Procedural learning impairments identified via predictive saccades in chronic traumatic brain injury

Neural mechanisms associated with sleep-dependent enhancement of motor learning after brain injury

This study aimed to examine the improvement in performance and functional magnetic resonance imaging correlates of motor learning after a daytime nap versus a period of resting wakefulness among individuals with traumatic brain injury. A sample of 32 individuals with traumatic brain injury was randomly assigned to a Sleep (N = 17) or Wake (N = 15) group after a period of training on a motor sequential learning task. A 45-min nap opportunity was provided for the Sleep group, while the Wake group watched a documentary for 45 min. Performance at the end of training was compared with their performance after the nap or wake intervention. Before and after the intervention, the motor sequential learning task was completed in the magnetic resonance imaging scanner to examine the relationship between change in performance and neural activation. Participants in the Sleep group showed significant gains from the end of training to after the intervention, whereas the Wake group did not. The functional magnetic resonance imaging results showed that relative to the Wake group, the Sleep group showed significantly decreased activation post-intervention in the anterior cingulate/paracingulate, cerebellum, cuneus/precuneus, and inferior parietal lobule including angular and supramarginal gyri. Importantly, across both groups, increased task performance at post-intervention was associated with decreased activation in the anterior cingulate/paracingulate and cerebellum. This study demonstrated the enhancing effect of a nap on motor learning performance in a sample of individuals with traumatic brain injury, with patterns of neural activation suggesting that the sequence was more automatized in the Sleep group. Strategic placement of a nap after an intense period of motor learning in the medical rehabilitation setting may have important implications for maximizing recovery after traumatic brain injury.

Memory and Traumatic Brain Injury: Assessment and Management Practices of Speech-Language Pathologists

PURPOSE

Memory impairments are among the most commonly reported deficits and among the most frequent rehabilitation targets for individuals with traumatic brain injury (TBI). Memory and learning are also critical for rehabilitation success and broader long-term outcomes. Speech-language pathologists (SLPs) play a central role in memory management for individuals with TBI across the continuum of care. Yet, little is known about the current practice patterns of SLPs for post-TBI memory disorders. This study aims to examine the clinical management of memory disorders in adults with TBI by SLPs and identify opportunities to improve post-TBI memory outcomes.

METHOD

SLPs from across the continuum of care were recruited to complete an online survey. The survey assessed key practice areas specific to memory and memory disorders post-TBI, including education and training, knowledge and confidence, and assessment and treatment patterns.

RESULTS

Surveys from 155 SLPs were analyzed. Results revealed that TBI-specific training remains low in the field. Respondents varied in their practice patterns in assessing and treating memory disorders. Most SLPs do not appear to have access to appropriate standardized assessments to measure unique forms of memory. Respondents also reported a range of barriers and opportunities to advance memory outcomes following TBI and provided suggestions of areas in which they would like to see more basic and clinical research.

CONCLUSIONS

These findings establish a baseline of the current practices for clinical management of memory impairment in adults with TBI by SLPs. Improved opportunities for clinician training, the development of a single tool to assess multiple forms of memory, better access to existing memory assessments, and implementation of evidence-based interventions promise to lead to improved memory outcomes for individuals with TBI.

Heterogeneity Is a Hallmark of Traumatic Brain Injury, Not a Limitation: A New Perspective on Study Design in Rehabilitation Research

Purpose In both basic science and intervention research in traumatic brain injury (TBI), heterogeneity in the patient population is frequently cited as a limitation and is often interpreted as a factor reducing certainty in the generalizability of research findings and as a source of conflicting findings across studies. Historically, much of TBI research in rehabilitation and cognition has relied upon case-control studies, with small to modest sample sizes. In this context, heterogeneity is indeed a significant limitation. Here, however, we argue that heterogeneity in patient profiles is a hallmark characteristic of TBI and therefore cannot be avoided or ignored. We argue that this inherent heterogeneity must be acknowledged and accounted for prior to study design. Fortunately, advances in statistical methods and computing power allow researchers to leverage heterogeneity, rather than be constrained by it. Method In this article, we review sources of heterogeneity that contribute to challenges in TBI research, highlight methodological advances in statistical analysis and in other fields with high degrees of heterogeneity (e.g., psychiatry) that may be fruitfully applied to decomposing heterogeneity in TBI, and offer an example from our research group incorporating this approach. Conclusion Only by adopting new methodological approaches can we advance the science of rehabilitation following TBI in ways that will impact clinical practice and inform decision making, allowing us to understand and respond to the range of individual differences that are a hallmark in this population.

Procedural Memory Following Moderate-Severe Traumatic Brain Injury: Group Performance and Individual Differences on the Rotary Pursuit Task

The impact of traumatic brain injury (TBI) on procedural memory has received significantly less attention than declarative memory. Although to date studies on procedural memory have yielded mixed findings, many rehabilitation protocols (e.g., errorless learning) rely on the procedural memory system, and assume that it is relatively intact. The aim of the current study was to determine whether individuals with TBI are impaired on a task of procedural memory as a group, and to examine the presence of individual differences in performance. We administered to a sample of 36 individuals with moderate-severe TBI and 40 healthy comparisons (HCs) the rotary pursuit task, and then examined their rate of learning, as well as their retention of learning. Our analyses revealed that while individuals with TBI spent a significantly shorter amount of time on target as a group, they did not retain significantly less procedural learning, and as a group their rate of learning was not different from HCs. However, there were high individual differences in both groups, indicating that some individuals might not be able to take advantage of treatment methods designed to leverage intact procedural memory system. Future work is needed to better assess and characterize procedural memory in individuals with TBI across a larger battery of tasks in experimental and clinical setting as memory and learning status may predict rehabilitation success.

The Area under the Main Sequence as an Alternative Method to Measure Saccadic Dynamics

SIGNIFICANCE

This study shows that the area under the main sequence (MSAREA) is a valid alternative to the standard peak-velocity main sequence in measuring saccadic dynamics. A one-parameter area model, MSAREA = GPW = 1.55 × SACSIZE, with SACSIZE as the size of the saccade, 1.55 as a power factor, and GPW = 1.55 as a gain parameter, is presented.

PURPOSE

SACPEAK = Vmax × (1 - e) is the traditional model used to describe the saccadic main sequence, the relationship between the size of the movement and its peak velocity (SACPEAK). In the previous article, we have shown that there is a strong linear correlation between the two parameters Vmax and SAT, which severely affects the model's clinical applicability. The purpose of this study is to see if, by using the MSAREA as an alternative approach, we can overcome the limitations of the traditional model.

METHODS

Participants and main sequence data are the same as the previous study. A trapezoidal integration was used to estimate the MSAREAs as a function of SACSIZE.

RESULTS

A two-parameter area model was computed to determine the range of variability of its parameters and R values. These were then used as reference values in the search for one-parameter alternatives. The one-parameter model MSAREA = GPW = 1.55 × SACSIZE performed well for all data sets. We tested its validity by performing a comparison with other one-parameter area models.

CONCLUSIONS

Area models are superior to peak-velocity models in terms of R and stability and can be reduced to robust one-parameter expressions with only limited degradation in R. This not only greatly simplifies the determination if a set is inside or outside a reference population but also allows for direct comparisons between sets, with the saccadic dynamics expressed by a simple linear gain factor (GPW = 1.55).

Saccadic impairment in chronic traumatic brain injury: examining the influence of cognitive load and injury severity

OBJECTIVE

Previous research suggests that saccadic eye movements can be uniquely sensitive to impairment in chronic traumatic brain injury (TBI). This study was conducted to examine saccadic eye movements across varying levels of cognitive load and TBI history/severity. We hypothesized that saccadic impairment in chronic mild and moderate-severe TBI would be most pronounced under conditions of high cognitive load.

METHODS

In total, 61 participants (including n = 20 with chronic mild TBI, n = 15 with chronic moderate-severe TBI, and 26 uninjured controls) completed a battery of conventional neuropsychological tests and the Fusion n-Back Test, which measures manual and saccadic response time (RT) across varying cognitive load and cueing conditions.

RESULTS

Consistent with our hypotheses, chronic mild and moderate-severe TBI were associated with substantial saccadic impairment under conditions of high cognitive load. Participants with moderate-severe TBI also demonstrated saccadic impairment at low levels of cognitive load. TBI groups and uninjured controls did not differ significantly on manual metrics or conventional neuropsychological measures.

CONCLUSIONS

This study provides additional support for the value of eye tracking for enhanced assessment of TBI. Additionally, findings suggest that TBI is associated with greatest susceptibility to oculomotor interference under high levels of cognitive load.

Deficits in saccades and smooth-pursuit eye movements in adults with traumatic brain injury: a systematic review and meta-analysis

PURPOSE

To conduct a review of literature and quantify the effect that traumatic brain injury (TBI) has on oculomotor functions (OM).

METHODS

A systematic review and meta-analysis was conducted from papers that objectively measured saccades and smooth-pursuit eye movements in mild and severe TBI.

RESULTS

The overall impact of TBI on OM functions was moderate and significant with an effect size of 0.42 from 181 OM case-control comparisons. The heterogeneity, determined using the random effect model, was found to be significant (Q (180) = 367, p < 0.0001, I² = 51) owing to the variety of OM functions (reflexive saccades, antisaccades, memory-guided saccades, self-paced saccades and pursuits) measured and varying post-injury periods.The overall effect on OM functions were similar in mild and severe TBI despite differences in combined effect size of various OM functions. OM functions involving complex cognitive skills such as antisaccades (in mild and severe TBI) and memory-guided saccades (in mild TBI) were the most adversely affected, suggesting that OM deficits may be associated with cognitive deficits in TBI.

CONCLUSION

TBI often results in long-standing OM deficits. Experimental measures of OM assessment reflect neural integrity and may provide a sensitive and objective biomarker to detect OM deficits following TBI.

Oculomotor-Based Vision Assessment in Mild Traumatic Brain Injury: A Systematic Review

OBJECTIVE

The purpose of this article is to synthesize and appraise the evidence regarding the use of oculomotor-based vision assessment to identify and monitor recovery from mild traumatic brain injury (mTBI). Specific objectives are to (1) identify changes in oculomotor-based vision following mTBI; (2) distinguish methods of assessment; (3) appraise the level and quality of evidence; and, if warranted, (4) determine clinical recommendations for assessment.

METHODS

A systematic review was undertaken to identify and appraise relevant literature. A search was conducted of 7 databases of peer-reviewed literature from January 1990 to January 2015. Articles were included if study populations were clearly identified as having mTBI and used an assessment of oculomotor-based vision. Articles with pooled data (eg, mTBI and stroke), addressing afferent visual function (eg, visual field deficits) or using single case designs, were excluded.

RESULTS

Twenty articles were selected for inclusion. Exploratory findings suggest that measurements of saccades, smooth pursuit, and vergence are useful in detecting changes associated with mTBI. Assessment methods included eye tracker protocols, optometric assessment, and the King-Devick test.

CONCLUSION

The strength of this evidence is not yet sufficient to warrant clinical recommendations. Research using rigorous methods is required to develop reliable, valid, and clinically useful assessment protocols.

Visual problems associated with traumatic brain injury

Traumatic brain injury (TBI) and its associated concussion are major causes of disability and death. All ages can be affected but children, young adults and the elderly are particularly susceptible. A decline in mortality has resulted in many more individuals living with a disability caused by TBI including those affecting vision. This review describes: (1) the major clinical and pathological features of TBI; (2) the visual signs and symptoms associated with the disorder; and (3) discusses the assessment of quality of life and visual rehabilitation of the patient. Defects in primary vision such as visual acuity and visual fields, eye movement including vergence, saccadic and smooth pursuit movements, and in more complex aspects of vision involving visual perception, motion vision ('akinopsia'), and visuo-spatial function have all been reported in TBI. Eye movement dysfunction may be an early sign of TBI. Hence, TBI can result in a variety of visual problems, many patients exhibiting multiple visual defects in combination with a decline in overall health. Patients with chronic dysfunction following TBI may require occupational, vestibular, cognitive and other forms of physical therapy. Such patients may also benefit from visual rehabilitation, including reading-related oculomotor training and the prescribing of spectacles with a variety of tints and prism combinations.

King-Devick Test identifies real-time concussion and asymptomatic concussion in youth athletes

Background

Sports concussion has an annual incidence of approximately 3.8 million. Over half go unreported and a substantial number may be asymptomatic. A rapid, cost-effective, and reliable tool that facilitates diagnosis of concussion is needed. The King-Devick (K-D) test is a vision-based tool of rapid number naming for assessment of concussion. In this study, we evaluated the utility of the K-D test in real time for identification of symptomatic concussion in youth athletes and to determine if similar impairment (subclinical concussion) exists in youth athletes without an obvious head injury or symptoms.

Methods

Youth hockey players underwent K-D testing preseason, postseason, and immediately after suspected concussion. Additional testing was performed in a subgroup of nonconcussed athletes immediately before and after a game to determine effects of fatigue on K-D scores.

Results

Among 141 players tested, 20 had clinically diagnosed concussion. All 20 had immediate postconcussion K-D times >5 seconds from baseline (average 7.3 seconds) and all but 2 had worse postseason scores (46.4 seconds vs 52.4 seconds, p < 0.05, Wilcoxon signed rank test). Nonconcussed athletes saw minimal improvement postseason (43.9 seconds vs 42.1 seconds, p < 0.05) and 51 nonconcussed players assessed before and after a game revealed no significant time change as a result of fatigue.

Conclusions

Rapid number naming using the K-D test accurately identifies real-time, symptomatic concussion in youth athletes. Scores in concussed players may remain abnormal over time. Athletes should undergo preseason and postseason K-D testing, with additional evaluation real time to inform the assessment of suspected concussion.

Classification of Evidence

This study provides Class III evidence that the K-D test accurately identifies real-time concussions in youth athletes.

The King-Devick test of rapid number naming for concussion detection: meta-analysis and systematic review of the literature

Background:

Vision encompasses a large component of the brain's pathways, yet is not represented in current sideline testing.

Objectives:

We performed a meta-analysis of published data for a vision-based test of rapid number naming (King-Devick [K-D] test).

Studies & methods:

Pooled and meta-analysis of 15 studies estimated preseason baseline K-D scores and sensitivity/specificity for identifying concussed versus nonconcussed control athletes.

Result:

Baseline K-D (n = 1419) showed a weighted estimate of 43.8 s (95% CI: 40.2, 47.5; I² = 0.0%; p=0.85 – indicating very little heterogeneity). Sensitivity was 86% (96/112 concussed athletes had K-D worsening; 95% CI: 78%, 92%); specificity was 90% (181/202 controls had no worsening; 95% CI: 85%, 93%).

Conclusion:

Rapid number naming adds to sideline assessment and contributes a critical dimension of vision to sports-related concussion testing.

Beyond the cover test: the motor half of the sensorimotor exam

The cover tests fulfill both the "sensory" and the "motor" requirements of the sensorimotor exam because they not only detect and quantify strabismus but also evaluate control. Control is achieved through various types of vergence, but vergence is not the only type of eye movement that is integral to fusion. The function of all eye movements is to position and maintain similar images on corresponding areas of the retinae in order to sustain binocular vision. Therefore, a complete motor exam should include evaluation of all eye movement systems. Such an exam can be performed without expensive and complicated equipment, without supplementary education, without significantly extending exam time, and within the confines of an average exam lane, because much of the exam is concealed within the standard sensorimotor evaluation. The term "sensorimotor exam" underscores the fact that sensory and motor fusion, and their respective cortical pathways, are inextricably linked, and function simultaneously and cooperatively to achieve normal visual experience.

Functional MRI in the investigation of blast-related traumatic brain injury

This review focuses on the application of functional magnetic resonance imaging (fMRI) to the investigation of blast-related traumatic brain injury (bTBI). Relatively little is known about the exact mechanisms of neurophysiological injury and pathological and functional sequelae of bTBI. Furthermore, in mild bTBI, standard anatomical imaging techniques (MRI and computed tomography) generally fail to show focal lesions and most of the symptoms present as subjective clinical functional deficits. Therefore, an objective test of brain functionality has great potential to aid in patient diagnosis and provide a sensitive measurement to monitor disease progression and treatment. The goal of this review is to highlight the relevant body of blast-related TBI literature and present suggestions and considerations in the development of fMRI studies for the investigation of bTBI. The review begins with a summary of recent bTBI publications followed by discussions of various elements of blast-related injury. Brief reviews of some fMRI techniques that focus on mental processes commonly disrupted by bTBI, including working memory, selective attention, and emotional processing, are presented in addition to a short review of resting state fMRI. Potential strengths and weaknesses of these approaches as regards bTBI are discussed. Finally, this review presents considerations that must be made when designing fMRI studies for bTBI populations, given the heterogeneous nature of bTBI and its high rate of comorbidity with other physical and psychological injuries.

Individual differences in impulsivity predict anticipatory eye movements

Impulsivity is the tendency to act without forethought. It is a personality trait commonly used in the diagnosis of many psychiatric diseases. In clinical practice, impulsivity is estimated using written questionnaires. However, answers to questions might be subject to personal biases and misinterpretations. In order to alleviate this problem, eye movements could be used to study differences in decision processes related to impulsivity. Therefore, we investigated correlations between impulsivity scores obtained with a questionnaire in healthy subjects and characteristics of their anticipatory eye movements in a simple smooth pursuit task. Healthy subjects were asked to answer the UPPS questionnaire (Urgency Premeditation Perseverance and Sensation seeking Impulsive Behavior scale), which distinguishes four independent dimensions of impulsivity: Urgency, lack of Premeditation, lack of Perseverance, and Sensation seeking. The same subjects took part in an oculomotor task that consisted of pursuing a target that moved in a predictable direction. This task reliably evoked anticipatory saccades and smooth eye movements. We found that eye movement characteristics such as latency and velocity were significantly correlated with UPPS scores. The specific correlations between distinct UPPS factors and oculomotor anticipation parameters support the validity of the UPPS construct and corroborate neurobiological explanations for impulsivity. We suggest that the oculomotor approach of impulsivity put forth in the present study could help bridge the gap between psychiatry and physiology.