The neurobiology of posttraumatic stress disorder: dysfunction in the prefrontal-amygdala circuit?

Posttraumatic stress disorder (PTSD) is an anxiety disorder that can develop following exposure to a traumatic event, including terrifying or life-threatening situations such as sexual assault or natural disasters. The disorder is characterized by a reaction of intense fear, helplessness, or horror when the individual experiences, testifies about, or is faced with one or more events that involve death, severe wounds, or a threat to one's own or another's physical integrity. One of the most important symptoms of PTSD is the revival of the traumatic event, which has been interpreted as an inability to downregulate negative emotions. Neuroimaging studies that probed the ability to regulate emotions in healthy volunteers have found a pattern characterized by activation of the prefrontal cortex associated with a reduction in amygdala activity. This suggests an inhibitory prefrontal cortex-amygdala circuit that underlies emotional regulation. The hypothesis that increased amygdala activation associated with PTSD results from dysfunction in the inhibitory mechanism exerted by the prefrontal cortex has been the topic of debate. The present review investigates the validity of dysfunction in the prefrontal-amygdala pathway in PTSD. The studies provide evidence that the amygdala and prefrontal cortex exhibit distinct activation patterns in PTSD, thus supporting the model of a dysfunctional circuit. Inconsistencies in the literature may be attributable to distinct PTSD subgroups, different experimental approaches, different contrasts employed in neuroimaging studies, and small sample sizes.

Dynamics of a Stroop matching task: effect of alcohol and reversal with training

Using a Stroop matching task, we evaluated how alcohol affects the time needed to overcome Stroop conflict and whether practice might reverse the effect of alcohol. Participants (n = 16) performed two sessions in which they had to compare the color of a color-word with the meaning of a color-word in neutral color. The two task stimuli were presented simultaneously or with a Stimulus Onset Asynchrony (SOA) of 200, 500, or 800 ms. For half of the subjects, alcohol was administered in the first session, and for the other half, alcohol was administered in the second session. The results showed that the Stroop effect was significant at the 0 and 200 ms intervals in the sober subjects. Moreover, in untrained intoxicated individuals, interference endured until the 500 ms interval, a result that was abolished in trained intoxicated subjects. In conclusion, alcohol increased the time needed for Stroop matching task conflict resolution. However, this deleterious effect was minimized by a previous practice session.

Role of attention and translation in conflict resolution: implications for stroop matching task interference

We studied the influence of attention on the timecourse of Stroop-like conflict. Thirty-two volunteers performed a Stroop matching task in which they had to compare either the color (n = 16) or meaning (n = 16) of two stimuli. The first stimulus was always a color-name printed in yellow, red, or blue (i.e., Stroop stimulus), and the second stimulus was either a color-bar (Experiment 1) or color-word in white ink (Experiment 2). Stimulus onset asynchrony (SOA) was varied parametrically. Interference by incongruent Stroop stimuli was clearly modulated by SOA manipulation in both cases. The results are discussed in terms of interactions between translational and attentional models in which the degree of Stroop-like interference is attributed to time implementation of attentional mechanisms during color-to-color and color-to-word matching contexts