Case Study of a Breacher: Investigation of Neurotrauma Biomarker Levels, Self-reported Symptoms, and Functional MRI Analysis Before and After Exposure to Measured Low-Level Blast.

We report a case study on a single military member who received moderate blast overpressure (OP) exposure during routine breacher training. We extend previous research on blast exposure during training, which lacked sufficient data to assess symptom profiles and OP exposure. The present work was conducted because a subjective symptom profile similar to that seen in sports concussion has been reported by military personnel exposed to blast. Data collection for this study was carried out under a research protocol approved by the relevant Human Subjects Review Committees on one subject, who received the highest OP exposure during training. The volunteer was a 20-year-old male with no prior history of traumatic brain injury (TBI) or blast exposure. The volunteer was part of a breacher training team that completed a 2-week explosive entry course. The course included 3 classroom days and 9 days of practical training, held in the morning, afternoon, and evening sessions. Blast exposure occurred on five of the nine practical training days, with multiple exposures over the course of each day. Assessments of serum, self-reported symptoms, magnetic resonance imaging, and blast characterization were conducted. Results indicated changes in glial fibrillary acidic protein and ubiquitin C-terminal hydrolase-L1 postblast exposure but did not manifest changes in spectrin-derived breakdown product 150 or magnetic resonance imaging. No additional symptoms were reported by the subject. Objective markers of mild TBI remain elusive, but support for serum biomarkers as an early detection mechanism is promising. Additionally, this case study demonstrated an association between OP and high level of neurotrauma biomarker in an individual.

Longitudinal Investigation of Neurotrauma Serum Biomarkers, Behavioral Characterization, and Brain Imaging in Soldiers Following Repeated Low-Level Blast Exposure (New Zealand Breacher Study).

"Breachers" (dynamic entry personnel) are routinely exposed to low-level blast overpressure during training and occupational duties. Data were collected from 22 military breachers (mean 29.7 yr) over a 5-yr period to characterize the longitudinal effects of repeated low-level blast overpressure exposure. None of the participants reported a diagnosed concussion during the study period. Blood-based biomarker concentrations (n = 22) showed either no significant change or a significant decrease over time. Neurocognitive performance (n = 20) and symptom reporting (n = 22) did not change over time. Neuroimaging analyses resulted in no significant differences for within-subject (baseline vs follow-up, n = 8) and between-subject (naïve, n = 5 vs experienced, n = 8) comparisons. Changes to training doctrine mid-study reduced blast exposure (< 4 psi) and may have mitigated any measurable effects associated with long-term, low-level blast exposure. The results suggest that the first 5 yr of a breaching career in healthy, young individuals is unlikely to result in measurable effects when overpressure exposure is maintained within the 4 psi safe limit. The lack of any significant changes in these operators suggests that either no identifiable injuries occurred and/or measurement tools may not be sensitive enough to identify any negative subconcussive effects.

Relation of repeated low-level blast exposure with symptomology similar to concussion.

OBJECTIVE: To investigate anecdotal reports suggesting that repeated exposure to low-level explosive blast has myriad health impacts, including an array of neurological effects. PARTICIPANTS: A total of 184 anonymous survey respondents from military and nonmilitary law enforcement populations (135 exposed to occupational blast and 49 controls). DESIGN: Survey of self-reported history of occupational exposure to repeated low-level blast (breaching blast) and symptomology similar to concussion. RESULTS: Findings suggest that number and severity of symptoms increase with history of chronic blast exposure (F = 18.26, P < .001) and that symptoms can interfere with daily activity (t = 2.60, P = .010). CONCLUSION: Given the prevalence of repeated exposure to blast among some military and civilian law enforcement occupations, the results of this survey study support a role for blast surveillance programs as well as continued research on health impacts of low-level repeated blast exposure.

Automated Neuropsychological Assessment Metrics: repeated assessment with two military samples.

INTRODUCTION: U.S. military troops deploying to war zones are currently administered the Automated Neuropsychological Assessment Metrics (ANAM4) Traumatic Brain Injury (TBI) Battery to establish individual neurocognitive performance baselines. In part, the utility of the ANAM4 TBI Battery baseline measurement depends on test-retest reliability of this instrument. The purpose of this report was to evaluate performance following multiple administrations of the ANAM4 TBI Battery: does performance in a repeated measures paradigm constitute a stable, interpretable indication of baseline neurocognitive ability? METHODS: The data presented here are from the ANAM4 TBI Battery administered four times to a group of U.S. Marines in Study 1 and eight times to a group of New Zealand Defence Force personnel in Study 2. RESULTS: The results show practice effect in five of six performance subtests in both Study 1 and Study 2. DISCUSSION: Results are consistent with expectations that multiple test sessions are required to reach stable performance on some computerized tasks. These results have implications for taking ANAM4 TBI Battery practice effects into account in test administration and in data interpretation.

Does temporal asynchrony affect multimodal curvature detection?

Multiple sensory modalities gather information about our surroundings to plan appropriate movements based on the properties of the environment and the objects within it. This study was designed to examine the sensitivity of visual and haptic information alone and together for detecting curvature. When both visual and haptic information were present, temporal delays in signal onset were used to determine the effect of asynchronous sensory information on the interference of vision on the haptic estimate of curvature. Even under the largest temporal delays where visual and haptic information were clearly disparate, the presentation of visual information influenced the haptic perception of curvature. The uncertainty associated with the unimodal vision condition was smaller than that in the unimodal haptic condition, regardless of whether the haptic information was procured actively or under robot assistance for curvature detection. When both visual and haptic information were available, the uncertainty was not reduced; it was equal to that of the unimodal haptic condition. The weighting of the visual and haptic information was highly variable across subjects with some subjects making judgments based largely on haptic information, while others tended to rely on visual information equally or to a larger extent than the haptic information.

Effects of object compliance on three-digit grasping.

Compared with rigid objects, grasping and lifting compliant objects presents additional uncertainties. For any static grasp, forces at the fingertips depend on factors including the locations of the contact points and the contact forces must be coordinated to maintain equilibrium. For compliant objects, the locations and orientations of the contact surfaces change in a force-dependent manner, thus changing the force requirements. Furthermore, every force adjustment then results in additional changes in object shape. This study characterized force and muscle activation patterns in this situation. Fingertip forces were measured as subjects grasped and lifted a 200-g object using their thumb, index, and ring fingers. A spring was sometimes placed under the index and/or ring finger contact surface. Surface electromyographic activity was recorded from ten hand muscles and one proximal arm muscle. The patterns of grip (normal) force and muscle activity were similar across conditions during the load and lift phases, but their amplitude depended on whether the contact surface was compliant. Specifically, the grip force increased smoothly during the load phase of the task under all conditions. To the contrary, the tangential contact (load) force did not increase monotonically when one or more of the contact surfaces were compliant, resulting in a decoupling of the grip and load forces.

Multi-digit control of contact forces during rotation of a hand-held object.

Rotation of an object held with three fingers is produced by modulation of force amplitude and direction at one or more contact points. Changes in the moment arm through which these forces act can also contribute to the modulation of the rotational moment. Therefore force amplitude and direction as well as the center of pressure on each contact surface must be carefully coordinated to produce a rotation. Because there is not a single solution, this study sought to describe consistent strategies for simple position-to-position rotations in the pitch, roll, and yaw axes. Force amplitude and direction, and center of pressure on the contact surfaces (and thus the moment arm), were measured as human subjects rotated a 420 g force-transducer instrumented object, grasped with the thumb, index and ring fingers (average movement time: 500 ms). Electromyographic (EMG) activity was recorded from five intrinsic and three extrinsic hand muscles and two wrist muscles. Principal components analysis of force and EMG revealed just two main temporal patterns: the main one followed rotational position and the secondary one had a time course that resembled that of rotational velocity. Although the task could have been accomplished by dynamic modulation of the activity of wrist muscles alone, these two main dynamic EMG patterns were seen in intrinsic hand muscles as well. In contrast to previous reports of shifting in time of the phasic activity bursts of various muscles, in this task, all EMG records were well described by just two temporal patterns, resembling the position and velocity traces.