An fMRI study on over-generalization of social fear in patients with potential traumatic event

733 

Abstract Submission 

Minji Kim¹, Dasom Lee², Soo-Hee Choi³

¹Seoul National University College of Medicine, Seoul, Seoul, ²Seoul National University Hospital, Seoul, Seoul, ³Department of Psychiatry, Seoul National University Hospital, Seoul, Korea, Republic of

Minji Kim  
Seoul National University College of Medicine
Seoul, Seoul

Dasom Lee  
Seoul National University Hospital
Seoul, Seoul

Soo-Hee Choi  
Department of Psychiatry, Seoul National University Hospital
Seoul, Korea, Republic of

While most individuals experience at least one potentially traumatic event (PTE), only around 20% develop posttraumatic stress disorder (PTSD). The key to understanding the pathophysiology of PTSD lies in the abnormal fear conditioning and over-generalization, where fear responses extend to stimuli similar to the original threat. Although there is a wealth of research on fear learning in PTSD, studies addressing abnormal fear in patients experiencing chronic pain after PTE are lacking. Given the challenges in daily functioning and social interaction faced by these patients, further investigations into fear generalization in social context in this population are needed.

A fear conditioning paradigm (Fig.1.a) was assessed during fMRI scanning in 22 healthy controls (HC) and 22 chronic pain patients with PTE. In acquisition, participants were presented with photographs of female faces, some of which were repeatedly paired with an aversive unconditioned stimulus (US) consisting of an angry expression and contemptuous comments (CS+), or with a neutral expression and comments (CS-) (Fig.1.b). In generalization, eight morphed faces of CS in each continuum served as generalized stimuli (GSs, Fig.1.c). Participants were instructed to rate their perceived level of risk (US expectancy).
To investigate the neural activity in the generalization phase, functional regions-of-interest (fROIs) were selected based on the acquisition phase results (CS+ > CS-, Fig.2.a). These fROIs include the inferior frontal gyrus (IFG), inferior parietal lobule (IPL), insula, middle/inferior temporal gyrus, supplementary motor area, fusiform gyrus, thalamus, rostral anterior cingulate cortex (ACC), and amygdala. Ventromedial prefrontal cortex (vmPFC) and the adjacent rectal gyrus were also included, following relevant findings (Lissek et al., 2014). Statistical analysis involved a 2 × 6 repeated-measures ANOVA. Posttraumatic Diagnostic Scale was included as a covariate to account for group differences based on PTE exposure, irrespective of PTSD onset. One patient was excluded due to excessive head motion (> 0.5mm).

Behavioral results indicated higher US expectancy in PTE than HC during the generalization. While reaction time showed no group differences, post-hoc tests indicated that, unlike HC, PTE hesitated significantly longer for ambiguous stimuli (C2, C3) than for CS-. Imaging results revealed three distinct patterns. Firstly, in regions associated with fear inhibition including vmPFC, the two groups showed opposite pattern [Stimulus * Group: left, F=6.585, p=.003, right, F=5.931, p=.005] (Fig.2.b). Unlike HC, the PTE group exhibited persistent deactivation even for stimuli closer to CS-, implying challenges in fear inhibition processing. Secondly, in areas related to fear excitation (right IPL), PTE exhibited significantly higher excitation compared to the control group for C1 [Group: F=5.970, p=.019] (Fig.2.c). Lastly, PTE exhibited increased activity in thalamus in response to ambiguous GSs (C2, C3) [Stimulus * Group: left, F=2.159, p=.060, right, F=2.689, p=.034] (Fig.2.d), reflecting enhanced early perceptual processing of potential threat in patients.

Patients with PTE exhibited abnormal neural activity in regions involved in emotional regulation and early evaluation of potential threats, which may contribute to aberrant fear responses in this population.

Emotional Learning ¹

Learning and Memory Other ²

Emotions

FUNCTIONAL MRI

Learning

Memory

Psychiatric Disorders

Social Interactions

Trauma