Disrupted Gamma Synchrony after Mild Traumatic Brain Injury and Its Correlation with White Matter Abnormality

Abstract

Mild traumatic brain injury (mTBI) has been firmly associated with disrupted white matter integrity due to induced white matter damage and degeneration. However, comparatively less is known about the changes of the intrinsic functional connectivity mediated via neural synchronization in the brain after mTBI. Moreover, despite the presumed link between structural and functional connectivity, no existing studies in mTBI have demonstrated clear association between the structural abnormality of white matter axons and the disruption of neural synchronization. To investigate these questions, we recorded resting state EEG and diffusion tensor imaging (DTI) from a cohort of military service members. A newly developed synchronization measure, the weighted phase lag index was applied on the EEG data for estimating neural synchronization. Fractional anisotropy was computed from the DTI data for estimating white matter integrity. Fifteen service members with a history of mTBI within the past 3 years were compared to 22 demographically similar controls who reported no history of head injury. We observed that synchronization at low-gamma frequency band (25–40 Hz) across scalp regions was significantly decreased in mTBI cases compared with controls. The synchronization in theta (4–7 Hz), alpha (8–13 Hz), and beta (15–23 Hz) frequency bands were not significantly different between the two groups. In addition, we found that across mTBI cases, the disrupted synchronization at low-gamma frequency was significantly correlated with the white matter integrity of the inferior cerebellar peduncle, which was also significantly reduced in the mTBI group. These findings demonstrate an initial correlation between the impairment of white matter integrity and alterations in EEG synchronization in the brain after mTBI. The results also suggest that disruption of intrinsic neural synchronization at low-gamma frequency may be a characteristic functional pathology following mTBI and may prove useful for developing better methods of diagnosis and treatment.

Validation of IMU-based gait event detection during curved walking and turning in older adults and Parkinson’s Disease patients

“…Of course, this statement only applies to the sensor constellation as used in this study, and not, for example, to data from IMUs positioned at the low back. Although methods derived from low back- or foot-mounted IMUs [ 12 , 13 , 20 , 47 ] may be less susceptible to turns, literature suggested that GE detection is easier and more robust from shank-mounted IMUs. [ 17 – 19 ]…”

“…For both events we evaluated the detection performance in terms of correctly identified events (true positives, TP ), falsely identified events (false positives, FP ) and missed events (false negatives, FN ). TP s were defined as < 300 ms difference (in terms of magnitude) between an event detected by the IMU-based algorithm and the reference event [ 12 ]. From these metrics the recall, precision and F1 score were derived: Recall expressed how many of the gait events were detected and precision expressed how many of the detected gait events were true gait events.…”

“…The performance of IMU-based GE detection is, however, often tested only with treadmill walking [ 12 , 14 ] or from walking trials where only the straight-line segments of walking trajectories were included in the analysis [ 13 , 17 , 21 ]. For more complex walking tasks, such as slalom walking or dual-task walking, one often relies on visually counting of the number of steps, which does not allow to assess the time error of the GE detection and is more prone to errors.…”

Neuronal Degeneration Impairs Rhythms Between Connected Microcircuits

“…Likewise, learning and memory largely depend on coherence, which enables long-distance communication between brain regions (Dü Zel et al, 2010;Wang et al, 2010). Several human imaging studies demonstrate that TBI disrupts synchronization (Sharp et al, 2011;Venkatesan et al, 2015;Wang et al, 2017), leading to the likely increase or decrease in functional network connectivity that contributes to long-term cognitive effects.…”

Chronic traumatic encephalopathy—a blueprint for the bridge between neurological and psychiatric disorders

“…Similarly, memory processing is mainly contingent upon coherence, which allows long-distance interaction between various brain regions 38,39 . Recent findings in human imaging studies identified that TBI disturbs synchronization [40][41][42] , leading to the probable increase or decrease in functional network connectivity that contributes to long-term cognitive defects.…”