Community Violence and Alterations in Brain's Default Mode Network
Updated: Jul 19
Findings from Community Violence Exposure is Associated with Hippocampus–Insula Resting State Functional Connectivity in Urban Youth (Primary author- Mariam Reda)
To recap, while the amygdala is a part of the brain’s limbic system that generates emotions, the hippocampus (HPC) is a part involved in converting those short-term emotional moments into long-term memories. The insula is another important part of the brain, involved in paying attention to bodily and mental experiences related to stress and anxiety. Several other parts of the brain form the “default mode network” (DMN) which is active when we are passively resting or thinking about past events/ mind wandering. Our goal was to see how violence exposure affected kids’ hippocampus connectivity with DMN network (relating to self-rumination) and salience network (relating to sensory awareness). We hypothesized that children with higher violence exposure would have lower connectivity between hippocampus and insula, therefore leading to impaired fear circuitry even during resting state. We also thought the age of the child might play a role in how that connection is altered. In this study, we looked at something called resting state functional connectivity (rsFC), which is a measure of which parts of our brain are communicating with each other when we’re at rest (not engaged in any task or doing anything specific).
We found out that at rest, children with higher violence exposure had stronger connections between hippocampus and parts of the DMN. This change in functional connectivity may suggest that greater violence exposure leads to increased internally focused thoughts and self-rumination about negative past events. Furthermore, we also found that at rest, children with higher violence exposure had decreased connectivity between hippocampus and insula (part of the salience network). The insula is a key structure for sensory processing and bodily arousal during danger, thus an alteration in its connectivity with hippocampus could be a neural signature of childhood trauma and violence exposure. The combination of increased DMN connectivity and decreased salience network connectivity may lead to thinking constantly about past mistakes and having a hard time distinguishing perceived versus actual danger. One of the most important findings in this study was that violent events in the community affect these connections with the hippocampus more than violent events at school or home. Since children can perceive community events as being out of their control, those events may lead to more anxiety and self-rumination in kids even when they are at rest doing nothing.
Figure 1 (from paper):
The figure above shows that as number of community violent exposures in kids increases, there is weaker connection to insula (region associated with attention) and stronger connection in default mode network (PCC).
Community violence can have more lasting impacts on brain development in children living in urban areas. Parents and teachers can help by checking in with children about their experiences outside home and school to make sure kids aren’t stuck on rethinking past traumatic events. Parents can talk to their children about their experiences in the community to help them feel better and reduce their internal monologue regarding perceived dangers. It could also help if counselors at elementary and middle schools offered parenting and psychoeducation programs for caregivers in areas with greater community violence. Trauma at an early age can leave many invisible scars, but kids can be more resilient if they have a loving and supportive environment at home and at school. Mindfulness of breathing and heart rate can also help kids pay attention to their bodies when they are stressed and therefore improve their neural connections related to self-awareness. Other researchers have found improved wellbeing and reduced DMN activation in people who practice daily mindfulness meditation.
In conclusion, violence exposure at young age can alter neural connections
between the default mode network and hippocampus, as well as the salience network
(insula) and hippocampus even when kids are at rest doing nothing. But kids can increase resilience by talking with their parents, having psychoeducation at school, and
learning to be more mindful of their bodies’ sensations and reactions. In the next blog, we will have more information on how measuring body reactions such as skin conductance can be related to brain activity, and how that can allow us to predict
future mental health outcomes.