Smooth pursuit eye movements in twins discordant for schizophrenia

Increased saccadic rate during smooth pursuit eye movements in patients at Ultra High Risk for developing a psychosis

Abnormalities in eye tracking are consistently observed in schizophrenia patients and their relatives and have been proposed as an endophenotype of the disease. The aim of this study was to investigate the performance of patients at Ultra High Risk (UHR) for developing psychosis on a task of smooth pursuit eye movement (SPEM). Forty-six UHR patients and twenty-eight age and education matched controls were assessed with a task of SPEM and psychiatric questionnaires. Our results showed that both the corrective and non-corrective saccadic rates during pursuit were higher in the UHR group. There were however no differences in smooth pursuit gain between the two groups. The saccadic rate was related to positive UHR symptoms. Our findings indicate that abnormalities in SPEM are already present in UHR patients, prior to a first psychotic episode. These abnormalities occur only in the saccadic system.

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.

Which perspectives can endophenotypes and biological markers offer in the early recognition of schizophrenia?

The early recognition of schizophrenia seems crucial; various studies relate a longer duration-of-untreated-psychosis to a worse prognosis. We give an overview over common psychopathological early recognition instruments (BSABS, CAARMS, SIPS, IRAOS, ERIraos). However, many clinical symptoms of prodromal schizophrenia stages are not sufficiently specific. Thus we review recent contributions of neuroimaging and electrophysiological as well as genetic studies: which new diagnostic perspectives offer endophenotypes (such as P300, P50 sensory gating, MMN, smooth pursuit eye movements; indicating a specific genetic vulnerability) together with a better understanding of schizophrenic pathophysiology (state-dependent biological markers, e.g. aggravated motor neurological soft signs during psychosis) in prodromal schizophrenia when still ambiguous clinical symptoms are present. Several examples (e.g. from COMT polymorphisms to working memory deficits) illustrate more specific underlying neuronal mechanisms behind behavioural symptoms. This way, a characteristic pattern of disturbed cerebral maturation might be distinguished in order to complement clinical instruments of early schizophrenia detection.

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.

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.

Lithium effect on smooth pursuit eye movements of healthy volunteers

Smooth pursuit eye movement (SPEM) dysfunctions in major affective disorder patients have been reported to be associated with lithium treatment. We report that SPEM of 13 healthy volunteers, either taking lithium (n = 7) or placebo (n = 6), were not significantly impaired by lithium. This could point to a pathophysiologic difference between affective disorder patients and a normal population.

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.

Eye-tracking dysfunction in the affective psychoses and schizophrenia

Smooth pursuit eye movements to a sinusoidally moving target were recorded using the electro-oculogram in 49 subjects with bipolar disorder, 19 with major depressive disorder and 61 with definite schizophrenia, and compared with 145 normal controls. The signals were analysed in the frequency domain to yield a signal to noise ratio that is known to relate to accuracy of smooth pursuit. Smooth pursuit was found to be significantly poorer in schizophrenics than in bipolars, major depressed or controls. Eye-tracking performance was independent of the effects of neuroleptics, tricyclic antidepressants or lithium, and was not altered by the severity of depression in the affective psychoses. There was a small, but significant worsening of smooth pursuit with age in controls and schizophrenics, but this did not account for the group differences. The results support the view that among the major psychoses eye-tracking dysfunction is specific to schizophrenia.

DNA markers and biological vulnerability markers in families multiply affected with schizophrenia

A family is reported in which the monozygotic co-twin of a schizophrenic proband was diagnosed bipolar 1 and their mother had a history of unipolar major depression. Although their clinical manifestations varied, the ill members of this family shared an abnormality in P300 not found in the asymptomatic siblings. In 14 families, linkage to the 5q11-13 region was excluded when affection status was defined solely by P300 latency independently of the clinical findings. Linkage was also excluded when the analysis was restricted to the families that had no cases of bipolar illness and when the schizophrenic phenotype was narrowly or broadly defined. It is concluded that biological markers such as P300 and eye tracking may help to clarify the overlap of different types of psychosis and help to define the phenotype for linkage analyses.

The relationship between smooth pursuit eye movement impairment and psychological measures of psychopathology

Two hundred and eighty-four male college volunteers were screened for smooth pursuit eyetracking deficiencies, a commonly reported concomitant of schizophrenia. A sample of 36 subjects, weighted with poor eyetrackers, was brought into the National Institute of Mental Health laboratory and retested on electro-oculogram and infrared tracking procedures. They were also administered psychological tests which assessed nine dimensions relevant to schizophrenic, neuropsychological, and affective disorders. In the area of schizophrenia-like symptoms, measures of attention deficits, stimulation avoidance, and identity problems predicted poor eyetracking for the whole sample. Using the poor eyetracking subjects alone (N = 24), interpersonal withdrawal was also significantly related to poor performance but not stimulation avoidance. In the neuropsychological area, measures of attention control and perceptual-motor dysfunction for the total sample, and perceptual problems and general intellectual decrements for the poor eyetrackers were significantly related to poor performance. There was no relationship between measures of affective dysfunction and poor eyetracking.

Frontal lobe dysfunctions in schizophrenia--I. Eye movement impairments

The phenomena of eye movement impairments in schizophrenia are interpreted in this paper, Part I of a two-paper series, in the context of neural mechanisms of attention and eye movement control. The predominant pattern of attention and eye movement impairment in schizophrenia--a disruption of smooth pursuit by saccadic intrusions--is consistent with a disinhibition of saccades. This disinhibition may be related to a dysfunction of frontal eye field mechanisms involved in feedback regulation of saccades and smooth pursuit during visual tracking. A second, less specific type of smooth pursuit impairment consists of saccadic substitution, and may be interpreted in terms of a dysfunction of temporo-parietal mechanisms of task-engagement.

Relatives of unipolar and bipolar patients have normal pursuit

Impaired smooth pursuit eye movements are significantly less prevalent among the first-degree relatives of patients who have major affective disorders than among the first-degree relatives of schizophrenics. The distribution of normal and abnormal smooth pursuit among the relatives of unipolar and bipolar patients does not differ from that of normal individuals having no family history of major psychosis. Smooth pursuit impairment is thus specific to relatives of schizophrenic patients and is not characteristic of relatives of patients with major affective disorders.