Team Dynamics and Collaborative Problem-Solving for Lunar Construction: Lessons From Complex Construction Scenarios on Earth.

OBJECTIVE: This paper surveys the existing literature surrounding problem-solving and team dynamics in complex and unpredictable scenarios, and evaluates the applicability of studying Earth-based construction teams to identify training needs for Lunar construction crews. BACKGROUND: Lunar and other space exploration construction crews will work in extreme environments and face unpredictable challenges, necessitating real-time problem-solving to address unexpected contingencies. This work will require coordination with Mission Control and autonomous assistants, so crew training must account for multi-agent, distributed teamwork. METHOD: A narrative literature review identified processes, attributes, and skills necessary for the success of Lunar construction teams. We summarized relevant frameworks and synthesized collective findings into over-arching trends and remaining research gaps. RESULTS: While significant literature exists surrounding team performance, very little systematic inquiry has been done with a focus on Lunar construction crews and operations, particularly with respect to dynamic problem-solving and team-based decision-making. Established and standardized metrics for evaluating team performance are lacking, resulting in significant variation in reported outcomes between studies. CONCLUSION: Lunar and other space exploration construction teams will need training that focuses on developing the right approach to team-based problem-solving, rather than on preparing response execution for known contingencies. An investigation of successful Earth-based construction crews may facilitate the development of relevant metrics for training future Lunar construction crews. APPLICATION: Metrics and team training protocols developed for future Lunar construction teams may be adaptable and applicable to a wide range of extreme teams facing uncertain challenges, such as aircrews, surgical teams, first responders, and construction crews.

Scalp and skull influence on near infrared photon propagation in the Colin27 brain template.

Near-infrared neuromonitoring (NIN) is based on near-infrared spectroscopy (NIRS) measurements performed through the intact scalp and skull. Despite the important effects of overlying tissue layers on the measurement of brain hemodynamics, the influence of scalp and skull on NIN sensitivity are not well characterized. Using 3555 Monte Carlo simulations, we estimated the sensitivity of individual continuous-wave NIRS measurements to brain activity over the entire adult human head by introducing a small absorption perturbation to brain gray matter and quantifying the influence of scalp and skull thickness on this sensitivity. After segmenting the Colin27 template into five tissue types (scalp, skull, cerebrospinal fluid, gray matter and white matter), the average scalp thickness was 6.9 ± 3.6 mm (range: 3.6-11.2mm), while the average skull thickness was 6.0 ± 1.9 mm (range: 2.5-10.5mm). Mean NIN sensitivity - defined as the partial path length through gray matter divided by the total photon path length - ranged from 0.06 (i.e., 6% of total path length) at a 20mm source-detector separation, to over 0.19 at 50mm separations. NIN sensitivity varied substantially around the head, with occipital pole exhibiting the highest NIRS sensitivity to gray matter, whereas inferior frontal regions had the lowest sensitivity. Increased scalp and skull thickness were strongly associated with decreased sensitivity to brain tissue. Scalp thickness always exhibited a slightly larger effect on sensitivity than skull thickness, but the effect of both varied with SD separation. We quantitatively characterize sensitivity around the head as well as the effects of scalp and skull, which can be used to interpret NIN brain activation studies as well as guide the design, development and optimization of NIRS devices and sensors.

Human cognitive performance in spaceflight and analogue environments.

Maintaining intact cognitive performance is a high priority for space exploration. This review seeks to summarize the cumulative results of existing studies of cognitive performance in spaceflight and analogue environments. We focused on long-duration (>21 d) studies for which no review has previously been conducted. There were 11 published studies identified for long-duration spaceflight (N = 42 subjects) as well as 21 shorter spaceflight studies (N = 70 subjects). Overall, spaceflight cognitive studies ranged from 6-438 d in duration. Some 55 spaceflight analogue studies were also identified, ranging from 6 to 520 d. The diverse nature of experimental procedures and protocols precluded formal meta-analysis. In general, the available evidence fails to strongly support or refute the existence of specific cognitive deficits in low Earth orbit during long-duration spaceflight, which may be due in large part to small numbers of subjects. The studies consistently suggest that novel environments (spaceflight or other) induce variable alterations in cognitive performance across individuals, consistent with known astronaut experiences. This highlights the need to better quantify the magnitude and scope of this interindividual variability, and understand its underlying factors, when predicting in-flight cognitive functioning for extended periods.

Artificial Gravity: An Effective Countermeasure for Microgravity-Induced Headward Fluid Shift?

Long-duration spaceflight is associated with pathophysiological changes in the intracranial compartment hypothetically linked to microgravity-induced headward fluid shift. This study aimed to determine if daily artificial gravity (AG) sessions can mitigate these effects, supporting its application as a countermeasure to spaceflight. Twenty-four healthy adult volunteers (16 men) were exposed to 60 days of six-degree head-down tilt bed rest (HDTBR) as a ground-based analog of chronic headward fluid shift. Subjects were divided equally into three groups: No AG (control), daily 30-minute intermittent AG (iAG), and daily 30-minute continuous (cAG). Internal carotid artery (ICA) stroke volume (ICASV), ICA resistive index (ICARI), ICA flow rate (ICAFR), aqueductal cerebral spinal fluid flow velocity (CSFV), and intracranial volumetrics were quantified at 3T. MRI was performed at baseline, 14 and 52 days into HDTBR, and three days after HDTBR(recovery). A mixed model approach was used with intervention and time as the fixed effect factors and the subject as the random effect factor. Compared to baseline, HDTBR was characterized by expansion of lateral ventricular, white matter, gray matter, and brain + total intracranial cerebral spinal fluid volumes, increased CSFv, decreased ICASV, and decreased ICAFR by 52 days into HBTBR (All Ps <0.05). ICARI was only increased 14 days into HDTBR (P <0.05). Neither iAG nor cAG significantly affected measurements compared to HDTBR alone, indicating that thirty minutes of daily exposure was insufficient to mitigate the intracranial effects of headward fluid shift. Greater AG session exposure time, gravitational force or both are suggested for future countermeasure research.

Space exploration as a catalyst for medical innovations.

Aerospace research has a long history of developing technologies with industry-changing applications and recent history is no exception. The expansion of commercial spaceflight and the upcoming exploration-class missions to the Moon and Mars are expected to accelerate this process even more. The resulting portable, wearable, contactless, and regenerable medical technologies are not only the future of healthcare in deep space but also the future of healthcare here on Earth. These multi-dimensional and integrative technologies are non-invasive, easily-deployable, low-footprint devices that have the ability to facilitate rapid detection, diagnosis, monitoring, and treatment of a variety of conditions, and to provide decision-making and performance support. Therefore, they are primed for applications in low-resource and remote environments, facilitating the extension of quality care delivery to all patients in all communities and empowering non-specialists to intervene early and safely in order to optimize patient-centered outcomes. Additionally, these technologies have the potential to advance care delivery in tertiary care centers by improving transitions of care, providing holistic patient data, and supporting clinician wellness and performance. The requirements of space exploration have created a number of paradigm-altering medical technologies that are primed to revitalize and elevate our standard of care here on Earth.

Nourishing the brain on deep space missions: nutritional psychiatry in promoting resilience.

The grueling psychological demands of a journey into deep space coupled with ever-increasing distances away from home pose a unique problem: how can we best take advantage of the benefits of fresh foods in a place that has none? Here, we consider the biggest challenges associated with our current spaceflight food system, highlight the importance of supporting optimal brain health on missions into deep space, and discuss evidence about food components that impact brain health. We propose a future food system that leverages the gut microbiota that can be individually tailored to best support the brain and mental health of crews on deep space long-duration missions. Working toward this goal, we will also be making investments in sustainable means to nourish the crew that remains here on spaceship Earth.

Test-re-test reliability of the Hopkins Verbal Learning Test-Revised in individuals with traumatic brain injury.

PRIMARY OBJECTIVE: To determine test-re-test reliability of the Hopkins Verbal Learning Test-Revised (HVLT-R) in a group of individuals with traumatic brain injury (TBI). RESEARCH DESIGN: Single-group repeated measures design. METHODS AND PROCEDURES: Seventy-five individuals with TBI were administered the HVLT-R twice, with 6-8 weeks between the two test sessions. MAIN OUTCOMES AND RESULTS: Test-re-test reliability on HVLT-R scoring parameters ranged from 0.537-0.818, with seven of the eight scoring parameters exhibiting r > 0.6. At re-test, scores did not significantly change on any of the eight HVLT-R scoring parameters. CONCLUSIONS: HVLT-R use with individuals with TBI is supported. Test-re-test reliability of total recall and delayed recall sub-scores was particularly high.

Tacklers' Head Inertial Accelerations Can Be Decreased by Altering the Way They Engage in Contact with Ball Carriers' Torsos.

PURPOSE: This study aimed to investigate how four types of successfully executed, legal front-on, one-on-one torso tackles influence the tacklers' and ball carriers' inertial head kinematics. METHODS: A total of 455 successful front-on, one-on-one torso tackle trials completed by 15 rugby code players using three-dimensional motion capture were recorded. Tackles differed with respects to the height of the contact point on the ball carrier's torso. A series of mixed general linear models were conducted. RESULTS: The tackler sustained the highest peak resultant linear ( P < 0.001) and angular ( P < 0.01) head accelerations when contacting the lower torso to execute a "dominant" tackle compared with mid or upper torso, although these latter tackle types had the lowest ball carrier inertial head kinematics. When executing a "smother" tackle technique, a significant decrease in peak resultant linear head acceleration was observed with a vertical "pop" then lock action used, compared with the traditional upper torso tackling technique ( P < 0.001). CONCLUSIONS: Modifying the tackler's engagement with a ball carrier's torso, with respect to height and technical execution, alters the inertial head kinematics of the tackler and the ball carrier. The traditional thinking about optimal tackle technique, as instructed, may need to be reevaluated, with the midtorso being a potential alternative target contact height, whereas changes in tackle execution may be relatively protective for tacklers when executing either a dominant or smother tackle. This study provides critical scientific evidence to underpin revised coaching tackling technique interventions that might enhance player safety. Tackles in which the tackler contacts the ball carrier around the midtorso region, rather than lower torso, produce the lowest acceleration and thus may contribute to reducing head injury risk for the tackler.

Neuro-ophthalmic imaging and visual assessment technology for spaceflight associated neuro-ocular syndrome (SANS).

Spaceflight associated neuro-ocular syndrome (SANS) refers to a unique collection of neuro-ophthalmic clinical and imaging findings observed in astronauts after long-duration spaceflight. Current in-flight and postflight imaging modalities (e.g., optical coherence tomography, orbital ultrasound, and funduscopy) have played an instrumental role in the understanding and monitoring of SANS development; however, the precise etiology for this neuro-ophthalmic phenomenon is still not completely understood. SANS may be a potential barrier to future deep space missions, and therefore it is critical to further elucidate the underlying pathophysiology for effective countermeasures. The complexity and unique limitations of spaceflight require careful consideration and integration of leading technology to advance our knowledge of this extraterrestrial syndrome. We describe the current neuro-ophthalmic imaging modalities and hypotheses that have improved our current understanding of SANS, discuss newer developments in SANS imaging (including noninvasive near-infrared spectroscopy) and summarize emerging research in the development of an aspirational future head-mounted virtual reality display with multimodal visual assessment technology for the detection of neuro-ocular findings in SANS.

Safety Review and Perspectives of Transcranial Focused Ultrasound Brain Stimulation.

Ultrasound is an important theragnostic modality in modern medicine. Technical advancement of both acoustic focusing and transcranial delivery have enabled administration of ultrasound waves to localized brain areas with few millimeters of spatial specificity and penetration depth sufficient to reach the thalamus. Transcranial focused ultrasound (tFUS) given at a low acoustic intensity has been shown to increase or suppress the excitability of region-specific brain areas. The neuromodulatory effects can outlast the sonication, suggesting the possibility of inducing neural plasticity needed for neurorehabilitation. Increasing numbers of studies have shown the efficacy and excellent safety profile of the technique, yet comparisons among the safety-related parameters have not been compiled. This review aims to provide safety information and perspectives of tFUS brain stimulation. First, the acoustic parameters most relevant to thermal/mechanical tissue damage are discussed along with regulated parameters for existing ultrasound therapies/diagnostic imaging. Subsequently, the parameters used in studies of large animals, non-human primates, and humans are surveyed and summarized in terms of the acoustic intensity and the mechanical index. The pulse-mode operation and the use of low ultrasound frequency for tFUS-mediated brain stimulation warrant the establishment of new safety guidelines/recommendations for the use of the technique among healthy volunteers, with additional cautionary requirements for its clinical translation.

Prediction of Task Performance From Physiological Features of Stress Resilience.

In this paper, we investigate the potential of generic physiological features of stress resilience in predicting air traffic control (ATC) candidates' performance in a highly-stressful low-fidelity ATC simulator scenario. Stress resilience is highlighted as an important occupational factor that influences the performance and well-being of air traffic control officers (ATCO). Poor stress management, besides the lack of skills, can be a direct cause of poor performance under stress, both in the selection process of ATCOs and later in the workplace. 40 ATC candidates, within the final stages of their selection process, underwent a stimulation paradigm for elicitation and assessment of various generic task-unrelated physiological features, related to resting heart rate variability (HRV) and respiratory sinus arrhythmia (RSA), acoustic startle response (ASR) and the physiological allostatic response, which are all recognized as relevant psychophysiological markers of stress resilience. The multimodal approach included analysis of electrocardiography, electromyography, electrodermal activity and respiration. We make advances in computational methodology for assessment of physiological features of stress resilience, and investigate the predictive power of the obtained feature space in a binary classification problem: prediction of high- vs. low-performance on the developed ATC simulator. Our novel approach yields a relatively high 78.16% classification accuracy. These results are discussed in the context of prior work, while considering study limitations and proposing directions for future work.

A controlled treatment study of internal memory strategies (I-MEMS) following traumatic brain injury.

OBJECTIVE: To evaluate the effects of participation in a memory group intervention focusing on internal strategy use on persons with traumatic brain injury-related memory impairment. PARTICIPANTS: Ninety-four adults with traumatic brain injury (54 in the experimental group and 40 controls) and resulting memory impairment, with severities ranging from mild to severe. All participants were at least 18 years of age at the time of injury and at least 1 year post injury at the time of study. DESIGN: Non randomized pre/posttest group comparison design. MAIN OUTCOME MEASURES: Hopkins Verbal Learning Test-Revised and Rivermead Behavioral Memory Test II. RESULTS: Participation in the memory group intervention was associated with improved memory performance immediately postintervention, and improvements were maintained 1 month postintervention. Severe injury was associated with less improvement in memory outcomes than mild and moderate injuries. Age and preinjury education were not related to outcome. CONCLUSIONS: Individuals with traumatic brain injury may benefit from memory group intervention focusing on internal strategy use. Study hypotheses should be retested using a randomized, controlled design, and further research is needed to better delineate influences on intervention candidacy and outcomes.

Test-re-test reliability of the virtual planning test in individuals with traumatic brain injury.

PRIMARY OBJECTIVE: To determine test-re-test reliability of the VIrtual Planning Test (VIP) in a group of individuals with traumatic brain injury (TBI). RESEARCH DESIGN: Single-group repeated measures design. METHODS AND PROCEDURES: Seventy-five individuals with TBI were administered the VIP, with 6-8 weeks between the two test sessions. MAIN OUTCOMES AND RESULTS: Test-re-test reliability on VIP scoring parameters--as measured by Pearson correlation coefficients--ranged from 0.341-0.855, with five of the seven scoring parameters exhibiting r > 0.6. CONCLUSIONS: Based on the findings of the current study, the VIP has overall moderate test-re-test reliability when administered to individuals with TBI. Some VIP scoring parameters, i.e. Total correct/accuracy and Total absence, demonstrated high test-re-test reliability. Others, i.e. Planning time and Total wrong order, demonstrated low test-re-test reliability.

Performance on the Robotics On-Board Trainer (ROBoT-r) Spaceflight Simulation During Acute Sleep Deprivation.

Exploration of deep space poses many challenges. Mission support personnel will not be immediately available to assist crewmembers performing complex operations on future long-duration exploration operations. Consequently, it is imperative that crewmembers have objective, reliable, and non-invasive metrics available to aid them in determining their fitness for duty prior to engaging in potentially dangerous tasks. The Robotics On-Board Trainer (ROBoT) task is NASA's platform for training astronauts to perform docking and grappling maneuvers. It is regularly used by crewmembers during spaceflight for refresher training. The operational ROBoT system, however, does not record data. Thus, a research version of ROBoT, called ROBoT-r, was developed so that operationally relevant data could be mined to provide feedback to crewmembers. We investigated whether ROBoT-r metrics would change according to sleep loss and circadian phase in a 28-h laboratory-based sleep deprivation study. Overall, participants showed improvement over time despite sleep loss, indicating continued learning. Performance on the psychomotor vigilance task (PVT) followed an expected profile, with reduced performance across the night. These findings suggest that individuals may be able to temporarily compensate for sleep loss to maintain performance on complex, novel tasks. It is possible that some ROBoT-r metrics may be sensitive to sleep loss after longer bouts of wakefulness or after individuals have habituated to the task. Studies with additional participants and extended pre-training on the ROBoT-r task should be conducted to disentangle how brain activity may change as individuals learn and habituate to complex tasks during sleep loss.

Adaptive filtering to reduce global interference in non-invasive NIRS measures of brain activation: how well and when does it work?

In previous work we introduced a novel method for reducing global interference, based on adaptive filtering, to improve the contrast to noise ratio (CNR) of evoked hemodynamic responses measured non-invasively with near infrared spectroscopy (NIRS). Here, we address the issue of how to generally apply the proposed adaptive filtering method. A total of 156 evoked visual response measurements, collected from 15 individuals, were analyzed. The similarity (correlation) between measurements with far and near source-detector separations collected during the rest period before visual stimulation was used as indicator of global interference dominance. A detailed analysis of CNR improvement in oxy-hemoglobin (O(2)Hb) and deoxy-hemoglobin (HHb), as a function of the rest period correlation coefficient, is presented. Results show that for O(2)Hb measurements, 66% exhibited substantial global interference. For this dataset, dominated by global interference, 71% of the measurements revealed CNR improvements after adaptive filtering, with a mean CNR improvement of 60%. No CNR improvement was observed for HHb. This study corroborates our previous finding that adaptive filtering provides an effective method to increase CNR when there is strong global interference, and also provides a practical way for determining when and where to apply this technique.

Enhanced visual processing contributes to matrix reasoning in autism.

Recent behavioral investigations have revealed that autistics perform more proficiently on Raven's Standard Progressive Matrices (RSPM) than would be predicted by their Wechsler intelligence scores. A widely-used test of fluid reasoning and intelligence, the RSPM assays abilities to flexibly infer rules, manage goal hierarchies, and perform high-level abstractions. The neural substrates for these abilities are known to encompass a large frontoparietal network, with different processing models placing variable emphasis on the specific roles of the prefrontal or posterior regions. We used functional magnetic resonance imaging to explore the neural bases of autistics' RSPM problem solving. Fifteen autistic and eighteen non-autistic participants, matched on age, sex, manual preference and Wechsler IQ, completed 60 self-paced randomly-ordered RSPM items along with a visually similar 60-item pattern matching comparison task. Accuracy and response times did not differ between groups in the pattern matching task. In the RSPM task, autistics performed with similar accuracy, but with shorter response times, compared to their non-autistic controls. In both the entire sample and a subsample of participants additionally matched on RSPM performance to control for potential response time confounds, neural activity was similar in both groups for the pattern matching task. However, for the RSPM task, autistics displayed relatively increased task-related activity in extrastriate areas (BA18), and decreased activity in the lateral prefrontal cortex (BA9) and the medial posterior parietal cortex (BA7). Visual processing mechanisms may therefore play a more prominent role in reasoning in autistics.

Neurophysiological alterations during strategy-based verbal learning in traumatic brain injury.

BACKGROUND: Verbal learning and strategic processing deficits are common sequelae of traumatic brain injury (TBI); however, the neurophysiological mechanisms underlying such deficits remain poorly understood. METHODS: We performed functional magnetic resonance imaging (fMRI) in 25 individuals with chronic TBI (>1 year after injury) and 20 matched healthy controls. Subjects were scanned while encoding word lists, with free recall and recognition assessed after each scanning run. To vary the strategic processing load, participants learned semantically unrelated words (Unrelated condition), semantically related words under null instruction conditions (Spontaneous condition), and semantically related words following training on the use of a semantic clustering strategy (Directed condition). RESULTS: Behavioral performance on recall, recognition, and semantic clustering improved significantly as follows: Unrelated < Spontaneous < Directed. Individuals with TBI exhibited impaired yet parallel behavioral performance relative to control participants. The fMRI measures of brain activity during verbal encoding revealed decreased activity in participants with TBI relative to controls in left dorsolateral prefrontal cortex (DLPFC; BA 9) and in a region spanning the left angular and supramarginal gyri (BA 39/40). Functional connectivity analysis revealed evidence of a functional-but not anatomical-breakdown in the connectivity between the DLPFC and other regions specifically when participants with TBI were directed to use the semantic encoding strategy. CONCLUSION: After TBI, the DLPFC appears to be decoupled from other active brain regions specifically when strategic control is required. We hypothesize that approaches designed to help re-couple DLPFC under such conditions may aid TBI cognitive rehabilitation.

Operationally Relevant Behavior Assessment Using the Robotic On-Board Trainer for Research (ROBoT-r).

INTRODUCTION: Spaceflight can strain astronaut physical, physiological, and mental well-being, whereas maintaining astronaut operational performance remains an essential goal. Although various cognitive tests have been used for spaceflight assessment, these have been challenged on their lack of operational relevance.METHODS: To address this gap, we developed and characterized the Robotic On-Board Trainer for Research (ROBoT-r) system, based on the Robotic On-Board Trainer (ROBoT) currently used for astronaut training on Canadarm2 track-and-capture activities. The task requires use of dual hand-controllers (6 degrees of freedom) to grapple an incoming vehicle in free-drift in a time-limited setting. After developing a platform for conducting research studies, characterization testing of ROBoT-r was completed by 14 astronaut-like volunteers (35 ± 11 yr; N = 5 women) over 16 sessions each.RESULTS: We describe the design and capabilities of the ROBoT-r system for conducting operationally relevant research on human performance. Version 6.2 of the system supports H-II Transfer Vehicle track-and-capture operations within a multimillion component, physics-enabled 3D model using NASA's DOUG graphics platform. It has configurable task initialization and auto-run capabilities, saves 38 variables continuously at 20 Hz throughout each run, provides the user quantitative feedback after each run, and provides summaries after each session. Detailed performance characterization data is reported for future experimental planning purposes.DISCUSSION: ROBoT-r's range of performance variables enables detailed and quantitative performance assessment. Its use in spaceflight will help provide insight into operational performance, as well as allowing investigators to compare these results with more traditional cognitive tests to help better understand the interaction between individual cognitive abilities and operational performance.Ivkovic V, Sommers B, Cefaratti DA, Newman G, Thomas DW, Alexander DG, Strangman GE. Operationally relevant behavior assessment using the Robotic On-Board Trainer for Research (ROBoT-r). Aerosp Med Hum Perform. 2019; 90(9):819-825.

Technology Development for Simultaneous Wearable Monitoring of Cerebral Hemodynamics and Blood Pressure.

For many cerebrovascular diseases both blood pressure (BP) and hemodynamic changes are important clinical variables. In this paper, we describe the development of a novel approach to noninvasively and simultaneously monitor cerebral hemodynamics, BP, and other important parameters at high temporal resolution (250 Hz sampling rate). In this approach, cerebral hemodynamics are acquired using near infrared spectroscopy based sensors and algorithms, whereas continuous BP is acquired by superficial temporal artery tonometry with pulse transit time based drift correction. The sensors, monitoring system, and data analysis algorithms used in the prototype for this approach are reported in detail in this paper. Preliminary performance tests demonstrated that we were able to simultaneously and noninvasively record and reveal cerebral hemodynamics and BP during people's daily activity. As examples, we report dynamic cerebral hemodynamic and BP fluctuations during postural changes and micturition. These preliminary results demonstrate the feasibility of our approach, and its unique power in catching hemodynamics and BP fluctuations during transient symptoms (such as syncope) and revealing the dynamic features of related events.

Auditory stimulus repetition effects on cortical hemoglobin oxygenation: a near-infrared spectroscopy investigation.

The cortical response to repeated sensory stimuli plateaus (or declines) as repetition frequencies increase beyond 2-8 Hz. This study examined the underlying changes in cortical oxygenated and deoxygenated hemoglobin associated with this phenomenon using near-infrared spectroscopy. The optical signal was measured from 11 healthy volunteers listening to noise-burst trains presented at 2, 10, and 35 Hz. In a bilateral region consistent with the posterior superior temporal gyrus there was an inverse relationship between deoxyhemoglobin concentration change and stimulus frequency: greatest at 2 Hz, intermediate at 10 Hz, and smallest at 35 Hz. These findings provide preliminary support for a relationship between the perceptual characteristics of auditory stimuli and modulation of cortical oxygenation as measured via an emerging neuromonitoring technique.