In Search of the Trauma Memory: A Meta-Analysis of Functional Neuroimaging Studies of Symptom Provocation in Posttraumatic Stress Disorder (PTSD)

Abstract

Notwithstanding some discrepancy between results from neuroimaging studies of symptom provocation in posttraumatic stress disorder (PTSD), there is broad agreement as to the neural circuit underlying this disorder. It is thought to be characterized by an exaggerated amygdalar and decreased medial prefrontal activation to which the elevated anxiety state and concomitant inadequate emotional regulation are attributed. However, the proposed circuit falls short of accounting for the main symptom, unique among anxiety disorders to PTSD, namely, reexperiencing the precipitating event in the form of recurrent, distressing images and recollections. Owing to the technical demands, neuroimaging studies are usually carried out with small sample sizes. A meta-analysis of their findings is more likely to cast light on the involved cortical areas. Coordinate-based meta-analyses employing ES-SDM (Effect Size Signed Differential Mapping) were carried out on 19 studies with 274 PTSD patients. Thirteen of the studies included 145 trauma-exposed control participants. Comparisons between reactions to trauma-related stimuli and a control condition and group comparison of reactions to the trauma-related stimuli were submitted to meta-analysis. Compared to controls and the neutral condition, PTSD patients showed significant activation of the mid-line retrosplenial cortex and precuneus in response to trauma-related stimuli. These midline areas have been implicated in self-referential processing and salient autobiographical memory. PTSD patients also evidenced hyperactivation of the pregenual/anterior cingulate gyrus and bilateral amygdala to trauma-relevant, compared to neutral, stimuli. Patients showed significantly less activation than controls in sensory association areas such as the bilateral temporal gyri and extrastriate area which may indicate that the patients’ attention was diverted from the presented stimuli by being focused on the elicited trauma memory. Being involved in associative learning and priming, the retrosplenial cortex may have an important function in relation to trauma memory, in particular, the intrusive reexperiencing of the traumatic event.

The cannabinoid system in the retrosplenial cortex modulates fear memory consolidation, reconsolidation, and extinction

“…In humans, trauma-related stimuli cause a higher activation of the RSC in patients diagnosed with post-traumatic stress disorder (PTSD) than in controls (Sartory et al 2013). Therefore, based on our results, the requirement of the CB1R-dependent activity in the RSC during emotional memory processing may be taken into account when searching putative treatments for PTSD or other incapacitating psychopathologies in which aversive memories are maladaptive.…”

Neurobiology of PTSD and implications for treatment: An overview

“…Recent research studies offer a very complex picture of the neurobiological dynamic of PTSD. They focus on the exploration of different aspects of neurobiological changes in PTSD sufferers in regard to endocrinology, neurochemistry and brain circuitry and on the linkage that these changes might have to the clinical features of PTSD as hyperarousal, Impulsivity, dysregulated executive functions and memory (6,(8)(9)(10)(11).…”

Neurobiology and Stochastic Resonance: Going Deeper

“…In patients with posttraumatic stress disorder (PTSD), where the naturally occurring noise from descending cortico-thalamic feedback is presumed to be unavailable due to a decrease in thalamic activity (Bergmann, 2008;Sartory et al, 2013; Yan et al, 2013) seen in PTSD, the dual attention stimulation/bilateral stimulation (DAS/BLS) of EMDR therapy could be generating a random (stochastic) signal at the thalamic level. Stochastic resonance (SR) in this setting would presumably facilitate the sensing of a signal that would otherwise be subthreshold.…”

“…"FACES is what well-being is" (Siegel & Buczynski, 2014). Activity in the thalamus is decreased in PTSD patients as compared with non-PTSD patients (Bergmann, 2008;Sartory et al, 2013;Yan et al, 2013), so it is not surprising to observe that SR operates at this influential brain region. A form of signal "gating" is also believed to occur at the thalamic level.…”

“…We understand from neuroimaging studies (Sartory et al, 2013) that the thalamus is a vital brain structure in the integration of perceptual, somatosensory, memorial, and cognitive processes. This proposed function is referred to as thalamo-cortical-temporal binding, and it is a model in which data are normally metabolized into a functional memory network in the neocortex (Bergmann, 2008).…”