Smooth pursuit eye movements, attention, and schizophrenia

The schizophrenia syndrome, circa 2024: What we know and how that informs its nature

With new data about different aspects of schizophrenia being continually generated, it becomes necessary to periodically revisit exactly what we know. Along with a need to review what we currently know about schizophrenia, there is an equal imperative to evaluate the construct itself. With these objectives, we undertook an iterative, multi-phase process involving fifty international experts in the field, with each step building on learnings from the prior one. This review assembles currently established findings about schizophrenia (construct, etiology, pathophysiology, clinical expression, treatment) and posits what they reveal about its nature. Schizophrenia is a heritable, complex, multi-dimensional syndrome with varying degrees of psychotic, negative, cognitive, mood, and motor manifestations. The illness exhibits a remitting and relapsing course, with varying degrees of recovery among affected individuals with most experiencing significant social and functional impairment. Genetic risk factors likely include thousands of common genetic variants that each have a small impact on an individual's risk and a plethora of rare gene variants that have a larger individual impact on risk. Their biological effects are concentrated in the brain and many of the same variants also increase the risk of other psychiatric disorders such as bipolar disorder, autism, and other neurodevelopmental conditions. Environmental risk factors include but are not limited to urban residence in childhood, migration, older paternal age at birth, cannabis use, childhood trauma, antenatal maternal infection, and perinatal hypoxia. Structural, functional, and neurochemical brain alterations implicate multiple regions and functional circuits. Dopamine D-2 receptor antagonists and partial agonists improve psychotic symptoms and reduce risk of relapse. Certain psychological and psychosocial interventions are beneficial. Early intervention can reduce treatment delay and improve outcomes. Schizophrenia is increasingly considered to be a heterogeneous syndrome and not a singular disease entity. There is no necessary or sufficient etiology, pathology, set of clinical features, or treatment that fully circumscribes this syndrome. A single, common pathophysiological pathway appears unlikely. The boundaries of schizophrenia remain fuzzy, suggesting the absence of a categorical fit and need to reconceptualize it as a broader, multi-dimensional and/or spectrum construct.

Recent updates of eye movement abnormalities in patients with schizophrenia: A scoping review

AIM

Although eye-tracking technology expands beyond capturing eye data just for the sole purpose of ensuring participants maintain their gaze at the presented fixation cross, gaze technology remains of less importance in clinical research. Recently, impairments in visual information encoding processes indexed by novel gaze metrics have been frequently reported in patients with schizophrenia. This work undertakes a scoping review of research on saccadic dysfunctions and exploratory eye movement deficits among patients with schizophrenia. It gathers promising pieces of evidence of eye movement abnormalities in attention-demanding tasks on the schizophrenia spectrum that have mounted in recent years and their outcomes as potential biological markers.

METHODS

The protocol was drafted based on PRISMA for scoping review guidelines. Electronic databases were systematically searched to identify articles published between 2010 and 2020 that examined visual processing in patients with schizophrenia and reported eye movement characteristics as potential biomarkers for this mental illness.

RESULTS

The use of modern eye-tracking instrumentation has been reported by numerous neuroscientific studies to successfully and non-invasively improve the detection of visual information processing impairments among the screened population at risk of and identified with schizophrenia.

CONCLUSIONS

Eye-tracking technology has the potential to contribute to the process of early intervention and more apparent separation of the diagnostic entities, being put together by the syndrome-based approach to the diagnosis of schizophrenia. However, context-processing paradigms should be conducted and reported in equally accessible publications to build comprehensive models.

Visualization and quantification of eye tracking data for the evaluation of oculomotor function

Oculomotor dysfunction may originate from physical, physiological or psychological causes and may be a marker for schizophrenia or other disorders. Observational tests for oculomotor dysfunction are easy to administer, but are subjective and transient, and it is difficult to quantify deviations. To date, video-based eye tracking systems have not provided a contextual overview of gaze data that integrates the eye video recording with the stimulus and gaze data together with quantitative feedback of metrics in relation to typical values. A system was developed with an interactive timeline to allow the analyst to scroll through a recording frame-by-frame while comparing data from three different sources. The visual and integrated nature of the analysis allows localisation and quantification of saccadic under- and overshoots as well as determination of the frequency and amplitude of catch-up and anticipatory saccades. Clinicians will be able to apply their expertise to diagnose disorders based on abnormal patterns in the gaze plots. They can use the line charts to quantify deviations from benchmark values for reaction time, saccadic accuracy and smooth pursuit gain. A clinician can refer to the eye video at any time to confirm that observed deviations originated from gaze behaviour and not from systemic errors.

[Oculomotor activity as an indicator of disturbances in perception and programming in patients with schizotypal disorder]

AIM

To consider the patterns of stimuli analysis and task execution in conditions of voluntary and involuntary attention in people with schizotypal disorder from the psychopathological and psychological points of view.

MATERIAL AND METHODS

A total of 40 subjects were examined including 16 patients diagnosed with schizotypal disorder, 13 with personality disorders and 11 without psychiatric pathology (controls). In the first part of the study, subjects looked upon various static images without any instructions, followed by a test with antisaccade task in vertical and horizontal directions; the last task duplicated the first, but the subjects were asked to remember the presented images as best as possible.

RESULTS

In the group of patients with schizotypal disorder, an increase in average and maximum fixation variance, its greater variation between images, and a decrease in the scanpath length were found. These differences were associated with the intentional focus of attention and several indicators of the accomplish efficiency of the antisaccade task.

CONCLUSION

The changes in fixative eye movements observed in individuals with schizotypal disorder indicate violations of information selectivity and construction of an image of future action. Assumptions about inadequacy of their perceptual strategy to the simultaneous one and the primacy of the sense-bearing (motivational) violations in the programming of saccadic activity were made.

Using Smooth Pursuit Calibration for Difficult-to-Calibrate Participants

Although the 45-dots calibration routine of a previous study ( 2) provided very good accuracy, it requires intense mental effort and the routine proved to be unsuccessful for young children who struggle to maintain concentration. The calibration procedures that are normally used for difficult-to-calibrate participants, such as autistic children and infants, do not suffice since they are not accurate enough and the reliability of research results might be jeopardised. Smooth pursuit has been used before for calibration and is applied in this paper as an alternative routine for participants who are difficult to calibrate with conventional routines. Gaze data is captured at regular intervals and many calibration targets are generated while the eyes are following a moving target. The procedure could take anything between 30 s and 60 s to complete, but since an interesting target and/or a conscious task may be used, participants are assisted to maintain concentration. It was proven that the accuracy that can be attained through calibration with a moving target along an even horizontal path is not significantly worse than the accura-cy that can be attained with a standard method of watching dots appearing in random order. The routine was applied successfully for a group of children with ADD, ADHD and learning abilities. This result is important as it provides for easier calibration - especially in the case of participants who struggle to keep their gaze focused and stable on a stationary target for long enough.

Magnetic eye tracking in mice

Eye movements provide insights about a wide range of brain functions, from sensorimotor integration to cognition; hence, the measurement of eye movements is an important tool in neuroscience research. We describe a method, based on magnetic sensing, for measuring eye movements in head-fixed and freely moving mice. A small magnet was surgically implanted on the eye, and changes in the magnet angle as the eye rotated were detected by a magnetic field sensor. Systematic testing demonstrated high resolution measurements of eye position of <0.1°. Magnetic eye tracking offers several advantages over the well-established eye coil and video-oculography methods. Most notably, it provides the first method for reliable, high-resolution measurement of eye movements in freely moving mice, revealing increased eye movements and altered binocular coordination compared to head-fixed mice. Overall, magnetic eye tracking provides a lightweight, inexpensive, easily implemented, and high-resolution method suitable for a wide range of applications.

Do Eye Movements Have a Special Importance to Mental Activity?

Several areas of research are reviewed in which associations between eye movements and the nature of mental processes have been attributed to hypothesized third factors. It is suggested that a simpler hypothesis—that eye movements are related in some fundamental manner to cognitive functioning—deserves consideration. A metaphor is presented to show that the quality of information processing need not exclusively reflect processes deep inside the brain but could also be affected by peripheral motor mechanisms.

Eye movements and neurocognitive function in treatment resistant schizophrenia: a pilot study

Objectives: It is increasingly important to develop predictors of treatment response and outcome in schizophrenia. Neuropsychological impairments, particularly those reflecting frontal lobe function, appear to predict poor outcome. Eye movement abnormalities probably also reflect frontal lobe deficits. We wished to see if these two aspects of schizophrenia were correlated and whether they could distinguish a treatment resistant from a treatment responsive group.

Methods: Ten treatment resistant schizophrenic patients were compared with ten treatment responsive patients on three eye movement paradigms (reflexive saccades, antisaccades and smooth pursuit), clinical psychopathology (BPRS, SANS and CGI) and a neuropsychological test battery designed to detect frontal lobe dysfunction. Ten aged-matched controls also carried out the eye movement tasks.

Results: Both treatment responsive (p = 0.038) and treatment resistant (p = 0.007) patients differed significantly from controls on the antisaccade task. The treatment resistant group had a higher error rate than the treatment responsive group, but the difference was not statistically significant. Similar poor neuropsychological test performance was found in both groups.

Conclusions: To demonstrate the biological differences characteristic of treatment resistance, larger sample sizes and wider differences in outcome between the two groups are necessary.

Dynamic visuomotor synchronization: quantification of predictive timing

When a moving target is tracked visually, spatial and temporal predictions are used to circumvent the neural delay required for the visuomotor processing. In particular, the internally generated predictions must be synchronized with the external stimulus during continuous tracking. We examined the utility of a circular visual-tracking paradigm for assessment of predictive timing, using normal human subjects. Disruptions of gaze–target synchronization were associated with anticipatory saccades that caused the gaze to be temporarily ahead of the target along the circular trajectory. These anticipatory saccades indicated preserved spatial prediction but suggested impaired predictive timing. We quantified gaze–target synchronization with several indices, whose distributions across subjects were such that instances of extremely poor performance were identifiable outside the margin of error determined by test–retest measures. Because predictive timing is an important element of attention functioning, the visual-tracking paradigm and dynamic synchronization indices described here may be useful for attention assessment.

Saccadic eye movement applications for psychiatric disorders

OBJECTIVE

The study presented here analyzed the patterns of relationship between oculomotor performance and psychopathology, focusing on depression, bipolar disorder, schizophrenia, attention-deficit hyperactivity disorder, and anxiety disorder.

METHODS

Scientific articles published from 1967 to 2013 in the PubMed/Medline, ISI Web of Knowledge, Cochrane, and SciELO databases were reviewed.

RESULTS

Saccadic eye movement appears to be heavily involved in psychiatric diseases covered in this review via a direct mechanism. The changes seen in the execution of eye movement tasks in patients with psychopathologies of various studies confirm that eye movement is associated with the cognitive and motor system.

CONCLUSION

Saccadic eye movement changes appear to be heavily involved in the psychiatric disorders covered in this review and may be considered a possible marker of some disorders. The few existing studies that approach the topic demonstrate a need to improve the experimental paradigms, as well as the methods of analysis. Most of them report behavioral variables (latency/reaction time), though electrophysiological measures are absent.

Attentional modulation of the P50 suppression deficit in recent-onset and chronic schizophrenia

Schizophrenia is associated with deficits in P50 suppression to the second stimulus in a pair, a process often conceptualized as a preattentive index of sensory gating. This study assessed the malleability of the deficit by determining whether early attentional control can influence P50 gating across different phases of schizophrenia. Participants included 28 patients in the recent-onset (n = 16) or chronic (n = 12) phase of illness and 28 healthy comparison subjects. During the standard paradigm, chronic schizophrenia patients exhibited impaired P50 suppression relative to healthy subjects, whereas recent-onset schizophrenia patients were intermediate. Directing voluntary attention toward the initial stimulus yielded substantial improvements in the P50 ratio; recent-onset schizophrenia patients achieved ratio scores comparable to those of healthy participants, whereas chronic patients also improved and could no longer be distinguished clearly from the healthy comparison sample. Directing attention toward the second stimulus enhanced P50 amplitude to the second stimulus across groups, possibly because activation of the inhibitory mechanism was overridden or circumvented by task demands. Thus, P50 suppression may be primarily preattentive under standard conditions, but manipulation of early attention can exert a modulatory influence on P50, indicating that the suppression deficit is malleable in schizophrenia without pharmacological agents.

Schizophrenic patients have a preference for symmetrical rectangles: A comparison with preferences of university students

Objective. We examined figure preferences of 26 schizophrenic patients and a control group of 53 controls (university students). Methods. Figures utilized included a square and six different rectangles of equal area (26 cm(2)). The schizophrenic patients and normal university students were asked to draw either a horizontal or a vertical line to divide each rectangle at the most aesthetically pleasing location. Results. Both the schizophrenic patients and the normal university students tended to divide the rectangles into symmetric parts. This finding suggests that both groups prefer symmetry, in accordance with the Gestalt of Pragnanz, which states that symmetrical figures represent regularity and simplicity, and that people tend to prefer "good figures". Compared with normal university students, however, schizophrenic patients preferred extremely symmetrical figures to asymmetrical figures. Conclusion. We suggest that schizophrenic patients' extreme preference for symmetry reflects their generally static stances and poor flexibility, as well as a defect in their ability to synthesize a whole object from its parts.

Neurophysiological endophenotypes across bipolar and schizophrenia psychosis

The search for liability genes of the world's 2 major psychotic disorders, schizophrenia and bipolar disorder I (BP-I), has been extremely difficult even though evidence suggests that both are highly heritable. This difficulty is due to the complex and multifactorial nature of these disorders. They encompass several intermediate phenotypes, some overlapping across the 2 psychotic disorders that jointly and/or interactively produce the clinical manifestations. Research of the past few decades has identified several neurophysiological deficits in schizophrenia that frequently occur before the onset of psychosis. These include abnormalities in smooth pursuit eye movements, P50 sensory gating, prepulse inhibition, P300, mismatch negativity, and neural synchrony. Evidence suggests that many of these physiological deficits are distinct from each other. They are stable, mostly independent of symptom state and medications (with some exceptions) and are also observed in non-ill relatives. This suggests a familial and perhaps genetic nature. Some deficits are also observed in the BP-I probands and to a lesser extent their relatives. These deficits in physiological measures may represent the intermediate phenotypes that index small effects of genes (and/or environmental factors). The use of these measures in genetic studies may help the hunt for psychosis liability genes and clarify the extent to which the 2 major psychotic disorders share etio-pathophysiology. In spite of the rich body of work describing these neurophysiological measures in psychotic disorders, challenges remain: Many of the neurophysiological phenotypes are still relatively complex and are associated with low heritability estimates. Further refinement of these physiological phenotypes is needed that could identify specific underlying physiological deficits and thereby improve their heritability estimates. The extent to which these neurophysiological deficits are unique or overlap across BP-I and schizophrenia is unclear. And finally, the clinical and functional consequences of the neurophysiological deficits both in the probands and their relatives are not well described.

“Dark Nights of the Soul”: Phenomenology and Neurocognition of Spiritual Suffering in Mysticism and Psychosis

Phenomenological, clinical, and neurocognitive levels of analysis are combined to understand the cognitive bases of spirituality and spiritual suffering. In particular, the “dark night of the soul” in classical mysticism, with its painful “metapathological” loss of felt meaning is compared with the anhedonias central to the negative symptoms of schizophrenia and schizotypicality. Paul Schilder's early understanding of instabilities in the body image, as our core sense of self, offers a key to both the disorganized hallucinatory syndromes of psychosis and to the relative enhancements of body image/ecological self in spirituality. Expanded versus deleted felt presence/embodiment, as outwardly indexed in measures of physical balance and spatial abilities, becomes the general dimension underlying integrative versus disintegrative transformations of consciousness. “Dark night” suffering can be seen as a semantic satiation leading to a relative deletion of experienced presence in the context of its previous enhancement, a focalized version of the more general anhedonic despair shared by clinical schizotypy and aspects of a larger secularized culture.

Different extraretinal neuronal mechanisms of smooth pursuit eye movements in schizophrenia: An fMRI study

Smooth pursuit eye movements (SPEM) are necessary to follow slowly moving targets while maintaining foveal fixation. In about 50% of schizophrenic patients SPEM velocity is reduced. In this study we were interested in identifying the cortical mechanisms associated with extraretinal processing of SPEM in schizophrenic patients. During condition A, patients and healthy subjects had to pursue a constantly visible target (10 degrees /s). During condition B the target was blanked out for 1000 ms while subjects were instructed to continue SPEM. Eye movement data were assessed during scanning sessions by a limbus tracker. During condition A, reduced SPEM velocity in patients was associated with reduced activation of the right ventral premotor cortex and increased activation of the left dorsolateral prefrontal cortex, the right thalamus and the Crus II of the left cerebellar hemisphere. During condition B, SPEM velocity was reduced to a similar extent in both groups. While in patients a decrease in activation was observed in the right cerebellar area VIIIA, the activation of the right anterior cingulate, the right superior temporal cortex, and the bilateral frontal eye fields was increased. The results implicate that schizophrenic patients employ different strategies during SPEM both with and without target blanking than healthy subjects. These strategies predominantly involve extraretinal mechanisms.

Functional magnetic resonance imaging studies of eye movements in first episode schizophrenia: smooth pursuit, visually guided saccades and the oculomotor delayed response task

Schizophrenia patients show eye movement abnormalities that suggest dysfunction in neocortical control of the oculomotor system. Fifteen never-medicated, first episode schizophrenia patients and 24 matched healthy individuals performed eye movement tasks during functional magnetic resonance imaging studies. For both visually guided saccade and smooth pursuit paradigms, schizophrenia patients demonstrated reduced activation in sensorimotor areas supporting eye movement control, including the frontal eye fields, supplementary eye fields, and parietal and cingulate cortex. The same findings were observed for an oculomotor delayed response paradigm used to assess spatial working memory, during which schizophrenia patients also had reduced activity in dorsolateral prefrontal cortex. In contrast, only minimal group differences in activation were found during a manual motor task. These results suggest a system-level dysfunction of cortical sensorimotor regions supporting oculomotor function, as well as in areas of dorsolateral prefrontal cortex that support spatial working memory. These findings indicate that a generalized rather than localized pattern of neocortical dysfunction is present early in the course of schizophrenia and is related to deficits in the sensorimotor and cognitive control of eye movement activity.

Habituation of acoustic startle is disrupted by psychotomimetic drugs: differential dependence on dopaminergic and nitric oxide modulatory mechanisms

RATIONALE

A deficit in attention and information processing has been considered a central feature in schizophrenia, which might lead to stimulus overload and cognitive fragmentation. It has been shown that patients with schizophrenia display a relative inability to gate incoming stimuli. Thus, patients repeatedly subjected to acoustic startle-eliciting stimuli habituate less to these stimuli than controls. Furthermore, schizophrenia-like symptoms can be induced by pharmacological manipulations in humans by psychotomimetic drugs, e.g. phencyclidine (PCP) and D-amphetamine (D-AMP). Recent studies show that the behavioural and biochemical effects of PCP in rodents are blocked by nitric oxide synthase (NOS) inhibitors, suggesting that NO plays an important role in at least the pharmacological effects of PCP.

OBJECTIVES

The first aim of the present study was to investigate if PCP, MK-801 and D-AMP impair habituation of acoustic startle in mice. Secondly, we examine the effect of the NOS inhibitor, L-NAME, and the dopamine receptor antagonist, haloperidol, on drug-induced deficit in habituation.

RESULTS

PCP (4 mg/kg), MK-801 (0.4 mg/kg) and D-AMP (5.0 mg/kg), impaired habituation of the acoustic startle response in mice. This effect was reversed by the NOS inhibitor, L-NAME. The typical antipsychotic, haloperidol, reversed the effects of PCP and D-AMP, but not that of MK-801.

CONCLUSIONS

The finding that PCP, MK-801 and D-AMP impair habituation in mice is consistent with the idea that these treatments model certain filter deficits seen in schizophrenic patients. Furthermore, the present results suggest that NO is critically involved in these effects on habituation, whereas that of dopamine is less clear.

Proposal for a noradrenaline hypothesis of schizophrenia

In this article, we have reevaluated the role of noradrenergic dysfunction in the pathogenesis of schizophrenia in the light of today's neuroscience and clinical data. Neurophysiological, psychophysiological, psychopharmacological, and biochemical findings that have accumulated in last decades indicate that certain noradrenergic dysfunctions play important roles in the pathogenesis of the disorder. Moreover, these findings provide us with consistent evidence for the existence of two syndromes generated by either overactivity or underactivity of the central noradrenaline (NA) system. The former appears to correspond to the type I syndrome (positive symptoms) and the latter to the type II syndrome (negative symptoms). We conclude that the involvement of brain NA in cerebral metabolism and blood flow as well as the amine's role in brain development and neuronal differentiation may provide the mechanisms underlying the disease process in schizophrenia. Development of chemical agents acting specifically on the brain noradrenergic mechanisms may be a promising approach to novel treatments of the disorder.

Nicotine reduces antisaccade errors in task impaired schizophrenic subjects

Nicotine and/or smoking have been shown to reduce various cognitive deficits associated with schizophrenia. Here, we examine the effects of nicotine gum on repeated performance on a simple eye movement task. Eight schizophrenic subjects and eight controls participated in three days of testing on saccade (S) and antisaccade (AS) tasks. On each testing day, subjects participated in four testing sessions and received both of two nicotine gum treatments (4 and 6 mg) and both of two control conditions (placebo gum and no gum), each followed by a recovery period. Overall, schizophrenics showed significant impairments on the AS task. However, upon individual examination only four schizophrenics showed significant differences in AS errors or reaction times (RTs) when compared to controls. The other four schizophrenic subjects showed control level performance. All schizophrenic subjects showed normal and better than control level performance on the simple S task. Furthermore, no effects of nicotine were seen on the simple S task. There were significant treatment effects on the AS task. Nicotine treatment significantly decreased errors in the task impaired schizophrenic group and this effect was most pronounced at the 6 mg level. No nicotine effects were demonstrated for non-impaired schizophrenic subjects or controls. This study demonstrates a benefit of short exposure to nicotine in cognitively impaired schizophrenic subjects. These results support previous findings of cognitive benefits of nicotine in schizophrenics.

Visual and cognitive control of attention in smooth pursuit

In this chapter, we describe the role of attention in the control of smooth pursuit eye movements. As a voluntary and continuous eye movement, smooth pursuit is driven by both visual and cognitive signals. Here we show that whereas the entire process of smooth pursuit requires visual attention, the post-onset phase of the initiation and the maintenance smooth pursuit are under an additional sustained non-visual cognitive attention control. The temporal dynamics of these complementary controls of visual and non-visual cognitive attention support the continuous generation of smooth pursuit so that eye tracking of a moving target can be prompt and accurate.

Eye movements during the Rorschach test in schizophrenia

In order to understand relationships between scanning behaviors, characteristics of visual stimuli and the clinical symptoms in schizophrenia, eye movements of 37 schizophrenic patients and 36 controls were recorded using an eye-mark recorder during a free-response period in a Rorschach test. Four cards (I, II, V and VIII) were used. Data were analyzed during 15 s from the presentation of each card. For all cards, the number of eye fixations and the number of eye fixation areas were fewer, and total scanning length and mean scanning length were shorter for schizophrenic patients than for controls. For card II, in the non-popular response group, eye fixation frequency upon area 5 + 6 (red) was higher for schizophrenic patients. For card VIII, in the popular response group, eye fixation frequency upon area 5 + 6 (pink) was lower for schizophrenic patients. For cards II and VIII, the number of eye fixations was inversely correlated with negative symptoms. For card II, total scanning length tended to be inversely correlated with negative symptoms, and mean eye fixation time was correlated with negative symptoms. The number of eye fixation areas was inversely correlated with positive symptoms. For card VIII, eye fixation frequency in a stimulative area tended to be correlated with positive symptoms. Scanning behaviors in schizophrenic patients are affected by characteristics of visual stimuli, and partially by clinical symptoms.

Odor identification, eye tracking and deficit syndrome schizophrenia

BACKGROUND

Deficit syndrome (DS) schizophrenia patients have smooth pursuit eye movement (SPEM) dysfunction. We examined if they also had smell identification deficits, since social affiliation is related to olfaction in other mammals.

METHODS

Sixty-seven patients had DS assessments: 31 patients had SPEM and 50 had Smell Identification Test (SIT) assessments, and 14 patients had both measurements.

RESULTS

DS patients had worse SPEM and SIT performance than the non-DS patients. Areas under the receiver-operator characteristic (ROC) curves for SIT and SPEM were both fairly accurate in identifying the DS. The odds ratio (OR) for the DS for impaired versus normal SPEM was 6.21 (95% confidence interval [CI]: 1.21, 32.25) and for microsmia versus normosmia was 10.4 (95% CI: 1.23, 88.18). Further analyses showed that the association of SIT with both SPEM and the DS could account for the SPEM-DS association.

CONCLUSIONS

We found a strong association between the DS and SIT scores suggesting that the neural substrates of olfaction may be related to social affiliation in humans, as they are in other mammals. These data further support the notion that the DS defines a homogeneous subgroup of schizophrenia patients and further suggest that dysfunction in the neural circuitry of olfaction may contribute to its pathophysiology.

Quantitative characterization of eye tracking dysfunction in schizophrenia

The purpose of this study was to characterize the nature of the processes that are involved in eye tracking dysfunction (ETD). We identified a combination of quantitative measures that best distinguished qualitatively normal eye tracking from qualitatively abnormal eye tracking, using discriminant analysis. Discriminant scores distinguished schizophrenics with ETD from both schizophrenics with normal eye tracking and normal controls, but did not distinguish schizophrenics with normal eye tracking from normal controls, underscoring the heterogeneity of schizophrenic patients with respect to eye tracking. The results of the discriminant analysis indicated that ETD is a multivariate process involving a primary impairment in the smooth pursuit system characterized by increased catch-up saccades and reduced gain, and, secondarily, disinhibition of intrusive saccades, especially square-wave jerks. Quantitative characterization of ETD makes it possible to consider eye tracking as a quantitative trait in genetic investigations of a multidimensional phenotype.

Eye tracking in normals: spem asymmetries and association with schizotypy

SPEM was recorded electro-oculographically during visual tracking of sinusoidal targets oscillating at .4 and .8 cycles per second in one hundred nineteen undergraduates. The logarithms of median root mean square values were used to assess tracking accuracy for leftward and rightward halfcycles of tracking. Over the entire sample, there was a significant superiority of rightward over leftward tracking, which, given evidence for the ipsilateral mediation of SPEM at the cortical level, suggests a right hemisphere predominance in the control of SPEM in normal subjects. Individual tracking asymmetry was associated with overall tracking accuracy such that subjects with relatively deficient leftward tracking and those with a larger absolute magnitude of asymmetry had poorer overall tracking. High scores on an MMPI schizotypy measure (Sum 2-7-8-0) were significantly related to poorer overall SPEM accuracy, individual tracking asymmetry, the absolute magnitude of tracking asymmetry, and phase lag, though the subjects' sex, handedness, and crossed hand-foot dominance were found to affect the relationships between schizotypy and tracking accuracy. These findings suggest that although control of SPEM may be predominantly right hemispheric, in some persons with a vulnerability to schizophrenia spectrum disorders, expressed as poorer overall SPEM accuracy and high schizotypy scores, left hemisphere-mediated (leftward) SPEM may be particularly impaired.

Distinguishing schizophrenic patients from healthy controls by quantitative measurement of eye movement parameters

BACKGROUND

Eye tracking dysfunction is a putative trait marker for susceptibility to schizophrenia; however, it cannot be recommended as an additional tool for the diagnosis of schizophrenia, due to low sensitivity and specificity.

METHODS

To assess the diagnostic potentials of combinations of eye movement paradigms, four smooth pursuit experiments (1: constant velocity of 15 degrees/sec; 2 and 3: combination with either visual or auditory distractors; 4: constant velocity of 30 degrees/sec) and two saccadic eye movement experiments (1: reflexive saccades; 2: voluntary saccades) were conducted. Fourteen patients with residual schizophrenia and 17 healthy controls were studied. Two sets of discriminant analyses (each with the resubstitution and with the "leaving one out" method) were calculated.

RESULTS

In the first set, all 10 characteristic variables were included, whereas for the second set, the three most powerful parameters were selected (two from smooth pursuit tasks and one from a voluntary saccade experiment). This procedure provided the best classification results, regarding concordance between clinical diagnoses and eye movement dysfunction (kappa = .67-.80).

CONCLUSIONS

Schizophrenic patients of the residual subtype can be differentiated from healthy individuals with considerable criterion validity on the basis of paradigms from two different ocular motor systems.

Saccadic eye movements in schizophrenic patients

The nature of saccadic abnormalities in schizophrenia was investigated in three different paradigms: (1) the visually guided saccade; (2) the antisaccade; and (3) the remembered saccade paradigm. Subjects comprised 14 schizophrenic patients and 14 normal volunteers. Deficits in the schizophrenic group were observed in the antisaccade and remembered saccade tasks, both of which were characterized by increased latency and reduced gain. Moreover, in the antisaccade task, schizophrenic patients showed an increased number of errors compared with control subjects. Saccadic abnormalities in the patients were correlated with impaired performance on the Wisconsin Card Sorting Test. These data suggest that schizophrenic patients have difficulty in inhibiting reflexive saccades and in producing voluntary saccades. The implications of these findings for a prefrontal cortex dysfunction involved in oculomotor control in schizophrenia are discussed.

Eye-tracking dysfunction in offspring from the New York High-Risk Project: diagnostic specificity and the role of attention

Eye tracking abnormalities were studied in the offspring of schizophrenic, unipolar depressed and bipolar probands from the New York High-Risk Project to examine their familial specificity. Offspring of schizophrenic and depressed probands both had significant global performance deficits based on spectral purity measurements, but only the offspring of schizophrenic probands had an increased rate of intrusive anticipatory saccades. The greater specificity of high anticipatory saccade rate than global performance impairment suggests that this eye movement abnormality may provide a more specific biological marker of risk for schizophrenia than the global measure of eye tracking performance used in this study. Attention facilitation effectively normalized all performance deficits in the offspring of schizophrenic patients, suggesting that a problem sustaining focused visual attention may contribute to eye tracking deficits observed in the relatives of schizophrenic probands.

Neonatal excitotoxic hippocampal damage in rats causes post-pubertal changes in prepulse inhibition of startle and its disruption by apomorphine

Neonatal excitotoxic hippocampal damage in the rat results in postpubertal onset of a variety of abnormal behaviors related to excessive dopaminergic transmission in the mesolimbic/nigrostriatal system, and thus may be considered an animal model of some aspects of schizophrenia. Because sensorimotor gating is impaired in adult patients with schizophrenia and in rats with experimentally induced mesolimbic dopamine hyperactivity, the present experiments investigated the effects of neonatal (postnatal day 7, PD7) ibotenic acid (3 micrograms) lesions of the ventral hippocampus (VH) on the amplitude and prepulse inhibition (PPI) of acoustic startle in prepubertal (PD35) and postpubertal (PD56) rats. Startle was elicited using 105 and 118-dB pulses alone or preceded by 4, 8, or 16 dB above-background prepulses in rats treated with vehicle or apomorphine (APO; 0.025 or 0.1 mg/kg SC). At PD35, PPI in VH-lesioned rats did not differ significantly from these measures in sham operated rats. Apomorphine significantly increased startle amplitude and reduced PPI in both sham operated and VH-lesioned rats at PD35. At PD56, startle amplitude in VH-lesioned rats was not significantly different from controls, but PPI was reduced significantly compared to controls. Ventral hippocampus lesioned rats also exhibited an exaggerated reduction in PPI after treatment with APO. These findings provide further evidence of postpubertal impairments that may be related to increased mesolimbic dopamine transmission and receptor sensitivity in rats with neonatal hippocampal damage, and provide further support for the fidelity of this animal model of schizophrenia.

Information processing during eye tracking as revealed by event-related potentials in schizophrenics, alcoholics, and healthy controls

To further explore the hypothesis that schizophrenics are more distractable and/or have reduced processing resources available, event-related potentials (ERPs) and smooth pursuit eye movements (SPEM) were investigated in 20 medicated schizophrenics, 19 detoxified chronic alcoholics, and in a control group of 20 healthy subjects. Groups were matched for age and education. Eye tracking tasks and auditory oddball tasks were performed separately as well as simultaneously. In addition, an eye tracking condition with a task-irrelevant tone sequence was used to assess the effect of distraction. Schizophrenics showed a trend for poorer SPEM performance; alcoholics had no dysfunction in this task. Tracking accuracy did not change in either group when additional auditory stimuli were presented. P300 latency was delayed in both schizophrenics and alcoholics. P300 amplitude showed no overall group difference but it increased during the dual task in normals whereas it remained constant in patients. N100 amplitude was generally larger during the more complex conditions indicating heightened unspecific arousal. It is suggested that normals use increased arousal to mobilize additional resources and to allocate them to stimulus evaluation but schizophrenics and alcoholics are unable to do so. Results are more conform to a limited resources concept than to a filter deficit model of cognitive disturbances in schizophrenia and alcoholism.

Visual tracking behavior in low functioning head-injured adults

OBJECTIVE

To analyze visual tracking patterns of low functioning head-injured adults as follow-up to finding that visual tracking performance predicts rehabilitation-ready (RR) status.

DESIGN

Case series of patients in a 4-year study of predictors of early cognitive improvement.

SETTING

Private subacute care facility providing sensory stimulation and slowly paced rehabilitation.

PATIENTS

Convenience sample of 76 subjects: 45 achieved RR status; 31 did not (NRR). Men = 54; Women = 22. Age at injury: 12 to 73 years (median [Md] = 27). Time postinjury at initial assessment: 25 to 365 days (Md = 57). Cognitive status at initial assessment: Western Neuro Sensory Stimulation Profile (WNSSP) Score below 47.

INTERVENTION

Subjects assessed by WNSSP Visual Tracking subscale (VISTRACK) at admission and every 2 weeks thereafter for 2 to 48 months postinjury.

MAIN OUTCOME MEASURES

VISTRACK scores for Direction (horizontal vs vertical) and Stimulus (mirror, individual, picture, object) analyzed quantitatively and qualitatively at admission and longitudinally.

RESULTS

RR subjects showed significantly higher scores at admission when tracking face in mirror versus other stimuli. No differences were observed for NRR subjects. No statistical differences seen for direction of tracking for either group, but 48% of subjects showed preference for tracking in one direction versus the other at initial assessment.

CONCLUSIONS

Visual tracking not a unitary phenomenon but dependent on stimulus and direction. RR subjects' ability to track their own face in mirror seems to be critical variable in predictive value of VISTRACK subscale. Potency of human face as stimulus relates to developmental and neurophysiological factors. Awareness of effects of stimulus and direction on tracking function warrants comprehensive visual tracking assessment.

Anticipatory saccades in smooth pursuit: task effects and pursuit vector after saccades

The dramatic improvement in smooth pursuit performance seen while analyzing the pursuit target has been ascribed to attention enhancement. With a periodic constant velocity target trajectory we ran a concurrent listening condition instead, to see if this mild distraction would degrade performance. Performance improved somewhat with the listening task, suggesting that displacing attentional effort from pursuit accuracy, rather than increasing it, brings better pursuit performance. Catch-up saccades were evenly distributed across tracking, listening, and target analysis conditions, but anticipatory and overshooting saccades were almost eliminated with target analysis. Thus the poor pursuit seems to have been caused by anticipatory and overshooting saccades, produced erroneously in the attempt to perform purposive smooth pursuit. Pursuit velocity immediately following anticipatory saccades was reduced such that the target would catch up with the point of gaze when it reached the endpoint of its trajectory, indicating a predictive goal other than instantaneous target foveation and velocity match.

Impaired saccadic eye movements on stationary targets in patients with schizophrenia spectrum disorder

This study examined tracking eye movements on predetermined stationary targets in patients with schizophrenia spectrum disorder. The targets were 8 black points or 8 arabic-numbered points placed on the circumference of a circle. Self-paced eye movements during clockwise tracking of these points by 23 patients and 23 normal controls were recorded using an infrared eye-mark recorder. Eye movements were analyzed at two settings: firstly, when "fixation point" was defined as a point at which a gaze was held for at least 200-ms; and secondly, when held for at least 100-ms. The results indicated that at the 200-ms setting schizophrenic patients track with significantly fewer correct scores and more deviant scores than controls under black-point conditions. At the 100-ms setting, however, the correct scores of patients were not significantly different from those of controls, although patients displayed more aberrant paths than controls. The superfluous fixations in the patients improved significantly under numbered-point conditions, but patients still achieved lower correct scores than controls. Four of the 23 patients exhibited centering (aberrant path directed toward the center point), suggesting immature control of eye movements under black-point conditions, but not numbered-point conditions. These results suggest that some schizophrenic patients viewed the targets too quickly, and that they have impaired directed attention, which can be improved by cues, and may have impaired preprogramming of eye movements, which is not improved by external cues.

Comparison of the smooth eye tracking disorder of schizophrenics with that of nonhuman primates with specific brain lesions

The smooth pursuit eye tracking deficit (ETD) often associated with schizophrenia has generated enormous interest over the last 20 years. The deficit is observed in about 80% of schizophrenics and in half of their first degree relatives. It is not affected by neuroleptic medication and is not due to inattention. A review of 52 studies (and actual records when available) on ETD in schizophrenia reveals that the deficit can consistently be described as low gain pursuit augmented with catch-up saccades and often peppered with intrusive saccades. A review of the brain areas that have been shown to be involved in pursuit provides the necessary background for the subsequent section which details the nature of the smooth tracking deficits following experimental lesions. This section reveals that the ETD following lesions of the frontal lobe is unique in that it closely resembles the ETD of schizophrenics. This finding lends further support for frontal lobe theories of schizophrenia.

Thalamic abnormalities in schizophrenia visualized through magnetic resonance image averaging

Schizophrenia is a complex illness characterized by multiple types of symptoms involving many aspects of cognition and emotion. Most efforts to identify its underlying neural substrates have focused on a strategy that relates a single symptom to a single brain region. An alternative hypothesis, that the variety of symptoms could be explained by a lesion in midline neural circuits mediating attention and information processing, is explored. Magnetic resonance images from patients and controls were transformed with a "bounding box" to produce an "average schizophrenic brain" and an "average normal brain." After image subtraction of the two averages, the areas of difference were displayed as an effect size map. Specific regional abnormalities were observed in the thalamus and adjacent white matter. An abnormality in the thalamus and related circuitry explains the diverse symptoms of schizophrenia parsimoniously because they could all result from a defect in filtering or gating sensory input, which is one of the primary functions of the thalamus in the human brain.

The duration of the movement aftereffect as an index of psychiatric illness

The duration of the movement aftereffect (MAE) has sometimes been used to make inferences about the subject's state (for example, their level of arousal). Some studies are reviewed in which visual aftereffects (including the MAE) were measured in schizophrenia, with inconsistent results. Some relevant psychopharmacological and neurological evidence is considered. It is concluded that: (i) Differences in the clinical status of the schizophrenic subjects and whether they were receiving medication, but not the method used to measure aftereffects, may underlie the interstudy disagreements. (ii) The effect of schizophrenia is to increase MAE duration, and this is not due to some peripheral artefact. (iii) Longer MAEs in the illness could result from enhanced neurally signalled contrast and/or from the increased adaptability of cortical neurons.

Smooth-pursuit eye movement dysfunction in schizophrenia: the role of attention and general psychomotor dysfunctions

Smooth-pursuit eye-tracking performance was examined in 100 schizophrenic patients and various control groups under both attention-enhancing and attention-distracting conditions. The level of attentional demand was varied by introducing a secondary reaction time task that directed attention either toward or away from the visual-tracking target. Distraction from the target led to a significant deterioration of tracking performance in all subjects, which was most pronounced in the group of schizophrenic patients. Attention-enhancement, on the other hand, did not normalize performance in this group. In schizophrenic patients, mainly in the distraction condition, there was a moderate association between performance in tracking and tests presumably measuring prefrontal functions. Tracking accuracy from both conditions was related to general motor performance as measured by the Neurological Evaluation Scale. It was concluded that in schizophrenic patients attentional factors (distraction) may contribute to eye-tracking impairment, and that the impairment may be viewed as an aspect of general motor dysfunctions.

Possible noradrenergic dysfunction in schizophrenia

In spite of extensive studies over the last 2 decades to find direct evidence in support of the dopamine hypothesis of schizophrenia, no undisputed experimental data has been obtained. In contrast, estimation of noradrenalin (another major catecholamine) and its metabolites in postmortem brain and in the cerebrospinal fluid appears to be producing consistent results. To understand the meaning of this change for the pathogenesis of the illness, we have carried out animal experiments in which reproducibility of schizophrenic signs and symptoms by noradrenergic dysfunction, and treatability of the disorder by modulation of noradrenergic activity were studied. First, psychophysiological signs in skin conductance responsiveness (nonhabituating or nonresponding change) and smooth pursuit eye movement (spiky or stepwise pursuit) could be reproduced by enhancing or suppressing central noradrenergic activity. Behavioral abnormalities resembling schizophrenic symptoms are known to be reproducible by over- or underactivity of the system (overarousal or underarousal syndrome). Secondly, the action of various drugs capable of modulating schizophrenic symptoms was analyzed in relation to noradrenergic activity. Haloperidol, in particular, had a potent suppressing effect on skin conductance activity (spontaneous fluctuation rate and habituation rate) when administered chronically, suggesting its inhibitory action on noradrenergic activity.

Smooth pursuit eye movement dysfunction as a biological marker for prediction of disease courses of schizophrenia: a preliminary report

We investigated the relationship between a smooth pursuit eye movement (SPEM) dysfunction and long-term disease courses of schizophrenia. Many schizophrenic patients without the SPEM dysfunction tended to show an acute onset of illness, undulating courses and relatively good outcomes. On the other hand, patients with cogwheel-like SPEM dysfunction tended to show a chronic onset, simple courses, relatively severe outcomes and negative symptoms.

Normal eye tracking is associated with abnormal morphology of medial temporal lobe structures in schizophrenia

Eye tracking and brain morphology assessed by magnetic resonance imaging were examined in 48 patients in their first episode of schizophrenia and in 15 normal controls. Schizophrenic patients showed higher rates of eye tracking dysfunction and more abnormal brain morphology involving the lateral ventricles, medial temporal lobe (MTL) structures and the frontal-parietal cortex than controls. Enlargement of the lateral ventricles and global rating of abnormal brain morphology were significantly more prevalent in male schizophrenics than female schizophrenics. These findings indicate that abnormalities in a variety of brain regions are present in some schizophrenics during the period shortly after the first hospitalization and could not be a function of treatment or chronic illness. We found no relation between abnormal eye tracking and any single feature of abnormal brain morphology. However, normal eye tracking was significantly associated with MTL abnormalities in schizophrenics, reflecting an inverse association between quality of eye tracking and degree of abnormality in MTL structures. These results suggest that abnormal eye tracking is not mediated by the same processes that lead to structural brain anomalies in schizophrenia.

Behavioral markers of schizophrenia useful for genetic studies

The advent of powerful molecular biological techniques have already led to the discovery of chromosomal loci linked to some genetically transmitted diseases. These techniques, however, lose their power if applied to a disease trait that is not Mendelian in its transmission. The low familial prevalence of psychiatric diseases such as schizophrenia make these techniques unsuitable for linkage studies of these conditions, if identification of schizophrenia relies solely on the clinical manifestation of the schizophrenic psychosis. Broadening the disease phenotype in diseases such as schizophrenia, with low recurrence risk, and narrowing it in diseases such as major affective disorder, with very high recurrence risk, may be an effective strategy for linkage studies of these diseases. Several alternative phenotypes are discussed, including smooth pursuit eye movement abnormalities, event related potentials, and deficient attentional deployment as measured by the continuous performance test. The strategy assumes that schizophrenia is a pleiotropic disorder, and that the psychosis is the rare form of the condition. The paper focuses principally on smooth pursuit eye movement abnormalities, and claims a plausible place for them as an independent expression of schizophrenia. With this strategy, the possibility for successful linkage studies increases, since familial distributions of schizophrenia and pursuit abnormalities, considered together, appear to fit an autosomal dominant pattern.

Abnormalities of smooth pursuit and saccadic control in schizophrenia and affective disorders

Smooth pursuit abnormalities have been reported in patients with schizophrenia and their first-degree relatives, suggesting that abnormal tracking may serve as a biological marker for schizophrenia. Recent studies in schizophrenic patients have found reduced pursuit gain, low initial acceleration and abnormal gain-corrective saccade interactions. Impaired saccadic initiation has been noted in anti-saccade tasks and in predictive saccade generation, as has saccadic hypometria. While abnormalities have been found in affective disorder patients, studies of their first-degree relatives suggest that abnormalities during pursuit are more closely associated with schizophrenia. Identification of specific defects allows informed speculation about their neural substrates and suggests possible relationships between the ocular motor defects and other cognitive and perceptual abnormalities associated with the major psychiatric disorders.

Disorders of smooth pursuit eye movement and auditory N100 in schizophrenic patients

Attentional factors are thought to affect eye-tracking patterns. The present study examined the hypothesis that specific quantitative features of eye tracking would be correlated with the amplitude of a component of the auditory evoked potential, the N100, which is known to be enhanced by arousal and selective attention. We studied 12 clinically stable schizophrenic patients by means of DC-electro-oculography. The frequency and amplitude of different types of saccades (catchup, backup, anticipatory saccades, and square wave jerks) were assessed. The results suggest that small and large saccades, as classified by a simple amplitude criterion (4 degrees), have differential meanings and indicate that enhanced amplitudes of small saccades are an effect of arousal.

Two modes of central gaze fixation maintenance and oculomotor distractibility in schizophrenics

Distractibility defined operationally as a lack of stability in central-gaze fixation has been studied using two different oculomotor tasks that require the suppression of reflexive saccades triggered by the sudden appearance of novel, peripheral visual stimuli. In the first task ('Instructed'), maintenance of central gaze fixation was based on verbal instruction, whereas, in the second task ('Non-Instructed'), it was based upon a foveating mechanism maintained by sensory stimulation during the performance of a categorization task. 15 schizophrenics and 20 healthy control subjects were tested in the two tasks. Schizophrenics made more saccades than control subjects in the Instructed task only. The Instructed task saccade rate correlated significantly with scores on neuropsychological tests sensitive to frontal lobe dysfunction. Because the type of deficit observed in schizophrenics resembled that previously seen in patients with unilateral lesions of the ventrolateral convexity of frontal lobe, frontal lobe dysfunction was proposed as underlying the high task-specific distractibility of schizophrenics.

Impaired eye tracking performance in patients with presenile onset dementia

Smooth pursuit eye movements, saccades and eye blinks were electrooculographically recorded from 26 healthy subjects of different age and 35 patients with presumptive presenile onset dementia (mean age 54), who had to track a light spot which oscillated with different speeds. Older subjects (mean age 51) performed the eye tracking with less accuracy and more saccades than younger ones (mean age 22). 16 patients with stage CDR 1 according to Washington University Clinical Dementia Rating performed smooth pursuit eye movements significantly worse with increased saccade numbers than the healthy older subjects and lost attention significantly more often which was measured by omitted trackings to presented target oscillations. Their number of eye blinks was partly increased. The test is found suitable for early diagnosis of dementia onset, supporting clinical findings and presumptive diagnosis by objective parameters.

Effects of lithium treatment on eye movements

Smooth pursuit eye movements (SPEMs) of 11 bipolar manic patients were impaired during lithium treatment, which, however, improved their clinical condition. SPEM impairment was evident in a general qualitative degradation of eye tracking integrity, in a tendency for gain to be lowered, and in an increase in the number of saccadic events. Individual differences in the nature and magnitude of effects of lithium on eye movements were noteworthy.

The structure of schizotypy: a pilot multitrait twin study

This report of a pilot study examines 29 pairs of twins from a population-based registry on whom four domains of schizotypy have been measured: personal interview using the Structured Interview for Schizotypy, self-report questionnaire formed from eight published self-report scales, attentional battery of eight individual tests, and root mean square error on smooth pursuit eye tracking. Analyzing the twins as individuals revealed two independent dimensions of clinically rated schizotypy (positive symptom schizotypy and negative symptom schizotypy) and two independent dimensions of self-rated schizotypy (positive trait schizotypy and trait anhedonia). Positive symptom schizotypy was highly correlated with positive trait schizotypy, but not with attentional dysfunction or eye-tracking error. By contrast, negative symptom schizotypy was significantly related to trait anhedonia, attentional dysfunction, and eye-tracking error. Correlations in monozygotic and dizygotic twins suggested that genetic factors were important in all four domains of schizotypy. Except for eye-tracking error, the results are more consistent with a dimensional than a "disease" model of schizotypy. Replication of these results with a larger group of subjects is needed.

Smooth pursuit eye movements of normal and schizophrenic subjects tracking an unpredictable target

An experimental paradigm employed by several workers in the field of schizophrenic eye movements has involved finding sequences of stimuli that induce saccadic smooth pursuit in the eye movements of normal individuals. It is hoped that the identification of such stimuli will lead to clues concerning the etiology or nature of eye tracking dysfunction in schizophrenia. In this study, the pursuit eye movements of normal and schizophrenic subjects tracking an unpredictable target (composed of summed sine waves) were examined. Eye tracking performance was evaluated both qualitatively and quantitatively using percent root-mean-square (%RMS) error and pursuit gain scores. Schizophrenics are capable of tracking an unpredictable target. This finding has implications for our understanding of schizophrenic information processing during visual tracking.

P300 and smooth eye pursuit: concordance of abnormalities and relation to clinical features in DSM-III schizophrenia

Twenty-five DSM-III-diagnosed schizophrenics and 37 normal and age-matched controls were examined using an oddball paradigm for the generation of P300 and smooth eye-pursuit tasks. Results were compared between groups and related to clinical characteristics, including a family history of psychiatric illness. Group differences were found for P300 amplitudes, latencies and eye-tracking. A family history of psychiatric illness was associated with normal eye-tracking in patients. Small P300 amplitudes alone and in combination with long P300 latencies were associated with a family history in controls.