Abstract
Patients with posttraumatic stress disorder (PTSD) appear to manifest two opposing tendencies in their attentional biases and symptoms. However, whether common neural mechanisms account for their opposing attentional biases and symptoms remains unknown. We here propose a model in which reciprocal inhibition between the amygdala and ventromedial prefrontal cortex (vmPFC) predicts synchronized alternations between emotional under- and overmodulatory states at the neural, behavioral, and symptom levels within the same patients. This reciprocal inhibition model predicts that when the amygdala is dominant, patients enter an emotional undermodulatory state where they show attentional bias toward threat and manifest re-experiencing symptoms. In contrast, when the vmPFC is dominant, patients are predicted to enter an emotional overmodulatory state where they show attentional bias away from threat and avoidance symptoms. To test the model, we performed a behavioral meta-analysis (total N = 491), analyses of own behavioral study (N = 20), and a neuroimaging meta-analysis (total N = 316). Supporting the model, we found the distributions of behavioral attentional measurements to be bimodal, suggesting alternations between the states within patients. Moreover, attentional bias toward threat was related to re-experiencing symptoms, whereas attentional bias away from threat was related with avoidance symptoms. We also found that the increase and decrease of activity in the left amygdala activity was related with re-experiencing and avoidance symptoms, respectively. Our model may help elucidate the neural mechanisms differentiating nondissociative and dissociative subtypes of PTSD, which usually show differential emotional modulatory levels. It may thus provide a new venue for therapies targeting each subtype.
Highlights
Posttraumatic stress disorder (PTSD) is a debilitating disorder that develops after experiencing life-threatening traumatic events
In our “reciprocal inhibition model” we propose that PTSD patients alternate between emotional under- and overmodulatory states and that this occurs because the amygdala and ventromedial prefrontal cortex (vmPFC) take turns inhibiting one another
Studies have reported an array of clinical differences between PTSD patients with emotional undermodulation and those with emotional overmodulation [1, 4, 36], little is known about whether individual patients experience switching between the emotional under- and overmodulatory states
Summary
Posttraumatic stress disorder (PTSD) is a debilitating disorder that develops after experiencing life-threatening traumatic events. We propose that reciprocal inhibition occurs between the amygdala and the vmPFC, causing them to switch in dominance This reciprocal inhibition model comprehensively explains alternations between neural activity, attentional bias, and PTSD symptoms within patients, while providing one possible mechanism behind the emergence of PTSD subtypes. The second prediction is that if the same neural mechanism of reciprocal inhibition between the vmPFC and amygdala underlies both switches in attentional bias and in emotional modulatory state, these should be found to alternate together in a predictable manner This point is tested using the symptoms of re-experiencing and avoidance as proximates of under- and overmodulatory states. Subtraction of re-experiencing from “general” avoidance symptoms, referred to here as “symptom imbalance,” allowed us to index the (im)balance between emotional under- and overmodulatory states for each of our patients
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