Stimulus Screen Research Articles

Wearable technology-based metrics for predicting operator performance during cardiac catheterisation

IntroductionUnobtrusive metrics that can auto-assess performance during clinical procedures are of value. Three approaches to deriving wearable technology-based metrics are explored: (1) eye tracking, (2) psychophysiological measurements [e.g. electrodermal activity (EDA)] and (3) arm and hand movement via accelerometry. We also measure attentional capacity by tasking the operator with an additional task to track an unrelated object during the procedure.MethodsTwo aspects of performance are measured: (1) using eye gaze and psychophysiology metrics and (2) measuring attentional capacity via an additional unrelated task (to monitor a visual stimulus/playing cards). The aim was to identify metrics that can be used to automatically discriminate between levels of performance or at least between novices and experts. The study was conducted using two groups: (1) novice operators and (2) expert operators. Both groups made two attempts at a coronary angiography procedure using a full-physics virtual reality simulator. Participants wore eye tracking glasses and an E4 wearable wristband. Areas of interest were defined to track visual attention on display screens, including: (1) X-ray, (2) vital signs, (3) instruments and (4) the stimulus screen (for measuring attentional capacity).ResultsExperts provided greater dwell time (63% vs 42%, p = 0.03) and fixations (50% vs 34%, p = 0.04) on display screens. They also provided greater dwell time (11% vs 5%, p = 0.006) and fixations (9% vs 4%, p = 0.007) when selecting instruments. The experts’ performance for tracking the unrelated object during the visual stimulus task negatively correlated with total errors (r = − 0.95, p = 0.0009). Experts also had a higher standard deviation of EDA (2.52 µS vs 0.89 µS, p = 0.04).ConclusionsEye tracking metrics may help discriminate between a novice and expert operator, by showing that experts maintain greater visual attention on the display screens. In addition, the visual stimulus study shows that an unrelated task can measure attentional capacity.Trial registration This work is registered through clinicaltrials.gov, a service of the U.S. National Health Institute, and is identified by the trial reference: NCT02928796.

Comparing short‐duration electro‐oculogram with and without mydriasis in controls

AbstractPurpose In order to obtain artefact‐free EOG recordings the subject’s cooperation is necessary. The aim of our study is to evaluate recording characteristics of the short‐duration EOG and to compare the effect of mydriasis on EOG recordings in a cohort of controls.Methods EOG recordings were performed on a LED stimulus screen using a RETI‐port gamma plus2 system (RETIscanTM, Roland Consult). Dark phase included: pre‐adaptation (6min), alternate fixation (4min), fixation‐rest (20sek), 100 sweeps. Light phase included: light adaptation (4min), alternate fixation (10min), fixation‐rest (20sek), 250 sweeps. Amplifier was band pass filtered at 0.1‐50Hz. Background illumination in mydriasis was 100cd/m2 and in miosis 450cd/m2. Fast oscillations were set at 1.5sek (6 cycles; total duration 75sek).Results A total of 55 controls divided in three age‐groups participated (number; mean (years, y); ±SD): group 1: 18‐ 20y (19; 19.49y; ±0.89); group 2: 20‐40y (18; 27.91y; ±5.39) and group 3: 40‐60y (18; 48.66y; ±4.00). Arden ratio (AR), dark‐trough (DT) and light‐peak (LP) did not differ between recordings with or without mydriasis (p=0.885; p=0.860; p=0.776, linear mixed‐effects model). Age did not influence the AR, DT, LP (p= 0.206; p=0.112; p=0.155). AR, DT, LP were comparable between eyes tested (p=0.998; p=0.196; p=0.324).Conclusion Short‐duration EOG allows successful recording, where the application of mydriasis does not influence the quality of the recording.

Vection Is Not Determined by the Retinal Coordinate

We examined whether vection was determined by the retinal coordinate. The participants sat on a chair with their body rotated 0, 45, 90 and 135 degrees and with their head facing directly at the stimulus screen. Vection strength was changed by rotation of the body. Thus vection was affected by the body coordinate and it was not determined by the retinal coordinate alone.

Mental transformations of spatial stimuli in humans and in monkeys: Rotation vs. translocation

We studied the ability of monkeys and humans to orient in one spatial frame (“response frame”) according to abstract spatial stimuli presented in another spatial frame (“stimulus frame”). The stimuli were designed as simple maps of the “response space”. We studied how the transformations of these stimuli affected the performance.The subjects were trained to choose a particular position in the response frame – either on a touch screen (monkeys) or on a keyboard (humans) – according to schematic spatial stimuli presented on the stimulus screen. The monkeys responded by touching one of four circles shown in corners of a rectangle displayed on the touch screen. The correct position was signaled by the stimulus (“map”) presented on the stimulus screen. The map was a complementary rectangle, but only with one circle shown (“pointer”). The position of this circle indicated the correct position in the response frame.In the first experiment we only manipulated stimuli presented on the computer screen. The “map” was originally shown in the same position and orientation as the “response pattern” but later the position and the rotation of the map on the screen were changing.Such transformations of the stimuli allow us to study the mental operations that the animals performed and how particular mental transformations mutually differed.In the second experiment we tested whether the monkeys relied more on stimuli presented on the screen or on the surrounding stable environment and objects. We compared the performance of animals in tasks with rotated virtual maps in a stable surrounding environment with the performance in tasks where we rotated the surrounding frame (computer monitor), whereas the stimuli on the screen remained stable.In the third experiment we tested human subjects in analogous tests to compare the ability and cognitive strategies of monkeys and humans in this task.We showed that the mental strategies that monkeys used for orientation in one spatial frame according to the map presented in the other spatial frame depended on the type of stimulus manipulation.We demonstrated that for monkeys there was a difference between solving “mental rotation” and “mental translocation” in this experimental design. We showed that humans were able both to mentally rotate and translocate the displayed stimuli. However, the mental rotation was more difficult than mental translocation also for them.These experiments help us to understand how the monkeys perceive the abstract spatial information, create the representation of space and how they transform the information about the position obtained from one spatial frame into another. The comparison between humans and monkeys allows us to study this cognitive ability in phylogeny.

A Non-Verbal Turing Test: Differentiating Mind from Machine in Gaze-Based Social Interaction

In social interaction, gaze behavior provides important signals that have a significant impact on our perception of others. Previous investigations, however, have relied on paradigms in which participants are passive observers of other persons’ gazes and do not adjust their gaze behavior as is the case in real-life social encounters. We used an interactive eye-tracking paradigm that allows participants to interact with an anthropomorphic virtual character whose gaze behavior is responsive to where the participant looks on the stimulus screen in real time. The character’s gaze reactions were systematically varied along a continuum from a maximal probability of gaze aversion to a maximal probability of gaze-following during brief interactions, thereby varying contingency and congruency of the reactions. We investigated how these variations influenced whether participants believed that the character was controlled by another person (i.e., a confederate) or a computer program. In a series of experiments, the human confederate was either introduced as naïve to the task, cooperative, or competitive. Results demonstrate that the ascription of humanness increases with higher congruency of gaze reactions when participants are interacting with a naïve partner. In contrast, humanness ascription is driven by the degree of contingency irrespective of congruency when the confederate was introduced as cooperative. Conversely, during interaction with a competitive confederate, judgments were neither based on congruency nor on contingency. These results offer important insights into what renders the experience of an interaction truly social: Humans appear to have a default expectation of reciprocation that can be influenced drastically by the presumed disposition of the interactor to either cooperate or compete.

MfERG responses to long-duration white stimuli in glaucoma patients

The intent of our study was to evaluate whether the response to a long-duration white stimulus in the multifocal electroretinogram (mfERG) is sufficiently sensitive to detect early retinal dysfunction in glaucoma. On-off mfERGs were recorded from 15 NTG and 15 HTG patients and compared with 14 control subjects. Recording parameters were the following: LED stimulus screen (RETIscan™), 100-ms stimulus duration, 200-ms stimulus interval, 11-min total recording time, stimulus matrix of 61 elements, frame rate: 70Hz, Lmax: 180cd/m(2), Lmin: 0cd/m(2), and filter setting: 1-200Hz. The second negative response following stimulus onset (N2-on), as well as following stimulus offset (N2-off), was analyzed as an overall response and in quadrants, as well as in 4 small central and four adjoining peripheral areas per quadrant. The latency of the N2-on was significantly delayed in HTG in all response averages tested, while in NTG this was only seen in the overall response and in the small central response averages (P<0.05). The most sensitive measure in HTG was the latency of the N2-on of the small peripheral response average of the superior temporal quadrant with an area under the ROC curve of 0.881. For NTG, the most representative measure was the latency of the N2-on of the small central response average of the inferior nasal quadrant with an area under the ROC curve of 0.793. Our results showed that in stimulation with long-duration flashes, the second negative response following the on response, representative of the early PhNR, is affected in glaucoma where N2-on showed a latency delay in POAG patients. The latency delay of the N2-on was more prominent for HTG than for NTG.

Eye position influences contrast responses in V1 of alert monkey

Do our cells in V1 respond differently when we look in different places? To answer this question, we have studied neuronal responses to moving bars in V1 of an alert monkey while it maintained different directions of gaze. The monkey was trained to fixate on an LED attached to the stimulus screen while the screen was placed in three positions: straight ahead or 0 deg (0 position), approximately 10 deg to the right (10R) or or to the left (10L) in the horizontal plane (h) in a constant vertical position (v). Recorded mean +/− SE eye positions in minarc were: for 0 position (h,v) = (2.5+/− 5.7, 5.3+/−3.8), for 10R position (516+/−16, −32+/−3), for 10L position (−540+/−12, 31+/−5). We have recorded contrast responses in 21 cells. Changing eye position significantly influenced the maximum amplitude of the response in 13 cells. In 4 cells where maximum responses were unchanged, responses to lower contrasts changed significantly for different eye positions. In 7/17 cells in 0 position, in 5/17 cells in 10R position and in 5/17 in 10L position, responses were larger than in other two positions. We have fitted contrast responses r(c) with the Naka-Rushton equation: r(c) = Rmax*(c^n /(c^n + c50^n)), where Rmax is the maximum response, c — contrast, c50 -contrast at the half of Rmax, n — nonlinearity. We have analyzed only those responses with a sufficiently good fit (estimated by the RMS). In most cases changing the eye position had small influence on n, but significant influence on Rmax and c50. We have analyzed 18 contrast responses to increment and decrement bars. Rmax changed, more than 20%, in 12 cases and c50 in 14 cases. In 10 measurements both Rmax and c50 changed as the eye position changed. Our preliminary data also suggest that the eye position could differently influence the size of the increment and decrement zones in the classical receptive field of V1 cells.

Sexual Dimorphism in the Hoverfly Motion Vision Pathway

Many insects perform high-speed aerial maneuvers in which they navigate through visually complex surrounds. Among insects, hoverflies stand out, with males switching from stationary hovering to high-speed pursuit at extreme angular velocities [1]. In dipterans, 50-60 large interneurons -- the lobula-plate tangential cells (LPTCs) -- detect changes in optic flow experienced during flight [2-5]. It has been predicted that large LPTC receptive fields are a requirement of accurate "matched filters" of optic flow [6]. Whereas many fly taxa have three horizontal system (HS) LPTC neurons in each hemisphere, hoverflies have four [7], possibly reflecting the more sophisticated flight behavior. We here show that the most dorsal hoverfly neuron (HS north [HSN]) is sexually dimorphic, with the male receptive field substantially smaller than in females or in either sex of blowflies. The (hoverfly-specific) HSN equatorial (HSNE) is, however, sexually isomorphic. Using complex optic flow, we show that HSN, despite its smaller receptive field, codes yaw velocity as well as HSNE. Responses to a target moving against a plain or textured background suggest that the male HSN could potentially play a role in target pursuit under some conditions.

Single versus multiple probe blocks of P300-based concealed information tests for self-referring versus incidentally obtained information

The aim of the present study was to compare two protocols and two information types on detection of concealed knowledge. Four independent groups of subjects were run. Two were tested on probe stimuli of a self-referring (AUTO) nature and two were tested on incidentally acquired details of a mock crime (MOCK). Each pair of groups was run either in a one-probe (1PB) or multiple probe (6PB) block. In the single probe block, which was repeated three times with a different probe on each block, one probe item was randomly repeated multiple times in a Bernoulli series with frequently presented, meaningless or irrelevant items. There was also a rare target item designed to force attention to the stimulus screen. All stimulus types were of the same category within each block. In contrast, in the multiple probe (and category) block, rare probes, rare targets and frequent irrelevant items were repeatedly presented in a Bernoulli series within one block. Major results: There was a difference in task demand as measured by reaction time between the two protocols (the multiple probe protocol was more demanding), and a difference trend in P300 detection sensitivity between protocols for both information types combined in favor of the 1PB ( p < .07). With both protocols combined, there was a trend ( p < .07) favoring detection of familiar versus incidentally learned information. In terms of P300 amplitudes, both protocols showed the usual result that P300 to probes was greater than that to irrelevants. Also, as with detection rates, self-referring information was better detected in terms of Probe-Irrelevant P300 amplitude differences than mock crime information, regardless of protocol. There was no effect of time passage across the repeated blocks of the one-probe protocol. Methodological problems with the multiple probe protocol as utilized in most recent publications are discussed.

30 Hz-flicker mfERG in primary open-angle glaucoma patients

This study was performed in an attempt to gain more information on whether the 30 Hz-flicker mfERG indeed provides a sensitive measure of dysfunction in patients with primary open-angle glaucoma (POAG) as has been suggested previously. Eighteen POAG patients with visual field defects (MD > 2.2 dB) and glaucomatous optic neuropathies as well as 10 control subjects underwent mfERG recording as follows: 30 Hz-flicker mfERG, LED stimulus screen, 61 hexagons, Lmax: 180 cd/m2, Lmin: 0 cd/m2, recording time: approximately 5 min, filter setting: 10-200 Hz. The 30 Hz response (also called the fundamental or the first harmonic response (1HW) and the second harmonic wave at 60 Hz (2HW) were analysed as an overall response and in quadrants, as well as in 4 small neighbouring areas per quadrant. The patients' mfERGs were compared to those of the control group and to the mean defect values (MD) of the corresponding quadrants of the Octopus perimetry. Neither in the overall response, nor in the quadrants, nor in the smaller areas examined did amplitudes and phases of the 1HW and the 2HW or the amplitude ratio of the 2HW to the 1HW (DFT-ratio) differ from the controls (P > 0.05-ANOVA). There was no significant correlation between mfERG values and the MD (Spearman-test, Bonferroni). Thus, the 30 Hz-flicker mfERG does not seem to be sensitive enough to separate glaucoma patients from normal.

Recognition of small stimulus screen masks using the multifocal ERG.

To evaluate the ability of the multifocal ERG (mfERG) to detect small defects in the stimulus array was the objective of this paper. Seven normal subjects had mfERGs recorded with a VERIS system. Stimulus arrays composed of 61, 103 or 241 hexagons were covered in part by small masks of different light transmittance properties. Only masks that covered at least one-half of a single 103 hexagon stimulus cell caused a significant reduction in signal. Different-shaped masks of about 5 degrees diameter were detectable using a 61-hexagon array only when they fully covered a stimulus cell. Detection was better, but marginal for some of the masks, with the 103 hexagon array. The 241 hexagon array showed sharp defects for all masks. Masking the stimulus screen is not equivalent to having a pathologic scotoma, but it demonstrates the greatest possible spatial sensitivity of the mfERG system. Thus, the mfERG appears to be able to detect small retinal lesions if they reduce local retinal function by at least 50% and correspond to at least half the area of one stimulus hexagon. Scotomas 5 degrees or smaller would be best detected using a fine (241 hexagon) stimulus array. With coarser stimulus arrays (e.g. 103 or 61 hexagons), the effect of a small scotoma depends on its location relative to the stimulus cells. These issues should be considered when selecting mfERG recording conditions.

A biased view of attention.

A biased view of attention.

Measuring Frog Visual Acuity by a Novel Method

The sensory capabilities of animals have usually been measured either by lengthy conditioned discrimination procedures, or by using some specific unconditioned reflex. Amphibian visual acuity has previously been measured only by the latter type of method. Birukow's (1937 Zeitschrift für Vergleichende Physiologie25 92 – 142) optomotor response experiments on the common frog ( Rana temporaria) yielded an acuity of 4.3 cycles deg−1, which is surprisingly high in the sense that the retinal cell mosaics would suggest a substantially lower acuity. I have used a new method of measuring acuity based on the frog's prey-catching behaviour, a behaviour that has proved very useful for investigations of amphibian vision. Leopard frogs ( R. pipiens) were presented with a stimulus screen where two patches of identical black/white vertical grating were seen through two small horizontal oval windows (left and right) in a large screen displaying a horizontal grating pattern. The windows were of ‘mealworm’ size (18 mm long and 7 mm high, with the frog positioned 220 mm from the screen). One of the two vertical gratings was drifting in the window. If resolved, the movement triggered prey-catching behaviour in the frog: orienting, jumping towards the target, and even snapping. The spatial frequency of the two vertical gratings was varied, while the horizontal pattern of the screen was kept constant throughout the experiment. Orienting or jumping towards the moving grating was taken as an indication that the frog was able to resolve the spatial frequency in question. This method yielded a visual acuity of 2.8 cycles deg−1, which is in good agreement with the eye optics and the retinal grain of frogs (very similar for the common frog and the leopard frog). The method in itself implies that this is a ‘functional’ acuity value.

Binocular enhancement of the visual evoked potential in patients with Duane's syndrome.

Monocular and binocular visual evoked potentials were recorded in eight patients with Duane's syndrome who used an abnormal head posture to maintain binocular single vision. With their abnormal head posture, all patients had stereoscopic vision, although with mildly reduced stereoacuity, and the visual evoked potential showed binocular enhancement (mean binocular to monocular ratio, 1.44). Without their head posture, the patients experienced diplopia or suppressed vision in one eye. Binocular visual evoked potentials recorded under these conditions were of lower amplitude (mean binocular to monocular ratio, 1.05). However, without the abnormal head posture, a manifest strabismus was present and the deviating eye was not fixating the stimulus screen. Monocular visual evoked potentials recorded with the eye fixating just to one side of the screen gave little or no response, and this lack of fixation may account for the loss of binocular enhancement of the visual evoked potential in strabismus.

Approximate visual axis projection for the rhesus monkey using a funduscope and alignment laser

A technique was designed to align the rhesus monkey visual axis with a predetermined fixation point on a visual stimulus screen using a helium-neon laser and funduscope.

An Improved Technique for Monitoring Fixation in Tachistoscopic Tasks

A monocular lens mounted behind a stimulus screen was used to monitor fixation in a tachistoscopic recognition task. This technique was found superior to the often used “sideview technique” and as accurate as the method involving identification of a fixation stimulus. It was found that the “telescope technique” is preferable in those studies where presentation of a fixation stimulus might interfere with recognition or report of the experimental stimulus.

Intra-modality selective attention and evoked cortical potentials to randomly presented patterns

The effects of selective attention on visually evoked cortical responses (VERs) were investigated under conditions where transient changes in arousal level and peripheral orienting factors were reduced to a minimum. Four subjects were presented a random series of relevant and irrelevant light flashes and were instructed either to count or to make a reaction time response to the relevant stimulus. Stimuli were presented at a constant rate of 0.92 or 1.92 c/sec. Subjects fixated a central reference point on the stimulus screen throughout each trial. Averaged VERs from the occipital region showed a consistent increased negativity at latencies of 220–250 msec and positivity at latencies of 290–340 msec when the stimulus was attended as compared to not attended. The effects of attention on VERs did not differ significantly as a function of the response conditions or rate of stimulus presentation. The effects of selective attention on early and late evoked cortical activity were discussed in terms of the processing of sensory information in the peripheral and central nervous system, respectively.