Elsevier

Neuroscience

Volume 168, Issue 3, 14 July 2010, Pages 670-679
Neuroscience

Cognitive, Behavioral and Systems Neuroscience
Research Paper
Elevated response of human amygdala to neutral stimuli in mild post traumatic stress disorder: neural correlates of generalized emotional response

https://doi.org/10.1016/j.neuroscience.2010.04.024Get rights and content

Abstract

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.

Section snippets

Subjects

Ten patients with PTSD and 10 age, sex and education-matched healthy control subjects were recruited. All participants were bank clerks, victims of one or more armed bank assaults about 10 months before the experiments (range of 2–18 months). Table 1 reports their demographic information.

All participants underwent an extensive clinical examination carried out by an expert psychiatrist (GS) and a clinical psychologist (MB). A broader range of traumatic event types, including car accidents and

Behavioral data

Responses to negative (unpleasant) pictures were less accurate and had longer mean RTs compared to responses to neutral pictures.

Discussion

Previous fMRI evidence has shown that amygdala responses to emotionally neutral pictures are exaggerated at group levels in patients with severe PTSD (Hendler et al., 2003). The present fMRI study tested the hypothesis that elevated amygdala responses are not only linked to negative pictures but also to neutral pictures as a function of disease severity in PTSD patients with mild symptoms and in individuals who did not develop symptoms. To this end, an fMRI scan was performed on PTSD patients

Conclusion

In conclusion, the present fMRI study focused on the grey zone between asymptomatic bank clerk victims and mild PTSD patients. In the whole participants' sample, correlations between the severity of the PTSD symptoms, task performance, and amygdala activation during the processing of neutral pictures were described. Control subjects showed larger amygdala responses to emotionally negative pictures compared to neutral pictures response. On the contrary, the amygdala responses of the PTSD

Acknowledgments

The authors would like to thank Dott. Gianni Perrucci, ITAB-University “G. D'Annunzio of Chieti, for technical support, and Dott. Beth Fairfield, Faculty of Psychology-University “G. D'Annunzio of Chieti, for a careful editing of the manuscript. The authors would also like to thank local Bank Labour Union for collaboration in this research.

References (37)

  • S.L. Rauch et al.

    Exaggerated amygdala response to masked facial stimuli in posttraumatic stress disorder: a functional MRI study

    Biol Psychiatry

    (2000)
  • L.M. Williams et al.

    Trauma modulates amygdala and medial prefrontal responses to consciously attended fear

    Neuroimage

    (2006)
  • M.W. Woolrich et al.

    Temporal autocorrelation in univariate linear modeling of FMRI data

    Neuroimage

    (2001)
  • P. Yang et al.

    Evidence of early neurobiological alternations in adolescents with posttraumatic stress disorder: a functional MRI study

    Neurosci Lett

    (2004)
  • C. Zlotnick et al.

    Does “subthreshold” posttraumatic stress disorder have any clinical relevance?

    Compr Psychiatry

    (2002)
  • R. Admon et al.

    Human vulnerability to stress depends on amygdala's predisposition and hippocampal plasticity

    Proc Natl Acad Sci U S A

    (2009)
  • S.J. Bishop et al.

    Neural processing of fearful faces: effects of anxiety are gated by perceptual capacity limitations

    Cereb Cortex

    (2007)
  • S.J. Bishop

    Neural mechanisms underlying selective attention to threat

    Ann N Y Acad Sci

    (2008)
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