What parts of the brain are involved in fear renewal? Why does it make sense that these parts are involved?
The hippocampus, amygdala, and dorsomedial and ventromedial prefrontal cortex. The hippocampus is responsible for controlling emotions and memory, which makes sense why it would be involved in fear renewal. The amygdala also aids in emotions, and the prefrontal cortex is responsible for controlling most other aspects of human behavior (i.e. personality, expression, decision making, etc.)
What are several changes in the brain that are found to occur during PTSD and how do the results from this article explain why these changes cause such traumatic results?
PTSD patients have reduced vmPFC volumes, so they would be expected to have poorer extinction memory and therefore increased fear renewal, since the article showed that the vmPFC is associated with neural circuitry during extinction recall. The hippocampus and amygdala are the other components to this neural circuit of extinction recall, so the morphologic changes that occur in these structures during PTSD would also be expected to increase fear renewal.
There has been some pushback against the use of fMRIs, due to some improper statistical methods being used to analyze this neuroimaging technique and the fact that it there is a lot of competing evidence as to the functions of a particular brain region. How does this article try to rationalize their use of fMRIs?
The research in this article used a fairly large sample size (for fMRI research, since it is typically very expensive) of 43 participants and many of their significant statistical tests have a very small p value that is often much less than 0.05. Also, the authors claim that fMRI is an appropriate test for this experiment because they were able to compare data from the same participants from one day to the next (within-subjects design) and therefore were able to account for the large variance of blood oxygenation levels from one participant to the next.
Is there a way that to decrease the amount of interference between the dorsal hippocampus and the ventral hippocampus?
In this study there was limitations to the information between the hippocampus and the amygdala a correlation in fMRI responses between the ventral hippocampus and the amygdala could be artefactual and simply be influenced by the spatial proximity between the regions.
How did the results from this study differ than those from previous studies?
This study found increased signaling to the CS- relative to the CS+ during extinction recall in the vmPFC. Previous studies found increased signaling to the CS+ relative to the CS-.
Justification: In scientific studies, it is important to discuss results in relation to previous studies. If results are in agreement with previous studies, it increases the validity and credibility of the current study. However, if there are any discrepancies among results, this should prompt further research.
*Answer found in the discussion section
What potential conditions might this research help to understand?
First, and most clearly, would be PTSD (post-traumatic stress disorder). This is certainly the focal point of this research, as it was identified as the leading condition they were seeking to understand via these experiments. However, there are a few other potential candidates that may aid from this research.
As the second article described, it is likely that fear-acquisition occurs more rapidly and is more difficult to extinguish when the trauma occurs within short distances. Therefore, it is possible that this research might help to understand phobias, i.e. claustrophobia. Additionally, understanding the systems through which fear propagates will help us understand the phobias of our society (racism, stereotypes, generalizations) due to the fear-conditioning that occurs throughout our lives. Hidden, conditioned fears will bring us anxiety and fear, despite what context it may be presented in (as shown by the experiments in both articles).