Acute Posttrauma Resting-State Functional Connectivity of Periaqueductal Gray Prospectively Predicts Posttraumatic Stress Disorder Symptoms.

BACKGROUND: Posttraumatic stress disorder (PTSD) is characterized by hyperarousal, avoidance, and intrusive/re-experiencing symptoms. The periaqueductal gray (PAG), which generates behavioral responses to physical and psychological stressors, is also implicated in threat processing. Distinct regions of the PAG elicit opposing responses to threatening or stressful stimuli; the ventrolateral PAG evokes passive coping strategies (e.g., analgesia), whereas the dorsolateral PAG (dlPAG) promotes active responses (e.g., fight or flight). We investigated whether altered PAG resting-state functional connectivity (RSFC) prospectively predicted PTSD symptoms. METHODS: A total of 48 trauma-exposed individuals underwent an RSFC scan 2 weeks posttraumatic injury. Self-report measures, including the visual analog scale for pain and the Impact of Event Scale, were collected at 2 weeks and 6 months posttrauma. We analyzed whether acute bilateral PAG RSFC was a marker of risk for total 6-month symptom severity and specific symptom clusters. In an exploratory analysis, we investigated whether dlPAG RSFC predicted PTSD symptoms. RESULTS: After adjusting for physical pain ratings, greater acute posttrauma PAG-frontal pole and PAG-posterior cingulate cortex connectivity was positively associated with 6-month total PTSD symptoms. Weaker dlPAG-superior/inferior parietal lobule connectivity predicted both higher hyperarousal and higher intrusive symptoms, while weaker dlPAG-supramarginal gyrus RSFC was associated with only hyperarousal symptoms. CONCLUSIONS: Altered connectivity of the PAG 2 weeks posttrauma prospectively predicted PTSD symptoms. These findings suggest that aberrant PAG function may serve as a marker of risk for chronic PTSD symptoms, possibly by driving specific symptom clusters, and more broadly that connectivity of specific brain regions may underlie specific symptom profiles.

Rapidly training African giant pouched rats (Cricetomys ansorgei) with multiple targets for scent detection.

Since 1997, APOPO, a non-profit organization based in Tanzania, has deployed African giant pouched rats (Cricetomys ansorgei) to detect landmines in post-conflict areas. More recent research suggests the pouched rats can also be trained to detect tuberculosis in human sputum samples. Despite proven success on both tasks, the potential impact of each rat is limited by the required training time and constraint to a single target odor. The aim of this project was to establish a technique to rapidly train pouched rats to detect multiple odor targets. Eight pouched rats were trained to detect five unrelated target odors in Experiment 1. In addition to training duration, we measured maintenance of all odor targets. In Experiment 2, we examined response persistence under conditions of extinction. Experiment 3 investigated whether refresher sessions before tests would maintain detection accuracy. The animals mastered all odor targets in significantly fewer sessions than APOPO's operational rats require to master a single target odor. Importantly, rats demonstrated strong discrimination between targets and non-targets despite the potential for interference and forgetting, suggesting pouched rats can be trained to detect at least five targets simultaneously. These results have the potential to increase the impact of each detection rat by both decreasing training time and expanding operational versatility, e.g., a single rat could be trained to detect multiple diseases.