Brain volumetric correlates of inhibition and cognitive flexibility 16 years following childhood traumatic brain injury

Pediatric Moderate-Severe Traumatic Brain Injury and Gray Matter Structural Covariance Networks: A Preliminary Longitudinal Investigation

Pediatric traumatic brain injury (TBI) is prevalent and can disrupt ongoing brain maturation. However, the long-term consequences of pediatric TBI on the brain's network architecture are poorly understood. Structural covariance networks (SCN), based on anatomical correlations between brain regions, may provide important insights into brain topology following TBI. Changes in global SCN (default-mode network [DMN], central executive network [CEN], and salience network [SN]) were compared sub-acutely (<90 days) and in the long-term (approximately 12-24 months) after pediatric moderate-severe TBI (n = 16), and compared to typically developing children assessed concurrently (n = 15). Gray matter (GM) volumes from selected seeds (DMN: right angular gyrus [rAG], CEN: right dorsolateral prefrontal cortex [rDLPFC], SN: right anterior insula) were extracted from T1-weighted images at both timepoints. No group differences were found sub-acutely; at the second timepoint, the TBI group showed significantly reduced structural covariance within the DMN seeded from the rAG and the (1) right middle frontal gyrus, (2) left superior frontal gyrus, and (3) left fusiform gyrus. Reduced structural covariance was also found within the CEN, that is, between the rDLPFC and the (1) calcarine sulcus, and (2) right occipital gyrus. In addition, injury severity was positively associated with GM volumes in the identified CEN regions. Over time, there were no significant changes in SCN in either group. The findings, albeit preliminary, suggest for the first time a long-term effect of pediatric TBI on SCN. SCN may be a complementary approach to characterize the global effect of TBI on the developing brain. Future work needs to further examine how disruptions of these networks relate to behavioral and cognitive difficulties.

Mindfulness improves verbal learning and memory through enhanced encoding

Recent research has begun to demonstrate the effectiveness of mindfulness in improving certain cognitive abilities, including verbal learning and memory. However, no research has investigated the potential mechanism by which mindfulness may improve verbal learning and memory. We examined encoding, consolidation, and retrieval as potential mechanisms by which learning and memory may be increased on a list learning test (Rey Auditory Verbal Learning Task; RAVLT). After dividing participants into either a mindfulness or a control condition, in which they listened to a 10-min audio tape, results found that the mindfulness condition significantly outperformed the control condition on every RAVLT trial. Using the Item-Specific Deficit Approach, we discovered that this enhanced verbal learning and memory was specifically due to a significantly enhanced encoding process for the mindfulness group, which fully mediated the relationship between the mindfulness condition and performance on the RAVLT. There were no differences between the conditions on consolidation or retrieval. Furthermore, these improvements were not accompanied by improvements in verbal fluency or attention. In a second study, we presented a mindfulness or control audio before the first RAVLT delayed free-recall trial and another one before the second RAVLT delayed free-recall trial in order to better determine the effect of mindfulness on consolidation and retrieval. The results replicated Study 1, in that neither consolidation nor retrieval were significantly affected by mindfulness. This research indicates that mindfulness may primarily improve verbal learning and memory through improved encoding processes.