Cortical complexity in world trade center responders with chronic posttraumatic stress disorder

Abstract

Approximately 23% of World Trade Center (WTC) responders are experiencing chronic posttraumatic stress disorder (PTSD) associated with their exposures at the WTC following the terrorist attacks of 9/11/2001, which has been demonstrated to be a risk factor for cognitive impairment raising concerns regarding their brain health. Cortical complexity, as measured by analyzing Fractal Dimension (FD) from T1 MRI brain images, has been reported to be reduced in a variety of psychiatric and neurological conditions. In this report, we hypothesized that FD would be also reduced in a case-control sample of 99 WTC responders as a result of WTC-related PTSD. The results of our surface-based morphometry cluster analysis found alterations in vertex clusters of complexity in WTC responders with PTSD, with marked reductions in regions within the frontal, parietal, and temporal cortices, in addition to whole-brain absolute bilateral and unilateral complexity. Furthermore, region of interest analysis identified that the magnitude of changes in regional FD severity was associated with increased PTSD symptoms (reexperiencing, avoidance, hyperarousal, negative affect) severity. This study confirms prior findings on FD and psychiatric disorders and extends our understanding of FD associations with posttraumatic symptom severity. The complex and traumatic experiences that led to WTC-related PTSD were associated with reductions in cortical complexity. Future work is needed to determine whether reduced cortical complexity arose prior to, or concurrently with, onset of PTSD.

Functional changes in neural mechanisms underlying post-traumatic stress disorder in World Trade Center responders

“…Seven out of nine functional hubs differ between WTC-PTSD and non-PTSD in our study were located in the right hemisphere (Figure 1, Table 2), suggesting lateralization of the association between WTC-PTSD and centrality. These results align with our previous study in this cohort demonstrating anatomical changes with strong lateralization in the right hemisphere across several brain areas 6 . Lateralization may be due to specific functions of the right hemisphere such as the continuous interchange of information with the amygdala.…”

“…During these months on the pile, WTC responders were exposed to both traumatic event and a number of pollutants including lead, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and dioxins that all together might have played a role in the anatomical and functional changes observed 36–39 . These changes and their significant association with long-term WTC exposure involve only specific cortical and subcortical brain regions such as the whole hippocampus and its subfields 5 , parahippocampal gyrus, amygdala, and finally frontal and parietal brain regions 6 that seem more vulnerable to experience at the WTC site. These results might be explained by the fear-conditioning mechanism and novel neurocircuitry models 9–11 that suggest the triggering event, in this case WTC responders experienced during rescue and recovery efforts, targets brain areas known to be involved in PTSD, i.e., the parahippocampus and amygdala.…”

“…Recent studies of WTC-responders, including previous studies in our group, leverage structural MRI to characterize anatomical differences between WTC responders with PTSD (WTC-PTSD) and non-PTSD controls 5,6 and demonstrate evidence of anatomical changes such as reduced cortical complexity across brain areas (frontal, parietal, and temporal) 6 . The size of these structural changes was associated with increased PTSD symptoms scales (re-experiencing, avoidance, hyperarousal, negative thoughts) severity 6 . To date, no studies have used functional MRI to characterize PTSD in WTC-responders.…”

Cognitive Function among World Trade Center-Exposed Community Members with Mental Health Symptoms

“…Extensive studies of those involved in the rescue and recovery efforts after 11 September 2011 (WTC Responders) indicate that WTC exposures may be associated with neuroinflammation, neurodegeneration and increased cognitive impairment, and in turn, with increased risk of Alzheimer’s disease and related dementia in subsequent years [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. In particular, cognitive impairment among WTC Responders has been extensively studied using validated instruments for measuring objective cognitive dysfunctions including the Montreal Cognitive Assessment (MoCA, [ 9 ]), and in-depth assessments using well-established blood-based biomarkers and neuroimaging markers of cognitive impairment [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. These reports also include a large number of association studies of cognitive impairment with WTC exposures and associated mental health conditions among WTC Responders.…”

“…Studies have also found PTSD to be associated with cognitive impairment in both military and non-military populations [ 4 , 5 , 7 , 10 , 37 , 38 , 39 , 40 , 41 , 42 ]. Extensive research has been carried out on cognitive functioning and decline in the WTC Responder population including on self-reported cognitive complaints [ 10 , 41 ], an association with PTSD [ 4 , 5 , 7 ], dust exposure [ 1 ], as well as biomarkers and neuroimaging studies [ 2 , 3 , 8 ].…”