Smooth pursuit eye movements and neuropsychological tests in schizophrenic patients: possible involvement of attentional components

The relationship between antisaccades, smooth pursuit, and executive dysfunction in first-episode schizophrenia

BACKGROUND

Both oculomotor and neuropsychologic deficits have been used to support the hypothesis that schizophrenia is associated with prefrontal cortex dysfunction, but studies that have specifically investigated the relationships between these deficits have produced inconsistent findings.

METHODS

We measured both smooth pursuit and antisaccade performance in a large group (n = 109) of patients with first-episode schizophrenia and a group of matched control subjects (n = 59) and investigated the relationship between performance on these tasks and performance on a range of executive tasks. We additionally explored the relationship between these variables and measures of psychopathology at presentation and duration of untreated psychosis.

RESULTS

Antisaccade errors were significantly correlated with spatial working memory performance. Smooth pursuit gain did not correlate with any neuropsychologic measure. There were no reliable correlations between either oculomotor variables and measures of psychopathology and duration of untreated psychosis.

CONCLUSIONS

These findings suggest that in schizophrenia working memory and antisaccade performance reflect the same abnormal prefrontal substrates and that smooth pursuit is mediated by a separate neural abnormality.

Schizophrenia spectrum disorders and eye tracking dysfunction in singleton and multiplex schizophrenia families

One line of research which is helping to unravel the genetic susceptibility to schizophrenia (SZ) is the analysis of eye tracking dysfunction (ETD), a quantifiable phenotypic marker. To investigate if such a biological marker is also present in singleton schizophrenia families, we examined eye tracking in members of singleton families (N=53) and compared it to members of multiplex (N=76) and nonpsychiatric families (N=71) using high resolution infrared oculography. The prevalence of ETD defined by gain values (eye/target velocity) and saccadic frequencies during smooth pursuit at 15 degrees /s did not differ between multiplex and singleton families in either the schizophrenic index patients or their relatives, but was significantly different from nonpsychotic families. ETD rate was higher in those relatives with compared to those without a diagnosis of a schizophrenia spectrum disorder. In relatives with a spectrum disorder, ETD appeared to be associated with traits for "sensitivity" and "suspiciousness". In the group of relatives from singleton families without a schizophrenia spectrum disorder, we still found a higher prevalence of ETD than in nonpsychotic families. Our results suggest that eye tracking dysfunction is a very sensitive biological marker for the vulnerability to schizophrenia, even in those cases where no psychopathological symptoms or signs are obvious. ETD in schizophrenia is suggested to serve as a neurophysiological type model, indicating a perception deficit.

Educational level and age influence spatial working memory and Wisconsin Card Sorting Test performance differently: a controlled study in schizophrenic patients

The influence of educational level and age on executive function, as evaluated by the Wisconsin Card Sorting Test (WCST), and 'working memory,' as evaluated by means of a visual-manual delayed-response task, has been investigated in 25 schizophrenic patients and 35 healthy controls matched for age. Different patterns of correlations between educational level, age and cognitive variables were seen for the 'working memory' task but not for the WCST. No significant correlations between the WCST and the 'working memory' task indexes have been observed. Based on multivariate analyses, poor performance of schizophrenic patients on working memory and executive function tasks was observed; after covarying for the educational level, group differences were no longer significant for executive functions, but the difference in 'working memory' performance persisted. The implications of sociodemographic variables as well as the role of statistical manipulation are evaluated and their differential impact on 'working memory' and executive functions is proposed in further support of these neurocognitive constructs that may be dissociable.

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.

Delusional disorder and eye tracking dysfunction: preliminary evidence of biological and clinical heterogeneity

This study used eye tracking movement tests to examine the relationships between frontal field functions and clinical features. Smooth pursuit and voluntary saccadic eye movements were recorded and analyzed in 34 delusional disorder (DD) patients and in 40 normal subjects. The DD group differed significantly from the group of normal subjects in some eye tracking performances. As reported in our previous study (Gambini et al., 1993), DD patients showed abnormalities of voluntary saccadic eye movements. In this study, we also found abnormal smooth pursuit eye movements, indicating a cerebral dysfunction similar to those detected in schizophrenic patients. Moreover, normal smooth pursuit eye movement performance in DD patients was related to remitted depressive mood and probably to benefit from antipsychotic medications, thus supporting the idea of the biological and clinical heterogeneity of DD.

Relationships between neuropsychological and oculomotor measures in schizophrenia patients and normal controls

Establishing the relationship between oculomotor and neuropsychological impairments might facilitate a more coherent description of schizophrenia-associated neurocognitive deficits. Therefore, we assessed several aspects of neuropsychological and oculomotor function in 25 medicated schizophrenia patients and 24 age-matched controls. Neuropsychological tasks included the Wisconsin Cart Sort Test (WCST), the Trail Making Test (TMT), the Rey Auditory Verbal Learning Test, and finger tapping speed. Oculomotor functions assessed included smooth pursuit, initiation of smooth pursuit, predictive pursuit, fixation, visually guided saccades, remembered saccades, and antisaccades. Among the schizophrenia patients, predictive pursuit performance correlated significantly with finger tapping (dominant hand), TMT (both parts), and one WCST measure (categories completed). The only other significant correlation among the schizophrenia patients was between antisaccade performance and part A of the TMT. Perseverative errors during the WCST and antisaccade performance were the only measures significantly correlated among the normals. Closely related neurocognitive deficits may be responsible for impairments in TMT, WCST, predictive pursuit, and antisaccade performance in schizophrenia.

No deficit in Wisconsin Card Sorting Test performance of schizophrenic patients' first-degree relatives

The Wisconsin Card Sorting Test (WCST) was administered to 92 schizophrenic patients, 25 first-degree relatives and 60 normal subjects in order to investigate whether this task could be considered a trait marker of vulnerability to schizophrenia. The schizophrenic patients performed significantly worse than either their relatives or normal subjects, but unaffected relatives did not differ from controls. Our results suggest that WCST performance is more likely a feature inherent to the disease process rather than an index of the genetic susceptibility to the illness.

Eye movements and psychopathology in schizophrenia and bipolar disorder

The aim of this study was to examine multivariate patterns of relationships between oculomotor performance, psychopathology, and neuropsychology. Performance on smooth pursuit and saccadic eye movement tasks was assessed in three DSM-III-R diagnosis-based groups of subjects; normal (N = 55), schizophrenic (N = 29), and bipolar disorder (N = 26) and analyzed in relation to age, gender, scale for the Assessment of Negative Symptoms, Scale for the Assessment of Positive Symptoms, and Brief Psychiatric Rating Scale scores, Shipley intelligence quotient, and Wisconsin Card Sorting Test Performance. The greatest difference was a higher proportion of errors in the antisaccade task in the schizophrenic and bipolar groups, which was related to worse Wisconsin Card Sorting Test performance and was not accounted for by gender, age, education, or intelligence quotient. A significant gender and bipolar interaction showed bipolar women to have worse antisaccade performance. Abnormal smooth pursuit was more specific to schizophrenia. Antisaccade task and sine wave root-mean-square error were correlated in bipolar but not schizophrenic subjects. Scale for the Assessment of Negative Symptoms and Scale for the Assessment of Positive Symptoms scores had independent associations with the antisaccade task. Faster reaction times in the schizophrenic group to antisaccade errors were observed, suggesting an abnormality in visual attention processing and perhaps sensory gating functions. These results confirm abnormal smooth pursuit in schizophrenia and suggests that impairments in saccadic function are less specific to diagnostic group. Oculomotor performance and psychopathology seem related in complex ways to age, gender, intelligence quotient, and executive neuropsychological and possibly visual attention functions.