altered sense of body ownership and agency in PTSD and its dissociative subtype
Article Information
Title: Altered Sense of Body Ownership and Agency in Posttraumatic Stress Disorder and Its Dissociative Subtype: A Rubber Hand Illusion Study.Authors: Daniela Rabellino, Dalila Burin, Sherain Harricharan, Chantelle Lloyd, Paul A. Frewen, Margaret C. McKinnon, Ruth A. Lanius.Published in: Frontiers in Human Neuroscience.Date: May 01, 2018DOI: 10.3389/fnhum.2018.00163
Background
Concepts of Body Ownership and Agency
The constructs of body ownership and agency represent the conscious perception of one's own body and the feeling of control over one's actions. These concepts are crucial to our identity and personal experience, allowing individuals to navigate their physical environment confidently. Traumatic experiences, such as violent assaults or natural disasters, can lead to significant alterations in bodily perception and may contribute to the development of conditions like Post-Traumatic Stress Disorder (PTSD). In these cases, the sense of body ownership can be distorted, impacting the individual's psychological well-being and behavioral responses to stimuli.
PTSD and Dissociative Symptoms
Post-Traumatic Stress Disorder is characterized by a varied symptomatology, which may include intrusive memories, heightened arousal, avoidance behaviors, and negative alterations in cognition or mood. Notably, PTSD can encompass dissociative symptoms such as derealization (feeling detached from one's surroundings) and depersonalization (feeling detached from one's body). The dissociative subtype of PTSD is specifically marked by profound feelings of disconnection from oneself, which can complicate the recovery process and the individual's ability to engage with their bodily experiences.
Study Overview
Objective
This study aims to illuminate the alterations in body ownership and agency—global constructs that define our interaction with our bodies—through the lens of the Rubber Hand Illusion (RHI) within a sample of individuals diagnosed with PTSD.
Participants
The study involved three groups of participants:
4 individuals with PTSD.
6 individuals with PTSD and pronounced dissociative symptoms (PTSD+DS).
7 healthy controls (HC), who served as a baseline comparison group.
Rubber Hand Illusion (RHI) Study Design
Method
The RHI method manipulates sensory inputs—visual, tactile, and proprioceptive—to create the illusion that a rubber hand is part of the participant's own body. This experimental setup attempts to investigate how variations in sensory perception influence the sense of body ownership.
Assessment
Participants underwent assessments measuring proprioceptive drift, which is the perceived shift in the position of their own hand toward the rubber hand, and self-report questionnaires designed to evaluate their experience of the illusion and sense of agency, which includes their ability to manipulate actions voluntarily.
Hypotheses
It was hypothesized that:
Participants with PTSD+DS would exhibit a stronger sense of illusion than both PTSD and HC groups due to their heightened dissociative experiences.
The participants’ sense of agency would negatively correlate with the strength of the illusion, indicating that those with a weaker agency experience a stronger illusion effect.
Findings
Illusion Effect
The study revealed that the PTSD group experienced significantly diminished illusion effects compared to healthy controls, as evidenced by reduced proprioceptive drift. The PTSD+DS group displayed a wide variability in their responses, suggesting that factors influencing sensory integration and embodiment are distinctly altered in individuals with dissociation.
Correlation of Agency
Additionally, a notable finding was that a weaker sense of agency correlated with a stronger experience of the illusion for the PTSD group. This suggests a complex interplay where individuals with PTSD might have a disrupted feedback loop between their sense of control and bodily experience.
Cognitive Processes
It was posited that individuals with PTSD might employ rigid body representations as psychological avoidance strategies, potentially leading to less adaptive responses to treatment. Conversely, those in the PTSD+DS group showcased variable responses, highlighting their increased vulnerability to embodiment manipulation.
Implications
Understanding Bodily Consciousness
The findings enhance the understanding of how PTSD, particularly in its dissociative presentation, profoundly affects body ownership and agency. These insights can inform future research directions and clinical practices.
Therapeutic Approaches
The results underscore the necessity for therapeutic interventions targeting both trauma recovery and the amelioration of dissociative symptoms, such as employing mindfulness practices and sensorimotor psychotherapy, which aim to reintegrate the bodily self and restore agency.
Limitations
Despite the contributions of this study, several limitations exist, including the small sample size, which restricts the generalizability of findings. Future research should consider longitudinal studies that explore how psychological states evolve over time in response to varied therapeutic interventions.
Conclusion
This study offers valuable insights into the intricate relationships between cognitive control, body ownership, and the sense of agency in PTSD, particularly emphasizing the unique responses observed in the dissociative subtype of PTSD. It highlights the critical need for targeted interventions that directly address issues of body ownership and agency as integral components in trauma recovery processes.