Posttraumatic stress disorder may be associated with impaired fear inhibition: Relation to symptom severity

Abstract

One of the central problems in posttraumatic stress disorder (PTSD) is the inability to suppress fear even under safe conditions. The neural underpinnings of fear is a clinically relevant issue that is poorly understood. This study assessed fear potentiation and fear inhibition using fear-potentiated startle in a conditional discrimination procedure (AX+/BX-). We hypothesized that patients with PTSD would show normal fear potentiation and impaired fear inhibition. 28 healthy volunteers and 27 PTSD patients (14 with low current symptoms, 13 with high current symptoms) were presented with one set of colored lights (AX trials) paired with aversive air blasts to the throat, and a different series of lights (BX trials) presented without air blasts. We then presented A and B together (AB trials) to see whether B would inhibit fear potentiation to A. All groups showed robust fear potentiation in that they had significantly greater startle magnitude on AX trials compared to noise alone trials. However, the high symptom PTSD group did not show fear inhibition: these subjects had significantly greater fear potentiation on the AB trials than both the controls and the low symptom PTSD patients.

Conditioned Fear Acquisition and Generalization in Generalized Anxiety Disorder

“…Some previous differential conditioning studies in PD (Lissek et al, 2009) or PTSD (Jovanovic et al, 2009(Jovanovic et al, , 2010 suggest that these patients have difficulties in suppressing fear responses to the CS-(i.e., deficits in inhibition learning) but this question has not specifically been investigated in GAD (see Lissek et al, 2005). In any case, it must be noted that most previous studies conducted in this area do not provide a direct test of differences in inhibition learning (see Mineka & Oehlberg, 2008).…”

“…Impaired within-session fear extinction has been shown for individuals with panic disorder (PD; Michael, Blechert, Vriends, Margraf, & Wilhelm, 2007;Otto et al, 2014) or GAD (Pitman & Orr, 1986), whereas impaired extinction recall could be present in PTSD (Milad et al, 2008) or obsessive-compulsive disorder (OCD; Milad et al, 2013). Moreover, conditioned inhibition deficits may characterize PTSD (Jovanovic et al, 2009(Jovanovic et al, , 2010. However, these results have not been always replicated.…”

Hippocampal GABAB(1a) Receptors Constrain Generalized Contextual Fear

“…However, generalization can also occur under timeindependent mechanisms, such as those that modulate the retrieval of contextual cues (Lynch et al, 2013;Lynch et al, 2016;Lynch et al, 2014). Despite the importance of fear generalization as a fundamental component underlying many anxiety disorders (Brewin, 2001;Grillon and Morgan, 1999;Jovanovic et al, 2009), we do not fully understand how this phenomenon occurs. However, some recent evidence from our laboratory has uncovered specific brain regions (Cullen et al, 2015) and neural mechanisms underlying generalization (Cullen et al, 2014), and this evidence implicates a critical role for the GABAergic system.…”

Tenho medo de quê?

“…It appears that humans have a cerebral predisposition to protect themselves from situations that have put their lives at risk -and from those that still do -such as transmission of diseases, leading them to avoid animals such as cockroaches and rats (disgusting animals). People's fears do not only reflect traumas they have experienced themselves (28) (as in the specific places cited by the adolescents) or unconscious forces, but also situations that their ancestors had learnt, reproduced by their parents (6) .…”