Look away: the anti-saccade task and the voluntary control of eye movement

Cognitive independence and interactions between cerebral hemispheres

The two cerebral hemispheres can often operate independently. But interactions between them are critical for cognition and have been implicated in a number of neuropsychiatric disorders. Neurophysiological studies have long focused on a single hemisphere. Here, we review recent studies showing neurophysiological evidence showing both independence and interactions between the hemispheres during complex behavior.

Oculomotor deficits in children with sensory processing difficulties

Background

Atypically developing children often present with a variety of sensory processing difficulties which have been proposed to reflect abnormal development of pathways integrating sensation and action. A brain system in which the process of sensorimotor integration is particularly well understood is the oculomotor system, but no studies to date have used computerised eye tracking to assess eye movements in children with sensory processing difficulties.

Method

Ten children with sensory processing difficulties completed a battery of oculomotor tasks comprising pro-saccades, anti-saccades, smooth pursuit tracking and sustained fixation. Eye movements were recorded using a high-resolution eye tracker.

Results

Compared to age-matched controls, children with sensory processing difficulties were found to make more directional errors in the anti-saccade task and less-accurate smooth pursuit and sustained fixation.

Conclusion

Consistent differences were found in oculomotor ability in children with sensory processing difficulties which are likely to impact children's ability to process and respond to visual information within home and school contexts. Further research is needed to understand the relationship between oculomotor deficits in children with sensory processing difficulties and the presence/absence of neurodevelopmental diagnoses. Eye tracking may be of value in the future for assessment and objective evaluation of interventions for sensory processing difficulties such as sensory integration therapy.

Increased frontoparietal activity related to lower performance in neuropsychological assessment of working memory

Executive functions, including working memory, are typically assessed clinically with neuropsychological instruments. In contrast, computerized tasks are used to test these cognitive functions in laboratory human and animal studies. Little is known of how neural activity captured by laboratory tasks relates to ability measured by clinical instruments and, by extension, clinical diagnoses of pathological conditions. We therefore sought to determine what aspects of neural activity elicited in laboratory tasks are predictive of performance in neuropsychological instruments. We recorded neural activity from intracranial electrodes implanted in human epilepsy patients as they performed laboratory working memory tasks. These patients had completed neuropsychological instruments preoperatively, including the Weschler Adult Intelligent Scale and the Wisconsin Card Sorting test. Our results revealed that increased high-gamma (70-150 Hz) power in the prefrontal and parietal cortex after presentation of visual stimuli to be remembered was indicative of lower performance in the neuropsychological tasks. On the other hand, we observed a positive correlation between high-frequency power amplitude in the delay period of the laboratory tasks and neuropsychological performance. Our results demonstrate how neural activity around task events relates to executive function and may be associated with clinical diagnosis of specific cognitive deficits.

Urgency enforces stimulus-driven action across spatial and numerical cognitive control tasks

It has been shown that urgency in cognitive control tasks elicits a time-window in which responses are dominated by stimuli rather than goals. If stimulus information conflicts with goal-relevant information, urgency impairs goal-directed responses. This was shown for an antisaccade task as well as tasks using manual responses. Critically, however, all previous studies on manual responses used arrows as stimuli, leaving it unclear whether urgency affects cognitive control also in tasks using different stimuli. Here, we show that the urgency effect can also be elicited in three cognitive control tasks that do not use arrow stimuli. Participants completed either a Spatial Stroop task with word stimuli, in which they reacted to the word meaning while ignoring the spatial position, or a Numerical Stroop Task, in which they had to respond to the numerically larger of two presented numbers. The physical size of the numbers varied but was irrelevant to the task. The third task was a Simon task, where participants were instructed to react to the color of a stimulus while ignoring its spatial position. In all tasks, urgency evoked a time window, in which the position or the physical size dominated the response, which was evident from a drop of performance below chance level in conflict situations. These results reveal that the effect of urgency on cognitive control does not depend on arrow stimuli and emerges in a number of other spatially related tasks, specifically in spatial and numerical cognitive control tasks. As such, they suggest that urgency affects cognitive control more generally.

Microsaccade behavior associated with inhibitory control in athletes in the antisaccade task

The ability to achieve a state of readiness before upcoming tasks, known as a preparatory set, is critical for athletic performance. Here, we investigated these preparatory processes associated with inhibitory control using the anti-saccade paradigm, in which participants are instructed, prior to target appearance, either to automatically look at the target (pro-saccade) or to suppress this automatic response and intentionally look in the opposite direction (anti-saccade). We focused on microsaccadic eye movements that happen before saccade responses in either pro- or anti-saccade tasks, as these microsaccades reflect ongoing preparatory processes during saccade planning before execution. We hypothesized that athletes, compared to non-athletes, would demonstrate better preparation, given research generally indicating higher inhibitory control in athletes. Our findings showed that microsaccade rates decreased before target appearance, with lower rates observed during anti-saccade preparation compared to pro-saccade preparation. However, microsaccade rates and metrics did not differ significantly between athletes and non-athletes. Moreover, reduced microsaccade rates were associated with improved task performance in non-athletes, leading to higher accuracy and faster saccade reaction times (SRTs) in trials without microsaccades. For athletes, only SRTs were affected by microsaccade occurrence. Moreover, the modulation of microsaccadic inhibition on accuracy was more pronounced in non-athletes compared to athletes. In conclusion, while microsaccade responses were modulated by task preparation, differences between athletes and non-athletes were non-significant. These findings, for the first time, highlight the potential of using microsaccades as an online objective index to study preparatory sets in sports science research.

The use of eye-tracking technology in supporting children and adolescents with attention deficit/hyperactivity disorder: a comprehensive review

MATERIALS AND METHODS

Through the analysis of 74 studies, we examine how eye-tracking technology has been applied to address ADHD-related challenges, the specific methods used, and the correlations between eye-tracking metrics and ADHD symptoms in youth.Results and conclusions: The findings suggest that eye-tracking offers a non-invasive and reliable approach to objectively assess domains such as visual processing characteristics, early detection or interventions. By discussing both the achievements and limitations of the reviewed studies, this paper not only consolidates existing knowledge but also proposes avenues for future research to enhance support for children and adolescents with ADHD.

Effector general representation of movement goals in human frontal and parietal cortex

In the nonhuman primate, discrete parts of premotor frontal and parietal cortex appear to code for movements of different effectors. However, the evidence regarding homologous effector selectivity within the human brain remains inconclusive. Here, we measured neural activity in the human brain using functional magnetic resonance imaging while participants remembered a target location and planned either saccades or reaches that matched the rich kinematics used in seminal monkey studies. We compared activity patterns during the planning period and used assumption-free multivariate searchlight analysis to identify brain regions that could decode the spatial goals of planned movements. Critically, we performed two types of decoding analyses to determine if the spatial information embedded in activation patterns was effector-specific or effector-general. For effector-specific spatial coding, we compared brain regions that could decode target locations within each effector. However, we did not identify areas that coded spatial information in one effector but not the other. For effector-general spatial coding, we performed spatial decoding using trials across effectors and conducted cross-effector decoding. Both analyses identified several areas in the frontal and parietal regions that encoded spatial information for both effectors, including precentral sulcus, superior parietal lobe, and intraparietal sulcus. Our results indicate that premotor frontal and parietal cortex encode the spatial metrics of movement goals that can be read out and converted into effector-specific motor metrics for saccades and reaches.

Driving Factors in the Development of Eye Movement Patterns in Chinese Reading: The Roles of Linguistic Ability and Oculomotor Maturation

The mechanisms driving the development of eye movement patterns is an unresolved debate in children during reading, with three competing hypotheses: the oculomotor-tuning hypothesis, the linguistic-proficiency hypothesis, and the combined hypothesis that incorporates both. This study examined eye movement patterns in 215 Chinese children from first to fifth grade using sentence-reading tasks. Oculomotor maturation was measured through saccade tasks, and linguistic abilities were assessed using Chinese character recognition and vocabulary knowledge tests. Path analysis explored how these factors predict temporal and spatial eye movement measures. Results indicated that temporal measures were primarily driven by linguistic abilities, supporting the linguistic-proficiency hypothesis. Spatial measures, however, were influenced by both linguistic abilities and oculomotor maturation, supporting the combined hypothesis. These findings diverge from predictions of the E-Z Reader model in alphabetic scripts, likely due to the unique visual complexity of Chinese characters.

Rocking the cerebral blood flow: the influence of music listening and aerobic exercise on cortical hemodynamics and post-intervention executive function

A single bout of exercise transiently "boosts" executive function (EF) and is a benefit that may be linked to an increase in cerebral blood flow (CBF). In turn, some work has reported that music listening imparts a similar EF benefit and increases CBF. In the present work, we examined whether music listening provides an EF benefit comparable to aerobic exercise and whether combined music listening and aerobic exercise supports an additive benefit. To that end, healthy young adults (N = 22, 14 female, 19-28 years) completed 10-min single bouts of: (1) music listening (ML), (2) light intensity aerobic exercise (AE), (3) combined ML and AE (ML + AE), and (4) a non-AE and non-ML control condition. For all conditions, pre- and post-intervention EF was assessed via the antisaccade task (i.e., saccade mirror-symmetrical to a target) and transcranial Doppler ultrasound measured middle cerebral artery velocity (MCAv) to estimate CBF. Results showed that ML, AE and ML + AE conditions increased MCAv; however, only the latter two conditions produced a pre- to post-intervention reduction in antisaccade RTs and the benefit was not linked to a MCAv change. Moreover, frequentist and Bayesian statistics indicated that the reduction in antisaccade RTs was equivalent across AE and ML + AE conditions. Accordingly, a single bout of exercise - and not a single bout of music listening - supports a non-additive post-intervention EF benefit that is not related to an exercise-based increase in CBF. Such findings suggest that exercise serves as a simple and cost-effective tool that can "boost" EF in advance of occupational- or educational-demanding tasks.

Hot and cold inhibitory control in bipolar disorder: An antisaccade study of emotion processing and attentional modulation

BACKGROUND

Bipolar disorder (BD) is associated with inhibitory control impairments, but traditional inhibitory control tasks may be confounded by reading ability, which is impaired in some BD patients. Eye-movement tasks assessing antisaccade performance avoid these limitations, but few studies have examined inhibitory control in BD using such tasks, particularly those modulating valence and attention.

METHOD

We used eye-tracking in a sample of 44 euthymic BD patients and 30 controls to measure antisaccade performance on tasks employing emotional "hot" and nonemotional "cold" stimuli. Attentional modulation was examined by comparing performance across step and gap trials.

RESULTS

No significant between-group differences were found in antisaccade error rates or latencies for neutral or emotional stimuli. Both groups performed worse during neutral compared to emotional stimuli. BD patients showed a slight negativity bias, trending toward slower responses to negative compared to positive stimuli. Both groups performed more quickly and accurately during gap compared to step condition.

CONCLUSIONS

These findings suggest that inhibitory control in BD, as measured by antisaccade performance, is influenced by valence and attentional modulation in a similar way to controls. The lack of significant group differences contrasts with previous research, necessitating further investigation into the mechanisms of antisaccade performance in BD.

Genetic and environmental contributions to individual differences in visual attention and oculomotor control in early infancy

Infants differ in their level of eye movement control, which at the extreme could be linked to autism. We assessed eye movements in 450 twins (225 pairs, 57% monozygotic, 46% female, aged 5-6 months) using the gap-overlap eye-tracking task. Shorter latency in the gap condition was associated with having more parent-rated autistic traits at 2 years. Latency across the task's three conditions was primarily explained by one highly heritable latent factor likely representing individual differences in basic oculomotor efficiency and/or in visual information processing. Additionally, disengagement of attention was linked to unique genetic factors, suggesting that genetic factors involved in visual attention are different from those involved in basic visual information processing and oculomotor efficiency.

Saccadometry Findings in Migraine Patients Without Aura

INCLUDING

Migraine without aura is a common neurological disorder associated with structural and functional changes in the brain, which may lead to impairments in cognitive control and motor function. Functional magnetic resonance imaging (fMRI) has demonstrated changes in cortical gray matter volume associated with pain and ocular function in patients with migraine without aura.

OBJECTIVE

This study aims to evaluate prosaccade and antisaccade eye movements in patients with migraine without aura (MWOA) and determine whether the saccadometry test is an effective tool for identifying cognitive control and executive dysfunctions in these individuals.

METHODS

This study included 40 patients diagnosed with migraine without aura (MWOA) and 40 healthy controls. Prosaccade and anti-saccade eye movements were evaluated using a saccadometry test. The evaluation parameters were the latency, velocity, accuracy, overall error percentage, and directional error percentage.

RESULTS

The MWOA group performed worse on antisaccadic tasks compared to the control group. The MWOA group exhibited elevated overall and directional error rates, prolonged latency, and diminished accuracy (p = 0.0001) and velocity (p = 0.001) in comparison to the control group. No significant differences were seen in latency, velocity, and accuracy values for prosaccadic movements (p > 0.05), however general and directional error rates were significantly elevated (p = 0.014).

CONCLUSION

This study shows that migraine patients without aura experience difficulties in cognitive control and executive functions in antisaccadic eye movement tasks. Although prosaccade reflexive eye movements were generally preserved, significant difficulties were found in directional control and error suppression during the task. Our findings emphasize the potential for saccadometry to be an effective tool for assessing these impairments. The results may contribute to the development of more targeted treatment strategies for MWOA patients.

Sub-symptom threshold aerobic exercise improves executive function during the early stage of sport-related concussion recovery

We examined whether persons with a sport-related concussion (SRC) derive a postexercise executive function (EF) benefit, and whether a putative benefit is related to an exercise-mediated increase in cerebral blood flow (CBF). Participants with an SRC completed the Buffalo Concussion Bike Test to determine the heart rate threshold (HRt) associated with symptom exacerbation and/or voluntary exhaustion. On a separate day, SRC participants - and healthy controls (HC group) - completed 20-min of aerobic exercise at 80% HRt while middle cerebral artery velocity (MCAv) was measured to estimate CBF. The antisaccade task (i.e. saccade mirror-symmetrical to target) was completed pre- and postexercise to evaluate EF. SRC and HC groups showed a comparable exercise-mediated increase in CBF (ps < .001), and both groups elicited a postexercise EF benefit (ps < .001); however, the benefit was unrelated to the magnitude of the MCAv change. Moreover, SRC symptomology was not increased when assessed immediately postexercise and showed a 24 h follow-up benefit. Accordingly, persons with an SRC demonstrated an EF benefit following a single bout of sub-symptom threshold aerobic exercise. Moreover, the exercise intervention did not result in symptom exacerbation and thus demonstrates that a tailored aerobic exercise program may support cognitive and symptom recovery following an SRC.

Motor decision-making under uncertainty and time pressure

Purposeful movement often requires selection of a particular action from a range of alternatives, but how does the brain represent potential actions so that they can be compared for selection, and how are motor commands generated if movement is initiated before the final goal is identified? According to one hypothesis, the brain averages partially prepared motor plans to generate movement when there is goal uncertainty. This is consistent with the idea that motor decision-making unfolds through competition between internal representations of alternative actions. An alternative hypothesis holds that only one movement, which is optimized for task performance, is prepared for execution at any time. Under this conception, decisions about the best motor goal given current information are completed upstream from neural circuits that perform motor planning. To distinguish between these hypotheses, we modified an experiment (Alhussein L, Smith MA. eLife 10: e67019, 2021) in which participants had to start reaching toward targets associated with opposite curl force fields before knowing the correct target to reach. Crucially, we forced the participants to initiate movement immediately after target presentation (i.e., mean reaction times ∼250 ms) so that they had limited opportunity to deliberate between the available alternatives. We found that the reaching dynamics reflected only those learned for the selected reach direction, rather than a combination of those for the alternative targets presented, irrespective of the time available to initiate movement. The data are consistent with the conclusion that reaching dynamics were specified downstream of action selection under the target uncertainty conditions of this study.NEW & NOTEWORTHY Here we found no evidence of "motor averaging" of reach dynamics for multiple potential actions when people had to respond as quickly as possible to uncertain target location cues. People exerted forces appropriate for the specific reach direction they selected irrespective of movement initiation time, suggesting that reaching dynamics were specified downstream of action selection.

Neural Correlates of Proactive and Reactive Control Investigated Using a Novel Precued Antisaccade Paradigm

This ERP study investigated the neural correlates of proactive and reactive control using a novel precued antisaccade paradigm. Proactive control refers to preparatory processes during anticipation of a behaviorally relevant event; reactive control is activated after such an event to ensure goal attainment. A 64-channel EEG was obtained in 35 healthy subjects; video-based eye tracking was applied for ocular recording. In the task, a target (probe) appeared left or right of the fixation point 1800 ms after a central cue; subjects had to look toward the probe (prosaccade) or its mirror image position (antisaccade). Probes were positive, negative or neutral face expressions, with their frame colors instructing task requirements. The cue informed about antisaccade probability (70% vs. 30%) in each trial. High antisaccade probability was associated with larger CNV amplitude than low antisaccade probability. In trials with incongruence between expected and actual task requirements, probe N2 and P3a amplitudes were larger than in congruent trials. In incongruent trials, P3a was smaller for negative than positive and neutral probes. Task accuracy and speed were lower in incongruent trials and varied according to affective probe valence. EEG source imaging suggested the origin of the ERPs to be in orbitofrontal cortex and superior frontal gyrus. The effect on the CNV indicates greater cortical activity during higher proactive control demands. Larger N2 and P3a in incongruent trials reflect greater resource allocation to conflict monitoring and conflict resolution, i.e., reactive control. The influence of probe valence on P3a suggests reduced processing capacity due to negative information.

Distinct role of primate DLPFC and LIP in hierarchical control of learned saccade sequences

Learned action sequences are suggested to be organized hierarchically, but how the various hierarchical levels are processed by different cortical regions remains largely unknown. By training monkeys to perform heterogeneous saccade sequences, we investigated the role of the dorsolateral prefrontal cortex (DLPFC) and the lateral intraparietal cortex (LIP) in sequence planning and execution. The electrophysiological recording revealed that sequence-level initiation information was mostly signaled by DLPFC neurons, whereas subsequence-level transition was largely encoded by LIP neurons. Although electrical microstimulation on DLPFC weakly affected sequence performance, inactivating DLPFC significantly increased the initiation latency of the entire sequences, indicating that DLPFC was involved in the sequence initiation. In contrast, either microstimulation or inactivation of area LIP caused improper switches between subsequences, suggesting that LIP played a role in subsequence switch. Overall, these results demonstrated that frontal and parietal cortices play distinct yet complementary roles in controlling learned saccade sequences.

Frontoparietal activity related to neuropsychological assessment of working memory

Executive functions, including working memory, are typically assessed clinically with neuropsychological instruments. In contrast, computerized tasks are used to test these cognitive functions in laboratory human and animal studies. Little is known of how neural activity captured by laboratory tasks relates to ability measured by clinical instruments and, by extension, clinical diagnoses of pathological conditions. We therefore sought to determine what aspects of neural activity elicited in laboratory tasks are predictive of performance in neuropsychological instruments. We recorded neural activity from intracranial electrodes implanted in human epilepsy patients as they performed laboratory working memory tasks. These patients had completed neuropsychological instruments preoperatively, including the Weschler Adult Intelligent Scale and the Wisconsin Card Sorting test. Our results revealed that increased high-gamma (70-150 Hz) power in the prefrontal and parietal cortex after presentation of visual stimuli to be remembered was indicative of lower performance in the neuropsychological tasks. On the other hand, we observed a positive correlation between high-frequency power amplitude in the delay period of the laboratory tasks and neuropsychological performance. Our results demonstrate how neural activity around task events relates to executive function and may be associated with clinical diagnosis of specific cognitive deficits.

The inhibitory control deficit of internet gaming disorder: An Event-Related Potentials(ERPs) study

INTRODUCTION

The primary difficulty and challenge encountered by individuals with Internet Gaming Disorder (IGD) is inhibitory control deficit. Given that different types of inhibitory control have different effects on IGD patients, it is critical to investigate the neurological cognitive processes underlying various inhibitory control problems.

METHODS

The IGD-20 questionnaire was used to identify Internet game disorder and healthy control group, and finally Internet game disorder in (n=25) and healthy control group (n=28) in Flanker task, Internet game disorder (n=29) and health control group (n=24) in GO/NOGO task. The Flanker task was employed to investigate distractor interference inhibition control in those with IGD, while the Go/NoGo task was used to measure their prepotent response inhibitory control. Event-related potentials (ERPs) were used to evaluate the brain mechanisms difference of both IGD and healthy participants during these different inhibitory control tasks.

RESULTS

Findings indicate that compared to healthy control subjects, individuals with Internet Gaming Disorder (IGD) have deficits in inhibitory control tasks during both distraction inhibition and prepotent response inhibition tasks, and distraction inhibition occurs earlier than prepotent response inhibition. In distraction inhibition tasks, the IGD group's N2 amplitude is significantly lower than the healthy control groups. In prepotent response inhibition, the N2 amplitude provoked in the IGD group is not only significantly lower than in the healthy control group, but the P3 amplitude is also significantly larger in the IGD group. The main brain activity areas of interference inhibitory control are the frontal lobe and prefrontal lobe, while the main brain activity areas of prepotent response inhibitory control are the frontal lobe and occipital lobe.

CONCLUSION

The present study concentrates on the differential neurophysiological characteristics observed in individuals with Internet gaming problems, notably the ability to avoid distractions and prepotent reactions. The current research provides foundations for the assessment and development of tailored therapy and treatment methods to address the wide variety of cognitive problems reported in individuals with Internet Gaming Disorder (IGD).

Better than expected performance effect depends on the spatial location of visual stimulus

The process of perceptual decision-making in the real world involves the aggregation of pieces of evidence into a final choice. Visual evidence is usually presented in different pieces, distributed across time and space. We wondered whether adding variation in the location of the received information would lead to differences in how subjects integrated visual information. Seven participants viewed two pulses of random dot motion stimulus, separated by time gaps and presented at different locations within the visual field. Our findings suggest that subjects accumulate discontinuous information (over space or time) differently than when it is presented continuously, in the same location or with no gaps between them. These findings indicate that the discontinuity of evidence impacts the process of evidence integration in a manner more nuanced than that presumed by the theory positing perfect integration of evidence.

Event-related potentials and presaccadic activity in response to affective stimuli in participants with obsessive-compulsive disorder

Individuals with obsessive-compulsive disorder (OCD) have difficulty with regulating their emotions and show reduced functioning of inhibitory control. It was reported previously that OCD patients had delayed antisaccade response and increased error rate only when affective pictures with negative valence served as fixation stimuli in "the antisaccade emotional fixation task". Complementary to the previous research, eye movements and late positive potential (LPP) for fixation stimuli and the presaccadic positivity (PSP) and spike potential (SP) before saccade onset, were compared in two groups of OCD and healthy volunteers. Both groups exhibited increased fixation on emotional images, particularly on unpleasant ones, and showed heightened LPP responses without significant between-group differences. However, individuals with OCD had lower PSP and SP amplitudes for unpleasant images compared to the control group, although there were no differences within conditions for each group. These results suggest that while both groups displayed similar effects of unpleasant images on the involuntary orientation of attention, the findings on presaccadic potentials correlate with behavioral data on increased error rate in antisaccade tasks in OCD. This suggests that emotional dysregulation may contribute to impaired inhibitory control in individuals with OCD.

Is covert attention necessary for programming accurate saccades? Evidence from saccade-locked event-related potentials

For decades, researchers have assumed that shifts of covert attention mandatorily occur prior to eye movements to improve perceptual processing of objects before they are fixated. However, recent research suggests that the N2pc component-a neural measure of covert attentional allocation-does not always precede eye movements. The current study investigated whether the N2pc component mandatorily precedes eye movements and assessed its role in the accuracy of gaze control. In three experiments, participants searched for a letter of a specific color (e.g., red) and directed gaze to it as a response. Electroencephalograms and eye movements were coregistered to determine whether neural markers of covert attention preceded the initial shift of gaze. The results showed that the presaccadic N2pc only occurred under limited conditions: when there were many potential target locations and distractors. Crucially, there was no evidence that the presence or magnitude of the presaccadic N2pc was associated with improved eye movement accuracy in any of the experiments. Interestingly, ERP decoding analyses were able to classify the target location well before the eyes started to move, which likely reflects a presaccadic cognitive process that is distinct from the attentional process measured by the N2pc. Ultimately, we conclude that the covert attentional mechanism indexed by the N2pc is not necessary for precise gaze control.

Unexpected sounds induce a rapid inhibition of eye-movement responses

Unexpected sounds have been shown to trigger a global and transient inhibition of motor responses. Recent evidence suggests that eye movements may also be inhibited in a similar way, but it is not clear how quickly unexpected sounds can affect eye-movement responses. Additionally, little is known about whether they affect only voluntary saccades or also reflexive saccades. In this study, participants performed a pro-saccade and an anti-saccade task while the timing of sounds relative to stimulus onset was manipulated. Pro-saccades are generally reflexive and stimulus-driven, whereas anti-saccades require the generation of a voluntary saccade in the opposite direction of a peripheral stimulus. Unexpected novel sounds inhibited the execution of both pro- and anti-saccades compared to standard sounds, but the inhibition was stronger for anti-saccades. Novel sounds affected response latencies as early as 150 ms before the peripheral cue to make a saccade, all the way to 25 ms after the cue to make a saccade. Interestingly, unexpected sounds also reduced anti-saccade task errors, indicating that they aided inhibitory control. Overall, these results suggest that unexpected sounds yield a global and rapid inhibition of eye-movement responses. This inhibition also helps suppress reflexive eye-movement responses in favor of more voluntarily generated ones.

The impact of the degree of action voluntariness on sense of agency in saccades

Experiencing a sense of agency (SoA), the feeling of being in control over one's actions and their outcomes, typically requires intentional and voluntary actions. Prior research has compared the association of voluntary versus completely involuntary actions with the SoA. Here, we leveraged unique characteristics of oculomotor actions to partially manipulate the degree of action voluntariness. Participants performed either highly automatized prosaccades or highly controlled (voluntary) anti-saccades, triggering a gaze-contingent visual action effect. We assessed explicit SoA ratings and temporal action and effect binding as an implicit SoA measure. Anti-saccades were associated with stronger action binding compared to prosaccades, demonstrating a robust association between higher action voluntariness and a stronger implicit sense of action agency. We conclude that our manipulation of action voluntariness may have impacted the implicit phenomenological feeling of bodily agency, but it did not affect the SoA over effect outcomes or explicit agency perception.

Multimodal oculomotor assessment reveals prodromal markers of Parkinson's disease in non-manifesting LRRK2 G2019S mutation carriers

Oculomotor behaviour changes in patients with Parkinson's disease (PD) are a promising source of prodromal disease markers. Capitalizing on this phenomenon to facilitate early diagnosis requires oculomotor assessment in prodromal cohorts. We examined oculomotor behaviour in non-manifesting LRRK2 G2019S mutation carriers (LRRK2-NM), who have heightened PD risk.Seventeen LRRK2-NM participants, 47 patients with idiopathic PD, and 63 healthy age-matched control participants completed an interleaved pro- and antisaccade task while undergoing video-based eye-tracking. We analyzed between-group differences in saccade, pupil, blink, and fixation acquisition behaviour. Patients with PD showed previously demonstrated abnormalities (saccade hypometria, antisaccade errors). Relative to controls, LRRK2-NM participants and patients with PD both displayed increased short-latency prosaccades and reduced pupil velocity, plus altered fixation acquisition-less preemptive returning of gaze to the future fixation point location. Interestingly, the effect on blink probability was opposite-higher than controls in LRRK2-NM participants but lower in patients with PD. Future longitudinal studies must confirm the viability of these features as prodromal PD markers.

Passive and active exercise do not mitigate mental fatigue during a sustained vigilance task

Executive function (EF) is improved following a single bout of exercise and impaired when an individual experiences mental fatigue (MF). These performance outcomes have been linked to a bi-directional change in cerebral blood flow (CBF). Here, we sought to determine whether MF-induced by a sustained vigilance task (i.e., psychomotor vigilance task: PVT) is mitigated when preceded by a single bout of exercise. Participants completed 20-min single bouts of active exercise (cycle ergometry involving volitional muscle activation), passive exercise (cycle ergometry involving a mechanical flywheel) and a non-exercise control intervention. EF was assessed pre- and post-intervention via the antisaccade task. Following each intervention, a 20-min PVT was completed to induce and assess MF, and transcranial Doppler ultrasound of middle cerebral artery velocity (MCAv) was used to estimate intervention- and PVT-based changes in CBF. Active and passive exercise provided a post-intervention reduction in antisaccade reaction times; that is, exercise benefitted EF. Notably, however, frequentist and Bayesian statistics indicated the EF benefit did not mitigate MF during the PVT. As well, although exercise (active and passive) and the PVT respectively increased and decreased CBF, these changes were not correlated with behavioral measures of EF or MF. Accordingly, a postexercise EF benefit does not mitigate MF during a sustained vigilance task and a bi-directional change in CBF does not serve as a primary mechanism associated with EF and MF changes. Such results provide a framework for future work to explore how different exercise types, intensities and durations may impact MF.

Fixational eye movements and their associated evoked potentials during natural vision are altered in schizophrenia

Background

Visual exploration is abnormal in schizophrenia; however, few studies have investigated the physiological responses during selecting objectives in more ecological scenarios. This study aimed to demonstrate that people with schizophrenia have difficulties observing the prominent elements of an image due to a deficit mechanism of sensory modulation (active sensing) during natural vision.

Methods

An electroencephalogram recording with eye tracking data was collected on 18 healthy individuals and 18 people affected by schizophrenia while looking at natural images. These had a prominent color element and blinking produced by changes in image luminance.

Results

We found fewer fixations when all images were scanned, late focus on prominent image areas, decreased amplitude in the eye-fixation-related potential, and decreased intertrial coherence in the SCZ group.

Conclusions

The decrease in the visual attention response evoked by the prominence of visual stimuli in patients affected by schizophrenia is generated by a reduction in endogenous attention mechanisms to initiate and maintain visual exploration. Further work is required to explain the relationship of this decrease with clinical indicators.

Saccade Dynamics in the Acute and Recovery Phase of Abducens Nerve Palsy

Purpose

To examine the natural adaptive course of ocular motor system in unilateral abducens nerve palsy while addressing the scarce literature on saccade dynamics and natural adaptation.

Methods

Binocular horizontal eye movements were recorded from 18 healthy adults and 21 adults with unilateral abducens nerve palsy during the acute and chronic phases. Dynamics of the paretic and non-paretic eyes were compared, and the non-paretic eye dynamics were correlated with the respective prism diopters. Non-parametric tests were used for statistical comparisons.

Results

The paretic eye, compared to the non-paretic eye, presented a slightly lower saccadic gain and velocity/amplitude ratio and a higher duration/amplitude ratio. The non-paretic eye, compared to healthy controls, showed consistent amplitude gain ( > 1) and a tendency for a higher duration/amplitude ratio. In the acute phase, when the non-paretic eye was covered, the paretic eye's amplitude ratio was lower and the duration/amplitude ratio decreased significantly. In the acute phase, a greater degree of esotropia in the paretic eye was associated with a lower amplitude gain and duration/amplitude ratio in the non-paretic eye.

Conclusion

During adaptation in abducens nerve palsy, the saccade duration of the paretic eye increased, and a similar tendency was observed in the non-paretic eye. This finding likely reflects a change in the "pulse-step" pattern and may be related to plastic changes in central structures, such as the cerebellum, that support learning processes.

Individual differences in attention control: A meta-analysis and re-analysis of latent variable studies

A meta-analysis and re-analysis of prior latent variable studies was conducted in order to assess whether there is evidence for individual differences in broad attention control abilities. Data from 90 independent samples and over 23,000 participants suggested that most (84.4%) prior studies find evidence for a coherent attention control factor with average factor loadings of .51. This latent attention control factor was related to other cognitive ability factors including working memory, shifting, fluid intelligence, long-term memory, reading comprehension, and processing speed, as well as to self-reports of task-unrelated thoughts and task specific motivation. Further re-analyses and meta-analyses suggest that the results remained largely unchanged when considering various possible measurement issues. Examining the factor structure of attention control suggested evidence for sub-components of attention control (restraining, constraining and sustaining attention) which could be accounted for a by a higher-order factor. Additional re-analyses suggested that attention control represents a broad ability within models of cognitive abilities. Overall, these results provide evidence for attention control abilities as an important individual differences construct.

Concurrent oculomotor hyperactivity and deficient anti-saccade performance in obsessive-compulsive disorder

Existing studies mainly focused on the inhibition of the task-interfering response to understand the inhibitory deficits of obsessive-compulsive disorder (OCD). However, recent studies suggested that inhibitory function is broadly involved in response preparation and implementation. It is yet unknown if the inhibition dysfunction in OCD extends beyond the task-interfering response to the general inhibitory function. Here we address this issue based on the multidimensional eye-movement measurements, which can better capture the inhibitory deficits than manual responses. Thirty-one OCD patients and 32 healthy controls (HCs) completed the anti-saccade task where multidimensional eye-movement features were developed. Confirmatory factor analysis (CFA) suggested two components of inhibitory function that negatively correlated with each other: one component of oculomotor hyperactivity in generating oculomotor output which is characterized with early premature saccades, early cross rates and saccade number; the other component of task-specific oculomotor efficiency which is characterized with task accuracy, saccade latency, correction rate, and amplitude gain. Importantly, OCD showed both stronger oculomotor hyperactivity and deficient oculomotor efficiency than HCs, and the machine-learning-based classifications showed that the features of oculomotor hyperactivity had higher prediction accuracy than the features of oculomotor efficiency in distinguishing OCD from HCs. Our results suggested that OCD has concurrent deficits in oculomotor hyperactivity and oculomotor efficiency, which may originate from a common inhibitory dysfunction.

How Does the Presence of Others Influence Control Inhibition? Contradictory Evidence Using an Antisaccade and Stop Signal Task

Inhibitory control (IC) is defined as the (in)ability to change, suppress, or delay a response that is no longer required under the current circumstances. This ability was previously argued to increase in social contexts, based on Stroop's performance, showing that participants performed the Stroop task better in others' presence than alone. In this paper, we extend the testing of this same hypothesis to the use of two other tasks that Mitake et al. (2000) show to grasp the same IC ability; the Antisaccade and Stop signal tasks. If Stroop's performance was capturing the impact of the presence of others on CI abilities, the effect would generalize to performance on these tasks. This hypothesis was only generally supported by stop signal task performance; those in the presence condition were significantly more efficient than those in the alone conditions. For the Antisaccade tasks, evidence shows that higher levels of interference occurs in the presence of others condition for participants' fastest responses We discuss how this evidence contributes to the literature suggesting that the two tasks may index different constructs.

Age-related changes in pupil dynamics and task modulation across the healthy lifespan

The pupil is modulated by luminance, arousal, bottom-up sensory, and top-down cognitive signals, and has increasingly been used to assess these aspects of brain functioning in health and disease. However, changes in pupil dynamics across the lifespan have not been extensively examined, hindering our ability to fully utilize the pupil in probing these underlying neural processes in development and aging in healthy and clinical cohorts. Here, we examined pupil responses during the interleaved pro-/anti-saccade task (IPAST) in healthy participants across the lifespan (n = 567, 5-93 years of age). Based on the extracted measurements of pupil dynamics, we demonstrated age-related changes in pupil measures and task modulation. Moreover, we characterized the underlying factors and age-related effects in components of pupil responses that may be attributed to developmental and aging changes in the associated brain regions. Finally, correlations between factors of pupil dynamics and saccade behaviors revealed evidence of shared neural processes in the pupil and saccade control circuitries. Together, these results demonstrate changes in pupil dynamics as a result of development and aging, providing a baseline with which altered pupil responses due to neurological deficits at different ages can be studied.

Dynamics of Saccade Trajectory Modulation by Distractors: Neural Activity Patterns in the Frontal Eye Field

The sudden appearance of a visual distractor shortly before saccade initiation can capture spatial attention and modulate the saccade trajectory in spite of the ongoing execution of the initial plan to shift gaze straight to the saccade target. To elucidate the neural correlates underlying these curved saccades, we recorded from single neurons in the frontal eye field of two male rhesus monkeys shifting gaze to a target while a distractor with the same eccentricity appeared either left or right of the target at various delays after target presentation. We found that the population level of presaccadic activity of neurons representing the distractor location encoded the direction of the saccade trajectory. Stronger activity occurred when saccades curved toward the distractor, and weaker when saccades curved away. This relationship held whether the distractor was ipsilateral or contralateral to the recorded neurons. Meanwhile, visually responsive neurons showed asymmetrical patterns of excitatory responses that varied with the location of the distractor and the duration of distractor processing relating to attentional capture and distractor inhibition. During earlier distractor processing, neurons encoded curvature toward the distractor. During later distractor processing, neurons encoded curvature away from the distractor. This was observed when saccades curved away from distractors contralateral to the recording site and when saccades curved toward distractors ipsilateral to the recording site. These findings indicate that saccadic motor planning involves dynamic push-pull hemispheric interactions producing attraction or repulsion for potential but unselected saccade targets.

Compensatory mechanisms amidst demyelinating disorders: insights into cognitive preservation

Demyelination disrupts the transmission of electrical signals in the brain and affects neurodevelopment in children with disorders such as multiple sclerosis and myelin oligodendrocyte glycoprotein-associated disorders. Although cognitive impairments are prevalent in these conditions, some children maintain cognitive function despite substantial structural injury. These findings raise an important question: in addition to the degenerative process, do compensatory neural mechanisms exist to mitigate the effects of myelin loss? We propose that a multi-dimensional approach integrating multiple neuroimaging modalities, including diffusion tensor imaging, magnetoencephalography and eye-tracking, is key to investigating this question. We examine the structural and functional connectivity of the default mode and executive control networks due to their significant roles in supporting higher-order cognitive processes. As cognitive proxies, we examine saccade reaction times and direction errors during an interleaved pro- (eye movement towards a target) and anti-saccade (eye movement away from a target) task. 28 typically developing children, 18 children with multiple sclerosis and 14 children with myelin oligodendrocyte glycoprotein-associated disorders between 5 and 18.9 years old were scanned at the Hospital for Sick Children. Tractography of diffusion MRI data examined structural connectivity. Intracellular and extracellular microstructural parameters were extracted using a white matter tract integrity model to provide specific inferences on myelin and axon structure. Magnetoencephalography scanning was conducted to examine functional connectivity. Within groups, participants had longer saccade reaction times and greater direction errors on the anti- versus pro-saccade task; there were no group differences on either task. Despite similar behavioural performance, children with demyelinating disorders had significant structural compromise and lower bilateral high gamma, higher left-hemisphere theta and higher right-hemisphere alpha synchrony relative to typically developing children. Children diagnosed with multiple sclerosis had greater structural compromise relative to children with myelin oligodendrocyte glycoprotein-associated disorders; there were no group differences in neural synchrony. For both patient groups, increased disease disability predicted greater structural compromise, which predicted longer saccade reaction times and greater direction errors on both tasks. Structural compromise also predicted increased functional connectivity, highlighting potential adaptive functional reorganisation in response to structural compromise. In turn, increased functional connectivity predicted faster saccade reaction times and fewer direction errors. These findings suggest that increased functional connectivity, indicated by increased alpha and theta synchrony, may be necessary to compensate for structural compromise and preserve cognitive abilities. Further understanding these compensatory neural mechanisms could pave the way for the development of targeted therapeutic interventions aimed at enhancing these mechanisms, ultimately improving cognitive outcomes for affected individuals.

Oculomotor functional connectivity associated with motor sequence learning

Acquisition of learned motor sequences involves saccades directed toward the goal to gather visual information prior to reaching. While goal-directed actions involve both eye and hand movements, the role of brain areas controlling saccades during motor sequence learning is still unclear. This study aimed to determine whether resting-state functional connectivity of oculomotor regions is associated with behavioral changes resulting from motor sequence learning. We investigated connectivity between oculomotor control regions and candidate regions involved in oculomotor control and motor sequence learning. Twenty adults had brain scans before 3 days of motor task practice and after a 24-hour retention test, which was used to assess sequence-specific learning. During testing, both saccades and reaches were tracked. Stronger connectivity in multiple oculomotor regions prior to motor task practice correlated with greater sequence-specific learning for both saccades and reaches. A more negative connectivity change involving oculomotor regions from pre- to post-training correlated with greater sequence-specific learning for both saccades and reaches. Overall, oculomotor functional connectivity was associated with the magnitude of behavioral change resulting from motor sequence learning, providing insight into the function of the oculomotor system during motor sequence learning.

Impairment of Visual Fixation and Preparatory Saccade Control in Borderline Personality Disorder With and Without Comorbid Attention-Deficit/Hyperactivity Disorder

BACKGROUND

Borderline personality disorder (BPD) is associated with heightened impulsivity, evidenced by increased substance abuse, self-harm, and suicide attempts. Addressing impulsivity in individuals with BPD is a therapeutic objective, but its underlying neural basis in this clinical population remains unclear, partly due to its frequent comorbidity with attention-deficit/hyperactivity disorder (ADHD).

METHODS

We used a response inhibition paradigm-the interleaved pro-/antisaccade task-among adolescents diagnosed with BPD with and without comorbid ADHD (n = 25 and n = 24, respectively) during concomitant video-based eye tracking. We quantified various eye movement response parameters reflective of impulsive action during the task, including delay to fixation acquisition, fixation breaks, anticipatory saccades, and direction errors with express saccade (saccade reaction time: 90-140 ms) and regular saccade latencies (saccade reaction time > 140 ms).

RESULTS

Individuals with BPD exhibited deficient response preparation, as evidenced by reduced visual fixation on task cues and greater variability of saccade responses (i.e., saccade reaction time and peak velocity). The ADHD/BPD group shared these traits and made more anticipatory responses and direction errors with express saccade latencies and reduced error correction.

CONCLUSIONS

Saccadic deficits in BPD and ADHD/BPD stemmed not from an inability to execute antisaccades but rather from inadequate preparation for the upcoming task set. These distinctions may arise due to abnormal signaling in cortical areas like the frontal eye fields, posterior parietal cortex, and anterior cingulate cortex. Understanding these mechanisms could provide insights into targeted interventions focusing on task set preparation to manage response inhibition deficits in BPD and ADHD/BPD.

Changes in saccadic intrusions over time as an objective biomarker to follow ALS disease progression

Objective: Saccadic Intrusions (SIs) are abnormal eye movements during gaze fixation. Studies have indicated the clinical relevance of SIs, especially of square wave jerks (SWJ) in ALS. We used a software-based platform to extract SIs as a part of an interventional drug trial. The objective was to examine SIs' change over time as a potential biomarker of ALS disease progression. Methods: 28 ALS patients (61.95 ± 8.6 years) were assessed with the revised ALS Functional Rating Scale (ALSFRS-R) and with an oculometric test. Changes of SIs over time and correlations with ALSFRS-R and its bulbar subscale were calculated. A power calculation was conducted to understand the practical implications of results. Results: A significant increase of SWJ over trial duration was observed, with an increase in frequency (mean rise of 0.14 ± 0.28, p < 0.01), amplitude (0.001 ± 0.0016 degrees, p < 0.005), overall duration of SWJ (0.13 ± 0.25, in %, p < 0.01), and in their relative part out of all intrusions (0.18 ± 0.32, in %, p < 0.005). Negative correlations were found with the bulbar subscale (R=-0.43, -0.41, -0.39 and -0.47, respectively, p < 0.001). The required sample size for observing a 40% reduction in bulbar aspects when using the oculometric test (α = 0.05 and β = 0.8), was found to be 150 patients per arm, compared with 200 patients using the bulbar subscale. Conclusions: Evaluation of saccadic intrusions during fixation was able to detect disease progression over time, correlated with ALSFRS-R bulbar subscale. Eye movements can potentially serve as an objective biomarker in ALS clinical trials and reduce the required sample size to show clinical effect of therapies.

Diagnosis of schizophrenia by integrated saccade scores and associations with psychiatric symptoms, and functioning

Eye movement as a neurobiological biomarker of schizophrenia. We aim to estimate diagnostic accuracy of integrated pro/antisaccade eye movement measurements to discriminate between healthy individuals and schizophrenic patients. We compared the eye movement performance of 85 healthy individuals and 116 schizophrenia-stable patients during prosaccade and antisaccade tasks. The difference eye movement measurements were accumulated by stepwise discriminant analysis to produce an integrated score. Finally, the diagnostic value of the integrated score was calculated by the receiver operating characteristic (ROC) area under the curve (AUC), and the best sensitivity and specificity were calculated based on the given cutoff values. Using discriminant analysis, an integrated score included the residual gain and latency (step) during the prosaccade test, the error rate, and the corrected error rate during the antisaccade test. We found that the integrated score could well classify schizophrenia patients and healthy individuals with an accuracy of 80.6%. In the ROC, Youden's index was 0.634 (sensitivity = 81.0%, specificity = 82.4%) and AUC was 0.871. There were significant difference patterns of correlation between the severity of psychiatric symptoms and daily functioning and diagnostic eye movement measurements. Using only 2 saccade tasks to discriminate well between schizophrenia patients and healthy controls, suggesting that abnormalities in saccade behavior is a potential biomarker and efficient diagnostic tool for identifying schizophrenia. The underlying neuropathologic mechanisms associated with abnormal saccades may provide insights into the intervention and diagnosis of schizophrenia.

Development and validation of metrics for assessment of ultrasound-guided fascial block skills☆

BACKGROUND

As few anaesthetists provide lumbar erector spinae block for disc surgery, there is a need to provide training to enable a randomised controlled trial investigating analgesia after painful spinal surgery (NIHR153170). The primary objective of the study was to develop and measure the construct validity of a checklist for assessment of skills in performing lumbar and thoracic erector spinae fascial plane injection using soft-embalmed Thiel cadavers.

METHODS

Twenty-four UK consultant regional anaesthetists completed two iterations of a Delphi questionnaire. The final checklist consisted of 11 steps conducive to best practice. Thereafter, we validated the checklist by comparing the performance of 12 experts with 12 novices, each performing lumbar and thoracic erector spinae plane injections or fascia iliaca, serrato-pectoral (PEC II) and serratus injections, randomly allocated to the left and right sides of six soft-embalmed Thiel cadavers. Six expert, trained raters blinded to operator and site of block examined 120 videos each.

RESULTS

The mean (95% confidence interval) internal consistency of the 11-item checklist for erector spinae plane injection was 0.72 (0.63-0.79) and interclass correlation was 0.88 (0.82-0.93). The checklist showed construct validity for lumbar and thoracic erector spinae injection, experts vs novices {median (interquartile range [range]) 8.0 (7.0-10.0 [1-11]) vs 7.0 (5.0-9.0 [4-11]), difference 1.5 (1.0-2.5), P<0.001}. Global rating scales showed construct validity for lumbar and thoracic erector spinae injection, 28.0 (24.0-31.0 [7-35]) vs 21.0 (17.0-24.0 [7-35]), difference 7.5 (6.0-8.5), P<0.001. The most difficult items to perform were identifying the needle tip before advancing and always visualising the needle tip. Instrument handling and flow of procedure were the areas of greatest difficulty on the global rating scale (GRS). Checklists and GRS scores correlated. There was homogeneity of regression slopes controlling for status, type of injection, and rater. Generalisability analysis showed a high reliability using the checklist and GRS for all fascial plane blocks (Rho [ρ2] 0.93-0.96: Phi [ϕ] 0.84-0.87).

CONCLUSIONS

An 11-point checklist developed through a modified Delphi process to provide best practice guidance for fascial plane injection showed construct validity in performing lumbar and thoracic erector spinae fascial plane injection in soft-embalmed Thiel cadavers.

Aberrant inhibitory control as a transdiagnostic dimension of mental disorders - A meta-analysis of the antisaccade task in different psychiatric populations

This meta-analysis examined inhibitory control performance in the antisaccade task across mental disorders. Following PRISMA guidelines, we analyzed data from k = 146 studies (n = 13,807 participants) on antisaccade performance. Effect sizes were estimated using random-effects models and restricted maximum-likelihood estimation, with robustness tests for study heterogeneity and publication bias. Most disorders displayed elevated error rates, with schizophrenia showing the greatest impairments, followed by autism spectrum disorder, bipolar disorder and attention deficit hyperactivity disorder. Small to medium impairments were also found in eating disorders, major depressive disorder, obsessive-compulsive disorder and substance use disorder. Results were robust against corrections for publication bias and largely unaffected by confounding variables. Prolonged latencies were observed in schizophrenia, attention deficit hyperactivity disorder, bipolar disorder and obsessive compulsive disorder, with smaller and less robust effect sizes. Results indicate inhibitory control deficits in the antisaccade task across mental disorders, especially evident for error rates. While present in most disorders, results imply varying degrees of impairments, ranging from small to large in effect sizes, with largest impairments in schizophrenia.

Study of Eye Movements Abnormalities in Epilepsy

Idiopathic epilepsy (IE), is a group of epileptic syndromes with no structural brain lesion, but with microstructural changes in neuronal networks leading to neuropsychological consequences. Therefore, the assessment of saccadic eye movements can provide insight into the integrity of cerebral networks as it involves large cortical and subcortical brain areas and circuitries. Describe saccadic eye movement abnormalities in patients with IE and correlate them with disease characteristics and antiseizure medication. Case-control study including IE patients followed in the Neurology Department of Razi University Hospital and healthy controls matched. Participants underwent a recording of saccadic eye movements. Pursuit, prosaccade, and anti-saccade tasks were performed. 115 patients and 98 matched healthy controls were included. The gender ratio (male to female) was 0.6. The mean age at onset was 16.3 ± 12 years. Diagnosed epileptic syndromes were juvenile myoclonic epilepsy (JME), epilepsy with generalized tonic-clonic seizures, childhood absence epilepsy, temporal lobe epilepsy, frontal lobe epilepsy, and rolandic epilepsy. Saccadic eye movements were impaired in 52.2% of our patients and significantly more altered in those with JME (p = .021). Prolonged horizontal saccades latencies were the most frequent eye movement abnormalities (32.1%), followed by altered horizontal smooth pursuit (22.6%). A positive correlation was found between age at eye movements recording, age at onset, disease duration, global cognitive impairment, and saccadic eye movements. However, no definite relationship was identified. Saccadic eye movement illustrates extending anatomic alterations in IE including frontal and temporoparietal cortical areas and cortico-subcortical circuits. Eye movement recording is a useful and reproducible tool in the assessment of epileptic patients and provides a better understanding of neuronal mechanisms in epilepsy.

Noradrenergic modulation of saccades in Parkinson's disease

Noradrenaline is a powerful modulator of cognitive processes, including action decisions underlying saccadic control. Changes in saccadic eye movements are common across neurodegenerative diseases of ageing, including Parkinson's disease. With growing interest in noradrenergic treatment potential for non-motor symptoms in Parkinson's disease, the temporal precision of oculomotor function is advantageous to assess the effects of this modulation. Here, we studied the effect of 40 mg atomoxetine, a noradrenaline reuptake inhibitor, in 19 people with idiopathic Parkinson's disease using a single dose, randomized double-blind, crossover, placebo-controlled design. Twenty-five healthy adult participants completed the assessments to provide normative data. Participants performed prosaccade and antisaccade tasks. The latency, velocity and accuracy of saccades, and resting pupil diameter, were measured. Increased pupil diameter on the drug confirmed its expected effect on the locus coeruleus ascending arousal system. Atomoxetine altered key aspects of saccade performance: prosaccade latencies were faster and the saccadic main sequence was normalized. These changes were accompanied by increased antisaccade error rates on the drug. Together, these findings suggest a shift in the speed-accuracy trade-off for visuomotor decisions in response to noradrenergic treatment. Our results provide new evidence to substantiate a role for noradrenergic modulation of saccades, and based on known circuitry, we advance the hypothesis that this reflects modulation at the level of the locus coeruleus-superior colliculus pathway. Given the potential for noradrenergic treatment of non-motor symptoms of Parkinson's disease and related conditions, the oculomotor system can support the assessment of cognitive effects without limb-motor confounds on task performance.

A 10-min reduction in cerebral blood flow does not alter post-intervention executive function: evidence from lower-body negative pressure

A single bout of exercise as well as exposure to a hypercapnic environment increases cerebral blood flow (CBF) and is an adaptation linked to a post-intervention executive function (EF) benefit. In the present investigation we sought to determine whether a transient reduction in CBF impairs EF. Accordingly, we employed 10-min -30 mmHg and  -50 mmHg lower-body negative pressure (LBNP) interventions as well as a non-LBNP control condition. LBNP was employed because it sequesters blood in the lower legs and safely and reliably decreases CBF. Transcranial Doppler ultrasound was used to measure middle cerebral artery velocity (MCAv) to estimate CBF prior to and during LBNP conditions. As well, assessments of the inhibitory control component of EF (i.e., antipointing) were completed prior to (pre-) and immediately after (i.e., post-) each condition. Antipointing requires that an individual reach mirror-symmetrical to an exogenously presented target and is a task providing the resolution to detect subtle EF changes. Results showed that LBNP produced a 14% reduction in MCAv; however, null hypothesis, equivalence and Bayesian contrasts indicated that antipointing metrics did not vary from pre- to post-intervention, and LBNP-based changes in MCAv magnitude were not reliably correlated with antipointing planning times. Hence, a 10-min reduction in CBF did not impact the efficiency or effectiveness of an inhibitory control measure of EF.

The antisaccadic paradigm: A complementary neuropsychological tool in basal ganglia disorders

This review explores the role of the antisaccadic task in understanding inhibitory mechanisms in basal ganglia disorders. It conducts a comparative analysis of saccadic profiles in conditions such as Parkinson's disease, Tourette syndrome, obsessive-compulsive disorder, Huntington's disease, and dystonia, revealing distinct patterns and proposing mechanisms for impaired performance. The primary focus is on two inhibitory mechanisms: global, pre-emptive inhibition responsible for suppressing prepotent responses, and slower, selective response inhibition. The antisaccadic task demonstrates practicality in clinical applications, aiding in differential diagnoses, treatment monitoring and reflecting gait control. To further enhance its differential diagnostic value, future directions should address issues such as the standardization of eye-tracking protocol and the integration of eye-tracking data with other disease indicators in a comprehensive dataset.

Oculomotor behaviors in youth with an eating disorder: findings from a video-based eye tracking task

BACKGROUND

The oculomotor circuit spans many cortical and subcortical areas that have been implicated in psychiatric disease. This, combined with previous findings, suggests that eye tracking may be a useful method to investigate eating disorders. Therefore, this study aimed to assess oculomotor behaviors in youth with and without an eating disorder.

METHODS

Female youth with and without an eating disorder completed a structured task involving randomly interleaved pro-saccade (toward at a stimulus) and anti-saccade (away from stimulus) trials with video-based eye tracking. Differences in saccades (rapid eye movements between two points), eye blinks and pupil were examined.

RESULTS

Youth with an eating disorder (n = 65, Mage = 17.16 ± 3.5 years) were compared to healthy controls (HC; n = 65, Mage = 17.88 ± 4.3 years). The eating disorder group was composed of individuals with anorexia nervosa (n = 49), bulimia nervosa (n = 7) and other specified feeding or eating disorder (n = 9). The eating disorder group was further divided into two subgroups: individuals with a restrictive spectrum eating disorder (ED-R; n = 43) or a bulimic spectrum eating disorder (ED-BP; n = 22). In pro-saccade trials, the eating disorder group made significantly more fixation breaks than HCs (F(1,128) = 5.33, p = 0.023). The ED-BP group made the most anticipatory pro-saccades, followed by ED-R, then HCs (F(2,127) = 3.38, p = 0.037). Groups did not differ on rate of correct express or regular latency pro-saccades. In anti-saccade trials, groups only significantly differed on percentage of direction errors corrected (F(2, 127) = 4.554, p = 0.012). The eating disorder group had a significantly smaller baseline pupil size (F(2,127) = 3.60, p = 0.030) and slower pro-saccade dilation velocity (F(2,127) = 3.30, p = 0.040) compared to HCs. The ED-R group had the lowest blink probability during the intertrial interval (ITI), followed by ED-BP, with HCs having the highest ITI blink probability (F(2,125) = 3.63, p = 0.029).

CONCLUSIONS

These results suggest that youth with an eating disorder may have different oculomotor behaviors during a structured eye tracking task. The oculomotor behavioral differences observed in this study presents an important step towards identifying neurobiological and cognitive contributions towards eating disorders.

Parallel signatures of cognitive maturation in primate antisaccade performance and prefrontal activity

The ability to suppress inappropriate actions and respond rapidly to appropriate ones matures late in life, after puberty. We investigated the development of this capability in monkeys trained to look away from a lone, bright stimulus (antisaccade task). We evaluated behavioral performance and recorded neural activity in the prefrontal cortex both before and after the transition from puberty to adulthood. Compared to when young, adult monkeys processed the stimulus more rapidly, resisted more effectively the involuntary urge to look at it, and adhered to the task rule more consistently. The spatially selective visuomotor neurons in the prefrontal cortex provided neural correlates of these behavioral changes indicative of a faster transition from stimulus-driven (exogenous) to goal-driven (endogenous) control within the time course of each trial. The results reveal parallel signatures of cognitive maturation in behavior and prefrontal activity that are consistent with improvements in attentional allocation after adolescence.

Auditory guidance of eye movements toward threat-related images in the absence of visual awareness

The human brain is sensitive to threat-related information even when we are not aware of this information. For example, fearful faces attract gaze in the absence of visual awareness. Moreover, information in different sensory modalities interacts in the absence of awareness, for example, the detection of suppressed visual stimuli is facilitated by simultaneously presented congruent sounds or tactile stimuli. Here, we combined these two lines of research and investigated whether threat-related sounds could facilitate visual processing of threat-related images suppressed from awareness such that they attract eye gaze. We suppressed threat-related images of cars and neutral images of human hands from visual awareness using continuous flash suppression and tracked observers' eye movements while presenting congruent or incongruent sounds (finger snapping and car engine sounds). Indeed, threat-related car sounds guided the eyes toward suppressed car images, participants looked longer at the hidden car images than at any other part of the display. In contrast, neither congruent nor incongruent sounds had a significant effect on eye responses to suppressed finger images. Overall, our results suggest that only in a danger-related context semantically congruent sounds modulate eye movements to images suppressed from awareness, highlighting the prioritisation of eye responses to threat-related stimuli in the absence of visual awareness.

A single bout of aerobic exercise does not alter inhibitory control preparatory set cerebral hemodynamics: Evidence from the antisaccade task

A single bout of exercise improves executive function (EF) and is a benefit - in part -attributed to an exercise-mediated increase in cerebral blood flow enhancing neural efficiency. Limited work has used an event-related protocol to examine postexercise changes in preparatory phase cerebral hemodynamics for an EF task. This is salient given the neural efficiency hypothesis' assertion that improved EF is related to decreased brain activity. Here, event-related transcranial Doppler ultrasound was used to measure pro- (saccade to target) and antisaccades (saccade mirror-symmetrical target) preparatory phase middle cerebral artery velocity (MCAv) prior to and immediately after 15-min of aerobic exercise. Antisaccades produced longer reaction times (RT) and an increased preparatory phase MCAv than prosaccades - a result attributed to greater EF neural activity for antisaccades. Antisaccades selectively produced a postexercise RT reduction (ps < 0.01); however, antisaccade preparatory phase MCAv did not vary from pre- to postexercise (p=0.53) and did not correlate with the antisaccade RT benefit (p = 0.31). Accordingly, results provide no evidence that improved neural efficiency indexed via functional hyperemia is linked to a postexercise EF behavioural benefit. Instead, results support an evolving view that an EF benefit represents the additive interplay between interdependent exercise-mediated neurophysiological changes.

Saccade Latency and Metrics in the Interleaved Pro- and Anti-Saccade Task in Open Skill Sports Athletes

Evidence has demonstrated that athletes exhibit superior cognitive performance associated with executive control. In the oculomotor system, this function has been examined using the interleaved pro-saccade and anti-saccade task (IPAST), wherein participants, prior to target appearance, are instructed to either automatically look at the peripheral target (pro-saccade) or suppress the automatic response and voluntarily look in the opposite direction (anti-saccade). While the IPAST has provided much insight into sensorimotor and inhibitory processing, it has yet to be performed in athletes. Moreover, limited research has examined saccade metrics in athletes. Here, we examined saccade latency and movement kinematics in the IPAST among athletes (N = 40) and nonathletes (NON) (N = 40). Higher direction error rates were obtained in the anti-saccade compared to the pro-saccade condition, with no differences between athletes and NON noted. Significantly faster saccade latencies were observed in athletes compared to NON in both conditions, in addition to faster pro-saccades compared to anti-saccades. Furthermore, athletes showed significantly higher frequencies and faster latencies of express saccades compared to NON in correct pro-saccades. Additionally, athletes exhibited significantly faster latencies of express saccades compared to NON in erroneous anti-saccades. Differences in saccade metrics between athletes and NON were not seen. Overall, these findings demonstrate that athletes display altered saccade performance likely associated with sensorimotor and preparatory processing, highlighting the potential of using IPAST to objectively investigate sensorimotor and cognitive functions in athletes.

Multiunit Frontal Eye Field Activity Codes the Visuomotor Transformation, But Not Gaze Prediction or Retrospective Target Memory, in a Delayed Saccade Task

Single-unit (SU) activity-action potentials isolated from one neuron-has traditionally been employed to relate neuronal activity to behavior. However, recent investigations have shown that multiunit (MU) activity-ensemble neural activity recorded within the vicinity of one microelectrode-may also contain accurate estimations of task-related neural population dynamics. Here, using an established model-fitting approach, we compared the spatial codes of SU response fields with corresponding MU response fields recorded from the frontal eye fields (FEFs) in head-unrestrained monkeys (Macaca mulatta) during a memory-guided saccade task. Overall, both SU and MU populations showed a simple visuomotor transformation: the visual response coded target-in-eye coordinates, transitioning progressively during the delay toward a future gaze-in-eye code in the saccade motor response. However, the SU population showed additional secondary codes, including a predictive gaze code in the visual response and retention of a target code in the motor response. Further, when SUs were separated into regular/fast spiking neurons, these cell types showed different spatial code progressions during the late delay period, only converging toward gaze coding during the final saccade motor response. Finally, reconstructing MU populations (by summing SU data within the same sites) failed to replicate either the SU or MU pattern. These results confirm the theoretical and practical potential of MU activity recordings as a biomarker for fundamental sensorimotor transformations (e.g., target-to-gaze coding in the oculomotor system), while also highlighting the importance of SU activity for coding more subtle (e.g., predictive/memory) aspects of sensorimotor behavior.

Oculomotor atypicalities in motor neurone disease: a systematic review

Introduction

Cognitive dysfunction is commonplace in Motor Neurone Disease (MND). However, due to the prominent motor symptoms in MND, assessing patients' cognitive function through traditional cognitive assessments, which oftentimes require motoric responses, may become increasingly challenging as the disease progresses. Oculomotor pathways are apparently resistant to pathological degeneration in MND. As such, abnormalities in oculomotor functions, largely driven by cognitive processes such as saccades and smooth pursuit eye movement, may be reflective of frontotemporal cognitive deficits in MND. Thus, saccadic and smooth pursuit eye movements may prove to be ideal mechanistic markers of cognitive function in MND.

Methods

To ascertain the utility of saccadic and smooth pursuit eye movements as markers of cognitive function in MND, this review summarizes the literature concerning saccadic and smooth pursuit eye movement task performance in people with MND.

Results and discussion

Of the 22 studies identified, noticeable patterns suggest that people with MND can be differentiated from controls based on antisaccade and smooth pursuit task performance, and thus the antisaccade task and smooth pursuit task may be potential candidates for markers of cognition in MND. However, further studies which ascertain the concordance between eye tracking measures and traditional measures of cognition are required before this assumption is extrapolated, and clinical recommendations are made.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=376620, identifier CRD42023376620.