Effects of tracker location on the accuracy and precision of the Gazepoint GP3 HD for spectacle wearers.

Remote view eye-tracking systems are prone to errors when used on spectacle wearers due to reflections from the lenses and frame that result in inaccurate tracking. Traditionally, these trackers are situated below a computer monitor and the viewer's eye moments are recorded while they view the screen. Reflections may be influenced by the pantoscopic tilt of the spectacles, whereby the tilt angle causes incident light to be reflected to the camera. To overcome this problem, we propose mounting the tracker above the monitor to avoid these reflections and test the accuracy and precision of subjects with single vision spectacles, multifocals, and no correction, using both mounting positions. Experimental results showed that this alternate position had overall worse accuracy (4.06° ± 0.13) and precision (0.67° ± 0.05) compared to the standard configuration (2.15° ± 0.06 vs. 0.50° ± 0.03), with more invalid readings (5.91 vs. 19.19%) for single vision lens wearers. Multifocals performed better for the top-mounting position for the top portion of the monitor, suggesting higher-order aberrations from the bottom portion of the lens negatively impact data quality. Higher pantoscopic tilt angles displayed an improved accuracy for this alternate position (r(9) = - 0.69, p = 0.02), with superior accuracy for tilt angles greater than 14° compared to the standard configuration. This study quantifies the impact of spectacle wear on eye-tracking performance and suggests other alternate mounting positions may be viable in certain situations.

Programmatically Localizing Diabetic Retinopathy Features in 45-Degree Retinal Photographs Using Anatomical Colocation.

Background: The aim in this study was to investigate the localization of diabetic retinopathy features at the posterior pole. Methods: This study extracted diabetic retinopathy feature locations from 757 macula-centered 45-degree fundus photographs in the publicly available DDR dataset. Arteriole and venule locations were also extracted from the RITE (n = 35) and IOSTAR (n = 29) datasets. Images were normalized to collocate optic disc and macula positions, and feature positions were collated to generate a frequency distribution matrix. Sørensen-Dice coefficients were calculated to compare the location of different features. Results: Arterioles occurred in two main, distinct arcuate patterns. Venules showed a more diffuse distribution. Microaneurysms were diffusely located around the posterior pole. Hemorrhages and exudates occurred more frequently at the temporal aspect of the macula. Cotton wool spots occurred in a region approximating the radial peripapillary capillaries. Intraretinal microvascular abnormalities and neovascularization were seen throughout the posterior pole, with neovascularization at the disc (n = 65) being more common than neovascularization elsewhere (n = 46). Venous beading occurred primarily between the first and third bifurcations of the venules. Diabetic retinopathy overall was more frequent in the temporal aspect of the macula. The location of cotton wool spots and exudates showed moderate similarity (0.52) when all data were considered, reducing to low similarity (0.18) when areas of low frequency were removed. Conclusions: Diabetic retinopathy occurs throughout the posterior pole but is more frequent in the temporal aspect of the macula. Understanding the location of diabetic retinopathy features may help inform visual search strategies for diabetic retinopathy screening.

A guide to optometrists for appraising and using artificial intelligence in clinical practice.

Artificial intelligence systems are becoming increasingly available as diagnostic aids for optometric practice. These perform well but are often 'black-box' systems offering little or no insight into how a decision was reached. While there is potential for artificial intelligence to improve patient outcomes, clinicians without training in computer science may find it difficult to ascertain whether these technologies are suitable for their practice, or how they should be used. This review provides an overview of how artificial intelligence systems work in optometry, their strengths, weaknesses, and regulatory considerations. A checklist is provided for appraising a system, covering regulatory approvals, ascertaining what the system can and cannot do, how it can be used in practice, whether it is suitable for the clinical population, and whether the outputs can be explained. Artificial intelligence has the potential to improve accuracy and efficiency in many areas of optometry if used correctly, and should be embraced by clinicians as an assistive tool.

Medial frontal negativities predict performance improvements during motor sequence but not motor adaptation learning.

Alterations in our environment require us to learn or alter motor skills to remain efficient. Also, damage or injury may require the relearning of motor skills. Two types have been identified: movement adaptation and motor sequence learning. Doyonet al. (2003, Distinct contribution of the cortico-striatal and cortico-cerebellar systems to motor skill learning. Neuropsychologia, 41(3), 252-262) proposed a model to explain the neural mechanisms related to adaptation (cortico-cerebellar) and motor sequence learning (cortico-striatum) tasks. We hypothesized that medial frontal negativities (MFNs), event-related electrocortical responses including the error-related negativity (ERN) and correct-response-related negativity (CRN), would be trait biomarkers for skill in motor sequence learning due to their relationship with striatal neural generators in a network involving the anterior cingulate and possibly the supplementary motor area. We examined 36 participants' improvement in a motor adaptation and a motor sequence learning task and measured MFNs elicited in a separate Spatial Stroop (conflict) task. We found both ERN and CRN strongly predicted performance improvement in the sequential motor task but not in the adaptation task, supporting this aspect of the Doyon model. Interestingly, the CRN accounted for additional unique variance over the variance shared with the ERN suggesting an expansion of the model.

Performance monitoring during sleep inertia after a 1-h daytime nap.

Performance monitoring is an essential function involved in the correction of errors. Deterioration of this function may result in serious accidents. This function is reflected in two event-related potential (ERP) components that occur after erroneous responses, specifically the error-related negativity/error negativity (ERN/Ne) and error positivity (Pe). The ERN/Ne is thought to be associated with error detection, while the Pe is thought to reflect motivational significance or recognition of errors. Using these ERP components, some studies have shown that sleepiness resulting from extended wakefulness may cause a decline in error-monitoring function. However, the effects of sleep inertia have not yet been explored. In this study, we examined the effects of sleep inertia immediately after a 1-h daytime nap on error-monitoring function as expressed through the ERN/Ne and Pe. Nine healthy young adults participated in two different experimental conditions (nap and rest). Participants performed the arrow-orientation task before and immediately after a 1-h nap or rest period. Immediately after the nap, participants reported an increased effort to perform the task and tended to estimate their performance as better, despite no objective difference in actual performance between the two conditions. ERN/Ne amplitude showed no difference between the conditions; however, the amplitude of the Pe was reduced following the nap. These results suggest that individuals can detect their own error responses, but the motivational significance ascribed to these errors might be diminished during the sleep inertia experienced after a 1-h nap. This decline might lead to overestimation of their performance.

Long-Distance Runners and Sprinters Show Different Performance Monitoring - An Event-Related Potential Study.

Previous findings have reported that track and field athletes may monitor and utilize internal information, including anxiety level, suggesting that the ability to inwardly monitor one's own functioning and utilize anxiety are required to achieve superior performance. Performance monitoring has been investigated using two event-related potential components; the error (-related) negativity (Ne/ERN) and error positivity (Pe). It is unknown whether performance monitoring differs among various types of athletes. It has also been reported that Ne/ERN amplitude is increased in individuals who are more anxious and the prevalence and effect of anxiety also differs among various types of athletes. In this study, we recorded both Ne/ERN and Pe from long-distance runners (n = 24) and sprinters (n = 24) while they were performing a spatial Stroop task under motivation and no motivation conditions. We also collected scores on the Sport Competitive Anxiety Test (SCAT). Mean error rate on incongruent trials was lower in the motivation condition than in the no motivation condition. There was neither group effect, nor condition effect found in Ne/ERN amplitude. However, for the long-distance runners, Pe amplitude was larger in the motivation condition than in the no motivation condition. We also investigated the relationships between Ne/ERNs and individual differences in performance anxiety using the SCAT. A multiple linear regression analysis in the motivation condition revealed an interaction between type of runner and SCAT scores, indicating that long-distance runners with higher SCAT scores showed larger Ne/ERN amplitudes whereas the sprinters with high SCAT scores tended to exhibit smaller Ne/ERN amplitudes. Our findings provide further evidence that performance monitoring differs across various types of athletes.

Brain activities associated with learning of the Monty Hall Dilemma task.

The Monty Hall Dilemma (MHD) poses a counterintuitive probabilistic problem to the players of this game. In the MHD task, a participant chooses one of three options where only one contains a reward. After one of the unchosen options (always no reward) is disclosed, the participant is asked to make a final decision: either change to the remaining option or stick with their first choice. Although the probability of winning if they change is higher (2/3) compared to sticking with their first choice (1/3), most people stick with their original selection and often lose. In accordance with previous research, repetitive exposure to the MHD task increases the change behavior without any obvious understanding of the mathematical reasons why changing increases their chance of being rewarded. We recorded the stimulus-preceding negativity (SPN), an ERP that might reflect the informative value of the feedback. In the second half of the task, feedback was predicted to be less informative because learning had taken place. Indeed, the SPN amplitude became smaller over the frontal region. Also, the SPN amplitude was larger for change than for stick trials. These results suggest that learning in the MHD might be manifest in affective-motivational anticipation as indicated by the SPN.

Stimulus-preceding negativity represents a conservative response tendency.

Humans tend to be conservative and typically will retain their initial decision even if an option to change is provided. We investigated whether the stimulus-preceding negativity (SPN), an event-related potential associated with the affective-motivational anticipation of feedback in gambling tasks, represents the strong response tendency to retain an initial decision. We compared SPNs in three different card-gambling tasks wherein the participants were given the opportunity to change their initial decision after they chose one of three cards. In two of these tasks, the winning probability was equiprobable (1/3 and 1/2, respectively) whether or not the participants changed their initial decision. However, in the Monty Hall dilemma task, changing the initial decision stochastically doubled the probability of winning (2/3) compared with retaining (1/3). In this counterintuitive probabilistic dilemma task, after the participant chose an option among three cards, a nonreward (losing) option is revealed. Then, the participants are offered a chance to change their mind and asked to make their final decision: to retain their initial choice or change to the alternate option. In all tasks, maintenance of previous behaviors was observed, although the rate of retaining earlier choices tended to be lower in the Monty Hall dilemma task than in the other two tasks. The SPNs were larger on retain trials than on change trials irrespective of task. These results suggest that underlying brain activities associated with the strong tendency to retain the initial decision can be observed by the SPN and thus it reflects expectancy of outcomes in terms of self-chosen behaviors.

The functional significance of the skilled performance positivity: An update.

The skilled performance positivity (SPP) emerges approximately 450 ms after button presses in a skilled performance task (SPT) where the participant is required to initiate a visual sweep with a left-hand button press and then stop it with a right-hand button press within a predetermined time frame (ranging from 40 to 60 ms). The SPP has been thought to represent appraisal of performance results independent of the reafferent activity, and reported to reduce in amplitude following inaccurate timing performance. We hypothesized that reduced SPP on incorrect trials merely indicates superimposition of the feedback-related negativity (FRN) that is elicited by negative outcomes, because the right-hand button press not only stops the visual sweep but also presents visual feedback. Further, we assumed that the SPP essentially represents a P300 elicited by the visual feedback. To address these questions, we compared the SPT condition and a delayed-feedback (DFB) condition where feedback was presented approximately 1 s after the left-hand button press. We observed the SPP only in the SPT condition, and found feedback-elicited P300s in the DFB condition. Both of these positivities shared a similar scalp distribution. We also replicated the reduced SPP on incorrect trials that shared a similar topography with the FRN elicited by the negative feedback. According to these findings, it is reasonable to conclude that the SPP represents the feedback-elicited P300, and after incorrect performance an FRN is superimposed on it.

Factors related to the occurrence of isolated sleep paralysis elicited during a multi-phasic sleep-wake schedule.

STUDY OBJECTIVES: To further investigate mechanisms of isolated sleep paralysis (ISP) in normal individuals, we experimentally elicited ISPs by facilitating sleep onset REM periods (SOREMP), a prerequisite of ISPs, and examined behavioral and psychological measurements relating to ISP appearances. DESIGN: The multi-phasic sleep/wake schedule (MPS) began at approximately midnight and ended when net sleep reached 7.5 hours. Participants were awakened after every 5 min of REM sleep to obtain a maximum number of SOREMPs. Upon each awakening, mentation reports and subjective measurements were collected. Performance tests were then assigned. SETTING: Sleep lab, Tokyo Metropolitan Institute for Neurosciences, Japan. PARTICIPANTS: Thirteen healthy Japanese students (10 males) with high self-reported frequencies of ISPs but no other narcolepsy-related symptoms. MEASUREMENTS AND RESULTS: From 184 sleep interruptions, 8 ISP episodes were obtained. In within participant comparisons between episodes with and without ISPs, the vigilance task (VT) reaction times were elevated before SOREMPs with ISPs. In between analyses (ISP vs non-ISP), the ISP group showed poorer performance, more complaints of physical, mental, and neurotic symptoms, increased subjective fatigue and increased stage 1 throughout the entire schedule. VT hit rates remained constant in the non-ISP group, but dropped in the later part of schedule in the ISP group. Subjective sleepiness dropped over time in the non-ISP group while it slightly increased in the ISP group. CONCLUSIONS: ISP is likely to appear as a phenotype of REM dissociation during SOREMP when participants with low tolerance for disrupted sleep-wake rhythms are placed in this type of schedule.

Elicitation of sleep-onset REM periods in normal individuals using the sleep interruption technique (SIT).

Use of the sleep interruption technique (SIT) to elicit sleep onset REM periods (SOREMPs) in normal individuals is introduced along with its theoretical bases, empirical findings, and potential applications. Capitalizing upon the circadian and ultradian nature of REM sleep, the SIT has been developed to examine various psychophysiological characteristics related to REM sleep. The SIT allows us to: (1) obtain SOREMPs at the discretion of the researcher; (2) avoid the contaminating effects of preceding non-REM (NREM)-REM stage ordering on subsequent target sleep episodes; and (3) obtain many REM episodes in a short time by repeating the sleep interruptions. The SIT has been applied in several studies, such as examination of physiological precursors to REM periods, correlates of dream mechanisms, and induction of sleep paralysis in normal individuals. Guidelines for eliciting SOREMP using the SIT, including the parameters to be manipulated, are provided, e.g. NREM duration before sleep interruption, time of night of awakenings, duration of sleep interruption and tasks employed. Directions for further research such as determining optimal type of task to promote SOREMP occurrences, generalization of SOREMP as usual REM periods, and forms of SOREMP occurrences under different conditions in normal individuals and clinical patients are discussed. Finally, possible future uses of the SIT, including combining this technique with new technologies, are also suggested.

EEG activities during elicited sleep onset REM and NREM periods reflect different mechanisms of dream generation. Electroencephalograms. Rapid eye movement.

OBJECTIVE: To be the first to compare EEG power spectra during sleep onset REM periods (SOREMP) and sleep onset NREM periods (NREMP) in normal individuals and relate this to dream appearance processes underlying these different types of sleep periods. METHODS: Eight healthy undergraduates spent 7 consecutive nights in the sleep lab including 4 nights for SOREMP elicitation using the Sleep Interruption Technique. This enabled us to control preceding sleep processes between SOREMP and NREMP. EEG power spectra when participants did and did not report 'dreams' were compared between both types of sleep. Sleep stages, subjective measurements including dream property scores, sleepiness, mood, and tiredness after awakenings were also examined to determine their consistency with EEG findings. RESULTS: Increased alpha EEG activities (11.72-13.67 Hz) observed mainly in the central area were related to the absence of SOREMP dreams and appearance of NREMP dreams. Analyses of sleep stages combining two studies (16 participants) also supported the Fast Fourier Transform findings, showing that when dreams were reported there were decreased amounts of stage 2 and increased stage REM in SOREMP and increased stage W in NREMP. SOREMP dreams were more bizarre than NREMP dreams. Participants felt more tired after SOREMP with dreams than without dreams, while the opposite was observed after NREMP episodes. CONCLUSIONS: EEG power spectra patterns reflected different physiological mechanisms underlying generation of SOREMP and NREMP dreams. The same relationships were also reflected by sleep stage analyses as well as subjective measurements including dream properties and tiredness obtained after awakenings. This study not only supports the hypothesized relationships between REM mechanisms and REM dreams as well as arousal processes and NREM dreams, it also provides a new perspective to dream research due to its unique techniques to awaken participants and collect REM dreams during experimentally induced SOREMP.

Eliminating the P300 rebound in short oddball paradigms.

In short oddball paradigms, the P3 (or P300) amplitude often shows a curvilinear "rebound" pattern, such that an initial drop during the first few trials is followed by an increase in later trials. While the initial attenuation has been attributed to habituation, no explanation has been offered for the later increase. Our hypothesis was that this curvilinear pattern is due to anticipation of the end of each fixed-length block. In study 1, a series of 16 short, fixed-length auditory oddball tests (with six targets each) replicated the rebound effect. In study 2, a further set of 16 variable-length blocks (7-10 targets) eliminated the rebound, and the P300 amplitude decreased linearly as expected. Results are interpreted in light of various constructs related to the P3: habituation, attentional salience, and updating in working memory.

Foreshadowing of performance accuracy by event-related potentials: evidence from a minimal-conflict task.

BACKGROUND: Recent studies employing stimulus-response compatibility tasks suggest that an increase in the amplitude of the positive deflection of the response-locked event-related potential (ERP) foreshadows errors on forthcoming trials. However, no studies have tested the generalizability of error-foreshadowing positivity to tasks without stimulus-response interference. METHODOLOGY/PRINCIPAL FINDINGS: The present study adopted an alternating-response task, in which the participants responded to the pointing direction of an arrowhead (up or down). Although the arrowhead direction alternated for the majority of trials (95%), occasionally this pattern was broken by a repeated stimulus, termed a lure trial. We compared the matched-reaction-time correct-preceding ERP with the error-preceding ERP on lure-preceding trials. There was no evidence that errors are foreshadowed by the increase of a positive electroencephalogram (EEG) deflection. To the contrary, analyses of ERPs time-locked to electromyogram (EMG) onset on the five consecutive lure-preceding trials showed larger positive deflections on correct-preceding than error-preceding trials. The post-response negativity did not differ between correct-preceding and error-preceding trials. CONCLUSIONS/SIGNIFICANCE: These results suggest that in minimal conflict tasks a decreased positivity may foreshadow incorrect performance several trials prior to the error, possibly reflecting the waning of task-related efforts. Therefore, error-foreshadowing brain signals may be task-specific.

The error-related negativity associated with different strength of stimulus-response interference.

OBJECTIVE: The present study was aimed at clarifying the effect of stimulus-response compatibility (SRC) interference on the ERN. METHODS: We compared ERNs in two tasks differing in the level of interference, an arrow (AR) task classified as a Simon task and a more complex arrow-orientation (AO) task classified as a spatial-Stroop task. We also compared ERNs between partial errors (with initial incorrect movement corrected by a proper full response) and overt (uncorrected) errors. RESULTS: Behavioral response time and error rate indicated that both interference and ERN amplitude were larger for the AO task than for the AR task. There was no significant difference in the ERN amplitude between the partial and overt errors. CONCLUSIONS: The ERN becomes larger as a function of the SRC interference. SIGNIFICANCE: Our study presented evidence that the ERN may represent response-monitoring associated with the SRC interference.

The effects of a nighttime nap on the error-monitoring functions during extended wakefulness.

STUDY OBJECTIVES: To examine the effects of a 1-hr nighttime nap, and the associated sleep inertia, on the error-monitoring functions during extended wakefulness using the 2 event-related potential components thought to reflect error detection and emotional or motivational evaluation of the error, i.e., the error-related negativity/error-negativity (ERN/Ne) and error-positivity (Pe), respectively. DESIGN: Participants awakened at 07:00 the morning of the experimental day, and performed a stimulus-response compatibility (arrow-orientation) task at 21:00, 02:00, and 03:00. SETTING: A cognitive task with EEG data recording was performed in a laboratory setting. PARTICIPANTS: Twenty young adults (mean age 21.3 ± 1.0 yr, 14 males) participated. INTERVENTIONS: Half of the participants took a 1-hr nap, and the others had a 1-hr awake-rest period from 01:00-02:00. MEASUREMENTS AND RESULTS: Behavioral performance and amplitude of the Pe declined after midnight (i.e., 02:00 and 03:00) compared with the 21:00 task period in both groups. During the task period starting at 03:00, the participants in the awake-rest condition reported less alertness and showed fewer correct responses than those who napped. However, there were no effects of a nap on the amplitude of the ERN/Ne or Pe. CONCLUSIONS: Our results suggest that a 1-hr nap can alleviate the decline in subjective alertness and response accuracy during nighttime; however, error-monitoring functions, especially emotional or motivational evaluation of the error, might remain impaired by extended wakefulness even after the nap. This phenomenon could imply that night-shift workers experiencing extended wakefulness should not overestimate the positive effects of a nighttime 1-hr nap during extended wakefulness.

Retest reliability of medial frontal negativities during performance monitoring.

The error-related negativity (ERN) and feedback-related negativity (FRN) have been used as electrophysiological indices of performance monitoring produced in response to internally generated (errors) and externally generated (feedback) activations of the anterior cingulate cortex (ACC). No studies to date have systematically examined the measurement reliability of these components. In this article, we present the retest reliability of the ERN and FRN during response tasks designed to elicit errors or feedback responses on two occasions. Data from four experiments are presented in which participants performed tasks over various periods of time. Results indicate good retest reliability of the ERN and FRN amplitudes and source generation of these components. The present article provides important validation of the ERN and FRN as stable and trait-like electrophysiological reflections of performance monitoring and ACC functional integrity.

The effect of sleepiness on performance monitoring: I know what I am doing, but do I care?

The behavioral, cognitive, and psychophysiological effects of extended wakefulness are well known. As time awake increases, errors become more common and are often attributed to lapses in attention. Such lapses can be reflected in the error-related negativity (Ne/ERN), a negative electroencephalogram deflection occurring after errors and is thought to be related to error detection or response conflict. Following the Ne/ERN, a positive deflection (error positivity, Pe) is also observed and is thought to reflect further evaluation of the error. To elicit Ne/ERNs, the Eriksen Flanker Task was administered to 17 women (aged 19-45 years) at two levels of alertness (4 and 20 h awake). After extended wakefulness, participants reported being subjectively sleepier and performing worse, but showed no significant difference in subjective effort. Across alertness conditions, they reported a similar number of subjective errors which closely matched an objective analysis of the errors. The Ne/ERN was not significantly reduced by sleepiness in contrast to the Pe which was reduced. Behavioral slowing after errors was larger in the alert than in the sleepy condition. These results show that after 20 h of wakefulness, individuals are reacting to their errors. However, further evaluation of the error, and remediation of these errors may be impaired despite continued effort.