Eye Movement Behavior Research Articles

Shedding Light on Nocturnal Movements in Parkinson's Disease: Evidence from Wearable Technologies.

In Parkinson’s disease (PD), abnormal movements consisting of hypokinetic and hyperkinetic manifestations commonly lead to nocturnal distress and sleep impairment, which significantly impact quality of life. In PD patients, these nocturnal disturbances can reflect disease-related complications (e.g., nocturnal akinesia), primary sleep disorders (e.g., rapid eye movement behaviour disorder), or both, thus requiring different therapeutic approaches. Wearable technologies based on actigraphy and innovative sensors have been proposed as feasible solutions to identify and monitor the various types of abnormal nocturnal movements in PD. This narrative review addresses the topic of abnormal nocturnal movements in PD and discusses how wearable technologies could help identify and assess these disturbances. We first examine the pathophysiology of abnormal nocturnal movements and the main clinical and instrumental tools for the evaluation of these disturbances in PD. We then report and discuss findings from previous studies assessing nocturnal movements in PD using actigraphy and innovative wearable sensors. Finally, we discuss clinical and technical prospects supporting the use of wearable technologies for the evaluation of nocturnal movements.

Distinguishing Intermediate and Novice Surgeons by Eye Movements.

Surgical skill-level assessment is key to collecting the required feedback and adapting the educational programs accordingly. Currently, these assessments for the minimal invasive surgery programs are primarily based on subjective methods, and there is no consensus on skill level classifications. One of the most detailed of these classifications categorize skill levels as beginner, novice, intermediate, sub-expert, and expert. To properly integrate skill assessment into minimal invasive surgical education programs and provide skill-based training alternatives, it is necessary to classify the skill levels in as detailed a way as possible and identify the differences between all skill levels in an objective manner. Yet, despite the existence of very encouraging results in the literature, most of the studies have been conducted to better understand the differences between novice and expert surgical skill levels leaving out the other crucial skill levels between them. Additionally, there are very limited studies by considering the eye-movement behaviors of surgical residents. To this end, the present study attempted to distinguish novice- and intermediate-level surgical residents based on their eye movements. The eye-movement data was recorded from 23 volunteer surgical residents while they were performing four computer-based simulated surgical tasks under different hand conditions. The data was analyzed using logistic regression to estimate the skill levels of both groups. The best results of the estimation revealing a 91.3% recognition rate of predicting novice and intermediate surgical residents on one scenario were selected from four under the dominant hand condition. These results show that the eye-movements can be potentially used to identify surgeons with intermediate and novice skills. However, the results also indicate that the order in which the scenarios are provided, and the design of the scenario, the tasks, and their appropriateness with the skill levels of the participants are all critical factors to be considered in improving the estimation ratio, and hence require thorough assessment for future research.

Therapeutic Effect of Levodopa/Carbidopa/Entacapone on Sleep Disturbance in Patients with Parkinson's Disease.

Objective To investigate the efficacy of levodopa/carbidopa/entacapone (LCE) at bedtime for treating sleep disturbance in patients with Parkinson’s disease (PD) with motor fluctuations.Methods Participants included 128 PD patients with motor fluctuations. All patients were assessed for motor, nonmotor, and sleep-specific symptoms using the United Parkinson’s Disease Rating Scale (UPDRS), the Korean version of the Nonmotor Symptom Scale, the Parkinson’s Disease Sleep Scale (PDSS), the Epworth Sleepiness Scale, and the Rapid Eye Movement Sleep Behavior Disorder Screening Questionnaire (RBDSQ). We compared the baseline characteristics of patients with sleep disturbance (PDSS score < 120) and those without sleep disturbance (PDSS score ≥ 120). Thirty-nine patients with sleep disturbance who agreed to take LCE at bedtime completed 3-month follow-ups. We analyzed changes in the scores of motor, nonmotor, and sleep symptom scales over the 3 months.Results PD patients with sleep disturbance were at more advanced disease stages and had more severe motor, nonmotor, and sleep symptoms than those without sleep disturbance. Patients who took LCE at night showed improvements in motor (UPDRS part III, p = 0.007) and sleep symptoms (total PDSS, p < 0.001). Sleep features that benefitted from LCE included not only nocturnal motor components but also insomnia (PDSS items 2 and 3, p = 0.005 and p < 0.001) and rapid eye movement behavior disorder (PDSS item 6, p = 0.002; and RBDSQ, p < 0.001).Conclusion The use of LCE at bedtime may be a useful treatment for sleep disturbance in advanced PD patients with motor fluctuations.

Human scanpath estimation based on semantic segmentation guided by common eye fixation behaviors

To explore the dynamic process of complex human eye movement behavior, we proposed a new model to simulate human scanpath when subjects observed natural images freely. Previous methods almost focused on finding effective and advanced technology, such as machine learning or deep learning, for estimating human scanpath. In contrast, our proposed method devoted to find a new way that could use the intrinsic property of eye-tracking data between different races to guide the design of a deep network. Inspired by that, the model of human scanpath estimation was established, which based on a semantic segmentation module guided by common eye fixation behaviors between people with different cultures. The semantic segmentation module could deal with locating fixations positions and the fixations ranking problem in parallel and generate human scanpath combined with the output of common attention portions (CAP) generator. The common attention portions (CAP) generator was designed to optimize the performance of semantic segmentation module and extract the common eye fixation behaviors between people with different cultures. We evaluated the performance of our model on three public eye-tracking datasets by comparing the result generated from our model with the ground truth of scanpath produced by a new method in this work. The proposed model also achieved the encouraging performance compared with some classic and fashionable models.

Eye-movements during number comparison: Associations to sex and sex hormones

Multi-digit numbers are of a hierarchical nature with whole number magnitudes depending on digit magnitudes. Processing of multi-digit numbers can occur in a holistic or decomposed fashion. The unit-decade compatibility effect during number comparison is often used as a measure of decomposed processing. It refers to the fact that performance is reduced when the larger number contains the smaller unit digit (e.g. 73 vs. 26). It has been demonstrated that women show a larger compatibility effect than men, which is in accordance with their general tendency towards focusing on stimulus details during processing of visual hierarchical stimuli (local processing style). Such a local processing style has been related to higher progesterone and lower testosterone levels. One method to study individual processing styles is eye-tracking. The aim of the present study was to examine whether sex and sex hormones (estradiol, progesterone, testosterone) relate to eye movement behavior in the number comparison task. Unlike previous studies we found no evidence for sex differences in the behavioral compatibility effect. Nevertheless, women look more often and longer at individual digits and show a stronger compatibility effect in fixation durations compared to men, while men show more saccades between numbers than women. Estradiol and progesterone were related to fewer fixations and shorter fixation durations and more saccades between numbers in men, but not in women. Furthermore, the compatibility effect in the number of fixations and fixation durations was negatively related to testosterone in women. In summary, this is the first study to demonstrate sex differences and sex hormone influences on eye gaze behavior during number comparison.

The impact of uninformative parafoveal masks on L1 and late L2 speakers.

Much reading research has found that informative parafoveal masks lead to a reading benefit for native speakers (see 1). However, little reading research has tested the impact of uninformative parafoveal masks during reading. Additionally, parafoveal processing research is primarily restricted to native speakers. In the current study we manipulated the type of uninformative preview using a gaze contingent boundary paradigm with a group of L1 English speakers and a group of late L2 English speakers (L1 German). We were interested in how different types of uninformative masks impact on parafoveal processing, whether L1 and L2 speakers are similarly impacted, and whether they are sensitive to parafoveally viewed language-specific sub-lexical orthographic information. We manipulated six types of uninformative masks to test these objectives: an Identical, English pseudo-word, German pseudo-word, illegal string of letters, series of X’s, and a blank mask. We found that X masks affect reading the most with slight graded differences across the other masks, L1 and L2 speakers are impacted similarly, and neither group is sensitive to sub-lexical orthographic information. Overall these data show that not all previews are equal, and research should be aware of the way uninformative masks affect reading behavior. Additionally, we hope that future research starts to approach models of eye-movement behavior during reading from not only a monolingual but also from a multilingual perspective.

Changes in eye movement parameters in the presence of an artificial central scotoma.

Central vision loss, such as in the case of age-related macular degeneration (AMD), has a a major negative impact on patients' quality of life. However, some patients have shown spontaneous adaptive strategies development, mostly relying on their peripheral vision. This study assesses eye movement and eccentric visual function adaptive behaviors of a healthy population in the presence of simulated central vision loss. We wished to determine how central vision loss affects eye movements, specifically the foveal-target alignment. Fifteen healthy participants (7 females, M = 21.69, SD = 2.13) discriminated the orientation of a Gabor relative to the vertical located at 12 deg of eccentricity to the right of fixation, in the presence of a gaze-contingent artificial central scotoma either visible or invisible. The artificial central scotoma was 4° diameter in order to simulate an earlier stage of degenerative disease while still impairing foveal vision. The target's orientation varied between 10° counter-clockwise and 10° clockwise. Each participant performed four blocks of 75 trials each per day over 10 days, the first day being a baseline without scotoma. We found changes in the endpoints of the 1st saccade over the practice days. The most common pattern was a gradual upward shift. We also observed a significant increase in discrimination performance over the 9 days of practice. We did not find any difference linked to the scotoma types. These findings suggest that the presence of an artificial central scotoma combined with a challenging discrimination task induces both changes in saccade planning mechanisms, resulting in a new eccentric-target alignment, and improvements in eccentric visual functions. This demonstrates the potential of this research paradigm to understand and potentially improve visual function in patients with central vision loss.

The information gathering framework - a cognitive model of regressive eye movements during reading

In this article we present a new eye movement control framework that describes the interaction between fixation durations and regressive saccades during reading: The Information Gathering Framework (IGF).Based on the FC model proposed by Bicknell and Levy [15], the basic idea of the IGF is that a confidence level for each word is computed while being monitored by three independent thresholds. These thresholds shape eye movement behavior by increasing fixation duration, triggering a regression, or guiding regression target selection. In this way, the IGF does not only account for regressive eye movements but also provides a framework able to model eye movement control during reading across different scenarios. Importantly, within the IGF it is assumed that two different types of regressive eye movements exist which differ with regard to their releases (integrations difficulties vs. missing evidence) but also with regard to their time course.We tested the predictions of the IGF by re-analyzing an experiment of Weiss et al. [57] and found, inter alia, clear evidence for shorter fixation durations before regressive saccades relative to progressive saccades, with the exception of the last region. This clearly supports the assumptions of the IGF. In addition, we found evidence that there exists a window of about 15–20 characters to the left of the current fixation that plays an important role in target selection, probably indicating the perceptual span during a regressive saccade.

소프트볼 타자의 타격 수행 시 숙련성에 따른 시각탐색 전략 및 선구안 능력 차이

Purpose: The purpose of this study is to classify female softball players into two groups (high batting average and low batting average) and to identify characteristics of gaze behavior patterns and predict the pitch of the ball.<BR> Method: For the study, a total of 16 softball players (8 high, 8 low average) participated in the experiment. The experiment challenged the actual pitcher throwing the ball at a distance of 11.44m, with 15 hits per player. After hitting each ball, the task was to verbally express what pitcher threw. Players’ eye movement behavior patterns were measured using Tobii’s wireless eye movement tracking equipment.<BR> Results: In order to examine the difference in the actual blow performance of the athletes, the analysis was conducted by dividing into preparation action-stretch action (1 section), power position-release (2 sections), and pitching-batter swing (3 sections). In the two groups, the number of fixations was statistically different in all three sections, and the gaze fixation duration was found in the first and second sections. In the task of identifying the pitch of the ball, there was a difference between high and low batting averages groups.<BR> Conclusion: According to the skill of softball players, the results will be meaningful in providing basic information on how gaze behavior patterns appear and how visual information is used.

To look or not to look: Subliminal abruptonset cues influence constrained free-choice saccades.

Subliminal cues have been shown to capture attention and modulate manual response behaviour but their impact on eye movement behaviour is not well-studied. In two experiments, we examined if subliminal cues influence constrained free-choice saccades and if this influence is under strategic control as a function of task-relevancy of the cues. On each trial, a display containing four filled circles at the centre of each quadrant was shown. A central coloured circle indicated the relevant visual field on each trial (Up or Down in Experiment 1; Left or Right in Experiment 2). Next, abrupt-onset cues were presented for 16 ms at one of the four locations. Participants were then asked to freely choose and make a saccade to one of the two target circles in the relevant visual field. The analysis of the frequency of saccades, saccade endpoint deviation and saccade latency revealed a significant influence of the relevant subliminal cues on saccadic decisions. Latency data showed reduced capture by spatiallyirrelevant cues under some conditions. These results indicate that spatial attentional control settings as defined in our study could modulate the influence of subliminal abrupt-onset cues on eye movement behaviour. We situate the findings of this study in the attention-capture debate and discuss the implications for the subliminal cueing literature.

Rapid Eye Movement Sleep Behavior Disorder (RBD)

Normal skeletal muscle atonia's intermittent absence, which results in acting out patient's dreams, is the characteristic of the Rapid eye movement Behavior Disorder or RBD. The occurrence of RBD is in the last third part of the night. In this part, the REM sleep is much more common. The dreams during RBD would be vivid and patient's violent and aggressive behavior and movements can be dangerous for the patient and his/her bed partner. RBD is most common in older men. Its etiology is not clear but RBD is associated with some neurodegenerative diseases like multiple system atrophy, parkinson's disease and lewy body dementia. This association specifically with parkinson's disease is high, since about 50 percent of the patients with RBD develop parkinson's disease during years. In the association between RBD and neurodegenerative diseases, RBD's occurrence would usually be preceded such neurodegenerative diseases by several years.

Evaluation of eye movements and visual performance in patients with cataract

Eye movement is an essential component of visual perception. Eye movement disorders have been observed in many eye disease, and are thought to affect various visual performance in daily life. However, eye movement behaviors of the elderly with cataract are poorly understood, and the impact of cataract surgery on eye movements has not been investigated. In this study, we observed the eye movement behaviors in thirty patients with bilateral age-related cataract while performing three performance-based tasks (visual search, face recognition and reading). Eye movements were automatically recorded by an eye tracker during task performance. We found an overall improved visual performance postoperatively, presented as elevated percentage of correctly identified objects and faces, reduced search time and increased reading speed. Eye movement parameters were found significantly altered after cataract surgery. Fixation count, total fixation duration and total visit duration were markedly increased in the visual search task and face recognition task. The proportion of regressive saccades was obviously decreased in the reading task. These eye movement parameters were found to be correlated with the measures of visual performance. Our findings suggested a potential association between the eye movement disturbance and impaired visual performance, and provided a new insight on the potential usefulness of eye movement as an objective and valid tool to understand visual impairments caused by cataract, as well as evaluate practical outcomes of cataract surgery.

Metformin as a Potential Neuroprotective Agent in Prodromal Parkinson's Disease-Viewpoint.

To date, there are no clinically effective neuroprotective or disease-modifying treatments that can halt Parkinson's disease (PD) progression. The current clinical approach focuses on symptomatic management. This failure may relate to the complex neurobiology underpinning the development of PD and the absence of true translational animal models. In addition, clinical diagnosis of PD relies on presentation of motor symptoms which occur when the neuropathology is already established. These multiple factors could contribute to the unsuccessful development of neuroprotective treatments for PD. Prodromal symptoms develop years prior to formal diagnosis and may provide an excellent tool for early diagnosis and better trial design. Patients with idiopathic rapid eye movement behavior disorder (iRBD) have the highest risk of developing PD and could represent an excellent group to include in neuroprotective trials for PD. In addition, repurposing drugs with excellent safety profiles is an appealing strategy to accelerate drug discovery. The anti-diabetic drug metformin has been shown to target diverse cellular pathways implicated in PD progression. Multiple studies have, additionally, observed the benefits of metformin to counteract other age-related diseases. The purpose of this viewpoint is to discuss metformin's neuroprotective potential by outlining relevant mechanisms of action and the selection of iRBD patients for future clinical trials in PD.

PyTrack: An end-to-end analysis toolkit for eye tracking

Eye tracking is a widely used tool for behavioral research in the field of psychology. With technological advancement, we now have specialized eye-tracking devices that offer high sampling rates, up to 2000 Hz, and allow for measuring eye movements with high accuracy. They also offer high spatial resolution, which enables the recording of very small movements, like drifts and microsaccades. Features and parameters of interest that characterize eye movements need to be algorithmically extracted from raw data as most eye trackers identify only basic parameters, such as blinks, fixations, and saccades. Eye-tracking experiments may investigate eye movement behavior in different groups of participants and in varying stimuli conditions. Hence, the analysis stage of such experiments typically involves two phases, (i) extraction of parameters of interest and (ii) statistical analysis between different participants or stimuli conditions using these parameters. Furthermore, the datasets collected in these experiments are usually very large in size, owing to the high temporal resolution of the eye trackers, and hence would benefit from an automated analysis toolkit. In this work, we present PyTrack, an end-to-end open-source solution for the analysis and visualization of eye-tracking data. It can be used to extract parameters of interest, generate and visualize a variety of gaze plots from raw eye-tracking data, and conduct statistical analysis between stimuli conditions and subject groups.

1027 Differences in Polysomnography-Based Sleep Disorders Between HIV-Infected Persons and Matched Controls

Abstract Introduction Sleep disturbance is a prevalent problem among HIV-infected persons. The recognition of comorbid sleep disorders in patients with HIV is currently hampered by limited knowledge of sleep-related symptoms, sleep architecture, and types of sleep disorders. We aimed to compare the differences in sleep-related symptoms and polysomnography-based sleep disorders between HIV-infected persons and controls. Methods The study included 170 men with a Pittsburgh sleep quality index (PSQI) greater than 5, composed of 44 HIV-infected men and 126 male controls who were frequency-matched by sex, age (-/+ 3.0 years) and BMI (-/+ 3.0 kg/m2). For all participants an overnight sleep study using a Somte V1 monitor was conducted. Differences in sleep-related symptoms and sleep disorders between HIV-infected patients and controls were examined using t-tests or Chi-square tests. Results HIV-infected persons with sleep disturbances more often had psychological disturbances (72.7% vs. 40.5%, p&amp;lt;0.001) and suspected rapid eye movement (REM) behavior disorder (RBD) (25.0% vs. 4.8%, p&amp;lt;0.01) than that of controls. The sleep-disordered breathing (SDB) in HIV-infected persons was less common than that in controls (56.8% vs. 87.3%, p&amp;lt;0.001). The mean percentage of REM sleep among HIV-infected patients was higher than that among the controls (20.6% vs. 16.6%, p&amp;lt;0.001). Enuresis was more common in HIV-infected persons than controls (40.9% vs. 22.2%, p=0.02). Conclusion Psychological disturbances and SDB can be the possible explanations of sleep disturbances in HIV-infected persons, in which suspected RBD is notable. Further studies are warranted to examine underlying factors of suspected RBD among HIV-infected persons with sleep disturbances. Support This work was supported by the Ministry of Science and Technology, Executive Yuan of Taiwan [MOST 105-3011-E-006-002], and National Cheng Kung University Hospital [NCKUH-10702022]

0003 LGI1 and CASPR2 Autoimmunity: Sleep Symptoms, Polysomnography, and Quantitative REM Sleep without Atonia

Abstract Introduction Sleep disturbances, including rapid eye movement (REM) behavior disorder (RBD), are known manifestations of voltage-gated-potassium-channel-complex VGKC-IgG seropositivity (VGKC+). Discovery of leucine-rich, glioma inactivated protein 1 (LGI1) and contactin-associated protein 2 (CASPR2) have refined our understanding of VGKC+. VGKC+ without LGI1/CASPR2-IgG (“double-negative”) has lost its clinical significance. Previous detailed sleep analysis of these subtypes has been limited. Methods We performed a retrospective study to characterize clinical and polysomnographic features of LGI1/CASPR2 seropositive (LGI1+/CASPR2+) and VGKC double-negative patients, including quantitative REM sleep without atonia (RSWA). Quantified RSWA was compared to matched controls and normative RSWA percentiles. Results Eleven LGI1+/CASPR2+ (LGI1+, 9) and twelve VGKC double-negative patients were analyzed. Insomnia was seen in 55% of LGI1+/CASPR2+ and 8% of VGKC double-negative patients (p=0.05). The LGI1+/CASPR2+ group had reduced slow wave sleep compared to the VGKC double-negative group. Five LGI1+ patients had clinical dream enactment behavior (DEB). Eight LGI1+ patients met quantitative diagnostic levels of RSWA. Higher RSWA levels were seen in the LGI1+/CASPR2+ group. Ten LGI1+/CASPR2+ patients received immunotherapy; all ten neurologically benefited with sleep benefits in 6/10. Conclusion Sleep disorders such as insomnia and RBD are part of the LGI1/CASPR2 autoimmune phenotype. Objective sleep manifestations can be seen on polysomnogram in the form of reduced N3 and elevated RSWA as compared to controls. Quantitative RSWA analysis identified RBD in more LGI1+ patients than clinical report or qualitative RSWA. In this study, RBD was only seen with LGI1+, not CASPR2+. The intermediate RSWA levels of the VGKC double-negative patients may suggest a spectrum of abnormal motor activity in these related antibodies. Additional studies are needed to further explore the biomarker potential of quantitative RSWA in autoimmune neurological conditions. Support This project was supported by the National Center forResearch Resources, National Institutes of Health, through Grant Number 1 UL1 RR024150- 01.

Natural Reading in Parkinson's Disease With and Without Mild Cognitive Impairment.

Background: Patients with Parkinson’s disease (PD) show eye movement abnormalities and frequently complain about difficulties in reading. So far, it is unclear whether basal ganglia dysfunction or cognitive impairment has a greater impact on eye movements during reading.Objective: To analyze eye movement behavior during a natural reading task with respect to cognitive state and dopaminergic therapy in PD and healthy controls.Methods: Eye movements of 59 PD patients and 29 age- and education-matched healthy controls were recorded during mute, self-paced reading of a text. 25 cognitively normal PD patients performed the task additionally in off medication state. Clinical assessment included a comprehensive neuropsychological test battery and the motor section of MDS—Unified Parkinson’s Disease Rating Scale (MDS-UPDRS).Results: PD-mild cognitive impairment (MCI) was diagnosed in 21 patients. Reading speed was significantly reduced in PD-MCI compared to healthy controls and PD patients without MCI due to higher numbers of progressive saccades. Cognitively intact PD patients showed no significant alterations of reading speed or eye movement pattern during reading. The fixation duration tended to be prolonged in PD compared to healthy controls and decreased significantly after levodopa intake. Scores for executive functions, attention, and language correlated with reading speed in the PD group.Conclusion: The present study is the first to reveal (1) reduced reading speed with altered reading pattern in PD with MCI and (2) a relevant impact of levodopa on fixation duration during reading in PD. Further research is needed to determine whether therapeutic interventions, e.g., levodopa or neuropsychological training, improve the subjective reading experience for patients with PD.

Effects of Analogical Learning Approaches and Presentation Modalities on Ninth Graders’ Learning Outcome and Eye Movements: a Preliminary Study

This study analyzed the impact of different analogical learning approaches (analogies or metaphors) integrated with different presentation modalities (pictures or texts) on middle school students’ learning performance of electricity with supporting evidence from their eye movement behaviors. Eighty ninth-grade middle school students were randomly assigned into four groups to receive four different versions of an online electricity learning program, including pictorial analogies, textual analogies, pictorial metaphors, and textual metaphors. Data regarding students’ eye movement behaviors were collected simultaneously during their online learning. All the students took a pre-test, post-test, and retention test covering their comprehension of electricity concepts. Our results revealed that the analogy group provided more mapping and integration behaviors between the analog and target concepts about electricity, resulting in gaining better performance than the metaphor group. Additionally, students receiving pictorial modality generated more mapping and integration behaviors between the analog and target concepts, resulting in a better understanding of electricity concepts than students learning with textual modality. The associated implications for analogical learning approaches and presentation modalities concerning science learning and eye movement behaviors are also discussed in the paper.

Non-motor Clinical and Biomarker Predictors Enable High Cross-Validated Accuracy Detection of Early PD but Lesser Cross-Validated Accuracy Detection of Scans Without Evidence of Dopaminergic Deficit.

Background: Early stage (preclinical) detection of Parkinson's disease (PD) remains challenged yet is crucial to both differentiate it from other disorders and facilitate timely administration of neuroprotective treatment as it becomes available.Objective: In a cross-validation paradigm, this work focused on two binary predictive probability analyses: classification of early PD vs. controls and classification of early PD vs. SWEDD (scans without evidence of dopamine deficit). It was hypothesized that five distinct model types using combined non-motor and biomarker features would distinguish early PD from controls with > 80% cross-validated (CV) accuracy, but that the diverse nature of the SWEDD category would reduce early PD vs. SWEDD CV classification accuracy and alter model-based feature selection.Methods: Cross-sectional, baseline data was acquired from the Parkinson's Progressive Markers Initiative (PPMI). Logistic regression, general additive (GAM), decision tree, random forest and XGBoost models were fitted using non-motor clinical and biomarker features. Randomized train and test data partitions were created. Model classification CV performance was compared using the area under the curve (AUC), sensitivity, specificity and the Kappa statistic.Results: All five models achieved >0.80 AUC CV accuracy to distinguish early PD from controls. The GAM (CV AUC 0.928, sensitivity 0.898, specificity 0.897) and XGBoost (CV AUC 0.923, sensitivity 0.875, specificity 0.897) models were the top classifiers. Performance across all models was consistently lower in the early PD/SWEDD analyses, where the highest performing models were XGBoost (CV AUC 0.863, sensitivity 0.905, specificity 0.748) and random forest (CV AUC 0.822, sensitivity 0.809, specificity 0.721). XGBoost detection of non-PD SWEDD matched 1–2 years curated diagnoses in 81.25% (13/16) cases. In both early PD/control and early PD/SWEDD analyses, and across all models, hyposmia was the single most important feature to classification; rapid eye movement behavior disorder (questionnaire) was the next most commonly high ranked feature. Alpha-synuclein was a feature of import to early PD/control but not early PD/SWEDD classification and the Epworth Sleepiness scale was antithetically important to the latter but not former.Interpretation: Non-motor clinical and biomarker variables enable high CV discrimination of early PD vs. controls but are less effective discriminating early PD from SWEDD.

Eye Movements of Developing Chinese Readers: Effects of Word Frequency and Predictability

ABSTRACT The frequency and contextual predictability of words have a fundamental role in determining where and when the eyes move during reading in both alphabetic and non-alphabetic languages. However, surprising little is known about the how the influence of these variables develops, although this is important for understanding how children learn to read. Accordingly, to gain insight into their use during reading development, we examined the effects of orthogonally manipulating the frequency and contextual predictability of a specific target word in sentences on the eye movements of developing Chinese readers. The findings show that both factors influence eye movement behavior associated with the early processing of words during reading, but that effects of contextual predictability are mediated by the lexical frequency of words. We consider these effects in the context of visual and linguistic demands associated with reading Chinese and in relation to current models of eye movement control during reading.