Elevated response of human amygdala to neutral stimuli in mild post traumatic stress disorder: Neural correlates of generalized emotional response

Institute of Advanced Biomedical Technologies, University of Chieti, Chieti, Italy.
Neuroscience (Impact Factor: 3.36). 04/2010; 168(3):670-9. DOI: 10.1016/j.neuroscience.2010.04.024
Source: PubMed


Previous evidence from functional magnetic resonance imaging (fMRI) studies has shown that amygdala responses to emotionally neutral pictures are exaggerated at a group level in patients with severe post-traumatic stress disorder (PTSD) [Hendler T, Rotshtein P, Yeshurun Y, Weizmann T, Kahn I, Ben-Bashat D, Malach R, Bleich A (2003) Neuroimage 19(3):587-600]. The present fMRI study tested the hypothesis that amygdala responses are elevated not only in response to negative pictures but also to neutral pictures as a function of disease severity in patients with mild symptoms and in subjects who did not develop symptoms. To this end, fMRI scans were performed in 10 patients with mild PTSD and 10 healthy controls (both victims of a bank robbery), during the execution of a visuo-attentional task in which they were asked to observe emotionally negative or neutral pictures. Control subjects showed enhanced amygdala responses to emotionally negative stimuli compared to neutral stimuli. On the contrary, PTSD patients were characterized by high amygdala responses to both neutral and emotional pictures, with no statistically significant difference between the two classes of stimuli. In the entire group, we found correlations among the severity of the PTSD symptoms, task performance, and amygdala activation during the processing of neutral stimuli. Results of this study suggest that amygdala responses and the selectivity of the emotional response to neutral stimuli are elevated as a function of disease severity in PTSD patients with mild symptoms.

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Available from: Claudia Catani, Apr 07, 2014
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    • "The image acquisition parameters were identical to those in our previous study (Brunetti et al., 2010). BOLD contrast functional imaging was performed with a SIEMENS MAGNETOM VISION scanner at 1.5 T by means of T2*-weighted echo planar imaging (EPI), free-induction decay (FID) sequences with the following parameters: TR 3 s, TE 60 ms, matrix size 64 × 64, FOV 256 mm, in-plane voxel size 4 mm × 4 mm, flip angle 90 • , slice thickness 4 mm and no gap. "
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    ABSTRACT: Patients with post-traumatic stress disorder (PTSD) tend to misinterpret innocuous stimuli as potential threats, possibly due to a conditioning provoked by traumatic episodes. Previous neuroimaging evidence has shown an abnormal activation of the amygdala and prefrontal cortex in PTSD patients during fear conditioning and extinction. Nevertheless, the effects of a single-type adverse stressor on that circuit remain poorly explored. We tested the hypothesis that a single-type adverse episode is able to affect the prefrontal cortex and amygdala response to conditioned stimuli. To test this hypothesis, fMRI recordings were performed in PTSD patients and trauma-exposed controls during the observation of neutral and negative paired or non-paired pictures with an adverse stimulus by means of a single association. Results showed that left amygdala activation during negative reinforced stimuli was correlated with the score of PTSD clinical scale across all subjects. Furthermore, in the traumatized non-PTSD group, the activation of the dorso-medial prefrontal cortex and bilateral amygdala was lower during the observation of the reinforced (CS(+)) vs non-reinforced pictures (CS(-)) in response to emotionally negative stimuli. This was not the case in the PTSD patients. These results suggest that in PTSD patients, a single-episode conditioning unveils the failure of an inhibitory mechanism moderating the activity of the prefrontal cortex and amygdala in response to adverse and neutral stimuli. Copyright © 2015. Published by Elsevier Inc.
    Full-text · Article · Mar 2015 · Brain research bulletin
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    • "Like Phan et al (2006), who also did not observe an increased amygdala response to IAPS pictures in PTSD patients, we only studied males. The two studies that presented IAPS pictures and observed increased amygdala activity in PTSD patients included predominantly females (Brohawn et al. 2010; Brunetti et al. 2010). This could indicate an effect of sex on the amygdala response to (trauma-unrelated) emotional stimuli in PTSD, which has been suggested to explain the higher prevalence of PTSD in women (Hamann, 2005). "
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    ABSTRACT: Background: Post-traumatic stress disorder (PTSD) is thought to be characterized by general heightened amygdala activation. However, this hypothesis is mainly based on specific studies presenting fear or trauma-related stimuli, hence, a thorough investigation of trauma-unrelated emotional processing in PTSD is needed. Methods: In this study, 31 male medication-naive veterans with PTSD, 28 male control veterans (combat controls; CC) and 25 non-military men (healthy controls; HC) were included. Participants underwent functional MRI while trauma-unrelated neutral, negative and positive emotional pictures were presented. In addition to the group analyses, PTSD patients with and without major depressive disorder (MDD) were compared. Results: All groups showed an increased amygdala response to negative and positive contrasts, but amygdala activation did not differ between groups. However, a heightened dorsal anterior cingulate cortex (dACC) response for negative contrasts was observed in PTSD patients compared to HC. The medial superior frontal gyrus was deactivated in the negative contrast in HC, but not in veterans. PTSD+MDD patients showed decreased subgenual ACC (sgACC) activation to all pictures compared to PTSD-MDD. Conclusion: Our findings do not support the hypothesis that increased amygdala activation in PTSD generalizes to trauma-unrelated emotional processing. Instead, the increased dACC response found in PTSD patients implicates an attentional bias that extends to trauma-unrelated negative stimuli. Only HC showed decreased medial superior frontal gyrus activation. Finally, decreased sgACC activation was related to MDD status within the PTSD group.
    Full-text · Article · Jul 2014 · Psychological Medicine
    • "Additionally, as a control, a set of eight neutral food images were included in the stimulus set and presented in the same format as the other ones (see Table 1 for the pre-test ratings obtained in the same manner as described above, with 15 people). Neutral images presented raw vegetables only, since they are low in fat and sugar, which have already been shown not to alter individuals' mood or arousal levels (Privitera, Antonelli, & Creary, 2013; for fMRI studies neural responses of people to viewing images of vegetables see Brunetti et al., 2010; Killgore et al., 2003). "
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    ABSTRACT: Wanting and rejecting food are natural reactions that we humans all experience, often unconsciously, on a daily basis. However, in the food domain, the focus to date has primarily been on the approach tendency, and researchers have tended not to study the two opposing tendencies in a balanced manner. Here, we develop a methodology with which to understand people's implicit and explicit reactions to both positive (appealing) and negative (disgusting) foods. It consists of a combination of direct and indirect computer-based tasks, as well as a validated food image stimulus set, specifically designed to investigate motivational approach and avoidance responses towards foods. Fifty non-dieting participants varying in terms of their hunger state (hungry vs. not hungry) reported their explicit evaluations of pleasantness, wanting, and disgust towards the idea of tasting each of the food images that were shown. Their motivational tendencies towards those food items were assessed indirectly using a joystick-based approach-avoidance procedure. For each of the food images that were presented, the participants had to move the joystick either towards or away from themselves (approach and avoidance movements, respectively) according to some unrelated instructions, while their reaction times were recorded. Our findings demonstrated the hypothesised approach avoidance compatibility effect: a significant interaction of food valence and direction of movement. Furthermore, differences between the experimental groups were observed. The participants in the no-hunger group performed avoidance (vs. approach) movements significantly faster; and their approach movements towards positive (vs. negative) foods were significantly faster. As expected, the self-report measures revealed a strong effect of the food category on the three dependent variables and a strong main effect of the hunger state on wanting and to a lesser extent on pleasantness.
    No preview · Article · Apr 2014 · Appetite
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