Browsing by Author "Tekgun, Ege"

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Bedensel Öz-bilincin Nörolojik Temelleri ve İlişkili Psikopatolojiler
(2020) Tekgun, Ege; Erdeniz, Burak
Bedenden gelen farklı duyusal bilgilerin dinamik bir şekilde işlenmesine bağlı olarak insanların bedensel farkındalıklarının değişmesi, bedensel öz-bilinç yaklaşımının ortaya çıkmasına neden olmuştur. Son yıllarda yapılan çalışmalara göre farklı duyu sistemlerinden gelen bu duyusal bilgilerin (örn. vestibüler, bedensel-duyusal) birlikte işlenmesi ve yorumlanması, bedensel özbilincin oluşması için temel bir gereksinim olarak gözükmektedir. Bu bağlamda duyusal sinyallerin uyumlu ya da uyumsuz olması sonucunda hem uzuv hem de tüm beden algısında çarpıcı değişimler gözlenmektedir. Bu alanda yürütülen çalışmaların temel varsayımı, bedensel deneyimlerin farklı duyulardan gelen sinyallerin tümleştirilerek birlikte işlenmesi sayesinde olduğu yönündedir. Bu makaledebedensel öz bilincin deneysel olarak nasıl çalıştığını incelenmesi ve altında yatan duyusal süreçlerin tartılması amaçlanmıştır. Buna ek olarak, daha önce yapılan deneysel çalışmaların kısıtları tartışılmıştır.
Citation - WoS: 2
Citation - Scopus: 3
Bodily Self-Consciousness in Dreams Questionnaire (bsd-Q) and Its Relation To Waking Dissociative Experiences
(Educational Publishing Foundation-American Psychological Assoc, 2022) Erdeniz, Burak; Tekgun, Ege; Mentes, Ozge; Coban, Aslihan; Bilge, Selma; Serin, Emin
According to virtual reality dream theory (Hobson & Friston, 2014), while dreaming, brains generate a dream world similar to a virtual reality environment, and this world uses the same predictive self/world modeling capacity as that used during wakefulness. The theory proposes that phenomenology of dreaming experience is based on the waking experience, a view widely accepted by dream researchers. In the current research, we argued that individuals with different intensities of dissociative experiences during waking, will report corresponding differences in the profoundness of sensory modality experiences, such as touching in dreams. To test this hypothesis, first we developed a novel Bodily Self-Consciousness in Dreams Questionnaire, that was completed by 414 participants. The questionnaire measured the intensity of different sensory modality experiences in past dreams. The results showed that a four-factor solution explains 64% of the total variance, and yielded sufficient reliability with McDonald's to ranging from .62 to .84, and Cronbach's a ranged from .61 to .84. Along with the Bodily Self-Consciousness in Dreams Questionnaire, we administered the Dissociation Questionnaire (Vanderlinden et al, 1993), which showed a significant positive correlation between the bodily self-consciousness in dreams and dissociative experiences during waking. In conclusion, the results showed that all of the modalities pertain to bodily self-consciousness in dreams and are significantly correlated with waking state dissociative experiences.
Citation - WoS: 2
Citation - Scopus: 2
Contributions of Body-Orientation To Mental Ball Dropping Task During Out-Of Experiences
(Frontiers Media Sa, 2022) Tekgun, Ege; Erdeniz, Burak
Out-of-body experiences (OBEs) provide fascinating insights into our understanding of bodily self-consciousness and the workings of the brain. Studies that examined individuals with brain lesions reported that OBEs are generally characterized by participants experiencing themselves outside their physical body (i.e., disembodied feeling) (Blanke and Arzy, 2005). Based on such a characterization, it has been shown that it is possible to create virtual OBEs in immersive virtual environments (Ehrsson, 2007; Ionta et al., 2011b; Bourdin et al., 2017). However, the extent to which body-orientation influences virtual OBEs is not well-understood. Thus, in the present study, 30 participants (within group design) experienced a full-body ownership illusion (synchronous visuo-tactile stimulation only) induced with a gender-matched full-body virtual avatar seen from the first-person perspective (1PP). At the beginning of the experiment, participants performed a mental ball dropping (MBD) task, seen from the location of their virtual avatar, to provide a baseline measurement. After this, a full-body ownership illusion (embodiment phase) was induced in all participants. This was followed by the virtual OBE illusion phase of the experiment (disembodiment phase) in which the first-person viewpoint was switched to a third-person perspective (3PP), and participants' disembodied viewpoint was gradually raised to 14 m above the virtual avatar, from which altitude they repeated the MBD task. During the experiment, this procedure was conducted twice, and the participants were allocated first to the supine or the standing body position at random. Results of the MBD task showed that the participants experienced increased MBD durations during the supine condition compared to the standing condition. Furthermore, although the findings from the subjective reports confirmed the previous findings of virtual OBEs, no significant difference between the two postures was found for body ownership. Taken together, the findings of the current study make further contributions to our understanding of both the vestibular system and time perception during OBEs.
Citation - WoS: 4
Citation - Scopus: 7
Influence of Vestibular Signals on Bodily Self-Consciousness: Different Sensory Weighting Strategies Based on Visual Dependency
(Academic Press Inc Elsevier Science, 2021) Tekgun, Ege; Erdeniz, Burak
Previous studies showed that the vestibular system is crucial for multisensory integration, however, its contribution to bodily self-consciousness more specifically on full-body illusions is not well understood. Thus, the current study examined the role of visuo-vestibular conflict on a fullbody illusion (FBI) experiment that was induced during a supine body position. In a mixed design experiment, 56 participants underwent through a full-body illusion protocol. During the experiment, half of the participants received synchronous visuo-tactile stimulation, and the other half received asynchronous visuo-tactile stimulation, while their physical body was lying in a supine position, but the virtual body was standing. Additionally, the contribution of individual sensory weighting strategies was investigated via the Rod and Frame task (RFT), which was applied both before (pre-FBI standing and pre-FBI supine) and after the full-body illusion (post-FBI supine) protocol. Subjective reports of the participants confirmed previous findings suggesting that there was a significant increase in ownership over a virtual body during synchronous visuo-tactile stimulation. Additionally, further categorization of participants based on their visual dependency (by RFT) showed that those participants who rely more on visual information (visual field dependents) perceived the full-body illusion more strongly than non-visual field dependents during the synchronous visuo-tactile stimulation condition. Further analysis provided not only a quantitative demonstration of full-body illusion but also revealed changes in perceived selforientation based on their field dependency. Altogether, findings of the current study make further contributions to our understanding of the vestibular system and brought new insight for individual sensory weighting strategies during a full-body illusion.
Citation - WoS: 1
Citation - Scopus: 1
Virtual Body Anthropomorphism Increases Drift in Self-Location: Further Support for the Humanoid Shape Rule
(Wiley, 2022) Tekgun, Ege; Uludagli, Muhtar C.; Akcan, Hüseyin; Erdeniz, Burak
Previous studies on bodily self-consciousness (BCS) have shown that self-location and body ownership are prone to changes based on the perceptual appearances of the fake virtual body. In the current study with 36 participants, we assessed the influence of virtual avatar anthropomorphism and the synchronicity of the visuo-tactile stimulation on self-location using a virtual reality full-body illusion experiment. During the experiment, half of the participants observed a gender-matched full-body humanoid avatar from a first-person perspective (1PP) and the other half observed a less anthropomorphic full-body cubical avatar from 1PP while they were receiving synchronous and asynchronous visuo-tactile stimulation. Results showed a significant main effect of the synchronicity of the visuo-tactile stimulation and avatar body type on self-location but no significant interaction was found between them. Moreover, the results of the self-report questionnaire provide additional evidence showing that participants who received synchronous visuo-tactile stimulation, experienced not only greater changes in the feeling of self-location, but also, increased ownership, and referral of touch. Our results provided further support for the previous findings that showed evidence for the effect of virtual avatar appearance on BCS.
Visual Perspective, Distance, and Felt Presence of Others in Dreams
(Academic Press Inc., 2023) Erdeniz, Burak; Tekgun, Ege; Lenggenhager, B.; Lopez, C.
The peripersonal space, that is, the limited space surrounding the body, involves multisensory coding and representation of the self in space. Previous studies have shown that peripersonal space representation and the visual perspective on the environment can be dramatically altered when neurotypical individuals self-identify with a distant avatar (i.e., in virtual reality) or during clinical conditions (i.e., out-of-body experience, heautoscopy, depersonalization). Despite its role in many cognitive/social functions, the perception of peripersonal space in dreams, and its relationship with the perception of other characters (interpersonal distance in dreams), remain largely uncharted. The present study aimed to explore the visuospatial properties of this space, which is likely to underlie self-location as well as self/other distinction in dreams. 530 healthy volunteers answered a web-based questionnaire to measure their dominant visuo-spatial perspective in dreams, the frequency of recall for felt distances between their dream self and other dream characters, and the dreamers’ viewing angle of other dream characters. Most participants reported dream experiences from a first-person perspective (1PP) (82%) compared to a third-person perspective (3PP) (18%). Independent of their dream perspective, participants reported that they generally perceived other dream characters in their close space, that is, at distance of either between 0 and 90 cm, or 90–180 cm, than in further spaces (180–270 cm). Regardless of the perspective (1PP or 3PP), both groups also reported more frequently seeing other dream characters from eye level (0° angle of viewing) than from above (30° and 60°) or below eye level (−30° and −60°). Moreover, the intensity of sensory experiences in dreams, as measured by the Bodily Self-Consciousness in Dreams Questionnaire, was higher in individuals who habitually see other dream characters closer to their personal dream self (i.e., within 0–90 cm and 90–180 cm). These preliminary findings offer a new, phenomenological account of space representation in dreams with regards to the felt presence of others. They might provide insights not only to our understanding of how dreams are formed, but also to the type of neurocomputations involved in self/other distinction. © 2023 Elsevier Inc.