Capturing Physiological Arousal and Synchronization During Clinical Phenomena: An In-Depth Analysis of a Single-Case Study

Introduction: The literature focusing on the psychophysiological components of complex clinical processes is still in its infancy. To the best of our knowledge, only a few studies (e.g., Kleinbub et al., 2025) have highlighted the correspondence between specific clinical dynamics and physiological responses during therapy. This contribution presents a single- case study conducted within the IBISCO – Interpersonal Biofeedback Intervention Supporting Caregivers Online (PRIN) Project and explores physiological and clinical phenomena that emerge during brief psychological treatment. Namely, therapist interventions, the patient’s conflictual theme, and defense mechanisms in relation to patient arousal and patient–therapist physiological synchronization (PS) are examined. Methods: A 45-year-old female patient participated in eight remote, audio- and video- recorded, psychodynamically oriented clinical sessions. Transcripts were coded using the Psychodynamic Intervention Rating Scale (Cooper & Bond, 1992), incorporating recent refinements to the scale proposed by Palmieri et al. (2025). Additionally, the Core Conflictual Relationship Theme (Luborsky & Crits-Christoph, 1998) and the Defense Mechanisms Rating Scale (Perry, 1990) were applied to the verbatim transcripts. Physiological signals were recorded moment-by-moment using Shimmer3 wireless GSR sensors and analyzed using the DyadSync R package (Kleinbub, 2023). Results: Increased arousal in the patient was observed in association with the use of more primitive defense mechanisms and the emergence of a core conflictual theme. Furthermore, therapist interventions related to emotional processing were linked to variations in arousal. Complex patterns of physiological synchronization also emerged. Discussion: Physiological indices were confirmed as a potential “window” (Ishikawa, 2023) into both the patient’s subjective experience and the dynamics of the therapeutic micro- process. These findings contribute to our understanding of the somatic underpinnings of clinical phenomena and highlight the potential of integrating biofeedback into remote psychological interventions.