Simulation Training in Neuroangiography-Validation and Effectiveness.

PURPOSE: Simulators are increasingly used in the training of endovascular procedures; however, for the use of the Mentice vascular interventional system trainer (VIST) simulator in neuroradiology, the validity of the method has not yet been proven. The study was carried out to test the construct validity of such a simulator by demonstrating differences between beginner and expert neurointerventionalists and to evaluate whether a training effect can be demonstrated in repeated cases for different levels of experience. METHODS: In this study 4 experts and 6 beginners performed 10 diagnostic angiographies on the VIST simulator (Mentice AB, Gothenburg, Sweden). Of the cases four were non-recurring, whereas three were repeated once and ten subjects performed all tasks. Additionally, another expert performed only five non-recurring cases. The simulator recorded total time, fluoroscopy time, amount of contrast medium and number of material changes. Furthermore, gaze direction and heart rate were recorded, and subjects completed a questionnaire on workload. RESULTS: Beginners and experts showed significant differences in total duration time, fluoroscopy time and amount of contrast agent (all p < 0.05). Gaze direction, dwell time and heart rate were similar between both groups. Only beginners improved during training with respect to total duration time, fluoroscopy time and amount of contrast agent. If a case was previously known to them, the total duration and fluoroscopy time were significantly shortened (p < 0.001). CONCLUSION: This study demonstrated both the construct validity of a diagnostic neuroangiography simulator as well as a significant training effect for beginners. Therefore, in particular beginner neurointerventionalists should use such simulation tools more extensively in their initial training.

Real-space navigation testing differentiates between amyloid-positive and -negative aMCI.

OBJECTIVE: To distinguish between patients with amyloid-positive (A+) and -negative (A-) amnestic mild cognitive impairment (aMCI) by simultaneously investigating navigation performance, visual exploration behavior, and brain activations during a real-space navigation paradigm. METHODS: Twenty-one patients with aMCI were grouped into A+ (n = 11) and A- cases by amyloid-PET imaging and amyloid CSF levels and compared to 15 healthy controls. Neuropsychological deficits were quantified by use of the Consortium to Establish a Registry for Alzheimer's Disease-plus cognitive battery. All participants performed a navigation task in which they had to find items in a realistic spatial environment and had to apply egocentric and allocentric route planning strategies. 18F-fluorodeoxyglucose was injected at the start to detect navigation-induced brain activations. Subjects wore a gaze-controlled, head-fixed camera that recorded their visual exploration behavior. RESULTS: A+ patients performed worse during egocentric and allocentric navigation compared to A- patients and controls (p < 0.001). Both aMCI subgroups used fewer shortcuts, moved more slowly, and stayed longer at crossings. Word-list learning, figural learning, and Trail-Making tests did not differ in the A+ and A- subgroups. A+ patients showed a reduced activation of the right hippocampus, retrosplenial, and parietal cortex during navigation compared to A- patients (p < 0.005). CONCLUSIONS: A+ patients with aMCI perform worse than A- patients with aMCI in egocentric and allocentric route planning because of a more widespread impairment of their cerebral navigation network. Navigation testing in real space is a promising approach to identify patients with aMCI with underlying Alzheimer pathology.

A bedside application-based assessment of spatial orientation and memory: approaches and lessons learned.

Spatial orientation and memory deficits are an often overlooked and potentially powerful early marker for pathological cognitive decline. Pen-and-paper tests for spatial abilities often do not coincide with actual navigational performance due to differences in spatial perspective and scale. Mobile devices are becoming increasingly useful in a clinical setting, for patient monitoring, clinical decision-making, and information management. The same devices have positional information that may be useful for a scale appropriate point-of-care test for spatial ability. We created a test for spatial orientation and memory based on pointing within a single room using the sensors in mobile phone. The test consisted of a baseline pointing condition to which all other conditions were compared, a spatial memory condition with eyes-closed, and two body rotation conditions (real or mental) where spatial updating were assessed. We examined the effectiveness of the sensors from a mobile phone for measuring pointing errors in these conditions in a sample of healthy young individuals. We found that the sensors reliably produced appropriate azimuth and elevation pointing angles for all of the 15 targets presented across multiple participants and days. Within-subject variability was below 6° elevation and 10° azimuth for the control condition. The pointing error and variability increased with task difficulty and correlated with self-report tests of spatial ability. The lessons learned from the first tests are discussed as well as the outlook of this application as a scientific and clinical bedside device. Finally, the next version of the application is introduced as an open source application for further development.

Gaze in Visual Search Is Guided More Efficiently by Positive Cues than by Negative Cues.

Visual search can be accelerated when properties of the target are known. Such knowledge allows the searcher to direct attention to items sharing these properties. Recent work indicates that information about properties of non-targets (i.e., negative cues) can also guide search. In the present study, we examine whether negative cues lead to different search behavior compared to positive cues. We asked observers to search for a target defined by a certain shape singleton (broken line among solid lines). Each line was embedded in a colored disk. In "positive cue" blocks, participants were informed about possible colors of the target item. In "negative cue" blocks, the participants were informed about colors that could not contain the target. Search displays were designed such that with both the positive and negative cues, the same number of items could potentially contain the broken line ("relevant items"). Thus, both cues were equally informative. We measured response times and eye movements. Participants exhibited longer response times when provided with negative cues compared to positive cues. Although negative cues did guide the eyes to relevant items, there were marked differences in eye movements. Negative cues resulted in smaller proportions of fixations on relevant items, longer duration of fixations and in higher rates of fixations per item as compared to positive cues. The effectiveness of both cue types, as measured by fixations on relevant items, increased over the course of each search. In sum, a negative color cue can guide attention to relevant items, but it is less efficient than a positive cue of the same informational value.

Visual Search in the Real World: Color Vision Deficiency Affects Peripheral Guidance, but Leaves Foveal Verification Largely Unaffected.

BACKGROUND: People with color vision deficiencies report numerous limitations in daily life, restricting, for example, their access to some professions. However, they use basic color terms systematically and in a similar manner as people with normal color vision. We hypothesize that a possible explanation for this discrepancy between color perception and behavioral consequences might be found in the gaze behavior of people with color vision deficiency. METHODS: A group of participants with color vision deficiencies and a control group performed several search tasks in a naturalistic setting on a lawn. All participants wore a mobile eye-tracking-driven camera with a high foveal image resolution (EyeSeeCam). Search performance as well as fixations of objects of different colors were examined. RESULTS: Search performance was similar in both groups in a color-unrelated search task as well as in a search for yellow targets. While searching for red targets, participants with color vision deficiencies exhibited a strongly degraded performance. This was closely matched by the number of fixations on red objects shown by the two groups. Importantly, once they fixated a target, participants with color vision deficiencies exhibited only few identification errors. CONCLUSIONS: In contrast to controls, participants with color vision deficiencies are not able to enhance their search for red targets on a (green) lawn by an efficient guiding mechanism. The data indicate that the impaired guiding is the main influence on search performance, while foveal identification (verification) is largely unaffected by the color vision deficiency.

The influence of anaesthetists' experience on workload, performance and visual attention during simulated critical incidents.

Development of accurate Situation Awareness (SA) depends on experience and may be impaired during excessive workload. In order to gain adequate SA for decision making and performance, anaesthetists need to distribute visual attention effectively. Therefore, we hypothesized that in more experienced anaesthetists performance is better and increase of physiological workload is less during critical incidents. Additionally, we investigated the relation between physiological workload indicators and distribution of visual attention. In fifteen anaesthetists, the increase of pupil size and heart rate was assessed in course of a simulated critical incident. Simulator log files were used for performance assessment. An eye-tracking device (EyeSeeCam) provided data about the anaesthetists' distribution of visual attention. Performance was assessed as time until definitive treatment. T tests and multivariate generalized linear models (MANOVA) were used for retrospective statistical analysis. Mean pupil diameter increase was 8.1% (SD ± 4.3) in the less experienced and 15.8% (±10.4) in the more experienced subjects (p = 0.191). Mean heart rate increase was 10.2% (±6.7) and 10.5% (±8.3, p = 0.956), respectively. Performance did not depend on experience. Pupil diameter and heart rate increases were associated with a shift of visual attention from monitoring towards manual tasks (not significant). For the first time, the following four variables were assessed simultaneously: physiological workload indicators, performance, experience, and distribution of visual attention between "monitoring" and "manual" tasks. However, we were unable to detect significant interactions between these variables. This experimental model could prove valuable in the investigation of gaining and maintaining SA in the operation theatre.

Mobile three dimensional gaze tracking.

Mobile eyetracking is a recent method enabling research on attention during real-life behavior. With the EyeSeeCam, we have recently presented a mobile eye-tracking device, whose camera-motion device (gazecam) records movies orientated in user's direction of gaze. Here we show that the EyeSeeCam can extract a reliable vergence signal, to measure the fixation distance. We extend the system to determine not only the direction of gaze for short distances more precisely, but also the fixation point in 3 dimensions (3D). Such information is vital, if gaze-tracking shall be combined with tasks requiring 3D information in the peri-personal space, such as grasping. Hence our method substantially extends the application range for mobile gaze-tracking devices and makes a decisive step towards their routine application in standardized clinical settings.

Head impulse testing using video-oculography.

Head impulses are a routine clinical test of semicircular canal function. At the bedside, they are used to detect malfunctioning of the horizontal semicircular canals. So far, 3-D-search-coil recording is required to reliably test anterior and posterior canal function and to determine the gain of the vestibulo-ocular reflex (VOR). Search-coil recording cannot be done at the bedside. Here we tested whether video-oculography (VOG) is suitable to assess VOR gain for individual canals at the bedside. We recorded head impulses in healthy subjects using a mobile high-frame-rate, head-mounted VOG-device and compared the results with those obtained with standard search-coil recording. Our preliminary results indicate that high-frame-rate VOG is a promising tool to measure and quantify individual semicircular canal function not only at the bedside.

On-line classification and prediction of eye movements by multiple-model Kalman filtering.

An extensible multiple-model Kalman filter framework for eye tracking and video-oculography (VOG) applications is proposed. The Kalman filter predicts future states of a system on the basis of a mathematical model and previous measurements. The predicted values are then compared against the current measurements. In a correcting step, the predicted state is enhanced by the measurements. In this work, the Kalman filter is used for smoothing the VOG data, for on-line classification of eye movements, as well as for predictive real-time control of a gaze-driven head-mounted camera (EyeSeeCam). With multiple models running in parallel, it was possible to distinguish between fixations, slow-phase eye movements, and saccades. Under the assumption that each class of eye movement follows a distinct model, one can decide which types of eye movement occurred by evaluating the probability for each model.

EyeSeeCam: an eye movement-driven head camera for the examination of natural visual exploration.

The prototype of a gaze-controlled, head-mounted camera (EyeSeeCam) was developed that provides the functionality for fundamental studies on human gaze behavior even under dynamic conditions like locomotion. EyeSeeCam incorporates active visual exploration by saccades with image stabilization during head, object, and surround motion just as occurs in human ocular motor control. This prototype is a first attempt to combine free user mobility with image stabilization and unrestricted exploration of the visual surround in a man-made technical vision system. The gaze-driven camera is supplemented by an additional wide-angle, head-fixed scene camera. In this scene view, the focused gaze view is embedded with picture-in-picture functionality, which provides an approximation of the foveated retinal content. Such a combined video clip can be viewed more comfortably than the saccade-pervaded image of the gaze camera alone. EyeSeeCam consists of a video-oculography (VOG) device and a camera motion device. The benchmark for the evaluation of such a device is the vestibulo-ocular reflex (VOR), which requires a latency on the order of 10 msec between head and eye (camera) movements for proper image stabilization. A new lightweight VOG was developed that is able to synchronously measure binocular eye positions at up to 600 Hz. The camera motion device consists of a parallel kinematics setup with a backlash-free gimbal joint that is driven by piezo actuators with no reduction gears. As a result, the latency between the rotations of an artificial eye and the camera was 10 msec, which is VOR-like.