Saccadic Error Research Articles

Eye-movement methodology reveals a shift in attention from threat to neutral stimuli with self-reported symptoms of social anxiety across children, adolescents and adults

ABSTRACT The current study used an eye-movement remote distractor paradigm (RDP) to examine the relationship between self-reported symptoms of social anxiety in children (9–11-year-olds), young adolescents (12–14-year-olds) and adults (18–43-year-olds) on saccade latencies to identify a target and saccadic errors to task irrelevant distractor (angry, neutral and happy faces). Distractors were presented simultaneously, either at the centre of the display, or at a contralateral parafoveal or peripheral location to the target. Symptoms of social anxiety in children were associated with increased saccade latencies in the presence of angry and neutral faces suggesting avoidance of these emotion expressions in this age group. Symptoms of social anxiety in adolescents and adults were respectively linked with longer latencies for neutral faces, indicating that neutral faces represent ambiguous and potentially negative stimuli for individuals with elevated social anxiety, and fit with research that has questioned the role of neutral faces as non-emotional control stimuli in attention research and anxiety.

Prediction of behavioral performance by alpha-band phase synchronization in working memory

Working memory (WM) is a cognitive system with limited capacity that can temporarily store and process information. The purpose of this study was to investigate functional connectivity based on phase synchronization during WM and its relationship with the behavioral response. In this regard, we recorded EEG/Eye tracking data of seventeen healthy subjects while performing a memory-guided saccade (MGS) task with two different positions (near eccentricity and far eccentricity). We computed saccade error as memory performance and measured functional connectivity using Phase Locking Value (PLV) in the alpha frequency band (8–12 Hz). The results showed that PLV is negatively correlated with saccade error. Our finding indicated that during the maintenance period, PLV between the frontal and visual area in trials with low saccade error increased significantly compared to trials with high saccade error. Furthermore, we observed a significant difference between PLV for near and far conditions in the delay period. The results suggest that PLV in memory maintenance, in addition to predicting saccade error as behavioral performance, can be related to the coding of spatial information in WM.

Effect of Repetitive Head Impacts on Saccade Performance in Canadian University Football Players.

Investigate the effect of cumulative head impacts on saccade latency and errors, measured across two successive football seasons. Participants were acquired from a sample of convenience-one Canadian university football team. Head impacts were collected during training camp, practices, eight regular season games, and four playoff games in each season. Saccade measurements were collected at five time points-before and after training camp, at midseason, after regular season, and after playoffs. Two seasons following players from a single USports football team during practices and games. Players who completed a baseline saccade measurement and a minimum of one follow-up measurement were included in the study. A total of 127 players were monitored across two competitive seasons, including 61 players who participated in both seasons. Head impact measurements were collected using helmet-mounted sensors. Saccade latency and number of errors were measured using high-speed video or electro-oculography. On average, each head impact increased prosaccade latency by 5.16 × 10-3 ms (95% confidence interval [CI], 2.26 × 10-4-1.00 × 10-2, P = 0.03) and antisaccade latency by 5.74 × 10-3 ms (95% CI, 7.18 × 10-4-1.06 × 10-2, P = 0.02). These latency increases did not decrease between the two seasons; in fact, prosaccade latencies were 23.20 ms longer (95% CI, 19.40-27.14, P < 0.001) at the second season's baseline measurement than the first. The number of saccade errors was not affected by cumulative head impacts. Repetitive head impacts in Canadian university football result in cumulative declines in brain function as measured by saccade performance. Football organizations should consider implementing policies focused on reducing head impacts to improve player safety.

Altered Oculomotor and Vestibulo-ocular Function in Children and Adolescents Postconcussion.

To document (1) oculomotor (OM) and vestibulo-ocular (VO) function in children with concussion who were symptomatic at the time of assessment and to compare it with that in children with concussion who were clinically recovered (asymptomatic) and in children with no concussive injury, and (2) the extent to which OM and VO function relates to postconcussion symptom severity in injured children. Participants were recruited from a concussion clinic or the community. A total of 108 youth with concussion (72 symptomatic; 36 recovered) and 79 healthy youth (aged 9-18 years). Youth with concussion were included if aged 9 to 18 years, had no previous concussion within the last 12 months, less than 90 days since injury, and no known existing visual disorders or learning disabilities. A prospective cross-sectional study. All participants were tested for OM and VO function with a commercial virtual reality (VR) eye-tracking system (Neuroflex ® , Montreal,Québec, Canada). Participants in the concussion group who completed the postconcussion symptoms were scored with the Post-Concussion Symptom Inventory. There was a significant group effect for vergence during smooth pursuit ( F2,176 = 10.90; P < .05), mean latency during saccades ( F2,171 = 5.99; P = .003), and mean response delay during antisaccades ( F2,177 = 9.07; P < .05), where children with symptomatic concussion showed poorer performance than clinically recovered and healthy children. Similar results were found in VO for average vestibular ocular reflex gain in the horizontal leftward ( F2,168 = 7; P = .001) and rightward directions ( F2,163 = 13.08; P < .05) and vertical upward ( F2,147 = 7.60; P = .001) and downward directions ( F2,144 = 13.70; P < .05). Mean saccade error was positively correlated to total Post-Concussion Symptom Inventory scores in younger clinically recovered children. VR eye tracking may be an effective tool for identifying OM and VO deficits in the subacute phase (<90 days) postconcussion.

Anti-saccades reveal impaired attention control over negative social evaluation in individuals with depressive symptoms

Depressed individuals are excessively sensitive to negative information but blunt to positive information, which has been considered as vulnerability to depression. Here, we focused on inhibitory control over attentional bias on social evaluation in individuals with depression. We engaged individuals with and without depressive symptoms (categorized by Beck Depression Inventory-II) in a novel attention control task using positive and negative evaluative adjectives as self-referential feedback given by social others. Participants were instructed to look at sudden onset feedback targets (pro-saccade) or the mirror location of the targets (anti-saccade) when correct saccade latencies and saccade errors were collected. The two indices showed that while both groups displayed longer latencies and more errors for anti-saccade relative to pro-saccade responses depressed individuals spent more time reacting correctly and made more errors than non-depressed individuals in the anti-saccade trials and such group differences were not observed in the pro-saccade trials. Although group differences in correct anti-saccade latencies were found for both positive and negative stimuli, depressed individuals spent more time making correct anti-saccade responses to negative social feedback than to positive ones whereas non-depressed individuals featured longer correct anti-saccade latencies for positive relative to negative evaluations. Our results suggest that depressed individuals feature an impaired ability in attention control for self-referential evaluations, notably those of negative valence, shedding new light on depression-distorted self-schema and corresponding social dysfunctions.

Multiple step saccades are generated by internal real-time saccadic error correction.

Multiple step saccades (MSSs) are an atypical form of saccade that consists of a series of small-amplitude saccades. It has been argued that the mechanism for generating MSS is due to the automatic saccadic plan. This argument was based on the observation that trials with MSS had shorter saccadic latency than trials without MSS in the reactive saccades. However, the validity of this argument has never been verified by other saccadic tasks. Alternatively, we and other researchers have speculated that the function of MSS is the same as that of the corrective saccade (CS), i.e., to correct saccadic errors. Thus, we propose that the function of the MSS is also to rectify saccadic errors and generated by forward internal models. The objective of the present study is to examine whether the automatic theory is universally applicable for the generation of MSSs in various saccadic tasks and to seek other possible mechanisms, such as error correction by forward internal models. Fifty young healthy subjects (YHSs) and fifty elderly healthy subjects (EHSs) were recruited in the present study. The task paradigms were prosaccade (PS), anti-saccade (AS) and memory-guided saccade (MGS) tasks. Saccadic latency in trials with MSS was shorter than without MSS in the PS task but similar in the AS and MGS tasks. The intersaccadic intervals (ISI) were similar among the three tasks in both YHSs and EHSs. Our results indicate that the automatic theory is not a universal mechanism. Instead, the forward internal model for saccadic error correction might be an important mechanism.

Does alcohol automatically capture drinkers' attention? Exploration through an eye-tracking saccadic choice task.

Dominant theoretical models postulate the presence of an automatic attentional bias (AB) towards alcohol-related stimuli in alcohol use disorder, such AB constituting a core feature of this disorder. An early alcohol AB has been documented in subclinical populations such as binge drinking (i.e., a drinking pattern prevalent in youth and characterized by repeated alternation between alcohol intoxications and withdrawals, generating cerebral consequences). However, the automatic nature of AB remains to be established. We investigated the automatic nature of AB in binge drinkers through the saccadic choice task. This eye-tracking paradigm consistently highlights the extremely fast and involuntary saccadic responses elicited by faces in humans, relative to other object categories. Through an alcohol-related adaptation of the saccadic choice task, we tested whether the early and automatic capture of attentional resources elicited by faces can also be found for alcohol-related stimuli in binge drinkers, as predicted by theoretical models. Forty-three binge drinkers and 44 control participants performed two versions of the saccadic choice task. In the original version, two images (a face, a vehicle) were displayed on the left and right side of the screen respectively. Participants had to perform a saccade as fast as possible towards the target stimulus (either face or vehicle). In the alcohol-related version, the task was identical, but the images were an alcoholic beverage and a non-alcoholic stimulus. We replicated the automatic attraction towards faces in both groups, as faces generated higher saccadic accuracy, speed, and amplitude than vehicles, as well as higher corrective saccade proportion. Concerning the alcohol-related adaptation of the task, groups did not differ for the accuracy, speed, and amplitude of the first saccade towards alcohol. However, binge drinkers differed from controls regarding the proportion of corrective saccade towards non-alcoholic stimuli after an error saccade towards alcohol, suggesting the presence of an alcohol disengagement bias specific to binge drinkers. Alcohol-related AB in binge drinkers is not characterized by an early and automatic hijacking of attention towards alcohol. This AB rather relies on later and more controlled processing stages, namely a difficulty to disengage attentional resources from alcohol-related stimuli.

A novel eye-movement impairment in multiple sclerosis indicating widespread cortical damage.

In multiple sclerosis, remyelination trials have yet to deliver success like that achieved for relapse rates with disease course modifying treatment trials. The challenge is to have a clinical, functional outcome measure. Currently, there are none that have been validated, other than visual evoked potentials in optic neuritis. Like vision, quick eye movements (saccades) are heavily dependent on myelination. We proposed that it is possible to extrapolate from demyelination of the medial longitudinal fasciculus in the brainstem to quantitative assessment of cortical networks governing saccadic eye movements in multiple sclerosis. We have developed and validated a double-step saccadic test, which consists of a pair of eye movements towards two stimuli presented in quick succession (the demonstrate eye movement networks with saccades protocol). In this single-centre, cross-sectional cohort study we interrogated the structural and functional relationships of double-step saccades in multiple sclerosis. Data were collected for double-step saccades, cognitive function (extended Rao's Brief Repeatable Battery), disability (Expanded Disability Status Scale) and visual functioning in daily life (National Eye Institute Visual Function Questionnaire). MRI was used to quantify grey matter atrophy and multiple sclerosis lesion load. Multivariable linear regression models were used for analysis of the relationships between double-step saccades and clinical and MRI metrics. We included 209 individuals with multiple sclerosis (mean age 54.3 ± 10.5 years, 58% female, 63% relapsing-remitting multiple sclerosis) and 60 healthy control subjects (mean age 52.1 ± 9.2 years, 53% female). The proportion of correct double-step saccades was significantly reduced in multiple sclerosis (mean 0.29 ± 0.22) compared to controls (0.45 ± 0.22, P < 0.001). Consistent with this, there was a significantly larger double-step dysmetric saccadic error in multiple sclerosis (mean vertical error -1.18 ± 1.20°) compared to controls (-0.54 ± 0.86°, P < 0.001). Impaired double-step saccadic metrics were consistently associated with more severe global and local grey matter atrophy (correct responses-cortical grey matter: β = 0.42, P < 0.001), lesion load (vertical error: β = -0.28, P < 0.001), progressive phenotypes, more severe physical and cognitive impairment (correct responses-information processing: β = 0.46, P < 0.001) and visual functioning. In conclusion, double-step saccades represent a robust metric that revealed a novel eye-movement impairment in individuals with multiple sclerosis. Double-step saccades outperformed other saccadic tasks in their statistical relationship with clinical, cognitive and visual functioning, as well as global and local grey matter atrophy. Double-step saccades should be evaluated longitudinally and tested as a potential novel outcome measure for remyelination trials in multiple sclerosis.

Inhibitory Control of Saccadic Eye Movements and Cognitive Impairment in Mild Cognitive Impairment

AbstractBackgroundMild cognitive impairment (MCI) may occur due to several forms of neurodegenerative diseases and non‐degenerative conditions and is associated with cognitive impairment that does not affect everyday activities. For a timely diagnosis of MCI to prevent progression to dementia, a screening tool of fast, low‐cost and easy access is needed. Recent research on eye movement hints it a potential application for the MCI screening. However, the precise extent of cognitive function decline and eye‐movement control alterations in patients with MCI is still unclear.MethodPatients with MCI (n = 79) and age‐matched cognitively healthy controls (HC) (n = 170) completed four saccadic eye‐movement paradigms: prosaccade (PS)/antisaccade (AS), Go/No‐go, and a battery of neuropsychological tests.ResultThe findings revealed significantly longer latency in patients with MCI than in HC during the PS task. Additionally, patients with MCI had a lower proportion of correct responses and a marked increase in inhibition errors for both PS/AS and Go/No‐go tasks. Furthermore, when patients with MCI made errors, they failed to self‐correct many of these inhibition errors. In addition to the increase in inhibition errors and uncorrected inhibition errors, patients with MCI demonstrated a trend toward increased correction latencies. We also showed a relationship between neuropsychological scores and correct and error saccade responses.ConclusionOur results demonstrate that, similar to patients with Alzheimer’s dementia (AD), patients with MCI generate a high proportion of erroneous saccades toward the prepotent target and fail to self‐correct many of these errors, which is consistent with an impairment of inhibitory control and error monitoring.

Increased saccadic latency in Amblyopia: Oculomotor and attentional factors

Amblyopia is a neurodevelopmental disorder of vision that arises from disrupted binocular vision during early childhood. Delayed initiation of saccadic eye movements is an established feature of amblyopia. The present study investigated whether oculomotor and/or attentional factors contribute to increased amblyopic eye saccadic latencies. Participants with normal vision (n = 10) and amblyopia (n = 10; 4 anisometropia, 6 strabismic/mixed) performed visually-guided saccades to targets presented via a mirror haploscope. Eye movements were recorded for both eyes even under monocular viewing conditions. In Experiment 1, we measured the latency, amplitude gain and peak velocity of saccades as targets were presented binocularly, or monocularly. Saccadic latencies were significantly longer for both eyes when targets were presented to only the amblyopic eye compared to all other conditions. Saccade gain and main sequence rate constants were similar across groups for all viewing conditions. In Experiment 2, we tested the hypothesis that shifts of overt attention may be deficient when viewing with the amblyopic eye. We presented the fixation target to one eye and the subsequent peripheral target (saccadic error signal) to the other eye. Shifting saccadic targets between the eyes expedited saccadic latencies irrespective of which eye viewed the target in the amblyopia group. These findings indicate that oculomotor factors related to saccade generation are unlikely to be responsible for amblyopic eye saccadic latency delays. We propose that an impairment in the ability to disengage attention from a fixation target and orient to a peripheral target when both targets are seen by the amblyopic eye may contribute to increased saccadic latency.

Cerebellar Volumes and Sensorimotor Behavior in Autism Spectrum Disorder.

BackgroundSensorimotor issues are common in autism spectrum disorder (ASD), though their neural bases are not well understood. The cerebellum is vital to sensorimotor control and reduced cerebellar volumes in ASD have been documented. Our study examined the extent to which cerebellar volumes are associated with multiple sensorimotor behaviors in ASD.Materials and MethodsFifty-eight participants with ASD and 34 typically developing (TD) controls (8–30 years) completed a structural MRI scan and precision grip testing, oculomotor testing, or both. Force variability during precision gripping as well as absolute error and trial-to-trial error variability of visually guided saccades were examined. Volumes of cerebellar lobules, vermis, and white matter were quantified. The relationships between each cerebellar region of interest (ROI) and force variability, saccade error, and saccade error variability were examined.ResultsRelative to TD controls, individuals with ASD showed increased force variability. Individuals with ASD showed a reduced volume of cerebellar vermis VI-VII relative to TD controls. Relative to TD females, females with ASD showed a reduced volume of bilateral cerebellar Crus II/lobule VIIB. Increased volume of Crus I was associated with increased force variability. Increased volume of vermal lobules VI-VII was associated with reduced saccade error for TD controls but not individuals with ASD. Increased right lobule VIII and cerebellar white matter volumes as well as reduced right lobule VI and right lobule X volumes were associated with greater ASD symptom severity. Reduced volumes of right Crus II/lobule VIIB were associated with greater ASD symptom severity in only males, while reduced volumes of right Crus I were associated with more severe restricted and repetitive behaviors only in females.ConclusionOur finding that increased force variability in ASD is associated with greater cerebellar Crus I volumes indicates that disruption of sensory feedback processing supported by Crus I may contribute to skeletomotor differences in ASD. Results showing that volumes of vermal lobules VI-VII are associated with saccade precision in TD but not ASD implicates atypical organization of the brain systems supporting oculomotor control in ASD. Associations between volumes of cerebellar subregions and ASD symptom severity suggest cerebellar pathological processes may contribute to multiple developmental challenges in ASD.

Inhibitory Control of Saccadic Eye Movements and Cognitive Impairment in Mild Cognitive Impairment.

BackgroundMild cognitive impairment (MCI) may occur due to several forms of neurodegenerative diseases and non-degenerative conditions and is associated with cognitive impairment that does not affect everyday activities. For a timely diagnosis of MCI to prevent progression to dementia, a screening tool of fast, low-cost and easy access is needed. Recent research on eye movement hints it a potential application for the MCI screening. However, the precise extent of cognitive function decline and eye-movement control alterations in patients with MCI is still unclear.ObjectiveThis study examined executive control deficits and saccade behavioral changes in patients with MCI using comprehensive neuropsychological assessment and interleaved saccade paradigms.MethodsPatients with MCI (n = 79) and age-matched cognitively healthy controls (HC) (n = 170) completed four saccadic eye-movement paradigms: prosaccade (PS)/antisaccade (AS), Go/No-go, and a battery of neuropsychological tests.ResultsThe findings revealed significantly longer latency in patients with MCI than in HC during the PS task. Additionally, patients with MCI had a lower proportion of correct responses and a marked increase in inhibition errors for both PS/AS and Go/No-go tasks. Furthermore, when patients with MCI made errors, they failed to self-correct many of these inhibition errors. In addition to the increase in inhibition errors and uncorrected inhibition errors, patients with MCI demonstrated a trend toward increased correction latencies. We also showed a relationship between neuropsychological scores and correct and error saccade responses.ConclusionOur results demonstrate that, similar to patients with Alzheimer’s dementia (AD), patients with MCI generate a high proportion of erroneous saccades toward the prepotent target and fail to self-correct many of these errors, which is consistent with an impairment of inhibitory control and error monitoring.SignificanceThe interleaved PS/AS and Go/No-go paradigms are sensitive and objective at detecting subtle cognitive deficits and saccade changes in MCI, indicating that these saccadic eye movement paradigms have clinical potential as a screening tool for MCI.

Eye movements and eating disorders: protocol for an exploratory experimental study examining the relationship in young-adult women with subclinical symptomatology

BackgroundRecent research indicates that patients with anorexia (AN) show specific eye movement abnormalities such as shorter prosaccade latencies, more saccade inhibition errors, and increased rate of saccadic intrusions compared to participants without AN. However, it remains unknown whether these abnormal eye movement patterns, which may serve as potential biomarkers and endophenotypes for an early diagnosis and preventive clinical treatments, start to manifest also in people with subclinical eating disorders (ED) symptomatology. Therefore, we propose a protocol for an exploratory experimental study to investigate whether participants with subclinical ED symptomatology and control participants differ in their performance on several eye movement tasks.MethodsThe sample will be recruited through convenience sampling. The Eating Disorder Examination Questionnaire will be administered as a screening tool to split the sample into participants with subclinical ED symptomatology and control participants. A fixation task, prosaccade/antisaccade task, and memory-guided task will be administered to both groups. Additionally, we will measure anxiety and premorbid intelligence as confounding variables. Means comparison, exploratory Pearson's correlations and discriminant analysis will be performed.DiscussionThis study will be the first to elucidate the presence of specific eye movement abnormalities in participants with subclinical ED symptomatology. The results may open opportunities for developing novel diagnostic tools/therapies being helpful to the EDs research community and allied fields.

Simultaneous assessment of posture and saccadic eye movement with visual stimuli using head‐mounted display virtual reality technology in healthy older adults

AbstractBackgroundPostural sway and saccadic eye movement could be potential biomarkers to diagnose Alzheimer’s disease (AD) [1, 2]. We developed a new assessment system to evaluate posture and saccadic eye movement simultaneously in healthy older adults (OA) with visual stimuli of distractors, lower contrast, and stereopsis, which are also considered to be another deficit in people with AD [3‐5]. We hypothesised that more latency and errors in saccade would be observed in the condition with visual stimuli.Method14 healthy older adults (71.9±4.8 years, 7 men / 7 women) joined the experiment after taking Montreal Cognitive Assessment (MoCA). The system consisted of stabilometer (GP‐5000, ANIMA Corporation, Japan) and a head‐mounted display virtual reality technology (VIVE Pro Eye, HTC Corporation, Taiwan). We measured both posture and eye movement simultaneously in the following test conditions: #1‐2) eyes‐open and closed without VR, #3‐4) pro‐ and anti‐saccade tests in 2D environment, and #5‐6) pro‐ and anti‐saccade tests in 3D environment. We developed the 2D environment for the baseline saccade measurement and 3D environment with more visual stimuli [6]. Each test took 60 seconds with 30 saccade trials.ResultThe participants achieved MoCA score of 27.5±1.6. We found significant difference in saccade latency between saccade types (mean: P &lt; 0.001, SD: P &lt; 0.001) but less significant difference between VR scenery (mean: P = 0.01, SD: P = 0.42). Moreover, we observed less significant difference in saccade error rate between saccade types (P = 0.07) and between VR scenery (P &gt; 0.77). We did not see significant difference in postural sway (P &gt; 0.05).ConclusionThe results may imply that the healthy OA had sufficient attentional resources to both conduct the saccade tasks and maintain their posture in the designed VR environment with visual stimuli. Further research is required to evaluate the difference between OA with and without cognitive impairment.

Gravitational effects of scene information in object localization

We effortlessly interact with objects in our environment, but how do we know where something is? An object’s apparent position does not simply correspond to its retinotopic location but is influenced by its surrounding context. In the natural environment, this context is highly complex, and little is known about how visual information in a scene influences the apparent location of the objects within it. We measured the influence of local image statistics (luminance, edges, object boundaries, and saliency) on the reported location of a brief target superimposed on images of natural scenes. For each image statistic, we calculated the difference between the image value at the physical center of the target and the value at its reported center, using observers’ cursor responses, and averaged the resulting values across all trials. To isolate image-specific effects, difference scores were compared to a randomly-permuted null distribution that accounted for any response biases. The observed difference scores indicated that responses were significantly biased toward darker regions, luminance edges, object boundaries, and areas of high saliency, with relatively low shared variance among these measures. In addition, we show that the same image statistics were associated with observers’ saccade errors, despite large differences in response time, and that some effects persisted when high-level scene processing was disrupted by 180° rotations and color negatives of the originals. Together, these results provide evidence for landmark effects within natural images, in which feature location reports are pulled toward low- and high-level informative content in the scene.

Alpha oscillation during the performance of a new variant of working memory-guided saccade task: Evidence from behavioral and electroencephalographic analyses

Working memory (WM) can be considered as a limited-capacity system which is capable of saving information temporarily with the aim of processing. The aim of the present study was to establish whether eccentricity representation in WM could be decoded from eletroencephalography (EEG) alpha-band oscillation in parietal cortex during delay-period while performing memory-guided saccade (MGS) task. In this regard, we recorded EEG and Eye-tracking signals of 17 healthy volunteers in a variant version of MGS task. We designed the modified version of MGS task for the first time to investigate the effect of locating stimuli in two different positions, in a near (6°) eccentricity and far (12°) eccentricity on saccade error as a behavioral parameter. Another goal of study was to discern whether or not varying the stimuli loci can alter behavioral and eletroencephalographical data while performing the variant version of MGS task. Our findings demonstrate that saccade error for the near fixation condition is significantly smaller than the far from fixation condition. We observed an increase in alpha power in parietal lobe in near vs far conditions. In addition, the results indicate that the increase in alpha (8–12 Hz) power from fixation to memory was negatively correlated with saccade error. The novel approach of using simultaneous EEG/Eye-tracking recording in the modified MGS task provided both behavioral and electroencephalographic analyses for oscillatory activity during this new version of MGS task.

Executive function deficits in mild cognitive impairment: evidence from saccade tasks

Objectives: Early detection of mild cognitive impairment (MCI) is necessary to prevent irreversible brain damage caused by incipient Alzheimer’s disease. It has been showing that amnestic MCI (a-MCI) subjects exhibit subtle deficits in executive function that can be tested using saccade eye movements. Eye-tracking technology is a sensitive method to measure cognitive impairments in dementia and MCI. Methods In this study, we used eye-tracking technology to explore saccade impairments to distinguish between a-MCI and the variants of reference controls. 21 patients with AD, 40 patients with a-MCI, and 59 normal participants were recruited in current study. We measured saccade reaction time, saccade errors, saccade omission, and uncorrected saccades using anti-saccade and pro-saccade tasks with ‘gap’ and ‘overlap’ procedures. These parameters were used as markers of executive function and visual attention deficits.Results: The findings revealed that more errors, more omissions, and fewer corrections characterized the saccade behavior of the a-MCI group compared to the reference group. These eye-tracking characteristics can be considered as inhibitory control and working memory deficits in a-MCI subjects. Our results thus demonstrate the applicability of the anti-saccade task as a cognitive marker in a-MCI. Conclusion The work provides further support for eye-tracking as a useful diagnostic biomarker in the assessment of executive function in aging with cognitive impairments.

Food-related impulsivity assessed by longitudinal laboratory tasks is reduced in patients with binge eating disorder in a randomized controlled trial

Food-related impulsivity, i.e. a food-related attentional bias proposed to be due to increased reward sensitivity and diminished inhibitory control, has been cross-sectionally associated with binge eating disorder. To analyze changes in food-related impulsivity, we implemented longitudinal analyses of objective laboratory tasks in a randomized controlled trial called IMPULS. Patients who attended an impulsivity-focused group intervention (IG N = 31) and control patients who did not take part in the intervention (CG N = 25) were compared before (T0) and after the intervention period (T1) and at three months follow-up (T2). Patients’ impulsive gaze behavior towards food vs. neutral stimuli was measured in two eye tracking paradigms, one addressing reward sensitivity and another addressing inhibitory control. Initial fixations of food vs. neutral stimuli were increased at T0 (IG: p = .014, CG: p = .001), but not at T1 and T2 in IG (T1: p = .178, T2: p = .203) and in CG after Bonferroni correction only at T2 (T1: p = .031, T2: p = .002). Patients from IG increased dwell time on neutral stimuli at T1 contrary to patients from CG (p = .016) and rated the presented food stimuli as less positive (e.g. pleasantness p < .001 at T1 and T2). A possible explanation for this observation is reduced reward sensitivity, which implies a short-term treatment effect. Both groups showed improvement in inhibiting eye movements towards food and neutral stimuli over time (i.e. first saccade errors overall p < .001, second saccade errors overall p < .003). This could indicate increased inhibitory control due to training effects from the study paradigm. The results suggest that food-related impulsivity represents an underlying mechanism of BED and that it is modifiable by cognitive behavioral interventions.

Isolated face features are sufficient to elicit ultra-rapid and involuntary orienting responses toward faces.

Previous studies have shown that face stimuli influence the programming of eye movements by eliciting involuntary and extremely fast saccades toward them. The present study examined whether holistic processing of faces mediates these effects. We used a saccadic choice task in which participants were presented simultaneously with two images and had to perform a saccade toward the one containing a target stimulus (e.g., a face). Across three experiments, stimuli were altered via upside-down inversion (Experiment 1) or scrambling of thumbnails within the images (Experiments 2 and 3) in order to disrupt holistic processing. We found that disruption of holistic processing only had a limited impact on the latency of saccades toward face targets, which remained extremely short (minimum saccadic reaction times of only ∼120–130 ms), and did not affect the proportion of error saccades toward face distractors that captured attention more than other distractor categories. It, however, resulted in increasing error rate of saccades toward face targets. These results suggest that the processing of isolated face features is sufficient to elicit extremely fast and involuntary saccadic responses toward them. Holistic representations of faces may, however, be used as a search template to accurately detect faces.

Stronger saccadic suppression of displacement and blanking effect in children.

Humans do not notice small displacements to objects that occur during saccades, termed saccadic suppression of displacement (SSD), and this effect is reduced when a blank is introduced between the pre- and postsaccadic stimulus (Bridgeman, Hendry, & Stark, 1975; Deubel, Schneider, & Bridgeman, 1996). While these effects have been studied extensively in adults, it is unclear how these phenomena are characterized in children. A potentially related mechanism, saccadic suppression of contrast sensitivity—a prerequisite to achieve a stable percept—is stronger for children (Bruno, Brambati, Perani, & Morrone, 2006). However, the evidence for how transsaccadic stimulus displacements may be suppressed or integrated is mixed. While they can integrate basic visual feature information from an early age, they cannot integrate multisensory information (Gori, Viva, Sandini, & Burr, 2008; Nardini, Jones, Bedford, & Braddick, 2008), suggesting a failure in the ability to integrate more complex sensory information. We tested children 7 to 12 years old and adults 19 to 23 years old on their ability to perceive intrasaccadic stimulus displacements, with and without a postsaccadic blank. Results showed that children had stronger SSD than adults and a larger blanking effect. Children also had larger undershoots and more variability in their initial saccade endpoints, indicating greater intrinsic uncertainty, and they were faster in executing corrective saccades to account for these errors. Together, these results suggest that children may have a greater internal expectation or prediction of saccade error than adults; thus, the stronger SSD in children may be due to higher intrinsic uncertainty in target localization or saccade execution.