The antisaccade: a review of basic research and clinical studies

Individual Differences in Working Memory Capacity Modulates Semantic Negative Priming from Single Prime Words

The present study investigated whether semantic negative priming from single prime words depends on the availability of cognitive control resources. Participants with high vs. low working memory capacity (as assessed by their performance in complex span and attentional control tasks) were instructed to either attend to or ignore a briefly presented single prime word that was followed by either a semantically related or unrelated target word on which participants made a lexical decision. Individual differences in working memory capacity (WMC) mainly affected the processing of the ignored primes, but not the processing of the attended primes: While the latter produced reliable positive semantic priming for both high- and low-WMC participants, the former gave rise to reliable semantic negative priming only for high WMC participants, with low WMC participants showing the opposite positive priming effect. The present results extend previous findings in demonstrating that (a) single negative priming can reliably generalize to semantic associates of the prime words, and (b) a differential availability of cognitive control resources can reliably modulate the negative priming effect at a semantic level of representation.

Conflict Resolution as Near-Threshold Decision-Making: A Spiking Neural Circuit Model with Two-Stage Competition for Antisaccadic Task

Automatic responses enable us to react quickly and effortlessly, but they often need to be inhibited so that an alternative, voluntary action can take place. To investigate the brain mechanism of controlled behavior, we investigated a biologically-based network model of spiking neurons for inhibitory control. In contrast to a simple race between pro- versus anti-response, our model incorporates a sensorimotor remapping module, and an action-selection module endowed with a “Stop” process through tonic inhibition. Both are under the modulation of rule-dependent control. We tested the model by applying it to the well known antisaccade task in which one must suppress the urge to look toward a visual target that suddenly appears, and shift the gaze diametrically away from the target instead. We found that the two-stage competition is crucial for reproducing the complex behavior and neuronal activity observed in the antisaccade task across multiple brain regions. Notably, our model demonstrates two types of errors: fast and slow. Fast errors result from failing to inhibit the quick automatic responses and therefore exhibit very short response times. Slow errors, in contrast, are due to incorrect decisions in the remapping process and exhibit long response times comparable to those of correct antisaccade responses. The model thus reveals a circuit mechanism for the empirically observed slow errors and broad distributions of erroneous response times in antisaccade. Our work suggests that selecting between competing automatic and voluntary actions in behavioral control can be understood in terms of near-threshold decision-making, sharing a common recurrent (attractor) neural circuit mechanism with discrimination in perception.

We propose a novel neural circuit mechanism and construct a spiking neural network model for resolving conflict between an automatic response and a volitional one. In this mechanism the two types of responses compete against each other under the modulation of top-down control via multiple neural pathways. The model is able to reproduce a wide range of neuronal and behavioral features observed in various studies and provides insights into not just how subjects make correct responses and fast errors, but also why they make slow errors, a type of error often overlooked by previous modeling studies. The model suggests critical roles of tonic (non-racing) top-down inhibition and near-threshold decision-making in neural competition.

Causal Inference for Cross-Modal Action Selection: A Computational Study in a Decision Making Framework

Animals try to make sense of sensory information from multiple modalities by categorizing them into perceptions of individual or multiple external objects or internal concepts. For example, the brain constructs sensory, spatial representations of the locations of visual and auditory stimuli in the visual and auditory cortices based on retinal and cochlear stimulations. Currently, it is not known how the brain compares the temporal and spatial features of these sensory representations to decide whether they originate from the same or separate sources in space. Here, we propose a computational model of how the brain might solve such a task. We reduce the visual and auditory information to time-varying, finite-dimensional signals. We introduce controlled, leaky integrators as working memory that retains the sensory information for the limited time-course of task implementation. We propose our model within an evidence-based, decision-making framework, where the alternative plan units are saliency maps of space. A spatiotemporal similarity measure, computed directly from the unimodal signals, is suggested as the criterion to infer common or separate causes. We provide simulations that (1) validate our model against behavioral, experimental results in tasks where the participants were asked to report common or separate causes for cross-modal stimuli presented with arbitrary spatial and temporal disparities. (2) Predict the behavior in novel experiments where stimuli have different combinations of spatial, temporal, and reliability features. (3) Illustrate the dynamics of the proposed internal system. These results confirm our spatiotemporal similarity measure as a viable criterion for causal inference, and our decision-making framework as a viable mechanism for target selection, which may be used by the brain in cross-modal situations. Further, we suggest that a similar approach can be extended to other cognitive problems where working memory is a limiting factor, such as target selection among higher numbers of stimuli and selections among other modality combinations.

Intrinsic Connectivity Provides the Baseline Framework for Variability in Motor Performance: A Multivariate Fusion Analysis of Low- and High-Frequency Resting-State Oscillations and Antisaccade Performance

Intrinsic brain activity provides the functional framework for the brain's full repertoire of behavioral responses; that is, a common mechanism underlies intrinsic and extrinsic neural activity, with extrinsic activity building upon the underlying baseline intrinsic activity. The generation of a motor movement in response to sensory stimulation is one of the most fundamental functions of the central nervous system. Since saccadic eye movements are among our most stereotyped motor responses, we hypothesized that individual variability in the ability to inhibit a prepotent saccade and make a voluntary antisaccade would be related to individual variability in intrinsic connectivity. Twenty-three individuals completed the antisaccade task and resting-state functional magnetic resonance imaging (fMRI). A multivariate analysis of covariance identified relationships between fMRI oscillations (0.01-0.2 Hz) of resting-state networks determined using high-dimensional independent component analysis and antisaccade performance (latency, error rate). Significant multivariate relationships between antisaccade latency and directional error rate were obtained in independent components across the entire brain. Some of the relationships were obtained in components that overlapped substantially with the task; however, many were obtained in components that showed little overlap with the task. The current results demonstrate that even in the absence of a task, spectral power in regions showing little overlap with task activity predicts an individual's performance on a saccade task.

A neural model of the frontal eye fields with reward-based learning

Decision-making is a flexible process dependent on the accumulation of various kinds of information; however, the corresponding neural mechanisms are far from clear. We extended a layered model of the frontal eye field to a learning-based model, using computational simulations to explain the cognitive process of choice tasks. The core of this extended model has three aspects: direction-preferred populations that cluster together the neurons with the same orientation preference, rule modules that control different rule-dependent activities, and reward-based synaptic plasticity that modulates connections to flexibly change the decision according to task demands. After repeated attempts in a number of trials, the network successfully simulated three decision choice tasks: an anti-saccade task, a no-go task, and an associative task. We found that synaptic plasticity could modulate the competition of choices by suppressing erroneous choices while enhancing the correct (rewarding) choice. In addition, the trained model captured some properties exhibited in animal and human experiments, such as the latency of the reaction time distribution of anti-saccades, the stop signal mechanism for canceling a reflexive saccade, and the variation of latency to half-max selectivity. Furthermore, the trained model was capable of reproducing the re-learning procedures when switching tasks and reversing the cue-saccade association.

The mental-attention Tai Chi effect with older adults

BACKGROUND

Tai Chi practice has some fitness, wellness, and general cognitive effects in older adults. However, benefits of Tai Chi on specific mental-attentional executive processes have not been investigated previously. We studied older Canadian adults of Chinese and non-Chinese origin and from low socioeconomic areas.

METHODS

Sixty-four adults (51-87 years old) took part in a 16-week Tai Chi program. There were two groups: Chinese-background (n = 35) and Non-Chinese-background (n = 29). They received four mental-attention executive tasks before and after the 16-week period. These tasks measured visuospatial reasoning, mental-attentional activation (working memory), attentional inhibition, and balance between these attention factors (field-dependence-independence).

RESULTS

Chinese participants showed significant gain on Figural Intersections Task (mental-attentional capacity), Antisaccade (attentional inhibition), and Matrix Reasoning (fluid intelligence measure). Both groups evidenced gain on the Water Level Task (attentional balance).

CONCLUSIONS

These gains suggest that Tai Chi can improve mental-attentional vigilance and executive control, when practitioners are sufficiently motivated to pursue this practice, and apply themselves (as our Chinese participants seem to have done). We found that Tai Chi enhanced mental attentional executives in the Chinese sample. The largely negative results with Non-Chinese participants might be explained by less strong motivation and by the relatively short Tai Chi practice period, which contrasts with the prior familiarity with Tai Chi of the Chinese participants.

Different involvement of subregions within dorsal premotor and medial frontal cortex for pro- and antisaccades

The antisaccade task has been widely used to investigate cognitive action control. While the general network for saccadic eye movements is well defined, the exact location of eye fields within the frontal cortex strongly varies between studies. It is unknown whether this inconsistency reflects spatial uncertainty or is the result of different involvement of subregions for specific aspects of eye movement control. The aim of the present study was to examine functional differentiations within the frontal cortex by integrating results from neuroimaging studies analyzing pro- and antisaccade behavior using meta-analyses. The results provide evidence for a differential functional specialization of neighboring oculomotor frontal regions, with lateral frontal eye fields (FEF) and supplementary eye field (SEF) more often involved in prosaccades while medial FEF and anterior midcingulate cortex (aMCC) revealed consistent stronger involvement for antisaccades. This dissociation was furthermore mirrored by functional connectivity analyses showing that the lateral FEF and SEF are embedded in a motor output network, while medial FEF and aMCC are integrated in a multiple demand network.

Frontal preparatory neural oscillations associated with cognitive control: A developmental study comparing young adults and adolescents

Functional magnetic resonance imaging (fMRI) studies suggest that age-related changes in the frontal cortex may underlie developmental improvements in cognitive control. In the present study we used magnetoencephalography (MEG) to identify frontal oscillatory neurodynamics that support age-related improvements in cognitive control during adolescence. We characterized the differences in neural oscillations in adolescents and adults during the preparation to suppress a prepotent saccade (antisaccade trials-AS) compared to preparing to generate a more automatic saccade (prosaccade trials-PS). We found that for adults, AS were associated with increased beta-band (16-38Hz) power in the dorsal lateral prefrontal cortex (DLPFC), enhanced alpha- to low beta-band (10-18Hz) power in the frontal eye field (FEF) that predicted performance, and increased cross-frequency alpha-beta (10-26Hz) amplitude coupling between the DLPFC and the FEF. Developmental comparisons between adults and adolescents revealed similar engagement of DLPFC beta-band power but weaker FEF alpha-band power, and lower cross-frequency coupling between the DLPFC and the FEF in adolescents. These results suggest that lateral prefrontal neural activity associated with cognitive control is adult-like by adolescence; the development of cognitive control from adolescence to adulthood is instead associated with increases in frontal connectivity and strengthening of inhibition signaling for suppressing task-incompatible processes.

Visual straight-ahead preference in saccadic eye movements

Ocular saccades bringing the gaze toward the straight-ahead direction (centripetal) exhibit higher dynamics than those steering the gaze away (centrifugal). This is generally explained by oculomotor determinants: centripetal saccades are more efficient because they pull the eyes back toward their primary orbital position. However, visual determinants might also be invoked: elements located straight-ahead trigger saccades more efficiently because they receive a privileged visual processing. Here, we addressed this issue by using both pro- and anti-saccade tasks in order to dissociate the centripetal/centrifugal directions of the saccades, from the straight-ahead/eccentric locations of the visual elements triggering those saccades. Twenty participants underwent alternating blocks of pro- and anti-saccades during which eye movements were recorded binocularly at 1 kHz. The results confirm that centripetal saccades are always executed faster than centrifugal ones, irrespective of whether the visual elements have straight-ahead or eccentric locations. However, by contrast, saccades triggered by elements located straight-ahead are consistently initiated more rapidly than those evoked by eccentric elements, irrespective of their centripetal or centrifugal direction. Importantly, this double dissociation reveals that the higher dynamics of centripetal pro-saccades stem from both oculomotor and visual determinants, which act respectively on the execution and initiation of ocular saccades.

Antisaccadic Eye Movements Are Correlated with Corpus Callosum White Matter Mean Diffusivity, Stroop Performance, and Symptom Burden in Mild Traumatic Brain Injury and Concussion

Antisaccades are thought to involve higher level inputs from neural centers involved in rapid eye movement inhibition and control. Previous work has demonstrated that performance on the antisaccade task can help in the assessment of injury in acute and/or chronic mild traumatic brain injury (mTBI). In this exploratory study, we performed cross-sectional and longitudinal comparisons of rapid eye movement, followed by correlations of antisaccade performance with assessments of symptom burden, diffusion tensor imaging, and a neuropsychological test of response inhibition. Significant deficits in antisaccade median latency, F(2, 31) = 3.65, p = 0.04 and prosaccade error mean duration, F(2, 31) = 3.63, p = 0.04 were found between patient groups and controls: the former was correlated with loss of white matter integrity in the splenium of the corpus callosum in acute mTBI, rho = 0.90, p = 0.0005. Furthermore, increased antisaccade median latency was also correlated with poor performance on an executive functioning task, r² = 0.439, p = 0.03, and greater symptom burden, r² = 0.480, p = 0.02 in the acute mTBI patients. Our preliminary research suggests that the antisaccade task could be useful as a neurological marker for mTBI and concussion, but more work is required.

Electrophysiological Endophenotypes for Schizophrenia

Endophenotypes are quantitative, heritable traits that may help to elucidate the pathophysiologic mechanisms underlying complex disease syndromes, such as schizophrenia. They can be assessed at numerous levels of analysis; here, we review electrophysiological endophenotypes that have shown promise in helping us understand schizophrenia from a more mechanistic point of view. For each endophenotype, we describe typical experimental procedures, reliability, heritability, and reported gene and neurobiological associations. We discuss recent findings regarding the genetic architecture of specific electrophysiological endophenotypes, as well as converging evidence from EEG studies implicating disrupted balance of glutamatergic signaling and GABAergic inhibition in the pathophysiology of schizophrenia. We conclude that refining the measurement of electrophysiological endophenotypes, expanding genetic association studies, and integrating data sets are important next steps for understanding the mechanisms that connect identified genetic risk loci for schizophrenia to the disease phenotype.

Eye Movement in Unipolar and Bipolar Depression: A Systematic Review of the Literature

BACKGROUND

The analysis of eye movements (EM) by eye-tracking has been carried out for several decades to investigate mood regulation, emotional information processing, and psychomotor disturbances in depressive disorders.

METHOD

A systematic review of all English language PubMed articles using the terms "saccadic eye movements" OR "eye-tracking" AND "depression" OR "bipolar disorders" was conducted using PRISMA guidelines. The aim of this review was to characterize the specific alterations of EM in unipolar and bipolar depression.

RESULTS

Findings regarding psychomotor disturbance showed an increase in reaction time in prosaccade and antisaccade tasks in both unipolar and bipolar disorders. In both disorders, patients have been reported to have an attraction for negative emotions, especially for negative pictures in unipolar and threatening images in bipolar disorder. However, the pattern could change with aging, elderly unipolar patients disengaging key features of sad and neutral stimuli. METHODological limitations generally include small sample sizes with mixed unipolar and bipolar depressed patients.

CONCLUSION

Eye movement analysis can be used to discriminate patients with depressive disorders from controls, as well as patients with bipolar disorder from patients with unipolar depression. General knowledge concerning psychomotor alterations and affective regulation strategies associated with each disorder can also be gained thanks to the analysis. Future directions for research on eye movement and depression are proposed in this review.

Disruption of pupil size modulation correlates with voluntary motor preparation deficits in Parkinson's disease

Pupil size is an easy-to-measure, non-invasive method to index various cognitive processes. Although a growing number of studies have incorporated measures of pupil size into clinical investigation, there have only been limited studies in Parkinson's disease (PD). Convergent evidence has suggested PD patients exhibit cognitive impairment at or soon after diagnosis. Here, we used an interleaved pro- and anti-saccade paradigm while monitoring pupil size with saccadic eye movements to examine the relationship between executive function deficits and pupil size in PD patients. Subjects initially fixated a central cue, the color of which instructed them to either look at a peripheral stimulus automatically (pro-saccade) or suppress the automatic response and voluntarily look in the opposite direction of the stimulus (anti-saccade). We hypothesized that deficits of voluntary control should be revealed not only on saccadic but also on pupil responses because of the recently suggested link between the saccade and pupil control circuits. In elderly controls, pupil size was modulated by task preparation, showing larger dilation prior to stimulus appearance in preparation for correct anti-saccades, compared to correct pro-saccades, or erroneous pro-saccades made in the anti-saccade condition. Moreover, the size of pupil dilation correlated negatively with anti-saccade reaction times. However, this profile of pupil size modulation was significantly blunted in PD patients, reflecting dysfunctional circuits for anti-saccade preparation. Our results demonstrate disruptions of modulated pupil responses by voluntary movement preparation in PD patients, highlighting the potential of using low-cost pupil size measurement to examine executive function deficits in early PD.

Detection of Subtle Cognitive Changes after mTBI Using a Novel Tablet-Based Task

This study examined the potential for novel tablet-based tasks, modeled after eye tracking techniques, to detect subtle sensorimotor and cognitive deficits after mild traumatic brain injury (mTBI). Specifically, we examined whether performance on these tablet-based tasks (Pro-point and Anti-point) was able to correctly categorize concussed versus non-concussed participants, compared with performance on other standardized tests for concussion. Patients admitted to the emergency department with mTBI were tested on the Pro-point and Anti-point tasks, a current standard cognitive screening test (i.e., the Standard Assessment of Concussion [SAC]), and another eye movement-based tablet test, the King-Devick(®) (KD). Within hours after injury, mTBI patients showed significant slowing in response times, compared with both orthopedic and age-matched control groups, in the Pro-point task, demonstrating deficits in sensorimotor function. Mild TBI patients also showed significant slowing, compared with both control groups, on the Anti-point task, even when controlling for sensorimotor slowing, indicating deficits in cognitive function. Performance on the SAC test revealed similar deficits of cognitive function in the mTBI group, compared with the age-matched control group; however, the KD test showed no evidence of cognitive slowing in mTBI patients, compared with either control group. Further, measuring the sensitivity and specificity of these tasks to accurately predict mTBI with receiver operating characteristic analysis indicated that the Anti-point and Pro-point tasks reached excellent levels of accuracy and fared better than current standardized tools for assessment of concussion. Our findings suggest that these rapid tablet-based tasks are able to reliably detect and measure functional impairment in cognitive and sensorimotor control within hours after mTBI. These tasks may provide a more sensitive diagnostic measure for functional deficits that could prove key to earlier detection of concussion, evaluation of interventions, or even prediction of persistent symptoms.

Predicting subsequent task performance from goal motivation and goal failure

Recent research has demonstrated that the cognitive processes associated with goal pursuit can continue to interfere with unrelated tasks when a goal is unfulfilled. Drawing from the self-regulation and goal-striving literatures, the present study explored the impact of goal failure on subsequent cognitive and physical task performance. Furthermore, we examined if the autonomous or controlled motivation underpinning goal striving moderates the responses to goal failure. Athletes (75 male, 59 female, Mage = 19.90 years, SDage = 3.50) completed a cycling trial with the goal of covering a given distance in 8 min. Prior to the trial, their motivation was primed using a video. During the trial they were provided with manipulated performance feedback, thus creating conditions of goal success or failure. No differences emerged in the responses to goal failure between the primed motivation or performance feedback conditions. We make recommendations for future research into how individuals can deal with failure in goal striving.

Anti-saccade error rates as a measure of attentional bias in cocaine dependent subjects

Cocaine-dependent (CD) subjects show attentional bias toward cocaine-related cues, and this form of cue-reactivity may be predictive of craving and relapse. Attentional bias has previously been assessed by models that present drug-relevant stimuli and measure physiological and behavioral reactivity (often reaction time). Studies of several CNS diseases outside of substance use disorders consistently report anti-saccade deficits, suggesting a compromise in the interplay between higher-order cortical processes in voluntary eye control (i.e., anti-saccades) and reflexive saccades driven more by involuntary midbrain perceptual input (i.e., pro-saccades). Here, we describe a novel attentional-bias task developed by using measurements of saccadic eye movements in the presence of cocaine-specific stimuli, combining previously unique research domains to capitalize on their respective experimental and conceptual strengths. CD subjects (N = 46) and healthy controls (N = 41) were tested on blocks of pro-saccade and anti-saccade trials featuring cocaine and neutral stimuli (pictures). Analyses of eye-movement data indicated (1) greater overall anti-saccade errors in the CD group; (2) greater attentional bias in CD subjects as measured by anti-saccade errors to cocaine-specific (relative to neutral) stimuli; and (3) no differences in pro-saccade error rates. Attentional bias was correlated with scores on the obsessive-compulsive cocaine scale. The results demonstrate increased saliency and differential attentional to cocaine cues by the CD group. The assay provides a sensitive index of saccadic (visual inhibitory) control, a specific index of attentional bias to drug-relevant cues, and preliminary insight into the visual circuitry that may contribute to drug-specific cue reactivity.

Prescription Stimulants' Effects on Healthy Inhibitory Control, Working Memory, and Episodic Memory: A Meta-analysis

The use of prescription stimulants to enhance healthy cognition has significant social, ethical, and public health implications. The large number of enhancement users across various ages and occupations emphasizes the importance of examining these drugs' efficacy in a nonclinical sample. The present meta-analysis was conducted to estimate the magnitude of the effects of methylphenidate and amphetamine on cognitive functions central to academic and occupational functioning, including inhibitory control, working memory, short-term episodic memory, and delayed episodic memory. In addition, we examined the evidence for publication bias. Forty-eight studies (total of 1,409 participants) were included in the analyses. We found evidence for small but significant stimulant enhancement effects on inhibitory control and short-term episodic memory. Small effects on working memory reached significance, based on one of our two analytical approaches. Effects on delayed episodic memory were medium in size. However, because the effects on long-term and working memory were qualified by evidence for publication bias, we conclude that the effect of amphetamine and methylphenidate on the examined facets of healthy cognition is probably modest overall. In some situations, a small advantage may be valuable, although it is also possible that healthy users resort to stimulants to enhance their energy and motivation more than their cognition.

Trial-type probability and task-switching effects on behavioral response characteristics in a mixed saccade task

Eye movement circuitry involved in saccade production offers a model for studying cognitive control: visually guided prosaccades are stimulus-directed responses, while goal-driven antisaccades rely upon more complex control processes to inhibit the prepotent tendency to look toward a cue, transform its spatial location, and generate a volitional saccade in the opposite direction. By manipulating the relative probability of these saccade types, we measured participants' behavioral responses to different levels of implicit trial-type probability and task-switching demands in conditions with relatively long inter-trial fixation and trial-type cue lengths. Results indicated that when prosaccades were less probable in a run, more prosaccade errors were generated; however, for antisaccades, trial-type probability had no effect on the percent of correct responses. For reaction times, specifically in runs with a larger probability of antisaccade trials, latencies increased for both anti- and pro-saccades. Furthermore, task switching resulted in a lower percentage of correct responses on switched trials, but a prior antisaccade trial led to slower reaction times for both trial types (i.e., a task switch cost for prosaccades and switch benefit for antisaccades). These findings indicate that cognitive control demands and residual inhibition from antisaccades alter performance relative to trial-type probability and task switching within a run, with the prosaccade task showing greater susceptibility to the influence of a large probability of cognitively complex antisaccades.

Linking attentional processes and conceptual problem solving: visual cues facilitate the automaticity of extracting relevant information from diagrams

This study investigated links between visual attention processes and conceptual problem solving. This was done by overlaying visual cues on conceptual physics problem diagrams to direct participants' attention to relevant areas to facilitate problem solving. Participants (N = 80) individually worked through four problem sets, each containing a diagram, while their eye movements were recorded. Each diagram contained regions that were relevant to solving the problem correctly and separate regions related to common incorrect responses. Problem sets contained an initial problem, six isomorphic training problems, and a transfer problem. The cued condition saw visual cues overlaid on the training problems. Participants' verbal responses were used to determine their accuracy. This study produced two major findings. First, short duration visual cues which draw attention to solution-relevant information and aid in the organizing and integrating of it, facilitate both immediate problem solving and generalization of that ability to new problems. Thus, visual cues can facilitate re-representing a problem and overcoming impasse, enabling a correct solution. Importantly, these cueing effects on problem solving did not involve the solvers' attention necessarily embodying the solution to the problem, but were instead caused by solvers attending to and integrating relevant information in the problems into a solution path. Second, this study demonstrates that when such cues are used across multiple problems, solvers can automatize the extraction of problem-relevant information extraction. These results suggest that low-level attentional selection processes provide a necessary gateway for relevant information to be used in problem solving, but are generally not sufficient for correct problem solving. Instead, factors that lead a solver to an impasse and to organize and integrate problem information also greatly facilitate arriving at correct solutions.

Pre-pulse inhibition and antisaccade performance indicate impaired attention modulation of cognitive inhibition in 22q11.2 deletion syndrome (22q11DS)

BACKGROUND

22q11.2 deletion syndrome (22q11DS) is associated with a number of physical anomalies and neuropsychological deficits including impairments in executive and sensorimotor function. It is estimated that 25% of children with 22q11DS will develop schizophrenia and other psychotic disorders later in life. Evidence of genetic transmission of information processing deficits in schizophrenia suggests performance in 22q11DS individuals will enhance understanding of the neurobiological and genetic substrates associated with information processing. In this report, we examine information processing in 22q11DS using measures of startle eyeblink modification and antisaccade inhibition to explore similarities with schizophrenia and associations with neurocognitive performance.

METHODS

Startle modification (passive and active tasks; 120- and 480-ms pre-pulse intervals) and antisaccade inhibition were measured in 25 individuals with genetically confirmed 22q11DS and 30 healthy control subjects.

RESULTS

Individuals with 22q11DS exhibited increased antisaccade error as well as some evidence (trend-level effect) of impaired sensorimotor gating during the active condition, suggesting a dysfunction in controlled attentional processing, rather than a pre-attentive dysfunction using this paradigm.

CONCLUSIONS

The findings from the present study show similarities with previous studies in clinical populations associated with 22q11DS such as schizophrenia that may indicate shared dysfunction of inhibition pathways in these groups.

Oculomotor inhibitory control in express saccade makers

Express saccade makers (ESMs) produce high proportions (>30 %) of low-latency (80-130 ms) express saccades in tasks in which such responses are usually suppressed. In addition, high directional error rates on the antisaccade (AS) task suggest a failure of oculomotor inhibitory mechanisms in ESMs. However, the AS task is complex and does not provide a measure of inhibitory processes in isolation. We therefore examined inhibitory control in 25 ESM and 28 non-ESM ('Norm') participants, using a minimally delayed oculomotor response (MDOR) task. After a randomised fixation period, a pro-saccade target appeared for 200 or 1,000 ms. Participants were instructed to maintain fixation and saccade to the target position upon target offset. In a control task, they saccaded on target onset. Overall, saccade latency was considerably increased in the MDOR task compared to the control task (354 vs. 170 ms; p < 0.001), and we also observed a latency modulation with display time (200: 399, 1,000: 302 ms; p < 0.001). However, there was no evidence of a difference between groups (p = 0.29). Errors consisted primarily of responses to target onsets and error rates were comparable between the groups (p = 0.33). The overproduction of fast, reflexive responses was still observed in ESMs who generated a higher proportion of their errors within the express latency range (p < 0.001). We confirmed that in the AS task, the ESMs exhibited a higher directional error rate (p = 0.03). These results suggest that the performance 'deficit' observed on the AS task in ESMs cannot be attributed to generally weaker inhibitory control.

What saccadic eye movements tell us about TMS-induced neuromodulation of the DLPFC and mood changes: a pilot study in bipolar disorders

The study assumed that the antisaccade (AS) task is a relevant psychophysical tool to assess (i) short-term neuromodulation of the dorsolateral prefrontal cortex (DLPFC) induced by intermittent theta burst stimulation (iTBS); and (ii) mood change occurring during the course of the treatment. Saccadic inhibition is known to strongly involve the DLPFC, whose neuromodulation with iTBS requires less stimulation time and lower stimulation intensity, as well as results in longer aftereffects than the conventional repetitive transcranial magnetic stimulation (rTMS). Active or sham iTBS was applied every day for 3 weeks over the left DLPFC of 12 drug-resistant bipolar depressed patients. To assess the iTBS-induced short-term neuromodulation, the saccadic task was performed just before (S1) and just after (S2) the iTBS session, the first day of each week. Mood was evaluated through Montgomery and Asberg Depression Rating Scale (MADRS) scores and the difference in scores between the beginning and the end of treatment was correlated with AS performance change between these two periods. As expected, only patients from the active group improved their performance from S1 to S2 and mood improvement was significantly correlated with AS performance improvement. In addition, the AS task also discriminated depressive bipolar patients from healthy control subjects. Therefore, the AS task could be a relevant and useful tool for clinicians to assess if the Transcranial magnetic stimulation (TMS)-induced short-term neuromodulation of the DLPFC occurs as well as a “trait vs. state” objective marker of depressive mood disorder.

Saccadic eye movements in depressed elderly patients

The primary aim of this study was to characterize oculomotor performances in elderly depressed patients. The second aim was to investigate whether cognitive inhibition measured by the antisaccade task was associated with a psychomotor retardation or rather with a more specific cognitive-motor inhibition deficit. Twenty patients with a major depressive disorder and forty-seven healthy subjects performed two eye movement tasks. Saccadic reaction time and error rates were analyzed in the prosaccade task to obtain basic parameters of eye movements. Saccade latency, error rates and correction rates were evaluated in the antisaccade task to investigate inhibition capacities. Performances were impaired in patients, who exhibited a higher reaction time and error rates compared to controls. The higher time cost of inhibition suggested that the reaction time was not related to global psychomotor retardation alone. The higher time cost of inhibition could be explained by a specific alteration of inhibition processes evaluated by the antisaccade task. These changes were associated with the severity of depression. These findings provide a new perspective on cognitive inhibition in elderly depressed patients and could have important clinical implications for our understanding of critical behaviors involving deficits in inhibitory processes in the elderly.

Testing sensory and cognitive explanations of the antisaccade deficit in schizophrenia

Recent research has suggested that people with schizophrenia (PSZ) have sensory deficits, especially in the magnocellular pathway, and this has led to the proposal that dysfunctional sensory processing may underlie higher-order cognitive deficits. Here we test the hypothesis that the antisaccade deficit in PSZ reflects dysfunctional magnocellular processing rather than impaired cognitive processing, as indexed by working memory capacity. This is a plausible hypothesis because oculomotor regions have direct magnocellular inputs, and the stimuli used in most antisaccade tasks strongly activate the magnocellular visual pathway. In the current study, we examined both prosaccade and antisaccade performance in PSZ (N = 22) and matched healthy control subjects (HCS; N = 22) with Gabor stimuli designed to preferentially activate the magnocellular pathway, the parvocellular pathway, or both pathways. We also measured working memory capacity. PSZ exhibited impaired antisaccade performance relative to HCS across stimulus types, with impairment even for stimuli that minimized magnocellular activation. Although both sensory thresholds and working memory capacity were impaired in PSZ, only working memory capacity was correlated with antisaccade accuracy, consistent with a cognitive rather than sensory origin for the antisaccade deficit.

Dorsolateral Prefrontal Cortex Deactivation in Monkeys Reduces Preparatory Beta and Gamma Power in the Superior Colliculus

Cognitive control requires the selection and maintenance of task-relevant stimulus-response associations, or rules. The dorsolateral prefrontal cortex (DLPFC) has been implicated by lesion, functional imaging, and neurophysiological studies to be involved in encoding rules, but the mechanisms by which it modulates other brain areas are poorly understood. Here, the functional relationship of the DLPFC with the superior colliculus (SC) was investigated by bilaterally deactivating the DLPFC while recording local field potentials (LFPs) in the SC in monkeys performing an interleaved pro- and antisaccade task. Event-related LFPs showed differences between pro- and antisaccades and responded prominently to stimulus presentation. LFP power after stimulus onset was higher for correct saccades than erroneous saccades. Deactivation of the DLPFC did not affect stimulus onset related LFP activity, but reduced high beta (20-30 Hz) and high gamma (60-150 Hz) power during the preparatory period for both pro- and antisaccades. Spike rate during the preparatory period was positively correlated with gamma power and this relationship was attenuated by DLPFC deactivation. These results suggest that top-down control of the SC by the DLPFC may be mediated by beta oscillations.

Antisaccade performance in schizophrenia: a neural model of decision making in the superior colliculus

Antisaccade performance deficits in schizophrenia are generally interpreted as an impaired top–down inhibitory signal failing to suppress the erroneous response. We recorded the antisaccade performance (error rates and latencies) of healthy and schizophrenia subjects performing the mirror antisaccade task. A neural rise-to-threshold model of antisaccade performance was developed to uncover the biophysical mechanisms giving rise to the observed deficits in schizophrenia. Schizophrenia patients displayed greater variability in the antisaccade and corrected antisaccade latency distributions, increased error rates and decreased corrected errors, relative to healthy participants. Our model showed that (1) increased variability is due to a more noisy accumulation of information by schizophrenia patients, but their confidence level required before making a decision is unaffected, and (2) competition between the correct and erroneous decision processes, and not a third top-down inhibitory signal suppressing the erroneous response, accounts for the antisaccade performance of healthy and schizophrenia subjects. Local competition further ensured that a correct antisaccade is never followed by an error prosaccade.

Modulation of antisaccade costs through manipulation of target-location probability: only under decisional uncertainty

Latencies of antisaccades made in the direction opposite to a peripheral target are typically slower longer than of prosaccades towards such a target by 50-100 ms. Antisaccades have proved to be an important tool for diagnostic purposes in neurology, psychology and psychiatry, providing invaluable insights into attentional function, decision making and the functionality of eye movement control. Recent findings have suggested, however, that latency differences between pro- and antisaccades can be eliminated by manipulating target-location probabilities. Pro- and antisaccades were equally fast to locations where a target rarely appeared, a finding that may be of promise for more elaborate diagnoses of neurological and psychiatric illness and further understanding of the eye movement system. Here, we tested probability manipulations for a number of different pro- and antisaccade tasks of varied difficulty. Probability only modulated antisaccade costs in a difficult antisaccade task involving decisional uncertainty with low target saliency. For other tasks including standard ones from the literature, target-location probability asymmetries had minimal effects. Probability modulation of antisaccade costs may therefore reflect effects upon decision making rather than saccade generation. This may limit the usefulness of probability manipulations of antisaccades for diagnostic purposes in neurology, psychology and related disciplines.

GazeParser: an open-source and multiplatform library for low-cost eye tracking and analysis

Eye movement analysis is an effective method for research on visual perception and cognition. However, recordings of eye movements present practical difficulties related to the cost of the recording devices and the programming of device controls for use in experiments. GazeParser is an open-source library for low-cost eye tracking and data analysis; it consists of a video-based eyetracker and libraries for data recording and analysis. The libraries are written in Python and can be used in conjunction with PsychoPy and VisionEgg experimental control libraries. Three eye movement experiments are reported on performance tests of GazeParser. These showed that the means and standard deviations for errors in sampling intervals were less than 1 ms. Spatial accuracy ranged from 0.7° to 1.2°, depending on participant. In gap/overlap tasks and antisaccade tasks, the latency and amplitude of the saccades detected by GazeParser agreed with those detected by a commercial eyetracker. These results showed that the GazeParser demonstrates adequate performance for use in psychological experiments.

Effect of maintaining neck flexion on anti-saccade reaction time: an investigation using transcranial magnetic stimulation to the frontal oculomotor field

Background

Reaction time for anti-saccade, in which the gaze is directed to the position opposite to an illuminated target, shortens during maintenance of neck flexion. The present study applied transcranial magnetic stimulation (TMS) to the frontal oculomotor field, and investigated the effect of maintaining neck flexion on information processing time in the anti-saccade neural pathway before the frontal oculomotor field.

Methods

The reaction time was measured with the chin resting on a stand (‘chin-on’ condition) and with voluntary maintenance of neck flexion (‘chin-off’ condition) at 80% maximal neck flexion angle, with and without TMS. The TMS timing producing the longest prolongation of the reaction time was first roughly identified for 10 ms intervals from 0 to 180 ms after the target presentation. Thereafter, TMS timing was set finely at 2 ms intervals from −20 to +20 ms of the 10 ms step that produced the longest prolongation.

Results

The reaction time without TMS was significantly shorter (21.9 ms) for the chin-off (235.9 ± 14.9 ms) than for the chin-on (257.5 ± 17.1 ms) condition. Furthermore, TMS timing producing maximal prolongation of the reaction time was significantly earlier (18.6 ms) for the chin-off than the chin-on condition. The ratio of the forward shift in TMS timing relative to the reduction in reaction time was 87.8%.

Conclusions

We confirmed that information processing time in the anti-saccade neural pathway before the frontal oculomotor field shortened while neck flexion was maintained, and that this reduction time accounted for approximately 88% of the shortening of reaction time.

The role of executive functioning in children's attentional pain control: an experimental analysis

Directing attention away from pain is often used in children's pain treatment programs to control pain. However, empirical evidence concerning its effectiveness is inconclusive. We therefore sought to understand other influencing factors, including executive function and its role in the pain experience. This study investigates the role of executive functioning in the effectiveness of distraction. School children (n=164) completed executive functioning tasks (inhibition, switching, and working memory) and performed a cold-pressor task. One half of the children simultaneously performed a distracting tone-detection task; the other half did not. Results showed that participants in the distraction group were engaged in the distraction task and were reported to pay significantly less attention to pain than controls. Executive functioning influenced distraction task engagement. More specifically, participants with good inhibition and working memory abilities performed the distraction task better; participants with good switching abilities reported having paid more attention to the distraction task. Furthermore, distraction was found to be ineffective in reducing pain intensity and affect. Executive functioning did not influence the effectiveness of distraction. However, a relationship was found between executive functioning and pain affect, indicating that participants with good inhibition and working memory abilities experienced the cold-pressor task as less stressful and unpleasant. Our findings suggest that distraction as a process for managing pain is complex. While it appears that executive function may play a role in adult distraction, in this study it did not direct attention away from pain. It may instead be involved in the overall pain experience.

Shifted neuronal balance during stimulus-response integration in schizophrenia: an fMRI study

Schizophrenia is characterized by marked deficits in executive and psychomotor functions, as demonstrated for goal-directed actions in the antisaccade task. Recent studies, however, suggest that this deficit represents only one manifestation of a general deficit in stimulus-response integration and volitional initiation of motor responses. We here used functional magnetic resonance imaging to investigate brain activation patterns during a manual stimulus-response compatibility task in 18 schizophrenic patients and 18 controls. We found that across groups incongruent vs. congruent responses recruited a bilateral network consisting of dorsal fronto-parietal circuits as well as bilateral anterior insula, dorsolateral prefrontal cortex (DLPFC) and the presupplementary motor area (preSMA). When testing for the main-effect across all conditions, patients showed significantly lower activation of the right DLPFC and, in turn, increased activation in a left hemispheric network including parietal and premotor areas as well as the preSMA. For incongruent responses patients showed significantly increased activation in a similar left hemispheric network, as well as additional activation in parietal and premotor regions in the right hemisphere. The present study reveals that hypoactivity in the right DLPFC in schizophrenic patients is accompanied by hyperactivity in several fronto-parietal regions associated with task execution. Impaired top-down control due to a dysfunctional DLPFC might thus be partly compensated by an up-regulation of task-relevant regions in schizophrenic patients.

Quantitative meta-analysis of fMRI and PET studies reveals consistent activation in fronto-striatal-parietal regions and cerebellum during antisaccades and prosaccades

The antisaccade task is a classic task of oculomotor control that requires participants to inhibit a saccade to a target and instead make a voluntary saccade to the mirror opposite location. By comparison, the prosaccade task requires participants to make a visually-guided saccade to the target. These tasks have been studied extensively using behavioral oculomotor, electrophysiological, and neuroimaging in both non-human primates and humans. In humans, the antisaccade task is under active investigation as a potential endophenotype or biomarker for multiple psychiatric and neurological disorders. A large and growing body of literature has used functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) to study the neural correlates of the antisaccade and prosaccade tasks. We present a quantitative meta-analysis of all published voxel-wise fMRI and PET studies (18) of the antisaccade task and show that consistent activation for antisaccades and prosaccades is obtained in a fronto-subcortical-parietal network encompassing frontal and supplementary eye fields (SEFs), thalamus, striatum, and intraparietal cortex. This network is strongly linked to oculomotor control and was activated to a greater extent for antisaccade than prosaccade trials. Antisaccade but not prosaccade trials additionally activated dorsolateral and ventrolateral prefrontal cortices. We also found that a number of additional regions not classically linked to oculomotor control were activated to a greater extent for antisaccade vs. prosaccade trials; these regions are often reported in antisaccade studies but rarely commented upon. While the number of studies eligible to be included in this meta-analysis was small, the results of this systematic review reveal that antisaccade and prosaccade trials consistently activate a distributed network of regions both within and outside the classic definition of the oculomotor network.

Control of the superior colliculus by the lateral prefrontal cortex

Several decades of patient, functional imaging and neurophysiological studies have supported a model in which the lateral prefrontal cortex (PFC) acts to suppress unwanted saccades by inhibiting activity in the oculomotor system. However, recent results from combined PFC deactivation and neural recordings of the superior colliculus in monkeys demonstrate that the primary influence of the PFC on the oculomotor system is excitatory, and stands in direct contradiction to the inhibitory model of PFC function. Although erroneous saccades towards a visual stimulus are commonly labelled reflexive in patients with PFC damage or dysfunction, the latencies of most of these saccades are outside of the range of express saccades, which are triggered directly by the visual stimulus. Deactivation and pharmacological manipulation studies in monkeys suggest that response errors following PFC damage or dysfunction are not the result of a failure in response suppression but can best be understood in the context of a failure to maintain and implement the proper task set.

Differentiating between Verbal and Spatial Encoding using Eye-Movement Recordings

Visual information processing is guided by an active mechanism generating saccadic eye movements to salient stimuli. Here we investigate the specific contribution of saccades to memory encoding of verbal and spatial properties in a serial recall task. In the first experiment, participants moved their eyes freely without specific instruction. We demonstrate the existence of qualitative differences in eye-movement strategies during verbal and spatial memory encoding. While verbal memory encoding was characterized by shifting the gaze to the to-be-encoded stimuli, saccadic activity was suppressed during spatial encoding. In the second experiment, participants were required to suppress saccades by fixating centrally during encoding or to make precise saccades onto the memory items. Active suppression of saccades had no effect on memory performance, but tracking the upcoming stimuli decreased memory performance dramatically in both tasks, indicating a resource bottleneck between display-controlled saccadic control and memory encoding. We conclude that optimized encoding strategies for verbal and spatial features are underlying memory performance in serial recall, but such strategies work on an involuntary level only and do not support memory encoding when they are explicitly required by the task.

The antisaccade task performance deficit and specific CNV abnormalities in patients with stereotyped paraphilia and schizophrenia

Antisaccade task performance and mean amplitudes of slow cortical potentials (contingent negative variation--CNV) were investigated in 19 healthy volunteers, 16 schizophrenic patients (SP), and 12 patients with stereotyped form of paraphilia (PP). Compared with healthy subjects, schizophrenic and paraphilic patients committed significantly more erroneous saccades. The clear between-group CNV differences were observed during the early CNV stage that is associated with cognitive aspects of preparatory set. In SP, as compared to controls, the significant decline of CNV amplitude was found at frontal-central area. PP have demonstrated the lack of CNV over central and parietal regions, but their CNV amplitudes in frontal area did not differ from values of control group. Thus, two distinct types of CNV abnormalities have been found. The SP results have been interpreted as support for frontal dysfunction in schizophrenia. The disconnection between prefrontal cortex, sensorimotor cortex, and related subcortical structures is hypothesized in paraphilia group.

The dorsal attentional system in oculomotor learning of predictive information

The dorsal attentional network is known for its role in directing top-down visual attention toward task-relevant stimuli. This goal-directed nature of the dorsal network makes it a suitable candidate for processing and extracting predictive information from the visual environment. In this review we briefly summarize some of the findings that delineate the neural substrates that contribute to predictive learning at both levels within the dorsal attentional system: including the frontal eye field (FEF) and posterior parietal cortex (PPC). We also discuss the similarities and differences between these two regions when it comes to learning predictive information. The current findings from the literature suggest that the FEFs may be more involved in top-down spatial attention, whereas the parietal cortex is involved in processing task-relevant attentional influences driven by stimulus salience, both contribute to the processing of predictive cues at different time points.

Fixational saccades reflect volitional action preparation

Human volitional actions are preceded by preparatory processes, a critical mental process of cognitive control for future behavior. Volitional action preparation is regulated by large-scale neural circuits including the cerebral cortex and the basal ganglia. Because volitional action preparation is a covert process, the network dynamics of such neural circuits have been examined by neuroimaging and recording event-related potentials. Here, we examined whether such covert processes can be measured by the overt responses of fixational saccades (including microsaccades), the largest miniature eye movements that occur during eye fixation. We analyzed fixational saccades while adult humans maintained fixation on a central visual stimulus as they prepared to generate a volitional saccade in response to peripheral stimulus appearance. We used the antisaccade paradigm, in which subjects generate a saccade toward the opposite direction of a peripheral stimulus. Appropriate antisaccade performance requires the following two aspects of volitional control: 1) facilitation of saccades away from the stimulus and 2) suppression of inappropriate saccades toward the stimulus. We found that fixational saccades that occurred before stimulus appearance reflected the dual preparatory states of saccade facilitation and suppression and correlated with behavioral outcome (i.e., whether subjects succeeded or failed to cancel inappropriate saccades toward the stimulus). Moreover, fixational saccades explained a large proportion of individual differences in behavioral performance (poor/excellent) across subjects. These results suggest that fixational saccades predict the outcome of future volitional actions and may be used as a potential biomarker to detect people with difficulties in volitional action preparation.