Anti-saccade as a tool to evaluate cognitive impairment in vestibular migraine.

Background: Vestibular migraine (VM), an intricate subtype of migraine, amalgamates the dual attributes of migraine and vestibular disorders. In clinical settings, individuals with VM frequently articulate concerns regarding the manifestation of subjective cognitive impairment. This cognitive dysfunction is intricately linked with diminished mobility, heightened susceptibility to falls, and increased absenteeism in afflicted patients. Consequently, comprehending the features of cognitive impairment in VM patients holds potential clinical significance. The pursuit of rapid and objective methods for detection and assessment is foundational and prerequisite for efficacious cognitive management of VM patients. Methods: The study encompassed 50 patients diagnosed with vestibular migraine and recruited 50 age-sex matched healthy controls. All participants underwent anti-saccade tasks, and cognitive evaluation was performed using the MMSE and MoCA to assess overall cognitive function. Additionally, RBANS scales were employed to measure specific cognitive domains. Results: The VM patients and normal controls demonstrated statistical parity in terms of age, gender, education, weight, and BMI, with no significant differences observed. Analysis of cognitive scores divulged a marked increase in the incidence of Mild Cognitive Impairment (MCI) in VM patients compared to Healthy Controls (HCs). Both MMSE and MoCA scores were notably lower in VM patients compared to their healthy counterparts. The RBANS cognitive test indicated significant impairment in immediate memory, visuospatial construction, language, attention, and delayed memory among VM patients. Notably, the Trail Making Test and Stroop Color-Word Test revealed compromised processing speed and executive function cognitive domains. The anti-saccadic task highlighted significantly elevated anti-saccadic latency and frequency of direction errors in vestibular migraine patients. Symptom severity, illness duration, and episode frequency in VM patients positively correlated with counter-scanning errors and negatively correlated with cognitive performance across diverse cognitive domains. Conclusion: VM patients exhibit cognitive decline across multiple cognitive domains during the interictal period. This cognitive impairment may not be fully reversible, underscoring its potential clinical significance for cognitive management in VM patients. The sensitivity of anti-saccade tasks to the cognitive status of VM patients positions them as promising objective indicators for diagnosis, intervention, and evaluation of cognitive impairment effects in VM in future applications.

Impairment of Visual Fixation and Preparatory Saccade Control in Borderline Personality Disorder with and without co-morbid 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 co-morbidity with attention-deficit/hyperactivity disorder (ADHD). METHODS: We employed a response inhibition paradigm - the interleaved pro-/anti-saccade task (IPAST) - 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 [SRT]: 90-140 ms) and regular saccade latencies (SRT > 140 ms). RESULTS: Individuals with BPD exhibited deficient response preparation, exampled by reduced visual fixation on task cues and greater variability of saccade responses (i.e., SRT and peak velocity). The ADHD/BPD group shared these traits, as well as produced an increased frequency of anticipatory responses and direction errors with express saccade latencies and reduced error correction. CONCLUSIONS: Saccadic deficits in BPD and ADHD/BPD stem not from an inability to execute anti-saccades, but rather from an 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.

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.

Menstrual cycle status does not impact exercise-based changes in cerebral blood flow or executive function benefits.

A single bout of exercise enhances executive function (EF) and may relate to an increase in cerebral blood flow (CBF). A limitation in the current literature is that biologically female participants are underrepresented given some evidence that changes in hormone levels across the menstrual cycle impact physiological and psychological variables. Here, biologically female participants completed separate single bouts of moderate intensity exercise (80% of estimated lactate threshold) during the follicular (FOL) and luteal (LUT) phases of their menstrual cycle. In addition, biologically male participants completed a same duration/intensity exercise session. Middle cerebral artery velocity (MCAv) was used to estimate CBF and pre- and postexercise EF was assessed via the antisaccade task. Results showed that resting MCAv was larger in the LUT than FOL phase; however, the exercise-mediated increase in MCAv was equivalent between menstrual cycle phases, and between female and male participants. Antisaccade reaction times reliably decreased from pre- to postexercise and frequentist and non-frequentist statistics demonstrated that the magnitude of the decrease was equivalent across FOL and LUT phases, and between female and male participants. Thus, results evince that menstrual cycle status should not serve as a basis limiting biologically female participants' inclusion in research examining exercise and EF.

Oculomotor Dysfunction in Idiopathic and LRRK2-Parkinson's Disease and At-Risk Individuals.

Background: Video-oculography constitutes a highly-sensitive method of characterizing ocular movements, which could detect subtle premotor changes and contribute to the early diagnosis of Parkinson's disease (PD). Objective: To investigate potential oculomotor differences between idiopathic PD (iPD) and PD associated with the G2019S variant of LRRK2 (L2PD), as well as to evaluate oculomotor function in asymptomatic carriers of the G2019S variant of LRRK2. Methods: The study enrolled 129 subjects: 30 PD (16 iPD, 14 L2PD), 23 asymptomatic carriers, 13 non-carrier relatives of L2PD patients, and 63 unrelated HCs. The video-oculographic evaluation included fixation, prosaccade, antisaccade, and memory saccade tests. Results: We did not find significant differences between iPD and L2PD. Compared to controls, PD patients displayed widespread oculomotor deficits including larger microsaccades, hypometric vertical prosaccades, increased latencies in all tests, and lower percentages of successful antisaccades and memory saccades. Non-carrier relatives showed oculomotor changes with parkinsonian features, such as fixation instability and hypometric vertical saccades. Asymptomatic carriers shared multiple similarities with PD, including signs of unstable fixation and hypometric vertical prosaccades; however, they were able to reach percentages of successful antisaccade and memory saccades similar to controls, although at the expense of longer latencies. Classification accuracy of significant oculomotor parameters to differentiate asymptomatic carriers from HCs ranged from 0.68 to 0.74, with BCEA, a marker of global fixation instability, being the parameter with the greatest classification accuracy. Conclusions: iPD and LRRK2-G2019S PD patients do not seem to display a differential oculomotor profile. Several oculomotor changes in asymptomatic carriers of LRRK2 mutations could be considered premotor biomarkers.

Antisaccade error rates in first-episode psychosis, ultra-high risk for psychosis and unaffected relatives of schizophrenia: A systematic review and meta-analysis.

BACKGROUND: Antisaccade, which is described as looking at the opposite location of the target, is an eye movements paradigm used for assessing cognitive functions in schizophrenia. Initiation and sustainment of saccades in antisaccade are managed by frontal and parietal cortical areas. Antisaccade abnormalities are well-established findings in schizophrenia. However, studies in the early phases of psychotic disorders and clinical/familial risk for psychosis reported inconsistent findings. The current systematic review aimed to review the results of studies investigating antisaccade error rates in first-episode psychosis (FEP), individuals with ultra-high-risk for psychosis (UHRP), and familial-high-risk for psychosis (FHRP) compared to healthy controls. METHOD: A meta-analysis of 17 studies was conducted to quantitatively review antisaccade errors in FEP, UHR-P and FHRP. The error rate (Hedges'g) was compared between the total of 860 FEP, UHRP, FHRP, and 817 healthy controls. Hedges' g for effect size, I2 for estimating the percentage of variability, and publication bias were evaluated through the R software. RESULTS: The outcomes of this meta-analysis suggested that FEP is associated with a robust deficit in the antisaccade error rate (g = 1.16, CI = 0.95-1.38). Additionally, both the clinical and familial high-risk groups showed small but significant increases in AS errors (g = 0.26, CI = 0.02-0.52 and g = 0.34, CI = 0.13-0.55, respectively). CONCLUSION: The large effect size estimated for FEP was compatible with previously reported results in chronic schizophrenia patients. Additionally, relatives had abnormalities with small to medium effect sizes and significant differences. The current findings suggest that antisaccade errors might be a potential endophenotype for psychotic disorders.

Emotional Face Processing in Autism Spectrum Condition: A Study of Attentional Orienting and Inhibitory Control.

A core feature of Autistic Spectrum Condition (ASC) is the presence of difficulties in social interactions. This can be explained by an atypical attentional processing of social information: individuals with ASC may show problems with orienting attention to socially relevant stimuli and/or inhibiting their attentional responses to irrelevant ones. To shed light on this issue, we examined attentional orienting and inhibitory control to emotional stimuli (angry, happy, and neutral faces). An antisaccade task (with both prosaccade and antisacade blocks) was applied to a final sample of 29 children with ASC and 27 children with typical development (TD). Whereas children with ASC committed more antisaccade errors when seeing angry faces than happy or neutral ones, TD children committed more antisaccade errors when encountering happy faces than neutral faces. Furthermore, latencies in the prosaccade and antisaccade blocks were longer in children with ASC and they were associated with the severity of ASC symptoms. Thus, children with ASC showed an impaired inhibitory control when angry faces were presented. This bias to negative high-arousal information is congruent with affective information-processing theories on ASC, suggesting that threatening stimuli induce an overwhelming response in ASC. Therapeutic strategies where train the shift attention to emotional stimuli (i.e. faces) may improve ASC symptomatology and their socials functioning.

10-min exposure to a 2.5% hypercapnic environment increases cerebral blood blow but does not impact executive function.

Space travel and exploration are associated with increased ambient CO2 (i.e., a hypercapnic environment). Some work reported that the physiological changes (e.g., increased cerebral blood flow [CBF]) associated with a chronic hypercapnic environment contributes to a "space fog" that adversely impacts cognition and psychomotor performance, whereas other work reported no change or a positive change. Here, we employed the antisaccade task to evaluate whether transient exposure to a hypercapnic environment influences top-down executive function (EF). Antisaccades require a goal-directed eye movement mirror-symmetrical to a target and are an ideal tool for identifying subtle EF changes. Healthy young adults (aged 19-25 years) performed blocks of antisaccade trials prior to (i.e., pre-intervention), during (i.e., concurrent) and after (i.e., post-intervention) 10-min of breathing factional inspired CO2 (FiCO2) of 2.5% (i.e., hypercapnic condition) and during a normocapnic (i.e., control) condition. In both conditions, CBF, ventilatory and cardiorespiratory responses were measured. Results showed that the hypercapnic condition increased CBF, ventilation and end-tidal CO2 and thus demonstrated an expected physiological adaptation to increased FiCO2. Notably, however, null hypothesis and equivalence tests indicated that concurrent and post-intervention antisaccade reaction times were refractory to the hypercapnic environment; that is, transient exposure to a FiCO2 of 2.5% did not produce a real-time or lingering influence on an oculomotor-based measure of EF. Accordingly, results provide a framework that - in part - establishes the FiCO2 percentage and timeline by which high-level EF can be maintained. Future work will explore CBF and EF dynamics during chronic hypercapnic exposure as more direct proxy for the challenges of space flight and exploration.

Success versus failure in cognitive control: Meta-analytic evidence from neuroimaging studies on error processing.

Brain mechanisms of error processing have often been investigated using response interference tasks and focusing on the posterior medial frontal cortex, which is also implicated in resolving response conflict in general. Thereby, the role other brain regions may play has remained undervalued. Here, activation likelihood estimation meta-analyses were used to synthesize the neuroimaging literature on brain activity related to committing errors versus responding successfully in interference tasks and to test for commonalities and differences. The salience network and the temporoparietal junction were commonly recruited irrespective of whether responses were correct or incorrect, pointing towards a general involvement in coping with situations that call for increased cognitive control. The dorsal posterior cingulate cortex, posterior thalamus, and left superior frontal gyrus showed error-specific convergence, which underscores their consistent involvement when performance goals are not met. In contrast, successful responding revealed stronger convergence in the dorsal attention network and lateral prefrontal regions. Underrecruiting these regions in error trials may reflect failures in activating the task-appropriate stimulus-response contingencies necessary for successful response execution.

Uncorrected errors and correct saccades in the antisaccade task distinguish between early-stage Alzheimer's disease dementia, amnestic mild cognitive impairment, and normal aging.

Alzheimer's disease (AD) dementia is a degenerative illness that is characterized by a gradual decline in cognitive abilities. Amnestic mild cognitive impairment (aMCI) is seen as a precursor to AD. The changes in antisaccade performance that can be seen in MCI may provide important clues in the early detection of AD. Therefore, the antisaccade deficits in AD and aMCI remain a research question. This study aimed to examine antisaccade responses and the relationship between antisaccade and cognitive function in AD, aMCI, and healthy controls (HC). This study included 30 patients with early-stage AD, 34 with aMCI, and 32 HC. Patients with AD showed higher rates of uncorrected error, anticipatory saccades and corrected errors, as well as decreased correct saccade rates, and shortened saccade latency compared to aMCI and HC in this study. Patients with aMCI exhibited increased rates of express saccades relative to HC. The antisaccade task and cognitive domains were found to be significantly related. Our study showed that the rate of correct saccades has the capacity to distinguish AD from HC with 87% sensitivity and 86% specificity (AUC = 0.93, p < 0.001). In addition, the rate of uncorrected errors was found to be capable of distinguishing AD from HC with 84% sensitivity and 83% specificity (AUC = 0.91, p < 0.001). This study presented promising findings that these parameters can be used clinically to differentiate AD and aMCI from healthy older individuals.

Sensorimotor and inhibitory control in aging FMR1 premutation carriers.

Aging FMR1 premutation carriers are at risk of developing neurodegenerative disorders, including fragile X-associated tremor/ataxia syndrome (FXTAS), and there is a need to identify biomarkers that can aid in identification and treatment of these disorders. While FXTAS is more common in males than females, females can develop the disease, and some evidence suggests that patterns of impairment may differ across sexes. Few studies include females with symptoms of FXTAS, and as a result, little information is available on key phenotypes for tracking disease risk and progression in female premutation carriers. Our aim was to examine quantitative motor and cognitive traits in aging premutation carriers. We administered oculomotor tests of visually guided/reactive saccades (motor) and antisaccades (cognitive control) in 22 premutation carriers (73% female) and 32 age- and sex-matched healthy controls. Neither reactive saccade latency nor accuracy differed between groups. FMR1 premutation carriers showed increased antisaccade latencies relative to controls, both when considering males and females together and when analyzing females separately. Reduced saccade accuracy and increased antisaccade latency each were associated with more severe clinically rated neuromotor impairments. Findings indicate that together male and female premutation carriers show a reduced ability to rapidly exert volitional control over prepotent responses and that quantitative differences in oculomotor behavior, including control of visually guided and antisaccades, may track with FXTAS - related degeneration in male and female premutation carriers.

Utilizing artificial intelligence-based eye tracking technology for screening ADHD symptoms in children.

Objective: To explore the potential of using artificial intelligence (AI)-based eye tracking technology on a tablet for screening Attention-deficit/hyperactivity disorder (ADHD) symptoms in children. Methods: We recruited 112 children diagnosed with ADHD (ADHD group; mean age: 9.40 ± 1.70 years old) and 325 typically developing children (TD group; mean age: 9.45 ± 1.59 years old). We designed a data-driven end-to-end convolutional neural network appearance-based model to predict eye gaze to permit eye-tracking under low resolution and sampling rates. The participants then completed the eye tracking task on a tablet, which consisted of a simple fixation task as well as 14 prosaccade (looking toward target) and 14 antisaccade (looking away from target) trials, measuring attention and inhibition, respectively. Results: Two-way MANOVA analyses demonstrated that diagnosis and age had significant effects on performance on the fixation task [diagnosis: F(2, 432) = 8.231, ***p < 0.001; Wilks' Λ = 0.963; age: F(2, 432) = 3.999, *p < 0.019; Wilks' Λ = 0.982], prosaccade task [age: F(16, 418) = 3.847, ***p < 0.001; Wilks' Λ = 0.872], and antisaccade task [diagnosis: F(16, 418) = 1.738, *p = 0.038; Wilks' Λ = 0.938; age: F(16, 418) = 4.508, ***p < 0.001; Wilks' Λ = 0.853]. Correlational analyses revealed that participants with higher SNAP-IV score were more likely to have shorter fixation duration and more fixation intervals (r = -0.160, 95% CI [0.250, 0.067], ***p < 0.001), poorer scores on adjusted prosaccade accuracy, and poorer scores on antisaccade accuracy (Accuracy: r = -0.105, 95% CI [-0.197, -0.011], *p = 0.029; Adjusted accuracy: r = -0.108, 95% CI [-0.200, -0.015], *p = 0.024). Conclusion: Our AI-based eye tracking technology implemented on a tablet could reliably discriminate eye movements of the TD group and the ADHD group, providing a potential solution for ADHD screening outside of clinical settings.

[Effects of postural control upon anti-saccade error rate in older people]. / Efectos del control postural en la tasa de error anti-sacádico en personas mayores.

BACKGROUND: The anti-saccadic (AS) error-rate is used to diagnose neurological disorders. The natural aging process could generate difficulty in carrying out parallel neural processes of conscious motor inhibition and eye movement. Therefore, if balance control is imposed on an elderly person in biped positions during an AS movement, an increase in the AS error-rate is expected. OBJECTIVE: To study the effects of postural control on the AS error-rate in older people. METHODS: An intra and intergroup comparison was made of AS error-rate in an experimental group of older people (PM) and another control group of young people (PJ). For this, blocks of AS and pro-saccadic movements (control) were used randomly in four different postures: (1)sitting (SENT), (2)standing normally (NORMAL), (3)feet together (REDUC), and (4)feet in line (TANDEM). RESULTS: The PM group, compared to the PJ group, showed a progressive increase in the AS error-rate from the sitting position to all standing positions, with the maximum AS error-rate in more complex vertical postures. In contrast, the PJ group did not present significative variability of this AS error-rate in all positions. CONCLUSIONS: It is confirmed that the aging process is associated with an increase in the AS error-rate. This study reveals for the first time a significant increase in the AS error-rate when control of body balance is required for PM, implying a decrease in the multiple processing capacity in PM for the execution of complex and parallel tasks.

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.

Antisaccade and memory-guided saccade in individuals at ultra-high-risk for bipolar disorder.

BACKGROUND: Ultra-high-risk for bipolar disorder (UHR-BD) is an important paradigm to investigate the potential early-stage biomarkers of bipolar disorder, including eye-tracking abnormalities and cognitive functions. Antisaccade (AS) described as looking in the opposite direction of the target, and memory-guided saccade (MGS), identified as maintaining fixation, and remembering the location of the target, were used in this study. The aim of this study was to evaluate the differences in saccadic eye movements between UHR-BD and healthy controls (HCs) via AS-MGS. METHODS: The study included 28 UHR-BD and 29 HCs. Participants were selected using a structured clinical interview for prodromal symptoms of BD. AS-MGS were measured with parameters like uncorrected errors, anticipatory saccades, and latency. Eye movements were recorded with the EyeLink 1000-Plus eye-tracker. RESULTS: In the AS, the number of correct saccades was significantly decreased in UHR-BD (p = 0.020). Anticipatory (p = 0.009) and express saccades (p = 0.040) were increased in UHR-BD. In the MGS paradigm, the correct saccades were reduced in UHR-BD (p = 0.031). In addition, anticipatory (p = 0.004) and express saccades (p = 0.012) were significantly increased in cue-screen in UHR-BD. CONCLUSIONS: To our knowledge, this is the first study to evaluate cognitive functions with eye movements in individuals at UHR-BD. The current findings showed that eye movement functions, particularly in saccadic parameters related to inhibition and spatial perception, may be affected in the UHR-BD group. Therefore, assessment of oculomotor functions may provide observation of clinical and cognitive functions in the early-stage of bipolar disorder. However, further research is needed because the potential effects of medication may affect saccadic results.

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

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

Success versus failure in cognitive control: meta-analytic evidence from neuroimaging studies on error processing.

Brain mechanisms of error processing have often been investigated using response interference tasks and focusing on the posterior medial frontal cortex, which is also implicated in resolving response conflict in general. Thereby, the role other brain regions may play has remained undervalued. Here, activation likelihood estimation meta-analyses were used to synthesize the neuroimaging literature on brain activity related to committing errors versus responding successfully in interference tasks and to test for commonalities and differences. The salience network and the temporoparietal junction were commonly recruited irrespective of whether responses were correct or incorrect, pointing towards a general involvement in coping with situations that call for increased cognitive control. The dorsal posterior cingulate cortex, posterior thalamus, and left superior frontal gyrus showed error-specific convergence, which underscores their consistent involvement when performance goals are not met. In contrast, successful responding revealed stronger convergence in the dorsal attention network and lateral prefrontal regions. Underrecruiting these regions in error trials may reflect failures in activating the task-appropriate stimulus-response contingencies necessary for successful response execution.

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

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

Saccadic Eye Movements in Patients with Mild Cognitive Impairment: A Longitudinal Study.

Saccadic eye movements are one of the sensitive and noninvasive methods to help monitor the cognitive course of mild cognitive impairment (MCI). The study aimed to evaluate both pro and anti-saccade longitudinally and the relationship between cognitive functions and eye movements in MCI subgroups and healthy controls (HCs) at a two-year follow-up. This study revealed that the anti-saccade anticipatory responses decreased in amnestic MCI (aMCI). Correct vertical pro-saccades increased in non-amnestic MCI (naMCI), while the express saccades decreased. Our study demonstrated that longer than two years of follow-up is necessary to monitor the course of MCI. Findings of the relationships between longitudinal changes of saccades and cognitive measurements demonstrated the usability of eye movements in evaluating the process of MCI.

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

Objectives: 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. Methods: 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. Results: 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. Conclusion: 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.