to adapt to the desynchroniza-
tion of visual and motor information in the Asynchronous condition may have specially altered event encoding.
Consistent with this claim is that participants in the Asynchronous condition exhibited longer navigation dura-
tion, which is a consequence of higher cognitive load40. However, by including this parameter as a covariate in
our analysis, we accounted for a portion of the dierences in cognitive load between our conditions. Furthermore,
the extent to which this explanation is valid is unclear. For example, adaptation time to a mismatch can be very
rapid, with some studies reporting adaptation aer only a few trials88 Moreover, it has been shown that visuomo-
tor adaptation rate is robust to cognitive load89. us, it is unlikely that visuo-motor adaptation was disturbed
by the experimental task. In the present study, participants in the Asynchronous condition performed nearly 80
movements during the induction phase, which is likely to have been sucient for adaptation to occur. Finally, an
explanation centered on executive functions cannot explain the lower performance in remembering and egocen-
tric spatial memory in the No-Body condition. erefore, while the present study does not completely rule out
the possibility that cognitive demands played a role in the impairment in event encoding in the Asynchronous
condition compared to the No-Body one, it is likely to have played a minor role. Nevertheless, further research
is needed to determine the extent to which visuomotor adaptation can account for the eect of BSC on EM.
New direction for a theoretical framework of the eects of BSC on EM
Our study unravels the links between sense of bodily-self in space and EM of naturalistic events by highlighting
that BSC supports memory performance (i.e., number of events, richness of details, associative information,
and discriminability), and preserves contextual information and sense of remembering over time. How can BSC
account for these results?
Neuroimaging studies have identied a network of interconnected brain regions, including frontoparietal,
temporoparietal, and subcortical areas associated with BSC, with dierent sub-networks supporting spatial
and self-components of BSC90. ese regions dynamically integrate available sensory signals from dierent
modalities to build a coherent sense of being a self in a body and have been associated with a variety of functions
including spatial navigation, EM and sense of self in space91–93. Interestingly, recent behavioral and neuroimag-
ing studies suggest that the multi-sensory processes involved in BSC are integrated into the memory trace to
support encoding and episodic remembering66,94. As such, it has been argued that the parietal areas support
the integration of multimodal memory features within an egocentric framework into the kind of rst-person-
perspective representation that enables the subjective reexperiencing of past events95. For example, it was found
that subjective reports of self-location correlated with the increased connectivity between posterior parietal
and hippocampal activity. Similarly, Moon etal.60 found that rst-person perspective navigation decreased
entorhinal cortex activity and increased retrosplenial cortex activity, linked with spatial navigation and spatial
memory performances. Moreover, Bergouignan etal.59,96 found that experimentally induced out-of-body experi-
ence reduced hippocampal activity during retrieval and the ability to remember events from a eld perspective.
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It suggests that multi-sensory processes in the posterior parietal regions are conveyed to the hippocampus to
build a coherent representation of the bodily-self, which may increase the richness of the memory trace, lead-
ing to better performance in our Synchronous condition compared to the other two. In parallel, interactions
with subnetworks related to the sense of agency and sense of self-identication may signal the self-relevance of
the event9,49,84, enhancing associative encoding for intra-event features and contextual information, increasing
memory precision and preventing memory decay over time50. Finally, at retrieval, these processes are reinstated
or reenacted, producing a rich and vivid recollection of the event centered around the bodily-self and imbued
with a sense of agency, and autonoetic consciousness. is claim was supported by a recent neuroimaging
study by Iriye etal.84. Using a similar paradigm as Iriye and Ehrsson53, they found increased similarity between
encoding and retrieval activity for highly vivid memories in brain regions including the hippocampus and the
bilateral angular gyrus, when events were encoded in the synchronous condition. e authors concluded that
sense of bodily-self in space during encoding is likely a fundamental contextual memory cue based on spatial
relationships that delineate oneself from the external world84. Continuing previous research9, we argue that the
multifaceted self-reference eect via grounding personal everyday experiences through bodily self in space and
narrative self is crucial to promote the formation of the self-memory system and long-lasting EM (i.e., episodic
autobiographical memory).
Limitations and future directions
e current study oers a unique perspective on the impact of bodily self-consciousness on EM, but there are
some limitations that may have inuenced the results and call for further investigation. Firstly, we cannot entirely
rule out the possibility that our ndings result partially from increased cognitive demand in the Asynchronous
condition. Future research could therefore explore the relationship between multi-sensory processing, executive
function, and EM, as this issue may not be restricted to visuo-motor stimulation. e implementation of control
devices such as eye-tracking systems could also help to track dierences in environmental exploration between
conditions. Another solution would be to manipulate interoceptive rather than exteroceptive signals to modulate
BSC97,98. Secondly, our study did not enable us to disentangle the specic role of each BSC component on EM.
A thorough examination of the role played by self and spatial components of BSC would help the eld to better
understand the link between BSC and EM and its functions. irdly, we need to substantiate how these ndings
are transferable to real life and contribute to the long-lasting EM, also referred to as episodic autobiographi-
cal memory2,6. While EM can refer to any event that happened to us in the past and any contextual learning of
new information, in contrast, episodic autobiographical memory concerns self-relevant specic experienced
events99. Future research should examine the role of BSC in EM according to the self-relevance of experienced
events. Overall, our study provides a foundation for further exploration of the role of bodily self-consciousness
in naturalistic episodic memory, but additional research is needed to address these limitations and expand our
understanding of this complex phenomenon.
Conclusion
In conclusion, our study provides new insights into the relationship between bodily-self in space and memory of
incidental encoding of specic events in a naturalistic environment. We found that manipulating the visuomotor
feedback associated with BSC during encoding can modulate the subsequent EM performance, even at long reten-
tion delay, showing for the rst time that BSC may play a role in feature binding and autonoetic consciousness
associated with the memory of everyday events. Our ndings are in accordance with previous studies showing
the importance of multi-sensory integration for EM and suggest that the bodily-self representation plays a crucial
role in this process. However, future work is needed to conrm our results as some issues persist regarding that
underly EM alteration performance when BSC is degraded and discard alternative explanations. is research
may have implications for the design of virtual environments as tools for learning and rehabilitation. By optimiz-
ing the feedback signals that promote BSC, it may be possible to optimize the encoding and retention of complex
events75. Furthermore, our study may contribute to the understanding of memory decits in bodily-self disorders
such as depersonalization and schizophrenia, which are characterized by a disruption of the integration between
body signals100. Future research could investigate whether similar eects on memory consolidation occur in
these populations and whether virtual reality interventions could help to alleviate their cognitive impairments.
Overall, this study highlights the importance of considering the multi-sensory processes that build the sense of
bodily-self as an integral part of the encoding and retrieval processes in memory consolidation, and it opens up
new avenues for investigating the neural and cognitive mechanisms underlying this phenomenon.
Data availability
e data of this study are available on request to the corresponding authors.
Received: 10 May 2023; Accepted: 28 September 2023
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Acknowledgements
e authors thank Elizabeth Rowley-Jolivet for the English proofreading.
Author contributions
S.P. and P.P. conceptualized the experiments, D.Y. programmed the recognition task, A.G.B. created the virtual
environment, S.P. and A.G.B created the virtual events, S.P. conducted the experiments, S.P. conducted the analy-
sis, S.P. and P.P. wrote the original dra. P.P. supervised the experiment, S.P. and P.P. reviewed the manuscript.
Funding
SP received a PhD scholarship from the French Ministry of Higher Education, Research, and Innovation.is
article was published with the support of the faculty Sociétés & Humanités atUniversitéParis Cité.
Competing interests
e authors declare no competing interests.
Additional information
Supplementary Information e online version contains supplementary material available at https:// doi. org/
10. 1038/ s41598- 023- 43823-2.
Correspondence and requests for materials should be addressed to S.P.orP.P.
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