History of Mild Traumatic Brain Injury Affects Static Balance under Complex Multisensory Manipulations.

A recent study in active-duty military in the Coast Guard suggested that lifetime experience with mild traumatic brain injury (mTBI) was associated with subtle deficits in postural control when exposed to multi-sensory discordance (i.e., rotating visual stimulation). The present study extended postural assessments to veterans recruited from the community. Service veterans completed the Defense Veteran Brain Injury Center TBI Screening Tool, Post-Traumatic Stress Disorder (PTSD) Checklist (PCL-5), and Neurobehavioral Symptom Inventory (NSI). Postural control was assessed using a custom-designed, virtual-reality-based device, which assessed center of pressure sway in response to six conditions designed to test sensory integration by systematically combining three visual conditions (eyes open, eyes closed, and rotating scene) with two somatosensory conditions (firm or foam surface). Veterans screening positive for lifetime experience of mTBI (mTBI+) displayed similar postural sway to veterans without a lifetime experience of mTBI (mTBI-) on basic assessment of eyes open or closed on a firm and foam surface. mTBI+ veterans displayed greater sway than mTBI- veterans in response to rotating visual stimuli while on a foam surface. Similar to previous research, degree of sway was affected by the number of lifetime experiences of mTBI. Increased postural sway was not related to PTSD, NSI, or balance-specific symptom expression. In summary, veterans who experienced mTBI over their lifetime exhibited dysfunction in balance control as revealed by challenging conditions with multi-sensory discordance. These balance-related signs were independent of self-reported balance-related symptoms or other symptom domains measured by the NSI, which can provide a method for exposing otherwise covert dysfunction long after the experience of mTBI.

Acute neurocognitive deficits in active duty service members following subconcussive blast exposure.

Military service members are frequently subjected to subconcussive blast events during training and deployment. Emerging evidence suggests blast exposures of these magnitudes may have long-term consequences for dimensions of cognitive function. Less is known about cognitive sequelae acutely following deployment-related subconcussive blast events. The current study addressed this knowledge gap by assessing the extent to which subconcussive blast exposure affected performance on the Automated Neuropsychological Assessment Metrics 4 TBI-MIL (ANAM). Baseline-referenced and normative comparisons of archival ANAM data were analyzed for a cohort of personnel who were exposed to blast (blast group; n = 27) and personnel who were not exposed to blast (no-blast group; n = 36) that were otherwise asymptomatic for a concussion. The blast group exhibited statistically significant lower scores compared to the no-blast group (between-subjects), baseline assessments (within-subjects), and an age-matched normative population. Normative comparisons revealed that the scores for the reaction time subtests (i.e., procedural and both simple reaction time tasks) were outside the range of normal functioning (1 SD) and reliable change indices revealed clinically meaningful change only for simple reaction time. The results highlight covert effects of subconcussive blast exposure that may warrant further monitoring in the immediate aftermath of a blast event.

Enhanced Acquisition and Retention of Conditioned Eyeblink Responses in Veterans Expressing PTSD Symptoms: Modulation by Lifetime History of Mild Traumatic Brain Injury.

Enhanced acquisition of eyeblink conditioning is observed in active duty military and veterans expressing PTSD symptoms (PTSD+) and those expressing temperamental vulnerabilities to develop PTSD after traumatic experiences, such as behaviorally inhibited temperament. There is a growing literature showing persistent cerebellar abnormalities in those experiencing mild traumatic brain injury (mTBI+) as well as linkages between mTBI and PTSD. With the dependency of eyeblink conditioning on cerebellar processes, the impact of mTBI on eyeblink conditioning in veterans expressing PTSD is unknown. The present study assessed eyeblink conditioning in veterans during two sessions separated by 1 week. With a focus on the accelerated learning of veterans expressing PTSD, training utilized a protocol which degrades learning through interspersing conditioned stimulus (CS) exposures amongst delay-type trials of CS and unconditional stimulus (US) co-terminating trials. Faster acquisition of the eyeblink conditioned responses (CR) was observed in PTSD during Week 1. The Week 2 assessment revealed an interaction of mTBI and PTSD, such that asymptotic performance of PTSD+ was greater than PTSD- among mTBI- veterans, whereas these groups did not differ in mTBI+ veterans. To further examine the relationship between enhanced sensitivity to acquire eyeblink conditioning and PTSD, cluster analysis was performed based on performance across training sessions. Those with enhanced sensitivity to acquire eyeblink conditioned responses expressed more PTSD symptoms, which were specific to Cluster C symptoms of avoidance, in addition to greater behavioral inhibition. These results support the continued investigation of the conditioned eyeblink response as a behavioral indicator of stress-related psychopathology.

Cardiorespiratory Response to Moderate Hypercapnia in Female College Students Expressing Behaviorally Inhibited Temperament.

Behaviorally inhibited (BI) temperament is marked by heightened behavioral sensitivity to environmental threats. The degree to which threat sensitivity is reflected in cardiorespiratory responses has been relatively unexplored. Female college students were exposed to modest hypercapnia (7.0% CO2) or ambient air (AA) while engaging in a computerized task with cued reinforcement features. All physiological variables except for blood pressure were processed in 4 min epochs corresponding to pre-exposure, exposure, and post-exposure. Primary respiratory measures were respiratory frequency (fb), tidal volume (VT), and minute ventilation (VE). Electrocardiograms (ECGs) were processed using ARTiiFACT software with resultant heart rate variability (HRV) measures in the frequency domain and time domain. Consistent with the literature, modest hypercapnia increased VT, Fb, and VE. No differences in respiratory parameters were detected between BI and non-behaviorally inhibited individuals (NI). For HRV in the time domain, RMSSD and NN50 values increased during CO2 inhalation which then returned to pre-exposure levels after CO2 cessation. Hypercapnia increased high frequency (HF) power which then recovered. BI exhibited reduced low frequency (LF) power during the pre-exposure period. For NI, LF power reduced over the subsequent phases ameliorating differences between BI and NI. Hypercapnia improved the task performance of BI. This is the largest study of female reactivity to hypercapnia and associated HRV to date. In general, hypercapnia increased time domain HRV and HF power, suggesting a strong vagal influence. Those expressing BI exhibited similar respiratory and HRV reactivity to NI despite inherently reduced LF power. Although 7% CO2 represents a mild challenge to the respiratory and cardiovascular systems, it is nonetheless sufficient to explore inherent difference in stress reactivity in those vulnerable to develop anxiety disorders.

Relationships Between Sleepiness, Mood, and Neurocognitive Performance in Military Personnel.

Neurocognitive computerized assessment tools (NCATs) were developed to assist military clinicians with the tracking of recovery from injury and return to full duty decisions with a recent focus on the setting of post-concussion evaluations. However, there is limited data on the impact of deployment on neurocognitive functioning, sleepiness, and mood in healthy, non-concussed Service members. Automated Neuropsychological Assessment Metrics version 4 TBI Military (ANAM) data was obtained for a sample of active duty deployed personnel (n = 72) without recent history of mild traumatic brain injury (mTBI). A linear regression was conducted to examine the effects of sleepiness and mood state on neurocognitive performance. The overall multivariate regression was statistically significant. Negative mood states were the most salient predictors of neurocognitive performance with higher levels of endorsement associated with lower scores. The findings support measures of negative mood state, but not sleepiness, as relevant predictors of neurocognitive performance as measured by the ANAM. These results indicate that mood needs to be considered when reviewing neurocognitive data to ensure that appropriate clinical decisions are made; in particular for return-to-duty decisions in deployed settings after concussion recovery.

Healthy Active Duty Military with Lifetime Experience of Mild Traumatic Brain Injury Exhibits Subtle Deficits in Sensory Reactivity and Sensory Integration During Static Balance.

Postural control and stress reactivity were investigated in active duty coast guard personnel to determine whether they are sensitive to lifetime effects of mild traumatic brain injury (mTBI). A custom-designed and validated virtual reality-based computerized posturography device was used to assess postural stability, whereas emotional reactivity was assessed using the acoustic startle response (ASR), and neurocognitive performance was assessed using the defense-automated neurobehavioral assessment (DANA). It was hypothesized that residual and subtle postural control imbalance and deficits in cognitive and sensory reactivity would be evident in those reporting multiple lifetime mTBI. Active duty military personnel (N = 36; 7 females and 29 males) with no Deployment Limiting Medical Condition were recruited and tested on all assessments. Medical history information provided a history of head injury. Thirty-nine percent of participants reported having a previous mTBI (nine reporting one and five reporting more than one incident). No participant had experienced a head injury within the past year and all were symptom free. A significant effect of number of mTBI was found in the postural assessment (p = 0.002). Lifetime mTBI was associated with suppressed ASR magnitude (p = 0.03) but did not affect neurocognitive performance. The current findings provide new insight into ongoing controversies concerning sensitivity to functional deficits following mTBI and when the window for treatment or restoration ends.

Context specificity of automatic influences of memory.

It has often been shown that intentional recollection is influenced by context manipulations, such as context reinstatement (e.g., Smith, 2013; Smith & Vela, 2001), but whether or not automatic retrieval (e.g., Jacoby, 1991) is likewise context dependent remains an open question. Here, we present two experiments that examined effects of context manipulations on indirect measures of memory. The first experiment tested anagram completion, and the second experiment used word fragment completion to test effects of context reinstatement; both experiments found reinstatement effects. To address potential problems of explicit contamination, we also asked participants if they were aware of the priming manipulations. Separating participants according to their test awareness showed effects of context manipulations for both aware and unaware participants. A greater effect size was found for aware participants only in Experiment 1, in which participants had enough time on each test trial for recollection to be used. We conclude that context reinstatement does affect automatic retrieval. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Neurocognitive and Fine Motor Deficits in Asymptomatic Adolescents during the Subacute Period after Concussion.

Adolescents are at high risk for sustaining concussions. There is considerable controversy regarding the sensitivity of neurocognitive tests to detect and track dysfunction in the aftermath of concussion. Two neurocognitive test batteries were compared during the subacute phase of recovery from concussion to determine sensitivity to concussion. Adolescents (ages 11-17 years) with a concussion diagnosis (eight males, seven females, 9-69 days after injury) were recruited through a concussion clinic and compared with community nonconcussed volunteers (11 males, three females). Adolescents completed the online version of the Immediate Post-Concussion Assessment and Cognitive Test (ImPACT) on a desktop computer and the Defense Automated Neurobehavioral Assessment (DANA) on a handheld device, as well as the Grooved Pegboard Test, which assessed manual dexterity and motor speed. There were no differences in self-reported symptoms on the Post-Concussion Symptom Scale comparing concussed and nonconcussed adolescents. No significant between-groups differences were observed in ImPACT performance. Performance deficits were apparent for the DANA assessment, reflecting lower throughput scores for simple reaction time and response inhibition parameters in those with concussion. Concussed adolescents also had slower Grooved Pegboard Test performance when using the nondominant hand. Both the DANA test battery and the Grooved Pegboard Test appear to have promise as tools to detect persistent cognitive and motor dysfunction in the subacute period after concussion.

Facilitated acquisition of the classically conditioned eyeblink response in active duty military expressing posttraumatic stress disorder symptoms.

OBJECTIVE: Learning diathesis models underscore the role of hyper-conditioning in the development of PTSD following trauma exposure. Eyeblink classical conditioning is one method of examining associative learning biases independent of fear and threat produced by trauma. Facilitated learning is apparent in individuals self-expressing PTSD symptoms, as well as behaviorally inhibited (BI) temperament, a vulnerability factor for PTSD. Here, we examine eyeblink conditioning in active duty military personnel and relate learning with PTSD symptomology. METHOD: Volunteers were 83 active duty United States Coast Guard personnel (18 females) recruited from small boat stations. Personnel were administered the PTSD Checklist (PCL) to assess current PTSD symptoms using DSM-IV criteria. BI temperament was assessed with the Adult Measure of Behavioural Inhibition (AMBI). Eyeblink conditioning was conducted using a partial reinforcement schedule, whereby paired trials (500-ms pure tone conditioned stimulus co-terminating with a 50-ms air-puff unconditional stimulus) were interpolated with 50% CS-alone trials. RESULTS: Consistent with previous work, there was a high degree of concordance between BI and incidence of PTSD. Further, PTSD was associated with faster learning during the acquisition period, with conditioned responding sustained through the extinction period. CONCLUSIONS: These results reinforce the relationship between BI and PTSD in an active duty military sample, supporting previous observations in veteran and civilian samples. The conditioning data are consistent with predictions derived from a learning diathesis model of stress and anxiety, suggesting facilitated associative learning may represent an additional vulnerability for the development and maintenance of stress-related pathology.

Stress-Related Mental Health Symptoms in Coast Guard: Incidence, Vulnerability, and Neurocognitive Performance.

U.S. Coast Guard (CG) personnel face occupational stressors (e.g., search and rescue) which compound daily life stressors encountered by civilians. However, the degree CG personnel express stress-related mental health symptoms of posttraumatic stress disorder (PTSD) and major depressive disorder (MDD) is understudied as a military branch, and little is known concerning the interplay of vulnerabilities and neurocognitive outcomes in CG personnel. The current study addressed this knowledge gap, recruiting 241 active duty CG personnel (22% female) to assess mental health, personality, and neurocognitive function. Participants completed a battery of scales: PTSD Checklist with military and non-military prompts to screen for PTSD, Psychological Health Questionnaire 8 for MDD, and scales for behaviorally inhibited (BI) temperament, and distressed (Type D) personality. Neurocognitive performance was assessed with the Defense Automated Neurobehavioral Assessment (DANA) battery. Cluster scoring yielded an overall rate of PTSD of 15% (95% CI: 11-20%) and 8% (95% CI: 3-9%) for MDD. Non-military trauma was endorsed twice that of military trauma in those meeting criteria for PTSD. Individual vulnerabilities were predictive of stress-related mental health symptoms in active duty military personnel; specifically, BI temperament predicted PTSD whereas gender and Type D personality predicted MDD. Stress-related mental health symptoms were also associated with poorer reaction time and response inhibition. These results suggest rates of PTSD and MDD are comparable among CG personnel serving Boat Stations to those of larger military services after combat deployment. Further, vulnerabilities distinguished between PTSD and MDD, which have a high degree of co-occurrence in military samples. To what degree stress-related mental healthy symptoms and attendant neurocognitive deficits affect operational effectiveness remains unknown and warrant future study.

The crutch of context-dependency: Effects of contextual support and constancy on acquisition and retention.

Paired associates (Tagalog-English word pairs) were studied and practiced with pairs superimposed over pictorial contexts, and tested with no context cues. On every retrieval practice (RP) incidental or conceptually supportive contexts were repeatedly shown with the same pair (constant context condition), or else new contexts were shown on every RP trial (varied context condition). Incidental contexts in the constant condition and supportive contexts in both constant and varied context conditions facilitated practice scores, but left learning susceptible to forgetting when context cues were not provided. In contrast, varying incidental contexts during practice resulted in slower acquisition, but greater retention in the absence of context cues. The results show that varying incidental contexts during practice can be a desirable difficulty.

Effects of varied and constant environmental contexts on acquisition and retention.

Four experiments examined the decontextualization of memories, the stage of learning in which memories can be recalled in the absence of episodic memory cues. Face-name pairs were studied with video-recorded environmental contexts in the background, and after 5 practice trials, recall of names associated with faces was tested in the absence of the original video context cues. In Experiments 1, 2, and 3, five retrieval practice trials for a pair occurred either always with the original video context (constant context condition) or with a new context on each trial (varied context condition). Final recall was tested either on the same day (Experiments 3 and 4) or 2 days later (Experiments 1 and 2), and either the recall test context for each face was a new (never seen) video (Experiment 1) or there was no context shown at test (Experiments 2, 3, and 4). In the first 3 experiments, acquisition was better for the constant context condition, but on the final recall test, performance was better for pairs learned under varied context conditions. In Experiment 4, which used multiple study trials rather than multiple retrieval practices during acquisition, no differences were found between the constant and varied context conditions, either for acquisition or for final retention. The results show that acquisition trials given in varied contexts can result in decontextualized memories, but only when acquisition involves retrieval practice, rather than simple restudy trials. These results are consistent with the new theory of disuse, but not with the theory of encoding variability.

Effects of similarity on environmental context cueing.

Three experiments examined the prediction that context cues which are similar to study contexts can facilitate episodic recall, even if those cues are never seen before the recall test. Environmental context cueing effects have typically produced such small effect sizes that influences of moderating factors, such as the similarity between encoding and retrieval contexts, would be difficult to observe experimentally. Videos of environmental contexts, however, can be used to produce powerful context-dependent memory effects, particularly when only one memory target is associated with each video context, intentional item-context encoding is encouraged, and free recall tests are used. Experiment 1 showed that a not previously viewed video of the study context provided an effective recall cue, although it was not as effective as the originally viewed video context. Experiments 2 and 3 showed that videos of environments that were conceptually similar to encoding contexts (e.g., both were videos of ball field games) also cued recall, but not as well if the encoding contexts were given specific labels (e.g., "home run") incompatible with test contexts (e.g., a soccer scene). A fourth experiment that used incidental item-context encoding showed that video context reinstatement has a robust effect on paired associate memory, indicating that the video context reinstatement effect does not depend on interactive item-context encoding or free recall testing.

Triggering memory recovery: effects of direct and incidental cuing.

The present study examined forgetting and recovery of narrative passages varying in emotional intensity, using what we refer to as the "dropout" method. Previous studies of this dropout procedure have used word lists as to-be-remembered material, but the present experiments used brief story vignettes with one-word titles (e.g., "Torture", "Insects"). These vignettes showed a strong dropout forgetting effect in free recall. Both text and picture cues from the vignettes eliminated the forgetting effect on a subsequent cued recall test. Vignette-related pictures in an incidental picture naming task, however, triggered little recovery of initially forgotten vignettes, as shown on a post-test. The results extend findings of large forgetting and memory recovery effects to materials that are more naturalistic than word lists. The findings also show that picture cues, which trigger strong memory recovery effects on a direct test of memory, had little effect on recovery when cues were encountered incidentally.