The antisaccade task as a research tool in psychopathology: a critical review

Antisaccade performance in schizophrenia patients, their first-degree biological relatives, and community comparison subjects: data from the COGS study

The antisaccade task is a widely used technique to measure failure of inhibition, an important cause of cognitive and clinical abnormalities found in schizophrenia. Although antisaccade performance, which reflects the ability to inhibit prepotent responses, is a putative schizophrenia endophenotype, researchers have not consistently reported the expected differences between first-degree relatives and comparison groups. Schizophrenia participants (n=219) from the large Consortium on the Genetics of Schizophrenia (COGS) sample (n=1078) demonstrated significant deficits on an overlap version of the antisaccade task compared to their first-degree relatives (n=443) and community comparison subjects (CCS; n=416). Although mean antisaccade performance of first-degree relatives was intermediate between schizophrenia participants and CCS, a linear mixed-effects model adjusting for group, site, age, and gender found no significant performance differences between the first-degree relatives and CCS. However, admixture analyses showed that two components best explained the distributions in all three groups, suggesting two distinct doses of an etiological factor. Given the significant heritability of antisaccade performance, the effects of a genetic polymorphism is one possible explanation of our results.

Catechol-O-methyltransferase Val 158 Met polymorphism and antisaccade eye movements in schizophrenia

The catechol-O-methyltransferase (COMT) enzyme catabolizes dopamine. The val(158)met single nucleotide polymorphism (rs4680) in the COMT gene has received considerable attention as a candidate gene for schizophrenia as well as for frontally mediated cognitive functions. Antisaccade performance is a good measure of frontal lobe integrity. Deficits on the task are considered a trait marker for schizophrenia. The aim of this study was to investigate the association of COMT val(158)met polymorphism with antisaccade eye movements in schizophrenia patients and healthy controls. Schizophrenia patients (N = 105) and healthy controls (N = 95) underwent infrared oculographic assessment of antisaccades. Subjects were genotyped for COMT val(158)met and divided into 3 groups according to genotype (val/val, val/met, and met/met). Patients displayed significantly more reflexive errors, longer and more variable latency, and lower amplitude gain than controls (all P < 0.02). A greater number of val(158) alleles was associated with shorter (P = 0.045) and less variable (P = 0.028) antisaccade latency and, nonsignificantly, with lower reflexive error rate (P = 0.056). None of these variables showed a group-by-genotype interaction (P > 0.1). There were no significant associations of genotype with measures of amplitude gain or spatial error (P > 0.2). The results suggest that COMT val(158) carrier status is associated with better performance on the antisaccade task. Possible explanations of this finding are discussed.

Cognitive control and attentional selection in adolescents with ADHD versus ADD

An important research question is whether Attention Deficit Hyperactivity Disorder (ADHD) is related to early- or late-stage attentional control mechanisms and whether this differentiates a nonhyperactive subtype (ADD). This question was addressed in a sample of 145 ADD/ADHD and typically developing comparison adolescents (aged 13-17). Attentional blink and antisaccade tasks were used to assay early- and late-stage control, respectively. ADD was defined using normative cutoffs to ensure low activity level in children who otherwise met full criteria for ADHD. The ADD group had an attenuated attentional blink versus controls and ADHD-combined. The effect was not produced using DSM--IV definition of ADHD-primarily inattentive type or DSM symptom counts. ADHD-combined showed greater weakness in response inhibition, as manifest in the antisaccade task. Combining tasks yielded an interaction differentiating group performance on the two tasks.

Response suppression deficits in treatment-naïve first-episode patients with schizophrenia, psychotic bipolar disorder and psychotic major depression

Recent evidence indicates common genetic, neurobiological, and psychopharmacological aspects of schizophrenia and psychotic affective disorders. Some similarities in neurocognitive deficits associated with these disorders have also been reported. We investigated performance on antisaccade and visually-guided saccade tasks in treatment-naïve first-episode psychosis patients (schizophrenia n=59, major depression n=15, bipolar disorder n=9), matched non-psychotic major depression patients (n=40), and matched healthy individuals (n=106). All psychosis groups displayed elevated antisaccade error rates relative to healthy individuals. Antisaccade latencies were elevated in schizophrenia, but no significant error rate or latency differences were observed among psychosis groups. For schizophrenia only, shorter visually guided saccade latencies were associated with higher antisaccade error rates. Schizophrenia was also the only group without a significant relationship between visually guided and antisaccade latencies. Reflexive saccades were unimpaired except in psychotic unipolar depression, where saccades were hypometric. As in schizophrenia, antisaccade abnormalities are present in affective psychoses, even early in the course of illness and prior to treatment. Disturbances in frontostriatal systems are believed to occur in both affective psychoses and schizophrenia, potentially causing some similar cognitive abnormalities across psychotic disorders. However, the distinct pattern of dysfunction in schizophrenia across oculomotor paradigms suggests possible unique causes of their observed oculomotor performance deficits.

Probing the attentional control theory in social anxiety: an emotional saccade task

Volitional attentional control has been found to rely on prefrontal neuronal circuits. According to the attentional control theory of anxiety, impairment in the volitional control of attention is a prominent feature in anxiety disorders. The present study investigated this assumption in socially anxious individuals using an emotional saccade task with facial expressions (happy, angry, fearful, sad, neutral). The gaze behavior of participants was recorded during the emotional saccade task, in which participants performed either pro- or antisaccades in response to peripherally presented facial expressions. The results show that socially anxious persons have difficulties in inhibiting themselves to reflexively attend to facial expressions: They made more erratic prosaccades to all facial expressions when an antisaccade was required. Thus, these findings indicate impaired attentional control in social anxiety. Overall, the present study shows a deficit of socially anxious individuals in attentional control-for example, in inhibiting the reflexive orienting to neutral as well as to emotional facial expressions. This result may be due to a dysfunction in the prefrontal areas being involved in attentional control.

Why do humans make antisaccade errors?

Antisaccade errors are attributed to failure to inhibit the habitual prosaccade. We investigated whether the amount of information about the required response the patient has before the trial begins also contributes to error rate. Participants performed antisaccades in five conditions. The traditional design had two goals on the left and right horizontal meridians. In the second condition, stimulus-goal confusability between trials was eliminated by displacing one goal upward. In the third, hemifield uncertainty was eliminated by placing both goals in the same hemifield. In the fourth, goal uncertainty was eliminated by having only one goal, but interspersed with no-go trials. The fifth condition eliminated all uncertainty by having the same goal on every trial. Antisaccade error rate increased by 2% with each additional source of uncertainty, with the main effect being hemifield information, and a trend for stimulus-goal confusability. A control experiment for the effects of increasing angular separation between targets without changing these types of prior response information showed no effects on latency or error rate. We conclude that other factors besides prosaccade inhibition contribute to antisaccade error rates in traditional designs, possibly by modulating the strength of goal activation.

Neuropsychological correlates of eye movement abnormalities in schizophrenic patients and their unaffected relatives

Impairments on neuropsychological and eye movement tasks have been demonstrated in schizophrenic patients and also reported in their unaffected relatives. However, it is not clear to what extent these phenotypes overlap. This study examined the relationship between specific eye movement and neuropsychological measures. The relationship between performance on eye movement and neuropsychological tasks was measured in 79 schizophrenic patients (63% from multiply affected families), 129 of their healthy first-degree relatives, and 72 normal controls. Antisaccade scores were correlated with most measures of neurocognitive functioning, and this correlation was strongest in schizophrenic patients in all cases. In the schizophrenic patients, but not their relatives or controls, the antisaccade distractibility error (ADE) score correlated significantly with current intelligence, verbal memory (immediate and delayed recall), and associative learning. In the case of crystallised IQ and delayed verbal memory, smaller correlations were present in unaffected relatives, although neither survived Bonferroni correction. Smooth pursuit performance was unrelated to any neuropsychological measure. Our study suggests that antisaccade errors are likely to represent part of a generalized neuropsychological deficit in schizophrenia.

Impaired control of the oculomotor reflexes in Parkinson's disease

To investigate the role of the basal ganglia in integrating voluntary and reflexive behaviour, the current study examined the ability of patients with Parkinson's disease to voluntarily control oculomotor reflexes. We measured the size of the fixation offset effect (the reduction in saccadic reaction time when a fixation point is removed) during a block of pro- and a block of anti-saccades. Healthy controls showed the expected reduction of the FOE during the anti-saccades, which results from efforts to suppress reflexive eye movements (a preparatory set characterized by increased internal control and reduced external control). However, there was no reduction of the FOE in the anti-saccade task in Parkinson's patients, indicating that they are impaired in exerting control over oculomotor reflexes.

Is persistent ketamine use a valid model of the cognitive and oculomotor deficits in schizophrenia?

BACKGROUND

Acute ketamine has been shown to model features of schizophrenia such as psychotic symptoms, cognitive deficits and smooth pursuit eye movement dysfunction. There have been suggestions that chronic ketamine may also produce an analogue of the disorder. In this study, we investigated the effect of persistent recreational ketamine use on tests of episodic and working memory and on oculomotor tasks of smooth pursuit and pro- and antisaccades.

METHODS

Twenty ketamine users were compared with 1) 20 first-episode schizophrenia patients, 2) 17 polydrug control subjects who did not use ketamine but were matched to the ketamine users for other drug use, and 3) 20 non-drug-using control subjects. All groups were matched for estimated premorbid IQ.

RESULTS

Ketamine users made more antisaccade errors than both control groups but did not differ from patients. Ketamine users performed better than schizophrenia patients on smooth pursuit, antisaccade metrics, and both memory tasks but did not differ from control groups.

CONCLUSIONS

Problems inhibiting reflexive eye movements may be a consequence of repeated ketamine self-administration. The absence of any other oculomotor or cognitive deficit present in schizophrenia suggests that chronic self-administration of ketamine may not be a good model of these aspects of the disorder.

Response switching in schizophrenia patients and healthy subjects: effects of the inter-response interval

Schizophrenia patients show impaired saccadic response switching, pointing to action control deficits at the level of response selection. Previous studies on healthy subjects suggested that response switch effects might decrease if the prior response is longer ago, reflecting a slow dissipation of the response program persisting from the previous trial. The present study aimed at directly investigating whether response switch effects in schizophrenia patients and healthy subjects depend on the inter-response interval (IRI). Effects of response switching on pro- and antisaccade performance were analyzed in 19 schizophrenia patients and 19 healthy controls at 3 different IRIs (2,500, 3,000, 4,000 ms). Response switch effects of healthy subjects did not vary with the IRI, suggesting that the previous response program persists as long as no contrary response program is activated. In schizophrenia, response switch deficits were replicated at an IRI of 3,000 ms, whereas at IRIs of 2,500 and 4,000 ms, effects of response switching did not significantly differ from healthy subjects. This might suggest that there is a specific IRI range particularly sensitive to response switch deficits in schizophrenia. However, effects of response switching at different IRIs remain to be consolidated.

Monkey prefrontal cortical pyramidal and putative interneurons exhibit differential patterns of activity between prosaccade and antisaccade tasks

Previous studies have shown that prefrontal cortex (PFC) neurons carry task-related activity; however, it is largely unknown how this selectivity is implemented in PFC microcircuitry. Here, we exploited known differences in extracellular action potential waveforms, and antidromic identification, to classify PFC neurons as putative pyramidal or interneurons, and investigate their relative contributions to task-selectivity. We recorded the activity of prefrontal neurons while monkeys performed a blocked pro/antisaccade task in which they were required to look either toward or away from a peripheral visual stimulus. We found systematic differences in activity between neuron classes. Putative pyramidal neurons had higher stimulus-related activity on antisaccade trials, whereas putative interneurons exhibited greater activity for prosaccades. These findings suggest that task-selectivity in the PFC may be shaped by interactions between these neuronal classes. They are also consistent with the robust deficits in antisaccade performance frequently observed in disease states associated with PFC dysfunction.

Turning it upside down: areas of preserved cognitive function in schizophrenia

Patients with schizophrenia demonstrate marked impairments on most clinical neuropsychological tests. These findings suggest that patients suffer from a generalized form of cognitive impairment, with little evidence of spared performance documented in several large meta-analytic reviews of the clinical literature. In contrast, we review evidence for relative sparing of aspects of attention, procedural memory, and emotional processing observed in studies that have employed experimental approaches adapted from the cognitive and affective neuroscience literature. These islands of preserved performance suggest that the cognitive deficits in schizophrenia are not as general as they appear to be when assayed with clinical neuropsychological methods. The apparent contradiction in findings across methods may offer important clues about the nature of cognitive impairment in schizophrenia. The documentation of preserved cognitive function in schizophrenia may serve to sharpen hypotheses about the biological mechanisms that are implicated in the illness.

Antisaccade performance in patients with multiple sclerosis

Commonly used measures of disability in patients with Multiple sclerosis (MS) inadequately reflect disease severity and progression. Further, cognitive deficits experienced by up to 70% of patients, are poorly represented by these measures. Saccadic eye movements may provide a powerful tool for the analysis of cognitive changes in MS, providing a surrogate measure of performance that extends more conventional measures. The cognitive control of eye movements has not previously been investigated in patients with MS. We studied antisaccade (AS) performance in 25 patients with MS and compared the results with 25 age matched healthy controls, to evaluate the resolution of response conflict between volitional and automatic processes. Experimental measures were also correlated with a battery of neuropsychological tests evaluating attention, working memory and executive processes, the most commonly reported cognitive deficits in MS. Compared to controls, patients with MS generated significantly more prosaccade errors, and AS latencies were prolonged and more variable. Error rates correlated significantly with scores on the commonly used PASAT. MS patients also exhibited poor spatial accuracy, with mean absolute error significantly larger and more variable than control subjects. The sensitivity of this task in dissociating function in MS, as well as clear correlation with a key measure of cognition, suggests that eye movements, may provide a surrogate measure of cognitive function in MS, with the potential to sensitively assess disease severity and progression.

Using the antisaccade task to investigate the relationship between the development of inhibition and the development of intelligence

A number of authors have proposed models of cognitive development that explain improvements in intelligence over the course of childhood via changes in the efficiency of inhibitory processes (Anderson, 2001; Bjorklund & Harnishfeger, 1990; Dempster, 1991, 1992; Dempster & Corkill, 1999a; Harnishfeger, 1995; Harnishfeger & Bjorklund, 1993). A review of the literature reveals little empirical support for the thesis. This is largely due to a failure to distinguish between age-related and non-age-related changes in both inhibitory ability and intelligence. Empirical evidence is presented from a developmental study employing the antisaccade task to provide support for the role of inhibitory processes in the development of intelligence. Additionally, a case is made for a functional difference underlying antisaccade errors that are subsequently corrected and those that remain uncorrected.

CHRFAM7A copy number and 2-bp deletion polymorphisms and antisaccade performance

Chromosome 15q13-q14 harbours the gene for the alpha7 nicotinic acetylcholine receptor subunit (CHRNA7) and a related gene (CHRFAM7A) which arises from a partly duplicated portion of CHRNA7. Recent evidence suggests that CHRFAM7A is a locus with a possible role in schizophrenia and cognitive functioning. We studied an antisaccade task as a fronto-parietal measure of executive function that reflects risk for schizophrenia. Association of CHRFAM7A genotype with antisaccade performance was assessed in 103 healthy Caucasian individuals. No significant associations of 2-bp deletion or CHRFAM7A copy number with antisaccade performance parameters were observed. The failure to observe an association between antisaccade performance and polymorphisms in CHRFAM7A gene is consistent with specificity of the gene effects on hippocampal and memory functions as previously demonstrated.

Cognitive control of saccadic eye movements

The saccadic eye movement system provides researchers with a powerful tool with which to explore the cognitive control of behaviour. It is a behavioural system whose limited output can be measured with exceptional precision, and whose input can be controlled and manipulated in subtle ways. A range of cognitive processes (notably those involved in working memory and attention) have been shown to influence saccade parameters. Researchers interested in the relationship between cognitive function and psychiatric disorders have made extensive use of saccadic eye movement tasks to draw inferences as to the cognitive deficits associated with particular psychopathologies. The purpose of this review is to provide researchers with an overview of the research literature documenting cognitive involvement in saccadic tasks in healthy controls. An appreciation of this literature provides a solid background against which to interpret the deficits on saccadic tasks demonstrated in patient populations.

Anxiety, Inhibition, Efficiency, and Effectiveness

Effects of anxiety on the antisaccade task were assessed. Performance effectiveness on this task (indexed by error rate) reflects a conflict between volitional and reflexive responses resolved by inhibitory processes (Hutton, S. B., & Ettinger, U. (2006). The antisaccade task as a research tool in psychopathology: A critical review. Psychophysiology, 43, 302–313). However, latency of the first correct saccade reflects processing efficiency (relationship between performance effectiveness and use of resources). In two experiments, high-anxious participants had longer correct antisaccade latencies than low-anxious participants and this effect was greater with threatening cues than positive or neutral ones. The high- and low-anxious groups did not differ in terms of error rate in the antisaccade task. No group differences were found in terms of latency or error rate in the prosaccade task. These results indicate that anxiety affects performance efficiency but not performance effectiveness. The findings are interpreted within the context of attentional control theory (Eysenck, M. W., Derakshan, N., Santos, R., & Calvo, M. G. (2007). Anxiety and cognitive performance: Attentional control theory. Emotion, 7 (2), 336–353).

Anxiety, Processing Efficiency, and Cognitive Performance

There have been many attempts to account theoretically for the effects of anxiety on cognitive performance. This article focuses on two theories based on insights from cognitive psychology. The more recent is the attentional control theory ( Eysenck, Derakshan, Santos, & Calvo, 2007 ), which developed from the earlier processing efficiency theory ( Eysenck & Calvo, 1992 ). Both theories assume there is a fundamental distinction between performance effectiveness (quality of performance) and processing efficiency (the relationship between performance effectiveness and use of processing resources), and that anxiety impairs processing efficiency more than performance effectiveness. Both theories also assume that anxiety impairs the efficiency of the central executive component of the working memory system. In addition, attentional control theory assumes that anxiety impairs the efficiency of two types of attentional control: (1) negative attentional control (involved in inhibiting attention to task-irrelevant stimuli); and (2) positive attentional control (involved in flexibly switching attention between and within tasks to maximize performance). Recent (including unpublished) research relevant to theoretical predictions from attentional control theory is discussed. In addition, future directions for theory and research in the area of anxiety and performance are presented.

Antisaccade performance is related to genetic loading for schizophrenia

Disturbances of the oculomotor system are promising endophenotypes for schizophrenia. Increased error rates in the antisaccade task and prolonged antisaccade latencies have been found in patients with schizophrenia and their first degree relatives. We investigated oculomotor performance in 41 parents of schizophrenia patients and 22 controls with a prosaccade task and an antisaccade task. Parents were grouped into parents with a positive family history for schizophrenia (N=9) and parents with a negative family history for schizophrenia (N=32). An overlap-paradigm was applied; eye movements were recorded using infrared oculography. The combined group of parents made more antisaccade direction errors than controls (p=0.005) and there was a linear increase in direction errors from controls via negative family history parents to positive family history parents (p=0.008). Antisaccade latencies were prolonged in the combined parent group (p=0.057) compared to controls and there was a linear increase in latency with genetic loading (p=0.018). No group differences were found for prosaccade parameters. These results support the hypothesis that antisaccade impairment is associated with genetic loading for schizophrenia.

Common neural circuitry supporting volitional saccades and its disruption in schizophrenia patients and relatives

BACKGROUND

People with schizophrenia and their biological relatives have deficits in executive control processes such as inhibition and working memory as evidenced by performance abnormalities on antisaccade (AS) and ocular motor delayed response (ODR) tasks.

METHODS

The present functional magnetic resonance imaging (fMRI) study was conducted to investigate brain activity associated with these putative indices of schizophrenia risk by: 1) directly comparing neural functioning in 15 schizophrenia patients, 13 of their first-degree biological relatives (primarily siblings), and 14 healthy participants; and 2) assessing executive function associated with volitional saccades by using a combination of AS and ODR tasks.

RESULTS

Behavioral data showed that patients and relatives both made more volitional saccade errors. Imaging data demonstrated that within the context of preserved activity in some neural regions in patients and relatives, there were two distinct patterns of disruptions in other regions. First, there were deficits observed only in the schizophrenia group (decreased activity in lateral frontal eye field and supplementary eye field), suggesting a change associated with disease manifestation. Second, there were deficits observed in both patients and relatives (decreased activity in middle occipital gyrus, insula, cuneus, anterior cingulate, and Brodmann area 10 in prefrontal cortex), indicating a potential association with disease risk.

CONCLUSIONS

Results indicate that decreased brain activation in regions involved in managing and evaluating early sensory and attention processing might be associated with poor volitional saccade control and risk for developing schizophrenia.

Catechol-O-methyltransferase (COMT) val158met genotype is associated with BOLD response as a function of task characteristic

The catechol-O-methyltransferase (COMT) val(158)met single nucleotide polymorphism (rs4680) has been shown to be associated with brain activation during a number of neurocognitive and emotional tasks. The present study evaluated genotypic associations with brain function during measurement of cognitive stability (prosaccades) and plasticity (antisaccades). A total of 36 healthy volunteers were genotyped for rs4680 and underwent functional magnetic resonance imaging (fMRI) at 1.5 T. Individuals with at least one val(158) allele (val(158) carriers, N=24) showed lower blood oxygen level-dependent (BOLD) response in ventromedial and dorsomedial prefrontal cortex during antisaccades compared to val(158) noncarriers, whereas met(158) homozygotes (N=12) showed lower BOLD response in a cluster in the posterior cingulate and precuneus during prosaccades compared to val(158) carriers. These findings suggest that associations of COMT val(158)met genotype with brain function may be mediated by task characteristics. The findings may be compatible with a hypothesis on the role of COMT val(158)met genotype in tonic and phasic dopamine levels in brain and differential effects on cognitive measures of stability (eg prosaccades) and plasticity (eg antisaccades).

Development of eye-movement control

Cognitive control of behavior continues to improve through adolescence in parallel with important brain maturational processes including synaptic pruning and myelination, which allow for efficient neuronal computations and the functional integration of widely distributed circuitries supporting top-down control of behavior. This is also a time when psychiatric disorders, such as schizophrenia and mood disorders, emerge reflecting a particularly vulnerability to impairments in development during adolescence. Oculomotor studies provide a unique neuroscientific approach to make precise associations between cognitive control and brain circuitry during development that can inform us of impaired systems in psychopathology. In this review, we first describe the development of pursuit, fixation, and visually-guided saccadic eye movements, which collectively indicate early maturation of basic sensorimotor processes supporting reflexive, exogenously-driven eye movements. We then describe the literature on the development of the cognitive control of eye movements as reflected in the ability to inhibit a prepotent eye movement in the antisaccade task, as well as making an eye movement guided by on-line spatial information in working memory in the oculomotor delayed response task. Results indicate that the ability to make eye movements in a voluntary fashion driven by endogenous plans shows a protracted development into adolescence. Characterizing the transition through adolescence to adult-level cognitive control of behavior can inform models aimed at understanding the neurodevelopmental basis of psychiatric disorders.

Imaging and imagining: current positions on the epistemic priority of theoretical concepts and data in psychiatric neuroimaging

PURPOSE OF REVIEW

To give an overview of recent developments in neuroimaging in psychiatry and on the current discussion about the relationship between theoretical concepts and data from neuroimaging studies.

RECENT FINDINGS

In psychiatric neuroimaging, broad concepts such as the self, well being, insight, empathy and volition form an integral part of the questions to be answered and cannot be avoided. Although, currently, the intradisciplinary discussion in neuroscience is mainly focused at the methodological and neurobiological level, psychological and philosophical theories are also needed for the interpretation of results. This raises questions regarding the epistemic priority of neuroimaging data and theories.

SUMMARY

In the current paper, we present the hypothesis that there is an interdependence of neuroimaging data and theoretical concepts. An approach to 'correlational neuroscience' with an awareness of this issue may help in avoiding misunderstandings and oversimplifications as well as building an interdisciplinary theoretical framework that is able to integrate findings from life sciences, mind sciences and humanities.

Eye movement dysfunction in first-degree relatives of patients with schizophrenia: a meta-analytic evaluation of candidate endophenotypes

Several forms of eye movement dysfunction (EMD) are regarded as promising candidate endophenotypes of schizophrenia. Discrepancies in individual study results have led to inconsistent conclusions regarding particular aspects of EMD in relatives of schizophrenia patients. To quantitatively evaluate and compare the candidacy of smooth pursuit, saccade and fixation deficits in first-degree biological relatives, we conducted a set of meta-analytic investigations. Among 18 measures of EMD, memory-guided saccade accuracy and error rate, global smooth pursuit dysfunction, intrusive saccades during fixation, antisaccade error rate and smooth pursuit closed-loop gain emerged as best differentiating relatives from controls (standardized mean differences ranged from .46 to .66), with no significant differences among these measures. Anticipatory saccades, but no other smooth pursuit component measures were also increased in relatives. Visually-guided reflexive saccades were largely normal. Moderator analyses examining design characteristics revealed few variables affecting the magnitude of the meta-analytically observed effects. Moderate effect sizes of relatives v. controls in selective aspects of EMD supports their endophenotype potential. Future work should focus on facilitating endophenotype utility through attention to heterogeneity of EMD performance, relationships among forms of EMD, and application in molecular genetics studies.

The effect of change in clinical state on eye movement dysfunction in schizophrenia

Measures of eye movement dysfunction have been considered as candidate endophenotypes for the study of genetic liability in schizophrenia. In this respect it is crucial to confirm a clinical state independentce of these measures. Twenty people with DSM-IV schizophrenia were assessed using a battery of oculomotor tasks in the acute phase of their disorder without being treated with antipsychotic medication and then again in the remission phase under treatment with antipsychotic medication. The saccade latency in the saccade task, the error rate and antisaccade latency in the antisaccade task, and the frequency of unwanted saccades in the active fixation task were stable in time both at the group level and within each individual, showing no relation to the significant improvement in different psychopathological dimensions of these patients. The root mean square error, gain and saccade frequency in the pursuit task were not stable over time, although again this instability was not related to the changes in psychopathological status of these patients. Finally, the saccade frequency in the active fixation task with distracters was not stable in time and was correlated with changes in specific dimensions of psychopathology. These results provide further evidence that saccade and smooth eye pursuit dysfunction measures are not affected by the substantial change in the clinical state of schizophrenia from the acute phase to remission, and strengthen the current view that they can be used as endophenotypes. On the other hand, active fixation might be state-dependent adding to the evidence against its use as a candidate endophenotype in schizophrenia.

Neurophysiology and neuroanatomy of reflexive and volitional saccades as revealed by lesion studies with neurological patients and transcranial magnetic stimulation (TMS)

This review discusses the neurophysiology and neuroanatomy of the cortical control of reflexive and volitional saccades in humans. The main focus is on classical lesion studies and studies using the interference method of transcranial magnetic stimulation (TMS). To understand the behavioural function of a region, it is essential to assess oculomotor deficits after a focal lesion using a variety of oculomotor paradigms, and to study the oculomotor consequences of the lesion in the chronic phase. Saccades are controlled by different cortical regions, which could be partially specialised in the triggering of a specific type of saccade. The division of saccades into reflexive visually guided saccades and intentional or volitional saccades corresponds to distinct regions of the neuronal network, which are involved in the control of such saccades. TMS allows to specifically interfere with the functioning of a region within an intact oculomotor network. TMS provides advantages in terms of temporal resolution, allowing to interfere with brain functioning in the order of milliseconds, thereby allowing to define the time course of saccade planning and execution. In the first part of the paper, we present an overview of the cortical structures important for saccade control, and discuss the pro's and con's of the different methodological approaches to study the cortical oculomotor network. In the second part, the functional network involved in reflexive and volitional saccades is presented. Finally, studies concerning recovery mechanisms after a lesion of the oculomotor cortex are discussed.

Neurophysiology and neuroanatomy of reflexive and volitional saccades: evidence from studies of humans

This review provides a summary of the contributions made by human functional neuroimaging studies to the understanding of neural correlates of saccadic control. The generation of simple visually guided saccades (redirections of gaze to a visual stimulus or pro-saccades) and more complex volitional saccades require similar basic neural circuitry with additional neural regions supporting requisite higher level processes. The saccadic system has been studied extensively in non-human (e.g., single-unit recordings) and human (e.g., lesions and neuroimaging) primates. Considerable knowledge of this system's functional neuroanatomy makes it useful for investigating models of cognitive control. The network involved in pro-saccade generation (by definition largely exogenously-driven) includes subcortical (striatum, thalamus, superior colliculus, and cerebellar vermis) and cortical (primary visual, extrastriate, and parietal cortices, and frontal and supplementary eye fields) structures. Activation in these regions is also observed during endogenously-driven voluntary saccades (e.g., anti-saccades, ocular motor delayed response or memory saccades, predictive tracking tasks and anticipatory saccades, and saccade sequencing), all of which require complex cognitive processes like inhibition and working memory. These additional requirements are supported by changes in neural activity in basic saccade circuitry and by recruitment of additional neural regions (such as prefrontal and anterior cingulate cortices). Activity in visual cortex is modulated as a function of task demands and may predict the type of saccade to be generated, perhaps via top-down control mechanisms. Neuroimaging studies suggest two foci of activation within FEF - medial and lateral - which may correspond to volitional and reflexive demands, respectively. Future research on saccade control could usefully (i) delineate important anatomical subdivisions that underlie functional differences, (ii) evaluate functional connectivity of anatomical regions supporting saccade generation using methods such as ICA and structural equation modeling, (iii) investigate how context affects behavior and brain activity, and (iv) use multi-modal neuroimaging to maximize spatial and temporal resolution.

A review on eye movement studies in childhood and adolescent psychiatry

The neural substrates of eye movement measures are largely known. Therefore, measurement of eye movements in psychiatric disorders may provide insight into the underlying neuropathology of these disorders. Visually guided saccades, antisaccades, memory guided saccades, and smooth pursuit eye movements will be reviewed in various childhood psychiatric disorders. The four aims of this review are (1) to give a thorough overview of eye movement studies in a wide array of psychiatric disorders occurring during childhood and adolescence (attention-deficit/hyperactivity disorder, oppositional deviant disorder and conduct disorder, autism spectrum disorders, reading disorder, childhood-onset schizophrenia, Tourette's syndrome, obsessive compulsive disorder, and anxiety and depression), (2) to discuss the specificity and overlap of eye movement findings across disorders and paradigms, (3) to discuss the developmental aspects of eye movement abnormalities in childhood and adolescence psychiatric disorders, and (4) to present suggestions for future research. In order to make this review of interest to a broad audience, attention will be given to the clinical manifestation of the disorders and the theoretical background of the eye movement paradigms.

Pilot study of response inhibition and error processing in the posterior medial prefrontal cortex in healthy youth

BACKGROUND

Recent neuroimaging work suggests that inhibitory and error processing in healthy adults share overlapping, but functionally distinct neural circuitries within the posterior medial frontal cortex (pMFC); however, it remains unknown whether the pMFC is differentially engaged by response inhibition compared to error commission in the developing brain. Developmental neuroimaging studies of response inhibition have found pMFC activation, but the possible contribution of error-related activation during inhibitory processing has not been well studied in youth.

METHOD

To examine the processing of correct response inhibition compared to errors in the developing brain, we performed functional magnetic resonance imaging scans in 11 healthy subjects, ages 8-14 years, during an antisaccade task while performance was monitored.

RESULTS

Successful antisaccades activated the pre-supplementary motor area. In contrast, errors on the antisaccade task activated the dorsal anterior cingulate cortex.

CONCLUSION

The findings suggest the functional sub-specialization of inhibitory and error processing within the pMFC in this pilot sample of children and adolescents. Future neuroimaging studies of developing inhibitory control should examine both between correct and error trials.

Eye movement deficits in schizophrenia: investigation of a genetically homogenous Icelandic sample

BACKGROUND

Deficits in antisaccade (AS) and smooth pursuit eye movements (SPEM) are promising endophenotypes in genetic studies of schizophrenia. The Icelandic population lends itself ideally to genetic studies due to its ethnic homogeneity and well-documented genealogy. The primary aim of this study was to assess AS and SPEM performance in a large Icelandic sample. Additional aims were to investigate the relationship between AS and SPEM task performance and to assess internal consistency, within-session performance changes and effects of SPEM target velocity on performance.

METHOD

Patients with schizophrenia (N = 118) and healthy controls (N = 109) matched for age and gender underwent infrared oculographic assessment of AS and SPEM (at target velocities of 12 degrees , 24 degrees and 36 degrees /s).

RESULTS

On the AS task patients displayed significantly more reflexive errors, longer latency, increased intra-individual latency variability, and reduced amplitude gain compared to controls. On the SPEM task, patients had significantly lower velocity gain and more frequent saccades during pursuit at all velocities, but group differences in velocity gain increased with increasing target velocity. Internal consistency of performance was high for all variables in both groups (Cronbach's alpha >0.77 for AS and >0.85 for SPEM) except for AS spatial error in patients (alpha = 0.38). A moderate association was found between AS and SPEM performance. By and large, patients and controls showed similar patterns of systematic within-session performance changes.

CONCLUSIONS

Our findings confirm the existence of robust eye movement deficits in schizophrenia in a large sample. These measures may be studied as endophenotypes in future studies of potential schizophrenia risk genotypes in the genetically homogenous Icelandic population.

Saccade generation and suppression in schizophrenia: effects of response switching and perseveration

Poor antisaccade performance is a reliable index of action control deficits in schizophrenia. To further elucidate the underlying cognitive impairments, the current study aimed to confirm effects of switching the response direction on saccadic performance and to investigate whether response switch effects relate to perseveration. Fourteen schizophrenia patients and 14 healthy controls performed sequences of 1 to 3 simple volitional saccades to one direction and a subsequent volitional saccade with distractor to the same or the opposite direction. Response switches increased error rates in schizophrenia if they followed 3 saccades to the opposite side, suggesting that response switching affects performance on conditions of strong persisting response programs. The increase of response switch error rates with multiple repetitions of the prior response points to a relationship between perseveration and response selection.

The "diagonal effect": a systematic error in oblique antisaccades

Antisaccades are known to show greater variable error and also a systematic hypometria in their amplitude compared with visually guided prosaccades. In this study, we examined whether their accuracy in direction (as opposed to amplitude) also showed a systematic error. We had human subjects perform prosaccades and antisaccades to goals located at a variety of polar angles. In the first experiment, subjects made prosaccades or antisaccades to one of eight equidistant locations in each block, whereas in the second, they made saccades to one of two equidistant locations per block. In the third, they made antisaccades to one of two locations at different distances but with the same polar angle in each block. Regardless of block design, the results consistently showed a saccadic systematic error, in that oblique antisaccades (but not prosaccades) requiring unequal vertical and horizontal vector components were deviated toward the 45 degrees diagonal meridians. This finding could not be attributed to range effects in either Cartesian or polar coordinates. A perceptual origin of the diagonal effect is suggested by similar systematic errors in other studies of memory-guided manual reaching or perceptual estimation of direction, and may indicate a common spatial bias when there is uncertain information about spatial location.

Reduced attentional engagement contributes to deficits in prefrontal inhibitory control in schizophrenia

BACKGROUND

Problems with the voluntary control of behavior, such as those leading to increased antisaccade errors, are accepted as evidence of prefrontal dysfunction in schizophrenia. We previously reported that speeded prosaccade responses, i.e., shorter response latencies for automatic shifts of attention to visual targets, were associated with higher antisaccade error rates in schizophrenia. This suggests that dysregulation of automatic attentional processes may contribute to disturbances in prefrontally mediated control of voluntary behavior.

METHODS

Twenty-four antipsychotic-naïve schizophrenia patients and 30 healthy individuals completed three tasks: a no-gap prosaccade task in which subjects shifted gaze toward a peripheral target that appeared coincident with the disappearance of a central fixation target and separate prosaccade and antisaccade tasks in which a temporal gap or overlap of the central target offset and peripheral target onset occurred. Sixteen patients were retested after 6 weeks of antipsychotic treatment.

RESULTS

Patients' prosaccade latencies in the no-gap task were speeded compared with healthy individuals. While patients were not atypical in the degree to which response latencies were speeded or slowed by the gap and overlap manipulations, those patients with diminished attentional engagement on the prosaccade task (i.e., reduced overlap effect) had significantly elevated antisaccade error rates. This effect persisted in patients evaluated after antipsychotic treatment.

CONCLUSIONS

This study provides evidence that a reduced ability to engage attention may render patients more distracted by sensory inputs, thereby further compromising impaired executive control during antisaccade tasks. Thus, alterations in attentional and executive control functions can synergistically disrupt voluntary behavioral responses in schizophrenia.

Cortical mechanisms of retinal and extraretinal smooth pursuit eye movements to different target velocities

Smooth pursuit eye movements (SPEM) are used to maintain focus upon moving targets. The generation of SPEM velocity is controlled by retinal information and extraretinal signals. Although there is a wealth of studies investigating retinal and extraretinal SPEM control, the main questions regarding the cortical mechanisms involved in the processing of SPEM to different stimulus velocities are still unresolved. We applied an innovative event-related fMRI-design by presenting target ramps at different velocities (5, 10, 15, 20 degrees/s) with both continuous target presentation and intervals of target blanking. The stimulus parameters were integrated into the statistical model and eye movements were registered to confirm SPEM performance. Our results clearly demonstrate that in humans the oculomotor network (V5, frontal and supplementary eye fields, lateral intraparietal area) is engaged in the processing of retinal and extraretinal SPEM velocity. Within this network neural activity increases with increasing target velocity. During extraretinal SPEM, additional engagement of the dorsolateral prefrontal cortex, angular gyrus, parahippocampal gyrus and superior temporal gyrus occurs. These regions encode cognitive functions such as memory, attention and monitoring. The activation of the inferior parietal cortex seems to be related to the interaction between velocity and blanking thereby underlining its relevance for task switching and sensorimotor transformation.

Schizoaffective disorder: diagnostic issues and future recommendations

OBJECTIVE

Difficulties surrounding the classification of mixed psychotic and affective syndromes continue to plague psychiatric nosology. This paper addresses the controversy regarding the diagnostic validity of schizoaffective disorder (SAD), a diagnosis that is used in both DSM-IV and ICD-10 and one that encroaches on both schizophrenia (SCZ) and bipolar disorder (BD).

METHODS

A systematic synthesis of clinical and empirical literature, including evidence from cognitive, neurobiological, genetic, and epidemiological research, was undertaken with the aim of evaluating the utility of the SAD classification.

RESULTS

Distinctions between the diagnostic categories of SCZ, SAD and BD are not clearly demarcated by findings from neuropsychological, neuroimaging, molecular neurobiology, or genetic epidemiology studies. On the contrary, convergent evidence purports overlap across current diagnostic boundaries in the heritability and pathophysiology of psychotic and affective disorders. However, there are some disorder-specific findings.

CONCLUSIONS

Schizoaffective disorder is a prototypic boundary condition that epitomizes the pitfalls of the current categorical classification system. Future revisions to the DSM should consider the implementation of one of two alternative models to account for individuals presenting with mixed psychotic and affective symptoms. These include the views that (i) SAD is a comorbid set of symptoms that occur as a by-product of two separate disorders (SCZ and BD) or, that (ii) SAD exists as the mid-point on a continuum between SCZ and BD, such that the incorporation of these two disorders onto one dimension may be a suitable alternative. Hence the category SAD should be omitted in future revisions of DSM, allowing the development of meaningful nomenclature that rests upon further rigorous investigation of differences and similarities between disorders.

Inhibition errors in borderline personality disorder with psychotic-like symptoms

BACKGROUND

The aim of this study was to examine whether patients with borderline personality disorder (BPD) have deficits in cognitive inhibition as measured with an anti-saccade eye task similar to patients with schizophrenia (Sz). Furthermore, we investigated whether these inhibition errors were more prominent among BPD patients with psychotic-like symptoms than among BPD patients without these symptoms.

METHODS

An anti-saccade task was administered in 32 BPD patients (among them, 20 had with psychotic-like symptoms), 21 patients with recent onset schizophrenia (Sz), and 25 healthy controls (HC). The percentage inhibition errors in the anti-saccade task were the primary outcome variable, in addition, the percentage of anticipatory errors was measured.

RESULTS

Sz patients showed more inhibition errors than HC and BPD (p<.001 and p<.05 resp.), whereas BPD patients scored in between Sz and HC. The difference with HC was significant as well (p<.05). BPD patients with psychotic-like symptoms showed more inhibition errors than BPD patients without these symptoms (p<.05). BPD patients showed more anticipatory errors than HC (p<.001), whereas Sz patients did not (p<.26).

CONCLUSION

The data demonstrate that inhibition deficits, as measured with anti-saccadic eye movement task, may be characteristic among BPD patients and in a larger extent in patients with psychotic-like symptoms. This inhibition deficit was distinct from a general predisposition to response impulsively as measured by anticipatory errors, which was found in the whole group of BPD patients. Psychotic-like symptoms may be an important target dimension for future BPD research and treatment.