Mental workload assessment by monitoring brain, heart, and eye with six biomedical modalities during six cognitive tasks.

Introduction: The efficiency and safety of complex high precision human-machine systems such as in aerospace and robotic surgery are closely related to the cognitive readiness, ability to manage workload, and situational awareness of their operators. Accurate assessment of mental workload could help in preventing operator error and allow for pertinent intervention by predicting performance declines that can arise from either work overload or under stimulation. Neuroergonomic approaches based on measures of human body and brain activity collectively can provide sensitive and reliable assessment of human mental workload in complex training and work environments. Methods: In this study, we developed a new six-cognitive-domain task protocol, coupling it with six biomedical monitoring modalities to concurrently capture performance and cognitive workload correlates across a longitudinal multi-day investigation. Utilizing two distinct modalities for each aspect of cardiac activity (ECG and PPG), ocular activity (EOG and eye-tracking), and brain activity (EEG and fNIRS), 23 participants engaged in four sessions over 4 weeks, performing tasks associated with working memory, vigilance, risk assessment, shifting attention, situation awareness, and inhibitory control. Results: The results revealed varying levels of sensitivity to workload within each modality. While certain measures exhibited consistency across tasks, neuroimaging modalities, in particular, unveiled meaningful differences between task conditions and cognitive domains. Discussion: This is the first comprehensive comparison of these six brain-body measures across multiple days and cognitive domains. The findings underscore the potential of wearable brain and body sensing methods for evaluating mental workload. Such comprehensive neuroergonomic assessment can inform development of next generation neuroadaptive interfaces and training approaches for more efficient human-machine interaction and operator skill acquisition.

Neuroadaptive Training via fNIRS in Flight Simulators.

Training to master a new skill often takes a lot of time, effort, and financial resources, particularly when the desired skill is complex, time sensitive, or high pressure where lives may be at risk. Professions such as aircraft pilots, surgeons, and other mission-critical operators that fall under this umbrella require extensive domain-specific dedicated training to enable learners to meet real-world demands. In this study, we describe a novel neuroadaptive training protocol to enhance learning speed and efficiency using a neuroimaging-based cognitive workload measurement system in a flight simulator. We used functional near-infrared spectroscopy (fNIRS), which is a wearable, mobile, non-invasive neuroimaging modality that can capture localized hemodynamic response and has been used extensively to monitor the anterior prefrontal cortex to estimate cognitive workload. The training protocol included four sessions over 2 weeks and utilized realistic piloting tasks with up to nine levels of difficulty. Learners started at the lowest level and their progress adapted based on either behavioral performance and fNIRS measures combined (neuroadaptive) or performance measures alone (control). Participants in the neuroadaptive group were found to have significantly more efficient training, reaching higher levels of difficulty or significantly improved performance depending on the task, and showing consistent patterns of hemodynamic-derived workload in the dorsolateral prefrontal cortex. The results of this study suggest that a neuroadaptive personalized training protocol using non-invasive neuroimaging is able to enhance learning of new tasks. Finally, we outline here potential avenues for further optimization of this fNIRS based neuroadaptive training approach. As fNIRS mobile neuroimaging is becoming more practical and accessible, the approaches developed here can be applied in the real world in scale.

Transcranial Direct Current Stimulation Modulates Neuronal Activity and Learning in Pilot Training.

Skill acquisition requires distributed learning both within (online) and across (offline) days to consolidate experiences into newly learned abilities. In particular, piloting an aircraft requires skills developed from extensive training and practice. Here, we tested the hypothesis that transcranial direct current stimulation (tDCS) can modulate neuronal function to improve skill learning and performance during flight simulator training of aircraft landing procedures. Thirty-two right-handed participants consented to participate in four consecutive daily sessions of flight simulation training and received sham or anodal high-definition-tDCS to the right dorsolateral prefrontal cortex (DLPFC) or left motor cortex (M1) in a randomized, double-blind experiment. Continuous electroencephalography (EEG) and functional near infrared spectroscopy (fNIRS) were collected during flight simulation, n-back working memory, and resting-state assessments. tDCS of the right DLPFC increased midline-frontal theta-band activity in flight and n-back working memory training, confirming tDCS-related modulation of brain processes involved in executive function. This modulation corresponded to a significantly different online and offline learning rates for working memory accuracy and decreased inter-subject behavioral variability in flight and n-back tasks in the DLPFC stimulation group. Additionally, tDCS of left M1 increased parietal alpha power during flight tasks and tDCS to the right DLPFC increased midline frontal theta-band power during n-back and flight tasks. These results demonstrate a modulation of group variance in skill acquisition through an increasing in learned skill consistency in cognitive and real-world tasks with tDCS. Further, tDCS performance improvements corresponded to changes in electrophysiological and blood-oxygenation activity of the DLPFC and motor cortices, providing a stronger link between modulated neuronal function and behavior.

Axon regeneration can facilitate or suppress hindlimb function after olfactory ensheathing glia transplantation.

Reports based primarily on anatomical evidence suggest that olfactory ensheathing glia (OEG) transplantation promotes axon regeneration across a complete spinal cord transection in adult rats. Based on functional, electrophysiological, and anatomical assessments, we found that OEG promoted axon regeneration across a complete spinal cord transection and that this regeneration altered motor responses over time. At 7 months after transection, 70% of OEG-treated rats showed motor-evoked potentials in hindlimb muscles after transcranial electric stimulation. Furthermore, a complete spinal cord retransection performed 8 months after injury demonstrated that this axon regeneration suppressed locomotor performance and decreased the hypersensitive hindlimb withdrawal response to mechanical stimulation. OEG transplantation alone promoted reorganization of lumbosacral locomotor networks and, when combined with long-term training, enhanced some stepping measures. These novel findings demonstrate that OEG promote regeneration of mature axons across a complete transection and reorganization of spinal circuitry, both of which contribute to sensorimotor function.

Further evidence of olfactory ensheathing glia facilitating axonal regeneration after a complete spinal cord transection.

Spinal Wistar Hannover rats injected with olfactory ensheathing glia (OEG) have been shown to recover some bipedal stepping and climbing abilities. Given the intrinsic ability of the spinal cord to regain stepping with pharmacological agents or epidural stimulation after a complete mid-thoracic transection, we asked if functional recovery after OEG injections is due to changes in the caudal stump or facilitation of functional regeneration of axons across the transection site. OEG were injected rostral and caudal to the transection site immediately after transection. Robotically assisted step training in the presence of intrathecal injections of a 5-HT(2A) receptor agonist (quipazine) was used to facilitate recovery of stepping. Bipedal stepping as well as climbing abilities were tested over a 6-month period post-transection to determine any improvement in hindlimb functional due to OEG injections and/or step training. The ability for OEG to facilitate regeneration was analyzed electrophysiologically by transcranially stimulating the brainstem and recording motor evoked potentials (MEP) with chronically implanted intramuscular EMG electrodes in the soleus and tibalis anterior with and without intrathecal injections of noradrenergic, serotonergic, and glycinergic receptor antagonists. Analyses confirmed that along with improved stepping ability and increased use of the hindlimbs during climbing, only OEG rats showed recovery of MEP. In addition the MEP signals were eliminated after a re-transection of the spinal cord rostral to the original transection and were modified in the presence of receptor antagonists. These data indicate that improved hindlimb function after a complete transection was coupled with OEG-facilitated functional regeneration of axons. This article is part of a Special Issue entitled: Understanding olfactory ensheathing glia and their prospect for nervous system repair.

Why variability facilitates spinal learning.

Spinal Wistar Hannover rats trained to step bipedally on a treadmill with manual assistance of the hindlimbs have been shown to improve their stepping ability. Given the improvement in motor performance with practice and the ability of the spinal cord circuitry to learn to step more effectively when the mode of training allows variability, we examined why this intrinsic variability is an important factor. Intramuscular EMG electrodes were implanted to monitor and compare the patterns of activation of flexor (tibialis anterior) and extensor (soleus) muscles associated with a fixed-trajectory and assist-as-needed (AAN) step training paradigms in rats after a complete midthoracic (T8-T9) spinal cord transection. Both methods involved a robotic arm attached to each ankle of the rat to provide guidance during stepping. The fixed trajectory allowed little variance between steps, and the AAN provided guidance only when the ankle deviated a specified distance from the programmed trajectory. We hypothesized that an AAN paradigm would impose fewer disruptions of the control strategies intrinsic to the spinal locomotor circuitry compared with a fixed trajectory. Intrathecal injections of quipazine were given to each rat to facilitate stepping. Analysis confirmed that there were more corrections within a fixed-trajectory step cycle and consequently there was less coactivation of agonist and antagonist muscles during the AAN paradigm. These data suggest that some critical level of variation in the specific circuitry activated and the resulting kinematics reflect a fundamental feature of the neural control mechanisms even in a highly repetitive motor task.

Issues in quantifying atrophic macular disease using retinal autofluorescence.

PURPOSE: To demonstrate the potential and limits of autofluorescence imaging in identifying and delineating areas of atrophy. METHODS: Fundus photographs and infrared scanning laser ophthalmoscope (SLO) imaging, SLO macular perimetry, and SLO autofluorescence imaging results were compared for two patients with geographic atrophy (GA) from age-related macular degeneration, one patient with pigmentary alteration of the retina, and two patients with Stargardt disease. The main outcome measure in this case series was the presence of reduced autofluorescence. RESULTS: Drusen may become undetectable during autofluorescence imaging for some patients, allowing simple identification of areas of GA with areas of reduced autofluorescence. In other patients, drusen themselves have decreased autofluorescence, despite having intact retinal function in the retina overlying them. Some patients may have areas of reduced autofluorescence that persist for many years, without evidence of the development of atrophy. In Stargardt disease, decreased autofluorescence can easily detect and delineate areas of scotoma. Areas with mottled autofluorescence may have overlying function, but the function may not be adequate to support a fixation locus in that area. CONCLUSIONS: Using decreased autofluorescence to delineate areas of atrophy may be helpful in atrophic macular disorders. For GA, correlation with fundus photographs or macular perimetry findings may be necessary to differentiate between drusen and atrophy. For Stargardt disease, the nature of areas of decreased autofluorescence may help explain visual function of those areas.

Limited macular translocation for atrophic maculopathy.

OBJECTIVES: To report visual improvement following bilateral limited macular translocation for a patient with atrophic macular disease, and to discuss issues related to the selection of potential candidates for this technique. DESIGN: Case report. RESULTS: A 78-year-old woman with bilateral atrophic maculopathy and no choroidal neovascularization had slowly progressive loss of visual acuity for at least 17 months in the right eye and 25 months in the left eye. She underwent bilateral limited macular translocation, using scleral infolding in the right eye and scleral outpouching in the left eye. Following translocation of her maculae, her best-corrected visual acuity improved from 20/200 to 20/30 OD and from 20/180 to 20/100 OS. She remained stable during 30 months of follow-up for the right eye and 22 months of follow-up for the left eye. CONCLUSION: Macular translocation may allow visual recovery in selected patients with atrophic maculopathy, even after a prolonged period of poor vision.