Reflexive Saccades Research Articles

Comparing saccades in Visually Enhanced Vestibular-Ocular Reflex and video head impulse test in vestibular assessment

ObjectiveThis study aimed to develop and evaluate a novel software tool for robust analysis of the Visually Enhanced Vestibular-Ocular Reflex (VVOR) and video head impulse test (vHIT) saccades. MethodsA retrospective study was conducted on 94 patients with Meniere's Disease (MD), unilateral vestibular hypofunction (UVH), and vestibular migraine (VM). The MATLAB-based VVOR Analysis System and Saccades All in One software were utilized for data processing. New techniques, VVOR_diff and VVOR_cycle, were deployed for saccade parameter extraction. ResultsSaccade incidence rates, examined through vHIT, VVOR_diff, and VVOR_cycle, exhibited distinct patterns in MD, UVH, and VM patients. Frequent instances of multiple saccades within a single cycle were noted on the affected side in MD and UVH patients. Statistically significant differences in saccade gain and incidence rates between the affected and unaffected sides were evident in MD and UVH patients. Notably, high inter-method and intra-method correlations suggested consistency across different methods and potential interactions within one. ConclusionThe software proved effective in extracting saccades and reducing noise in VVOR data, thereby enhancing the evaluation of vestibular function and potentially improving diagnostic accuracy for vestibular disorders.

Differentiation of peripheral and non-peripheral etiologies in children with vertigo/dizziness: The video-head impulse test and suppression head impulse paradigm

ObjectivesTo identify the etiology of vertigo/dizziness and determine the effectiveness of the video-head impulse test (vHIT) and the suppression head impulse paradigm (SHIMP) tests in distinguishing between peripheral and non-peripheral etiologies in children who presented to the otolaryngology department with complaints of vertigo/dizziness. MethodsThe vHIT and SHIMP tests were applied to the children. The vestibulo-ocular reflex (VOR) gain and saccade parameters were compared. ResultsIn 27 children presenting with vertigo/dizziness, the most common etiological factor was inner ear malformation (IEM) (n = 6/27, 22.2%), followed by cochlear implant surgery (11.1%) and migraine (11.1%). Vestibular hypofunction was indicated by the vHIT results at a rate of 60% (9/15 children) and SHIMP results at 73.3% (11/15 children) among the children with a peripheral etiology, while these rates were 8.3% (1/12 children) and 25% (3/12 children), respectively, in the non-peripheral etiology group. SHIMP-VOR and vHIT-VOR gain values had a moderate positive correlation (p = 0.01, r = 0.349). While there were overt/covert saccades in the vHIT, anti-compensatory saccade (ACSs) were not observed in the SHIMP test (p = 0.041). The rates of abnormal vHIT-VOR gain (p = 0.001), over/covert saccades (p = 0.019), abnormal vHIT response (p = 0.014), ACSs (p = 0.001), and abnormal SHIMP response (p = 0.035) were significantly higher in the peripheral etiology group. ConclusionsIEM was the most common etiological cause, and the rate of vestibular hypofunction was higher in these children with peripheral vertigo. vHIT and SHIMP are effective and useful vestibular tests for distinguishing peripheral etiology from non-peripheral etiology in the pediatric population with vertigo/dizziness. These tests can be used together or alone, but the first choice should be the SHIMP test, considering its short application time (approximately 4–5 min) and simplicity.

Exploring Cognitive Dysfunction in Long COVID Patients: Eye Movement Abnormalities and Frontal-Subcortical Circuits Implications via Eye-Tracking and Machine Learning

BackgroundCognitive dysfunction is regarded as one of the most severe aftereffects following coronavirus disease 2019 (COVID-19). Eye movements, controlled by several brain areas, such as the dorsolateral prefrontal cortex and frontal-thalamic circuits, provide a potential metric for assessing cortical networks and cognitive status. We aimed to examine the utility of eye movement measurements in identifying cognitive impairments in long COVID patients. MethodsWe recruited 40 long COVID patients experiencing subjective cognitive complaints and 40 healthy controls and used a certified eye-tracking medical device to record saccades and antisaccades. Machine learning was applied to enhance the analysis of eye movement data. ResultsPatients did not differ from the healthy controls regarding age, sex, and years of education. However, the patients' Montreal Cognitive Assessment total score was significantly lower than healthy controls. Most eye movement parameters were significantly worse in patients. These included the latencies, gain (computed as the ratio between stimulus amplitude and gaze amplitude), velocities, and accuracy (evaluated by the presence of hypermetric or hypometria dysmetria) of both visually and memory-guided saccades; the number of correct memory saccades; the latencies and duration of reflexive saccades; and the number of errors in the antisaccade test. Machine learning permitted distinguishing between long COVID patients experiencing subjective cognitive complaints and healthy controls. ConclusionOur findings suggest impairments in frontal subcortical circuits among long COVID patients who report subjective cognitive complaints. Eye-tracking, combined with machine learning, offers a novel, efficient way to assess and monitor long COVID patients' cognitive dysfunctions, suggesting its utility in clinical settings for early detection and personalized treatment strategies. Further research is needed to determine the long-term implications of these findings and the reversibility of cognitive dysfunctions.

Suppression head impulse test in children-experiences in a tertiary paediatric vestibular centre.

The suppression head impulse paradigm (SHIMP) involves suppression of the vestibulo-ocular reflex (VOR) and anticompensatory saccades generated thereof. SHIMP is gaining importance to understand vestibular compensation with its different parameters (VOR gain/peak saccadic velocity PSV/latency of saccades). SHIMP studies are emerging in adults, but pediatric studies have hardly been performed. This study is a retrospective case note audit over a period of 2 months in a tertiary pediatric vestibular center in the United Kingdom to investigate whether SHIMP is safe/robust to be used in children conforming to existing standards/norms in normal children and whether it yields any meaningful inferences in pediatric vestibular hypofunction. This is the largest pediatric SHIMP study to date. A total of 44 referred children (6-18 years, female children>male children) with a range of complaints from dizziness, imbalance, motor incoordination, postural instability, and hearing loss were included, and their SHIMP parameters were measured. All children underwent comprehensive functional/objective audiovestibular assessments. Two groups were defined-Group A with normal vestibular function and Group B with abnormal vestibular function. The normal population showed an average SHIMP VOR gain of 0.98+/-0.08 and latency of overt saccades at 215.68+/-46.16 milliseconds agreeing with published evidence. The PSV of overt saccades was 315.39+/-56.30/s, and there was a gain asymmetry of 7.42+/-4.68 between the sides. Statistically significant differences with moderate/large effect sizes were observed between the groups in terms of VOR gain and PSV but not in saccade latencies. Covert saccades were rare in SHIMP, while overt saccades were observed in 100% of children. VOR gain difference between the head impulse paradigm (HIMP) and the SHIMP was significant as well. We observed statistically significant differences in side asymmetry of VOR gain between the groups. Furthermore, we identified a group of children with cerebellar lesions where overt saccades in SHIMP were rather low in number. Further research is recommended to investigate pediatric PSV, asymmetry, and inability to generate overt saccades that may suggest useful means to assess compensation and central function. We conclude that SHIMP yields valuable information and is a safe, easy to perform, and a reliable test that should be used in children to supplement HIMP.

Normalization of the Suppression Head Impulse Test (SHIMP) and its correlation with the Head Impulse Test (HIMP) in healthy adults.

In our study, it was aimed to compare vestibulo-ocular reflex (VOR) gain and saccade parameters in HIMP and SHIMP tests between gender, right and left ears, and age groups in healthy adults and to examine the correlation between the tests regarding these parameters. The study included a total of 100 healthy participants aged 18-65 and without complaints of hearing loss, dizziness, lightheadedness, and/or imbalance. Participants underwent HIMP and SHIMP tests, respectively. No significant difference was found in HIMP and SHIMP VOR gain values according to gender and age groups. SHIMP duration was significantly longer in women. VOR gain values were lower in the right ear. HIMP amplitude values were higher and SHIMP amplitude values were lower with increasing age. In older age groups, SHIMP peak velocity and duration values were significantly decreased, while HIMP duration value increased and latency value was longer. In the 1st saccade, a significant difference was obtained between HIMP and SHIMP tests for all saccade parameters. There was a statistically significant positive correlation between the VOR gain values of HIMP and SHIMP tests. The present study showed that VOR gain and saccade parameters obtained in different age groups will be important in determining clinical outcomes in vestibular pathologies.

Reflexive and voluntary saccadic eye movements as biomarker of Huntington's Disease.

Subtle abnormalities in the preclinical stage of Huntington's Disease (HD) can be detected using saccadic eye movement assessment reflecting disease progression. This study was aimed to evaluate abnormalities in saccade parameters in asymptomatic carriers and symptomatic HD patients at various stages of HD. The study enrolled 104 participants, including 14 asymptomatic carriers of HTT mutations, 44 symptomatic HD patients, and 46 control subjects. HD severity was measured using the Unified Huntington's Disease Rating Scale Total Motor Score (UHDRS-TMS) and Total Functional Capacity Scale (TFC). The evaluation of rapid eye movements (reflexive saccades, anti-saccades, memory-guided saccades) was carried out using 'Saccadometer Research'. Measures of reflexive and volitional saccades did not differ between the asymptomatic carriers and controls. Significant latency prolongation and increased physiological variability of latency times, as well as higher error rates among HD patients, were found in all saccade tasks (p < 0.001) compared to the controls. Abnormalities in saccade parameters were more pronounced in the advanced stages of the disease. Latency of saccades and error rate of volitional saccades correlated with the UHDRS-TMS and TFC scores. The saccade parameters in asymptomatic HD carriers with a long time to disease development were similar to those in the control group. Saccade abnormalities appeared in symptomatic patients at the beginning of the disease, and correlated with HD severity.

Smooth Pursuit and Reflexive Saccade in Discriminating Multiple-System Atrophy With Predominant Parkinsonism From Parkinson's Disease.

Performing the differential diagnosis of Parkinson's disease (PD) and multiple-system atrophy of parkinsonian type (MSA-P) is challenging. The oculomotor performances of patients with PD and MSA-P were investigated to explore their potential role as a biomarker for this differentiation. Reflexive saccades and smooth pursuit were examined in 56 patients with PD and 34 with MSA-P in the off-medication state. Patients with PD and MSA-P had similar oculomotor abnormalities of prolonged and hypometric reflexive saccades. The incidence rates of decreased reflexive saccadic velocity and saccadic smooth pursuit were significantly higher in MSA-P than in PD (p<0.05 for both). Multiple logistic regression analysis indicated that slowed reflexive saccades (odds ratio [OR]=8.14, 95% confidence interval [CI]=1.45-45.5) and saccadic smooth pursuit (OR=5.27, 95% CI=1.24-22.43) were significantly related to MSA-P. The distinctive oculomotor abnormalities of saccadic smooth pursuit and slowed reflexive saccades in MSA-P may serve as useful biomarkers for discriminating MSA-P from PD.

Abnormal Ocular Movement in the Early Stage of Multiple-System Atrophy With Predominant Parkinsonism Distinct From Parkinson's Disease.

The eye-movement examination can be applied as a noninvasive method to identify multiple-system atrophy (MSA). Few studies have investigated eye movements during the early stage of MSA with predominant parkinsonism (MSA-P). We aimed to determine the characteristic oculomotor changes in the early stage of MSA-P. We retrospectively selected 17 patients with MSA-P and 40 with Parkinson's disease (PD) with disease durations of less than 2 years, and 40 age-matched healthy controls (HCs). Oculomotor performance in the horizontal direction was measured in detail using videonystagmography. We found that the proportions of patients with MSA-P and PD exhibiting abnormal eye movements were 82.4% and 77.5%, respectively, which were significantly higher than that in the HCs (47.5%, p<0.05). Compared with HCs, patients with MSA-P presented significantly higher abnormal proportions of fixation and gaze-holding (17.6% vs. 0%), without-fixation (47.1% vs. 0%), prolonged latency in reflexive saccades (29.4% vs. 5.0%), memory-guided saccades (93.3% vs. 10.0%), and catch-up saccades in smooth-pursuit movement (SPM, 41.2% vs. 0) (all p<0.05). Compared with those with PD, patients with MSA-P presented a significantly higher proportion of catch-up saccades in SPM (41.2% vs. 2.5%, p<0.001). MSA-P presented the characteristic of catch-up saccades in SPM in the early stage, which may provide some value in differentiating MSA-P from PD.

Age- and sex-related oculomotor manifestation of dopamine deficiency in Segawa disease

Objective: To investigate the oculomotor manifestations of Segawa disease (SD), considered to represent mild dopamine deficiency and discuss their pathophysiological basis. Methods: We recorded visually- (VGS) and memory-guided saccade (MGS) tasks in 31 SD patients and 153 age-matched control subjects to study how basal ganglia (BG) dysfunction in SD evolves with age for male and female subjects. Results: SD patients were impaired in initiating MGS, showing longer latencies with occasional failure. Patients showed impaired ability to suppress reflexive saccades; saccades to cues presented in MGS were more frequent and showed a shorter latency than in control subjects. These findings were more prominent in male patients, particularly between 13 and 25 years. Additionally, male patients showed larger delay in MGS latency in trials preceded by saccades to cue than those unpreceded. Conclusions: The findings can be explained by a dysfunction of the BG-direct pathway impinging on superior colliculus (SC) due to dopamine deficiency. The disturbed inhibitory control of saccades may be explained by increased SC responsivity to visual stimuli. Significance: Oculomotor abnormalities in SD can be explained by dysfunction of the BG inhibitory pathways reaching SC, with a delayed maturation in male SD patients, consistent with previous pathological/physiological studies.

Microsaccade rate activity during the preparation of pro- and antisaccades.

Microsaccades belong to the category of fixational micromovements and may be crucial for image stability on the retina. Eye movement paradigms typically requirefixational control, but this does not eliminate all oculomotor activity. The antisaccade task requires a planned eye movement in the direction opposite of an onset, allowing separation of planning and execution. We build on previous studies of microsaccades in the antisaccade task using a combination of fixed and mixed pro- and antisaccade blocks. We hypothesized that microsaccade rates may be reduced prior to the execution of antisaccades as compared with regular saccades (prosaccades). In two experiments, we measured microsaccades in four conditions across three trial blocks: one block each of fixed prosaccade and antisaccade trials, and a mixed block where both saccade types were randomized. We anticipated that microsaccade rates would be higher prior to antisaccades than prosaccades due to the need to preemptively suppress reflexive saccades during antisaccade generation. In Experiment 1, with monocular eye tracking, there was an interaction between the effects of saccade and block type on microsaccade rates, suggesting lower rates on antisaccade trials, but only within mixed blocks. In Experiment 2, eye tracking was binocular, revealing suppressed microsaccade rates on antisaccade trials. A cluster permutation analysis of the microsaccade rate over the course of a trial did not reveal any particular critical time for this difference in microsaccade rates. Our findings suggest that microsaccade rates reflect the degree of suppression of the oculomotor system during the antisaccade task.

Oculomotor abnormalities indicate early executive dysfunction in prodromal X-linked dystonia-parkinsonism (XDP)

BackgroundX-Linked dystonia-parkinsonism (XDP) is a movement disorder characterized by the presence of both dystonia and parkinsonism with one or the other more prominent in the initial stages and later on manifesting with more parkinsonian features towards the latter part of the disease. XDP patients show oculomotor abnormalities indicating prefrontal and striatal impairment. This study investigated oculomotor behavior in non-manifesting mutation carriers (NMC). We hypothesized that oculomotor disorders occur before the appearance of dystonic or parkinsonian signs. This could help to functionally identify brain regions already affected in the prodromal stage of the disease.MethodsTwenty XDP patients, 13 NMC, and 28 healthy controls (HC) performed different oculomotor tasks typically affected in patients with parkinsonian signs.ResultsThe error rate for two types of volitional saccades, i.e., anti-saccades and memory-guided saccades, was increased not only in XDP patients but also in NMC compared to HC. However, the increase in error rates of both saccade types were highly correlated in XDP patients only. Hypometria of reflexive saccades was only found in XDP patients. Initial acceleration and maintenance velocity of smooth pursuit eye movements were only impaired in XDP patients.ConclusionsDespite being asymptomatic, NMC already showed some oculomotor deficits reflecting fronto-striatal impairments, typically found in XDP patients. However, NMC did not show saccade hypometria and impaired smooth pursuit as seen in advanced Parkinson’s disease and XDP, suggesting oculomotor state rather than trait signs in these mutation carriers. Neurodegeneration may commence in the striatum and prefrontal cortex, specifically the dorsolateral prefrontal cortex.

Video-oculographic Differences between Parkinson Disease and Multiple System Atrophy (P9-11.016)

<h3>Objective:</h3> With video-oculography (VOG), this study aimed to explore and compare visually-guided and self-paced volitional saccades in Parkinson’s disease (PD) and multiple system atrophy (MSA). <h3>Background:</h3> Saccades, rapid eye movements, are divided into two distinct types: reflexive and voluntary. Reflexive saccades are proceeded after a visual, auditory or somatosensory stimulus, while voluntary saccades require internally-generated drive. Each saccade is presumed to require separate neural systems. The voluntary saccades are mediated through higher centers, including frontal eye fields and basal ganglia, in addition to superior colliculus. Saccades are one of the most useful eye movements in the evaluation of the movement disorders. Voluntary saccades have been poorly investigated in PD and MSA. <h3>Design/Methods:</h3> We investigated visually guided reflexive and memory guided voluntary saccades by video-oculography in 39 PD and 15 MSA patients. There were no differences for age, sex, and UPDRS motor scores between PD and MSA patients. Two saccades were recorded sequentially, using an infrared eye tracking system (SMI, South Korea). <h3>Results:</h3> Comparison of visually-guided reflexive saccades between PD and MSA patients showed no difference in accuracy and peak velocity. In self-paced volitional saccades, PD patients produced significantly longer mean accuracy than MSA patients. Pause at the left eccentric position was consistently longer in both PD and MSA, with no statistical group difference. Volitional saccadic velocity was significantly slower than reflexive saccadic velocity in both groups. Self-paced saccadic accuracy was higher than reflexive saccadic accuracy only in PD, with significant difference. MSA patients did not show significant differences of accuracy between two saccades, although mean accuracy tended to be decreased in volitional saccades paradigm. <h3>Conclusions:</h3> In both PD and MSA patients, saccadic eye movements driven by memory-guided voluntary effort had much slower velocity, compared to visually-guided reflexive saccades. PD patients showed hypermetric volitional saccades, meanwhile MSA groups had no difference in accuracy between two saccades. <b>Disclosure:</b> Ms. Kim has nothing to disclose. Dr. Kim has nothing to disclose. Dr. Kim has nothing to disclose. Dr. Chang has nothing to disclose. Kee Duk Park has nothing to disclose. Dr. Yun has nothing to disclose.

Antisaccadic eye movements in middle-aged individuals with a family history of Alzheimer's disease.

Antisaccade is closely associated with cognitive ability in Alzheimer's disease (AD). However, studies regarding antisaccade in the early stages of AD are scarce. Considering that first-degree family history is a well-established risk factor for AD, we explored the influence of family history on the performance of antisaccade tasks in individuals with normal cognition. In total, 44 participants (aged 50-66 years) with a family history of AD (FH+) and 44 age-, gender-, and educational level-matched controls (FH-) were enrolled in our study. After cognitive assessment using the Montreal Cognitive Assessment and Mini-mental State Examination, participants underwent antisaccade trials, and all parameters were recorded using an eye tracker. While the average velocity was relatively lower in FH+ individuals than in FH- individuals (107.9 ± 14.3°/s vs. 132.9 ± 23.7°/s, p < 0.001), FH+ individuals surprisingly showed relatively fewer uninhibited reflexive saccades (44.7 ± 26.0% vs. 56.2 ± 24.7%, p = 0.037) than the control group. They also required a relatively shorter time to detect and correct false saccades (121.6 ± 40.7 ms vs. 143.9 ± 37.0 ms, p = 0.023). This study showed that family history is associated with alterations in antisaccadic parameters, suggesting that eye tracking can be used to assess oculomotor control and executive function in individuals at risk of developing dementia.

Oculomotor Impairments in Children After Posterior Fossa Tumors Treatment.

Posterior fossa tumors (PFT) are the most common pediatric brain tumors, and the study of the somatic and cognitive status of PFT survivors still remains a critical problem. Since cerebellar damage can affect eye movement centers located in the vermis and hemispheres, such patients suffer from disturbances in visual perception, visual-spatial functions, reading, etc. Our investigation aimed at describing oculomotor impairments in PFT survivors linked to core oculomotor functions assessed through eye tracking method: gaze holding, reflexive saccades, and organization of voluntary saccades and their dependency on age at tumor diagnosis. Also, we investigated the relationship between oculomotor functions and ataxia measured with International Cooperative Ataxia Rating Scale (ICARS). A total of 110 children (patients and age-matched healthy controls, aged 9-17 years old) participated in the study. We found that the earlier the child had a tumor, the more impaired gaze holding (p = 0.0031) and fewer isometric saccades (p = 0.035) were observed at the time of examination. The above-mentioned functions in healthy controls improved with age. Visual scanning was also impaired compared to controls but was not related to age at diagnosis. A positive correlation between ICARS scores and number of hypermetric saccades (r = 0.309, p = 0.039), but no correlation with the number of hypometric saccades (r = - 0.008, p = 0.956). Furthermore, number of hypometric saccades did not differ between patients and controls (p = 0.238). Thus, primarily hypermetric saccades can be considered a prominent oculomotor symptom of cerebellar tumors. Our study provides basis for new methods of PFT diagnosis and rehabilitation procedure evaluation, both playing essential roles in modern pediatric neurooncology.

The impact of traumatic brain injury on inhibitory control processes assessed using a delayed antisaccade task

It has been well established that traumatic brain injury (TBI) can affect cognitive function such as attention, working memory and executive functions. In the present study, we further investigated TBI-related changes in cognitive functions by investigating the ability to reorient visuospatial attention using a modified antisaccade task. Performing an antisaccade requires disengaging attention, inhibiting a reflexive saccade, and then engaging attention to execute a voluntary saccade in a direction opposite to a peripheral target. Particularly we quantified the time (latency), and accuracy (directional and disinhibition errors) of 26 TBI and 33 normal participants in making an antisaccade after a variable period of delay (0, 0.0625, 0.125, 0.250, 0.500 or 1.0 s). Changing the delay period allowed to systematically quantify the temporal and spatial characteristics of preparing and initiating an antisaccade and whether this process is affected by TBI. TBI participants took longer (approximately 33–66 ms for variable delays) to generate correct delayed antisaccades and showed increased directional errors (2–11 % for variable delays) and increased disinhibition prosaccade errors (2–6 % for variable delays) compared to controls. However, both groups made similar disinhibition antisaccade errors. These findings indicate that TBI participants required a longer time to process information, and a possible poorer response inhibition and poor spatial information processing due to head injury.

The Conventional Head Impulse Test Versus the Suppression Head Impulse Test: A Clinical Comparative Study.

The suppression head impulse test is a new paradigm of the head impulse test, recently introduced for clinical use. The aim of this study was to assess the importance of the suppression head impulse paradigm in evaluating vestibular function. This comparative study was conducted from June 2020 to June 2022. The ears of the participants were divided into 2 groups: (i) ears with vestibular weakness and (ii) healthy controls. All participants underwent video head impulse tests at the time of presentation with both conventional head impulse paradigm and suppression head impulse paradigm, performed by the same examiner. The results of the 2 tests were compared, and the correlation between the corresponding parameters obtained (vestibulo-ocular reflex gain and saccades) was examined. Ninety-five participants were included in the study (190 ears) with a mean age of 42.2 ± 12.6 years. Forty-six ears had vestibular weakness, and 144 were healthy controls. The suppression head impulse paradigm test showed a significantly lower vestibulo-ocular reflex gain than the head impulse paradigm in both groups. A positive correlation emerged between the vestibulo-ocular reflex gain measured with both paradigms. Regarding the saccades, a negative correlation was observed between the overt saccades latency and amplitude measured with both paradigms. The new suppression head impulse paradigm complements the head impulse paradigm for a better evaluation of the vestibular function. The inconsistency of covert saccades in suppression head impulse paradigm makes it superior to head impulse paradigm in measuring vestibulo-ocular reflex gain, especially in patients with vestibular loss.

The latency of reflexive saccades is influenced by contrast and correlates over the horizontal and vertical visual field plane

The latency of reflexive saccades is influenced by contrast and correlates over the horizontal and vertical visual field plane

Cluster analysis reveals distinct patterns of saccade impairment and their relation to cognitive profiles in Parkinson's disease.

Saccade performance has been reported to be altered in Parkinson's disease (PD), however, with a large variability between studies as both motor and cognitive impairment interfere with oculomotor control. The aim of this study was to identify different patterns in saccade alterations in PD using a data-driven approach and to explore their relationship with cognitive phenotypes. Sixty-one participants with PD and 25 controls performed eye-tracking (horizontal and vertical prosaccades, antisaccades) and neuropsychological testing. Hierarchical cluster analysis was applied to the eye-tracking data to subsequently compare the clusters based on demographical, clinical and cognitive characteristics. The three identified clusters of saccade alterations differed in cognitive profiles from healthy controls, but not in PD-related motor symptoms or demographics. The rate of directive errors in the antisaccade task was increased in clusters 1 and 2. Further, cluster 1 was defined by a general disinhibition of reflexive saccades and executive dysfunction in the neuropsychological evaluation. In cluster 2, prolonged saccade latencies and hypometria were accompanied by multidomain cognitive impairment. The cluster 3 showed increased antisaccade latency and vertical hypometria despite lack of evidence for cognitive impairment. Our results suggest that there may be at least two opposing patterns of saccade alterations associated with cognitive impairment in PD, which may explain some of the contradictory results of previous studies.

The influence of stimulus eccentricity on prosaccade outcomes in patients with Alzheimer’s Disease dementia at an early stage and amnestic mild cognitive impairment

ABSTRACT Introduction Prosaccade task is a widely used objective method to evaluate reflexive saccade and visual attention. The study aimed to investigate prosaccade stimulus eccentricity, compare prosaccade parameters in patients with Alzheimer’s disease dementia (AD), amnestic mild cognitive impairment (aMCI), and neurotypical adults (NA), and examine the relationship between prosaccade and neuropsychological tests. Methods Thirty patients with AD, 34 with aMCI, and 32 NA were included in the study. Eye movements were recorded with the EyeLink 1000 Plus in the prosaccade task, and this study evaluated cognitive function with comprehensive neuropsychological tests assessing attention, memory, executive function, visuospatial function, and language domains. Results The correct saccade rates of patients with AD were significantly lower than NA in the 5° and 10° stimulus eccentricities. Patients with AD had significantly longer latencies in the 10° stimulus eccentricity than those with aMCI and NA. Patients with aMCI did not differ in prosaccade performance compared to NA. Prosaccade parameters were significantly correlated with all cognitive domains. As the amplitude of the stimuli increased, the rate of correct saccades decreased, while the express saccade rate, latency, amplitude, and peak velocity increased. Conclusion Our findings that correct saccade rates and latency may be distinguishing parameters of early AD are promising. This study also found that stimulus eccentricity affects prosaccade measures in AD, MCI, and NA.

Reflexive and volitional saccadic eye movements and their changes in age and progressive supranuclear palsy

Background and objectivesSaccades, rapid movements of the eyes towards a visual or remembered target, are useful in understanding the healthy brain and the pathology of neurological conditions such as progressive supranuclear palsy (PSP). We set out to investigate the parameters of horizontal reflexive and volitional saccades, both visually guided and memory-guided, over a 1 min epoch in healthy individuals and PSP patients. MethodsAn experimental paradigm tested reflexive, volitional visually guided, and volitional memory-guided saccades in young healthy controls (n = 14; 20–31 years), PSP patients (n = 11; 46–75 years) and older age-matched healthy controls (n = 6; 56–71 years). The accuracy and velocity of saccades was recorded using an EyeBrain T2® video eye tracker and analyses performed using the MyEyeAnalysis® software. Two-way analysis of variance (ANOVA) was used to identify significant effects (p < 0.01) between young and older controls to investigate the effects of ageing upon saccades, and between PSP patients and age-matched controls to study the effects of PSP upon saccades. ResultsIn both healthy individuals and PSP patients, volitional saccades are slower and less accurate than reflexive saccades. In PSP patients, accuracy is lower across all saccade types compared to age-matched controls, but velocity is lower only for reflexive saccades. Crucially, there is no change in accuracy or velocity of consecutive saccades over short (one-minute) timescales in controls or PSP patients. ConclusionsVelocity and accuracy of saccades in PSP does not decrease over one-minute timescales, contrary to that previously observed in Parkinson's Disease (PD), suggesting a potential clinical biomarker for the distinction of PSP from PD.