Smooth-pursuit eye tracking in first-episode psychotic patients and their relatives.

We wished to determine the specificity of smooth-pursuit eye tracking dysfunction to schizophrenia and the prevalences of dysfunction among functionally psychotic and normal individuals. Therefore, we investigated pursuit tracking in a large sample of psychotic patients, normal subjects, and first-degree relatives (N = 482). Patients were recruited as part of an epidemiological study of first-episode psychosis that used a broadly based referral network to identify all cases in a major metropolitan area over a 2 1/2-year period. Patients received diagnoses of schizophrenia, schizophreniform disorder, psychotic mood disorder, and paranoid or other psychotic disorder based on the third edition of the Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 1980). The distribution of tracking performance was bimodal for the schizophrenic patients and their relatives, perhaps reflecting major gene action. Moreover, poor tracking ran in families. Pursuit tracking dysfunction was relatively specific to schizophrenic patients and their relatives and occurred infrequently in other psychotic patients and normal subjects.     

I. Genotype-environment interaction in the schizophrenia spectrum: genetic liability and global family ratings in the Finnish Adoption Study

In the Finnish Adoption Study, a national sample of adoptees with high versus low genetic liability for schizophrenia spectrum disorders was indexed by DSM-III-R diagnoses of their biological, adopting-away mothers. The rearing-family environments of the adoptees were independently evaluated from global ratings of directly observed adoptive family relationships. The interaction of high genetic liability and dysfunction of the rearing families predicted highly significantly to schizophrenia spectrum disorder of the adoptees at 21-year follow-up. Either low genetic liability or healthy rearing protected against a spectrum outcomes for the adoptees. Initial adoptive parent diagnosis, as a proxy for rearing family dysfunction, predicted to adoptee outcome only as a trend.     

Neurophysiological markers of vulnerability to schizophrenia: sensitivity and specificity of specific quantitative eye movement measures

Eye-tracking deficits in schizophrenic patients and relatives have generated interest in using eye movements to mark schizophrenia liability. Efforts to develop specific quantitative measures have provided insight into the nature of the deficit and suggested what underlying neurophysiological mechanisms are involved. This study used receiver operating characteristic curve analyses to evaluate and compare the sensitivity, specificity, and overall accuracy of predicting disease liability using single and combined specific and global quantitative measures. Results indicate that measures of predictive pursuit and leading saccades significantly increased predictive accuracy compared with traditional global measures. Combining specific measures provided greater predictive accuracy compared with single measures. Implications for the use of specific eye movement measures to define schizophrenia-related phenotypes in genetic studies are discussed.     

Neuropsychology,genetic liability,and psychotic symptoms in those at high risk of schizophrenia

Neuropsychological assessments were compared among individuals at enhanced genetic risk of schizophrenia (n = 157) and controls (n = 34). The relationship between cognitive impairments and the presence of psychotic symptoms and measures of genetic risk was explored in the high-risk subjects. Neuropsychological differences were identified in many areas of function and were not accounted for by the presence of psychotic symptoms. Genetic liability was not associated with neuropsychological performance or with psychotic symptoms, but exploratory analysis showed some tests were associated with both liability measures. These results suggest that what is inherited is not the disorder itself but a state of vulnerability manifested by neuropsychological impairment, occurring in many more individuals than are predicted to develop the disorder.     

Effects of foveal processing difficulty on the perceptual span in reading: implications for attention and eye movement control

Two experiments were conducted to examine the effects of foveal processing difficulty on the perceptual span in reading. Subjects read sentences while their eye movements were recorded. By changing the text contingent on the reader's current point of fixation, foveal processing difficulty and the availability of parafoveal word information were independently manipulated. In Experiment 1, foveal processing difficulty was manipulated by lexical frequency, and in Experiment 2 foveal difficulty was manipulated by syntactic complexity. In both experiments, less parafoveal information was acquired when processing in the fovea was difficult. We conclude that the perceptual span is variable and attentionally constrained. We also discuss the implications of the results for current models of the relation between covert visual-spatial attention and eye movement control in reading.     

Changing-loudness aftereffect following simulated movement: implications for channel hypotheses concerning sound level change and movement.

Listening to a tone changing unidirectionally in sound level causes an illusion of changing loudness in a steady tone afterward. This aftereffect may indicate channels for detecting the feature of change in sound level, which would primarily concern dynamic sound localization. Three subjects, one of whom was the author, participated in this study. The author predicted that opposite adaptation of the ears (the adapting stimulus is heard to move from one ear to the other) should lead to a movement aftereffect. This was not reported by the subjects. However, the subjects did report a changing-loudness aftereffect in a monaural test stimulus, and the characteristics of the changing-loudness aftereffect (such as its magnitude) were consistent with previous data, suggesting a two-stage channel hypothesis: Output from channels for several features, including sound-level change, simultaneously stimulate movement channels.     

ILAB: A program for postexperimental eye movement analysis

The recording and analysis of eye movements are fundamental to a diverse set of research applications, including studies in which reading, visual search, and both overt and covert visuospatial attention are examined. Software tools supplied with commonly available eye-tracking equipment have generally been limited in functionality and nonextensible. Because of this dearth of available software, ILAB was createdto provide an extensible frame workfor analyzing various aspects of eye movements. The program consists of a series of open-source MATLAB functions. The program’s data structures keep raw data, analysis preferences, and analyzed data separate, thus maintaining data fidelity and promoting extensibility.     

Eye-tracking dysfunction and birth-month weather in schizophrenia.

The prevalence of eye-tracking dysfunction (ETD) is significantly elevated in individuals with a diagnosis of schizophrenia and in their nonschizophrenic relatives, suggesting that ETD marks a familial (most likely genetic) risk factor for schizophrenia. Birth in a season with intemperate weather is also a widely reported risk factor for schizophrenia and is particularly marked for the subgroup with no family history of the disorder. This study examined how these two risk factors covaried in 78 patients with a Diagnostic and Statistical Manual of Mental Disorders (3rd ed., rev.; American Psychiatric Association, 1987) diagnosis of schizophrenia. Eye tracking and birth-month weather were independently assessed. As hypothesized, patients without ETD were significantly more likely to be born in months with intemperate weather (both hot and cold) than either patients with ETD or people in the general population. Etiologic factors associated with severe weather near birth may be important sources of nonfamilial schizophrenia.     

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.     

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.     

Interocular transfer of movement after-effects in schizophrenia.

A group of 16 chronic schizophrenic subjects were compared with 15 age-matched control subjects for interocular transfer of movement after-effects. Contrary to the hypothesis that schizophrenic subjects would show a deficit on this measure schizophrenics showed increased transfer compared to the controls. This effect is not due to response perseveration and is not correlated with length of hospitalization, age or dose of antipsychotic drugs. It is suggested that the effect reflects a deficit in 'inhibitory processes' in schizophrenia.     

Linguistic focus and memory: An eye movement study

We report an eyetracking study investigating the effects of linguistic focus on eye movements and memory during two readings of a text. Across two presentations of the text, a critical word either changed to a semantically related word or remained unchanged. Focus on the critical word was manipulated using context. Eye movements were monitored during reading, and there was a secondary task of detecting the word change. Results indicated that when a word changed, participants were more successful at detecting it when it was in focus. In the second display, there were more fixations and longer viewing times on a changed than on an unchanged word, but only when the critical word was in focus; eye movement data for changed and unchanged words did not differ when the word was not in focus. We suggest that linguistic focus leads to more detailed lexical semantic representations but not more effortful initial encoding of information.     

Twin imitation for antisocial behavior: implications for genetic and family environment research.

When twin pairs influence each other's behavior, observed variance is greater for MZ twins than for DZ twins under at least 1 of 2 conditions: (a) the trait has some heritability and (b) MZ twins influence each other more than do DZ twins. Applied to a trait that has an underlying continuous distribution but is measured as a dichotomy, the presence of reciprocal twin influence predicts that if the base rate for the trait is not exactly 50%, then the prevalence of the trait should differ in MZ and DZ twin pairs. This prediction held for registered criminality in a large twin cohort. Methods of analysis that permit reciprocal twin interaction not only provide better statistical fits to the data but also yield estimates of heritability that agree with adoption data. The results suggest that the genetic influence on registered criminality may be more modest than previously thought.     

Latency of sequential eye movements: implications for reading

The best available estimates indicate that the average minimum latency of saccadic eye movements (175-200 msec) approaches the mean duration of fixations in reading (200-250 msec). This fact presents a problem for models of reading which assume that an eye movement is initiated only after substantial information is processed on a fixation. Three experiments are reported that support earlier estimates of saccadic latency; the experiments were conducted under conditions in which the length of measured latencies could not reflect a motoric refractory period, spatial uncertainty, or temporal uncertainty.     

Saccadic eye movement programming: sensory and attentional factors

The relationship between attention and eye movements is explored by consideration of the variety of ways attention may affect saccade programming. Four forms of attention are distinguished: one exogenous and three endogenous through either locations or objects or features. Each of these can control or influence the saccadic generation process. Visual onsets generate a rapid transient signal with low resolution that travels from the visual system to the oculomotor system. Generation of an eye movement is associated with an attentional signal, probably also with low resolution, travelling from the oculomotor system to the visual system. A high-resolution attentional signal, which appears to require voluntary effort, can also select saccadic targets.     

Psychophysiologic abnormalities in schizophrenia: some implications for therapy

On the basis of several studies, some psychophysiological activation abnormalities in schizophrenia are explained. These abnormalities give rise to at least three therapeutic aims: (1) As some psychophysiological systems may be under- and others overaroused in schizophrenic patients compared to normal controls, therapeutic interventions should approach the systems selectively. (2) The ability to modulate the psychophysiological activation, which is diminished in schizophrenic patients, should be improved. (3) Schizophrenic patients need a more differentiated perception of their own state of activation. These aims contrast somewhat with past therapeutic studies, which tried to change activation for the purpose of tension reduction. It seems advisable to link basic psychophysiological research more closely to the development of therapies.     

No effects of eye movements on the encoding of the visuospatial sketchpad and the phonological loop in healthy participants: Possible implications for eye movement desensitization and reprocessing therapy

Horizontal eye movement is an essential component of the psychological intervention “eye movement desensitization and reprocessing” (EMDR) used in posttraumatic stress disorder. A hypothesized mechanism of action is an overload of the visuospatial sketchpad and/or the phonological loop of the working memory.