A-101 Reaction Time and Reaction Time Variability with the Brain Gauge Somatosensory Device in Service Members with and without Acute Concussion

Objective Research has demonstrated reaction time variability (RTV) as a potentially sensitive metric for post-concussion assessments. The Brain Gauge Clinical Metrics battery (BG) device uses tactile sensory stimulation to elicit a response, increasing accuracy to <1 msec versus 30–100 msec in visually-based reaction time (RT) measures. We sought to determine if BG RTV could adequately identify individuals with acute concussion. Methods We administered BG to 98 healthy control service members (SMs) and 64 SMs within 7 days of a medically diagnosed concussion. The battery includes simple RT and repeated simple RT subtests with RT variability (RTV) for each test calculated as the sd of mean RT for each participant. We used t-tests and gamma regression to compare group RT and RTV means. “Cutoffs” based on percentiles of the control group RTV distribution were calculated and the proportion of each group falling below these cutoffs was determined. Results There were statistically significant differences with large effect sizes between groups across all four metrics. The proportion of participants in the concussion group falling below the cutoffs was higher than among controls, with large effect sizes. T-tests and gamma regression showed that group mean RT and RTV differed significantly under multiple distributional assumptions. Conclusions Both RT and RTV using the BG somatosensory device demonstrated the ability to discriminate between healthy control SMs and SMs with acute concussion. This is further evidence that RTV is a sensitive measure for acute concussion and the use of a tactile sensory stimulus may represent an improvement over a visual stimulus.

Program of Seven 45-min Dry Immersion Sessions Improves Choice Reaction Time in Parkinson’s Disease

The study hypothesis held that in subjects with Parkinson’s disease (PD), the reaction time (RT) tests of the higher cognition demand would have more readily improved under the program of analog microgravity (μG) modeled with “dry” immersion (DI). To test this hypothesis, 10 subjects with PD have passed through a program of seven DI sessions (each 45 min long) within 25–30 days, with overall μG dose 5 1/4 h. Five patients were enrolled as controls, without DI (noDI group). Simple RT (SRT), disjunctive RT (DRT), and choice RT (CRT) were assessed in four study points: before the DI program (preDI), 1 day after the DI program (postDI), 2 weeks after the DI program (DI2w), and 2 months after the DI program (DI2m). The motor time (MT) was assessed with the tapping test (TT). Additionally, signal detection time (SDT) and central processing time (CPT) were extracted from the data. Before the program of DI, the RT tests are in accordance with their cognition load: SRT (284 ± 37 ms), DRT (338 ± 38 ms), and CRT (540 ± 156 ms). In accordance with the hypothesis, CRT and DRT have improved under DI by, respectively, 20 and 8% at the study point “DI2w,” whereas SRT, SDT, and MT did not change (<5% in the preDI point, p > 0.05). Thus, the program of DI provoked RT improvement specifically in the cognitively loaded tasks, in a “dose of cognition-reaction” manner. The accuracy of reaction has changed in none of the RT tests. The neurophysiologic, hormonal/neuroendocrine, behavioral, neural plasticity, and acclimation mechanisms may have contributed to such a result.

Advanced Radiation Therapy Technology Use in the Treatment of Bone Metastases in a Public, Salary-Funded, Non-Incentivized Health Care System

PURPOSE: There is limited evidence to support the routine use of conformal radiotherapy (RT) techniques in the treatment of bone metastases. This study evaluated trends in advanced technique use within the province of British Columbia. MATERIALS AND METHODS: Data on patients who received RT for bone metastases between 2009 and 2016 (with the exception of 2012) at 6 regional cancer centers were reviewed. Descriptive statistics summarized radiation technique patterns. Logistic regression assessed the influence of patient, treatment, and provider variables on receipt of RT technique. RESULTS: A total of 24,215 RT courses were identified; 97% were planned by simple RT and 3% by advanced techniques (3-dimensional conformal radiotherapy, intensity-modulated radiotherapy, and stereotactic body radiotherapy). The use of advanced techniques was significantly higher in recent years compared with in 2009 (odds ratios [ORs], 2.2, 4.2, 4.2, and 6.3, respectively, for the years 2013 to 2016; P < .001). Patients with thyroid, sarcoma, and neuroendocrine malignancies (ORs, 10.3, 5.5, and 5.2, respectively; P < .005) were more likely to be treated with advanced techniques, as were skull, sternum, rib, and pelvic metastases (ORs, 8.0, 5.2, 2.2, and 2.2, respectively; P < .001). Advanced techniques were most commonly used in the setting of re-irradiation (38%). They were associated with slightly higher incompletion rates (3.0% v 1.5%, P < .005) and less use within 30 days of death (6% v 15%, P < .001). CONCLUSION: Within our publicly funded, salary-based provincial health care system, we found that the majority of bone metastases are still being treated by simple RT; however, the use of advanced techniques is increasing, and we identified select patterns in which they are being prescribed. Additional study into clinical benefit is required.

DEVELOPING AND MEASURING ATTENTION IN BOXERS: MIXED COACHES’ EXPERTISE AND REACTION TIME MEASURES

This study explored the problem of attention and its development in young boxers. A rapidly changing situation and a high level of traumatization in boxing are demanding the development of athletes’ attention. Focusing on technical or motivational training is among the reasons for underestimating the development of attentional skills. Study 1 involved seven expert coaches (males, mean age 45.4, mean working experience 20.3 years). The results revealed a relatively high assessment of the psychological component of training and a low agreement on the development of attentional skills. Coaches indicated that testing is the best measurement of attention. Study 2 focused on the measurement of reaction time (RT) in young boxers. Simple and complex RT of nine athletes, aged 12 to 15 (33% females), were assessed before and after the 15 minutes long warm-up. The results demonstrated no significant change in boxers' simple RT and a decrease (about 30 ms) in complex RT after the warm-up. The feedback was provided for athletes and their coaches. A contrast appeared between coaches’ view of well-known exercises for developing attention and their question “Could you suggest some exercise?” Simultaneously, coaches suggested a more specific RT measurement, including the full time of a punch.

Central Sympathetic Nervous System Effects on Cognitive-Motor Performance

The intriguing interplay between acute stress physiology and cognitive processes has long been noted. However, while stress-induced release of glucocorticoids has repeatedly been shown to impact brain mechanisms underlying cognition and memory, less experimental research addressed the effects of stress-induced central sympathetic nervous system (SNS) activation on cognitive performance. Moreover, despite the long-standing notion that the way performance is modulated by arousal may crucially depend on task complexity, mechanistic research demonstrating a direct, causal influence of altered SNS activity is scarce. Twelve healthy men participated in a placebo-controlled, pharmacologic dose–response study involving three within-subject assessments (1-week intervals). Subjective and objective indices of SNS activity as well as reaction time (RT) in three different tasks varying in cognitive demand (simple RT, choice RT, and verbal RT in complex mental arithmetic) were assessed during modulation of central SNS tone by intravenous infusions of dexmedetomidine (alpha2-agonist), yohimbine (alpha2-antagonist), and placebo. Cognitive performance was negatively affected by alpha2-agonism in all task conditions. By contrast, administration of yohimbine improved simple RT, while diminishing complex RT, supporting the assumption of a nonlinear way of action depending on task characteristics. Our results highlight the consequences of central (noradrenergic) SNS activation for cognitive-motor performance in RT tasks of varying complexity.

The Time Course of Motoneuronal Excitability during the Preparation of Complex Movements

For a simple RT task, movement complexity increases RT and also corticospinal excitability, as measured by the motor evoked potential (MEP) elicited by TMS of the motor cortex. However, it is unknown if complexity-related increases in corticospinal excitability during the preparation of movement are mediated at the cortical or spinal level. The purposes of this study were to establish a time course of motoneuronal excitability before prime mover activation and to assess task-dependent effects of complex movements on motoneuronal and cortical excitability in a simple RT paradigm. It was hypothesized that motoneuronal and cortical excitability would increase before prime mover activation and in response to movement complexity. In a seated position, participants completed ballistic elbow extension/flexion movements with their dominant arm to one, two, or three targets. TMS and transmastoid stimulation (TS) were delivered at 0%, 70%, 80% or 90% of mean premotor RT for each complexity level. Stimulus intensities were set to elicit MEPs and cervicomedullary MEPs (CMEPs) of ∼10% of the maximal M-wave in the triceps brachii. Compared with 0% RT, motoneuronal excitability (CMEP amplitude) was already 10% greater at 70% RT. CMEP amplitude also increased with movement complexity as both the two- and three-movement conditions had greater motoneuronal excitability than the one-movement condition ( p < .038). Importantly, when normalized to the CMEP, there was no increase in MEP amplitude. This suggests that complexity-related increases in corticospinal excitability are likely to be mediated more by increased excitability at a motoneuronal than cortical level.

Challenging the function of motor inhibition: Does it really assist action selection?

By applying transcranial magnetic stimulation (TMS) over the primary motor cortex (M1) to elicit motor-evoked potentials (MEPs) in muscles of the contralateral hand during reaction time (RT) tasks, many studies have reported a strong suppression of MEPs during action preparation, a phenomenon called preparatory inhibition. Several hypotheses have been put forward regarding the role of this inhibition, with the predominant view suggesting that it would help action selection. However, this assumption is still a matter of debate. Here, we aimed at directly addressing this idea by comparing MEPs in a task that required subjects to select a finger response within a set of predefined options (choice RT task: left or right index finger abduction) or when subjects simply had to provide the same finger response on every trial, in the absence of choice (simple RT task). Moreover, we minimized any effect that could be associated with other forms of inhibition. In both versions of the task, TMS was applied on both M1 (double-coil protocol) at several time points between the go signal and the left or right index finger response, eliciting MEPs bilaterally in the prime mover (index finger agonist) and in an irrelevant muscle (pinky agonist). Overall, MEP suppression was moderate in this study; it was only found for the irrelevant muscle. As such, MEPs in the index agonist were facilitated when elicited in a responding hand (e.g. left MEPs preceding left responses) and remained mostly unchanged in a non-responding hand (e.g. left MEPs preceding right responses). In contrast, MEPs were almost always suppressed in the pinky muscle when elicited in the non-responding hand and sometimes also in the responding hand. Importantly, this effect was more consistent in the choice than in the simple RT task, supporting the view that preparatory inhibition may assist action selection. Moreover, the fact that it sometimes concerned the responding hand is coherent with the idea of a global process, suppressing broadly the motor system.

Startle reveals decreased response preparatory activation during a stop-signal task

In a stop-signal task participants are instructed to initiate a movement in response to a go signal, but to inhibit this movement if an infrequent stop signal is presented after the go. Reaction time (RT) in a stop-signal task is typically longer compared with that in a simple RT task, which may be attributed to a reduced readiness to initiate the response caused by the possibility of having to inhibit the response. The purpose of this experiment was to probe the preparatory activation level of the motor response during a stop-signal task using a startling acoustic stimulus (SAS), which has been shown to involuntarily trigger sufficiently prepared responses at a short latency. Participants completed two separate tasks: a simple RT task, followed by a stop-signal RT task. During both tasks, an SAS (120 dB) was pseudorandomly presented concurrently with the go signal. As expected, RT during the simple RT task was significantly shorter than during the stop-signal task. A significant reduction in RT was noted when an SAS was presented during the simple RT task; however, during the stop-signal task, an SAS resulted in either a significant speeding or a moderate delay in RT. Additionally, the subset of SAS trial responses with the shortest RT latencies produced during the stop-signal task were also delayed compared with the short-latency SAS trial responses observed during the simple RT task. Despite evidence that a response was prepared in advance of the go signal during a stop-signal task, it appears that the amount of preparatory activation was reduced compared with that achieved during a simple RT task.

A robot for verifying the precision of total reaction time measurement

The level of variability in psychomotor behavior and the use of several distinct sets of equipments in Reaction Time (RT) assessments might jeopardize the validity and reliability of such measures. This study presents the development and verification of Emboici Robot-a robot capable of performing accurate RT assessments consisting of response to a visual stimulus by pressing a button-whose purpose is to measure the accuracy of RT assessments. We evaluated the accuracy and precision on four different days, each providing 300 measurements. These assessments generated a RT of 46.95ms (+6.04). No significant effects were found in the RTs obtained and, as a result, there is evidence that the Emboici Robotis stable, reliable, and precise. The robot can be a viable solution for verifying precision and accuracy of any given software with simple RT assessments with visual stimulus requiring as response the pressing of a button or key.