Emotional scene processing in biotypes of psychosis

Social-emotional deficits in psychosis may be indexed by deviations in emotional scene processing, but event-related potential (ERP) studies indicate such deviations may not map cleanly to diagnostic categories. Neurobiologically defined psychosis subgroups offer an alternative that may better capture neurophysiological correlates of social-emotional deficits. The current study investigates emotional scene-elicited ERPs in Biotypes of psychosis in a large (N = 622), well-characterized sample. Electroencephalography was recorded in healthy persons (N = 129), Biotype-1 (N = 195), Biotype-2 (N = 131), and Biotype-3 (N = 167) psychosis cases. ERPs were measured from posterior and centroparietal scalp locations. Neural responses to emotional scenes were compared between healthy and psychosis groups. Multivariate group discrimination analyses resulted in two composite variates that differentiated groups. The first variate displayed large differences between low-cognition (Biotype-1, Biotype-2) and intact-cognition groups (Biotype-3, healthy persons). The second indicated a small-to-moderate distinction of Biotypes-2 and -3 from Biotype-1 and healthy persons. Two multivariate correlations were identified indicating associations between 1) self-reported emotional experience and generalized cognition and 2) socio-occupational functioning and late-stage emotional processing. Psychosis Biotypes displayed emotional processing deficits not apparent in DSM psychosis subgroups. Future translational research may benefit from exploring emotional scene processing in such neurobiologically-defined psychosis groups.

Genome-wide association studies of smooth pursuit and antisaccade eye movements in psychotic disorders: findings from the B-SNIP study

Eye movement deviations, particularly deficits of initial sensorimotor processing and sustained pursuit maintenance, and antisaccade inhibition errors, are established intermediate phenotypes for psychotic disorders. We here studied eye movement measures of 849 participants from the Bipolar-Schizophrenia Network on Intermediate Phenotypes (B-SNIP) study (schizophrenia N=230, schizoaffective disorder N=155, psychotic bipolar disorder N=206 and healthy controls N=258) as quantitative phenotypes in relation to genetic data, while controlling for genetically derived ancestry measures, age and sex. A mixed-modeling genome-wide association studies approach was used including ~4.4 million genotypes (PsychChip and 1000 Genomes imputation). Across participants, sensorimotor processing at pursuit initiation was significantly associated with a single nucleotide polymorphism in IPO8 (12p11.21, P=8 × 10^-11), whereas suggestive associations with sustained pursuit maintenance were identified with SNPs in SH3GL2 (9p22.2, P=3 × 10^-8). In participants of predominantly African ancestry, sensorimotor processing was also significantly associated with SNPs in PCDH12 (5q31.3, P=1.6 × 10^-10), and suggestive associations were observed with NRSN1 (6p22.3, P=5.4 × 10^-8) and LMO7 (13q22.2, P=7.3x10^-8), whereas antisaccade error rate was significantly associated with a non-coding region at chromosome 7 (P=6.5 × 10^-9). Exploratory pathway analyses revealed associations with nervous system development and function for 40 top genes with sensorimotor processing and pursuit maintenance (P=4.9 × 10^-2-9.8 × 10^-4). Our findings suggest novel patterns of genetic variation relevant for brain systems subserving eye movement control known to be impaired in psychotic disorders. They include genes involved in nuclear trafficking and gene silencing (IPO8), fast axonal guidance and synaptic specificity (PCDH12), transduction of nerve signals (NRSN1), retinal degeneration (LMO7), synaptic glutamate release (SH3GL2), and broader nervous system development and function.

Response to the first stimulus determines reduced auditory evoked response suppression in schizophrenia: single trials analysis using MEG

OBJECTIVE

Reduced auditory evoked response (AER) suppression in a paired-stimulus paradigm may index genetic liability for schizophrenia. In most published studies of AER suppression, scores are based on data averaged over numerous stimulus presentations and recorded from few channels. It is unclear whether averaged data are equally representative of single trial responses in normal and schizophrenia subjects. In the present report, we used 148 channel magnetoencephalography to investigate grand-average and single trial responses on AER suppression.

METHODS

The typical paired-stimulus paradigm was used to evoke time-locked AERs from 20 normal and 20 schizophrenia patients. Gamma band response (GBR) and low frequency response (LFR) characteristics were measured on grand-averaged and single trial data. Generalized eigenvalue decomposition was used to reduce the multiple channel information to a vector that accounted for the most AER variance for the GBR and LFR.

RESULTS

Group performances on grand-average and single trials were similar. A remarkable difference, which replicates previous studies, was that schizophrenia subjects had smaller LFR amplitudes in response to the first stimulus than normal.

CONCLUSIONS

These findings are inconsistent with the "poor suppression" theory often used to explain schizophrenia-normal group differences when using the paired-stimulus paradigm.

Multichannel electroencephalographic assessment of auditory evoked response suppression in schizophrenia

Reduced auditory evoked response (AER) suppression in a paired-stimulus paradigm (where suppression equals the difference between S1 and S2 amplitudes divided by S1 amplitude) may index genetic liability for schizophrenia. The present report is a multiple-channel electroencephalographic (EEG) study of AER suppression among 20 normal and 20 schizophrenia subjects. The typical paired-stimulus paradigm was used to evoke time-locked AERs. AER responses were scored at P50 and N100 in the time domain using both single (Cz) and multichannel data (after reduction using principal components analysis, PCA), and were scored for information in the gamma (20-50 Hz) and low-frequency (1-20 Hz) ranges using multichannel information (also after PCA). The time domain analyses demonstrated that schizophrenia patients differ from normal in amplitude of response to the first, but not to the second, stimulus for both P50 and N100. The frequency domain data demonstrated that schizophrenia patients differed from normal on amplitude of the low-frequency response (LFR) to the first, but not to the second, stimulus. The groups did not differ significantly on amplitudes of the gamma-band responses. Group separations were largest for the multichannel N100 and LFR data, with the LFR demonstrating a modestly better risk ratio for differentiating schizophrenia from normal subjects. The present results suggest two novel differences from previous AER suppression studies: (1) S1 amplitudes largely determine differences between normal and schizophrenia groups on AER suppression, and (2) frequency domain analyses may provide important complimentary information when studying AERs in schizophrenia.

Timing and magnitude of frontal activity differentiates refixation and anti-saccade performance

EEG data were recorded while 10 subjects generated refixation saccades towards a visual target and antisaccades away from a visual cue. Theoretically, the same basic neural circuitry supports refixation and correct anti-saccade performances, with additional activity in primarily dorsolateral prefrontal cortex circuitry supporting antisaccade-associated inhibitory processes. Analyses demonstrated that sensory registration of visual stimuli is similar for refixation and anti-saccade conditions. Increased frontal brain activity at 5 and 15 Hz was observed preceding correct antisaccades when compared to refixation saccades. These analyses provide specific information suggesting that 160-60 ms before saccade generation is the critical period for response inhibition.

Behavioral and brain imaging studies of saccadic performance in schizophrenia

Data are reviewed from a series of saccadic studies demonstrating that schizophrenia subjects have normal performance on some types, and abnormal performance on other types, of tasks. Normal refixation saccade characteristics and BOLD signal change among schizophrenia subjects suggest that basic saccade generating circuitry is functionally intact among these subjects. Schizophrenia patients and their relatives, however, demonstrate difficulty with saccadic inhibition, a function ostensibly mediated by DLPFC circuitry. We review additional evidence for saccadic inhibition being associated with prefrontal circuitry provided by EEG and fMRI data. Minimum norm analysis of EEG data suggests that dipolar activity preceding correct antisaccades occurred preferentially in prefrontal cortex. Furthermore, there is an indication from the fMRI data that prefrontal activity may be increased in normal, but not in schizophrenia, subjects during antisaccade tasks. These data suggest that a research program relying on multiple functional imaging technologies may be helpful for furthering our understanding of schizophrenia's essential neuropathology.

Saccadic inhibition among schizotypal personality disorder subjects

Schizotypal personality disorder (SPD) is theoretically part of the schizophrenia spectrum both clinically and neurobiologically. A liability for developing schizophrenia may be associated with dysfunction of dorsolateral prefrontal cortex (DLPFC) and its cortical and/or subcortical circuitry. If so, abnormalities on tasks associated with DLPFC functioning among SPD subjects would support the thesis that SPD is neurobiologically related to schizophrenia. Antisaccade and ocular motor delayed response performance, both of which are ostensibly supported by DLPFC circuitry, were assessed among 29 SPD, 17 schizophrenia, and 25 normal subjects. Generally, the SPD subjects' performance was more similar to normal than to schizophrenia groups. There was evidence, however, for inhibition abnormalities in a subgroup of SPD subjects. Antisaccade performance identified more SPD subjects as "abnormal" than delayed response measures.

Ocular motor delayed-response task performance among patients with schizophrenia and their biological relatives

Schizophrenia patients and their relatives have saccadic abnormalities characterized by problems inhibiting a response. The dorsolateral prefrontal cortex and its associated circuitry ostensibly mediate inhibition and support correct delayed response performance. In this context, two components of delayed response task performance are of interest: memory saccade metrics and error saccades made during the delay. To evaluate these variables, an ocular motor delayed response task was presented to 23 schizophrenia patients, 25 of their first-degree biological relatives, and 19 normal subjects. The measure that best differentiated groups was an increased frequency of error saccades generated during the delay by schizophrenia subjects and relatives. Decreased memory saccade gain also characterized patients and relatives. The similar pattern of results demonstrated by the patients with schizophrenia and their relatives suggests that performance on ocular motor delayed response tasks, either alone or in combination with other saccadic variables, may provide useful information about neural substrates associated with a liability for developing schizophrenia.

Clinical and biological concomitants of resting state EEG power abnormalities in schizophrenia

BACKGROUND

This study investigated the clinical and biological concomitants of electroencephalogram power abnormalities in schizophrenia.

METHODS

We examined the power characteristics of resting electroencephalograms in 112 schizophrenic patients. Also collected were measures of psychotic symptomatology, brain morphology, ocular motor functioning, electrodermal activity, and nailfold plexus visibility. Seventy-eight nonschizophrenic psychosis patients (e.g., mood disorder patients with psychosis) and 107 nonpsychiatric control subjects were included for comparison.

RESULTS

Schizophrenic patients whose electroencephalograms were characterized by augmented low-frequency power and diminished alpha-band power had more negative symptoms, larger third ventricles, larger frontal horns of the lateral ventricles, increased cortical sulci widths, and greater ocular motor dysfunction compared with schizophrenic patients without these electroencephalogram characteristics. In nonschizophrenic psychosis patients, augmented low-frequency and diminished alpha-band powers failed to be associated with any clinical or biological indices.

CONCLUSIONS

Results suggest that clinical and biological concomitants of low-frequency and alpha-band power abnormalities in schizophrenia are unique, perhaps indicating the presence of thalamic and frontal lobe dysfunction.

Fixation stability among schizophrenia patients

Twenty-four schizophrenia and 26 normal subjects were presented targets for fixation at +/-17.5 degrees and 0 degrees of visual angle. The manner in which stimuli were presented allowed us to evaluate for the presence of gaze-evoked and rebound drifts, and for frequency of saccades at both eccentric and central fixation. Schizophrenia patients and normal subjects had remarkably similar performance regardless of stimulus condition. These results suggest that the gaze-holding apparatus is functioning normally among schizophrenia patients, a finding that is not easily attributable to either medication effects and/or low statistical power. These data are another indication that schizophrenia patients have specific, not general, abnormalities of ocular motor control.

Normal P50 suppression in schizophrenia patients treated with atypical antipsychotic medications

OBJECTIVE

Patients with schizophrenia have deficits in attention, cognition, and information processing. Measures such as P50 suppression are used to study cognitive and attentional dysfunction among these patients. P50 suppression is an operational measure of sensory gating that can be assessed by averaging electroencephalographic responses to multiple pairs of auditory clicks separated by 500 msec. Normally, the P50 response to the second click is smaller than the response to the first click. Many studies have demonstrated that schizophrenia patients have deficient P50 suppression, meaning that the difference between the first and second clicks is not as large as normal. Atypical antipsychotic medications may have superior clinical efficacy for negative symptoms and cognitive deficits. It is important, therefore, to evaluate the effects of atypical antipsychotic medications on measures such as P50 suppression.

METHOD

P50 suppression of 13 patients with schizophrenia receiving clinically effective doses of clozapine, olanzapine, or risperidone (classified as atypical antipsychotic medications) was compared to that of 13 patients receiving conventional antipsychotic medications.

RESULTS

The patient groups did not differ on clinical or demographic measures. The patients receiving atypical antipsychotic medications had normal-range P50 suppression (mean=72%). In contrast, the patients receiving typical antipsychotic medications had dramatically lower P50 suppression (mean=27%).

CONCLUSIONS

The results support the hypothesis that patients treated with atypical antipsychotic medications have normal P50 measures of sensory gating. Longitudinal within-subjects studies are warranted to clarify the mechanisms mediating this effect.

Hemispheric differences on auditory evoked response suppression in schizophrenia

Using binaural stimuli, schizophrenia subjects have worse auditory evoked response (AER) suppression than normals in a paired-click paradigm. In this study we investigated hemispheric differences in AER suppression between groups using monaural and binaural stimulus presentation. Auditory evoked responses from 12 schizophrenia and 12 normal subjects were recorded with a 148-channel whole-head biomagnetometer. One hundred and twenty pairs of clicks were presented in three counterbalanced blocks (left, right, binaural). With monaural stimuli, patients had worse M100 suppression than normals in ipsilateral (effect size -2.13) but not in contralateral hemisphere (effect size -0.43). The groups did not differ on gamma band response suppression. Overall, the best group separations were obtained with binaural stimulus presentation on M100 suppression (effect size -4.14).

Saccadic performance characteristics and the behavioural neurology of Tourette's syndrome

OBJECTIVE

To better understand the neuropathological correlates of Tourette's syndrome (TS), measures of saccadic eye movement performance were examined among patients with TS.

METHODS

A case-control design was used. Twenty one patients with DSM-IV TS (mean age 40.6 years (SD 11.0); 38% female) mainly recruited from UCSD Psychiatry Services, and a community based sample of 21 normal subjects (mean age 34.6 years (SD 13.4); 43% women) participated in this study. Participants were administered ocular motor tasks assessing visual fixation, and the generation of prosaccades, predictive saccades, and antisaccades. Saccadic reaction time, amplitude, duration, and mean and peak velocity were computed. Intrusive saccades during visual fixation and the proportion of correct antisaccade responses were also evaluated.

RESULTS

The groups had similar visual fixation performance. Whereas patients with TS generated prosaccades with normal reaction times and amplitudes, their saccade durations were shorter and their mean velocities were higher than in normal subjects. During a prosaccade gap task, patients with TS exhibited an increased proportion of anticipatory saccades (RTs<90). The proportion of "express" saccades (90<RTs<135) did not differ between groups. Patients with TS had fewer correct antisaccade responses than did normal subjects, an effect accounted for by 19% of the patients. Antisaccade reaction times among patients with TS were increased during an overlap version of the task.

CONCLUSION

These findings suggest that TS mildly affects the ocular motor control circuitry associated with saccade inhibition.

Measuring liability for schizophrenia using optimized antisaccade stimulus parameters

The ability to identify unaffected gene carriers within families may be crucial to the success of schizophrenia genetics studies. Data collected from three family samples (N = 365) demonstrated that poor antisaccade performance is an exceptionally promising indicator of liability for schizophrenia. A particular antisaccade task version provides large separations (5-6 sigma) between proband and normal groups. Poor antisaccade performance alone correctly identified 70% of patients in California, Utah, and Micronesia schizophrenia samples. Twenty-five to 50% of these patients' nonpsychotic first-degree relatives also had poor antisaccade performance, yielding risk ratios around 20:1 for simplex and 50:1 for multiplex schizophrenia families. Poor antisaccade performance is associated with dorsolateral prefrontal cortex pathology, suggesting that dysfunction of this circuitry also may predispose individuals to developing this disease.

Poor P50 suppression among schizophrenia patients and their first-degree biological relatives

OBJECTIVE

This study's goal was to replicate the finding that family members of schizophrenia patients show poor P50 suppression during a paired-click auditory evoked response paradigm.

METHOD

The paired-click paradigm was used to test 44 schizophrenia patients, 60 of their clinically unaffected first-degree relatives, and 45 normal subjects. Two clicks (83 dB[A] over a 60-dB[A] white noise background) separated by 500 msec were presented 60 times to all subjects. P50 responses to the first and second clicks were selected from the digitally filtered data by using standard methods and the Cz recording site.

RESULTS

The schizophrenia patients had smaller P50 responses to click 1 than either their relatives or the normal subjects; the patients and their relatives, who did not significantly differ, had larger P50 responses to click 2 than the normal subjects. Schizophrenia patients had worse P50 suppression than either their family members or the normal subjects; the patients' family members had worse P50 suppression than the normal subjects.

CONCLUSIONS

Family members of schizophrenia patients have worse P50 suppression than normal subjects. To the authors' knowledge, this is the first demonstration independent of the group associated with the University of Colorado that schizophrenia patients' family members have poor P50 suppression. This result is intrinsically important, perhaps especially because a recent report suggests genetic linkage of poor P50 suppression to the cholinergic receptor's alpha7 nicotinic subunit.

Failure of dominant left-hemispheric activation to right-ear stimulation in schizophrenia

Schizophrenia is associated with an absence of the lateralizations that typify the human brain. Previous evidence emphasized structural changes, particularly reduced asymmetry in extension and surface of the planum temporale, although gross structural deviations occur only in a minority of patients. The present study describes an absence of lateralization on a robust functional measure that characterized schizophrenia patients: healthy subjects but not schizophrenics displayed a contralateral left-hemispheric dominance of the auditory evoked magnetic field to right-ear auditory stimulation. Absence of contralateral dominance in response to auditory stimuli among schizophrenia patients may indicate a failure to establish unequivocal left-hemispheric dominance of the phonological loop as hypothesized by Crow.

Psychophysiological measures of (dis)inhibition as liability indicators for schizophrenia

Two psychophysiological measures, poor suppression of midlatency auditory-evoked responses in a paired stimulus paradigm and ocular motor abnormalities, may index genetic liability for schizophrenia. An important feature of these measures is that both patients and their nonpsychotic relatives exhibit basically the same performance. These measures may be successful endophenotypes for schizophrenia because they assess poor response inhibition associated with dysfunction of dorsolateral prefrontal cortex circuitry. Data bearing on this hypothesis are reviewed, and it is posited that assessment of the auditory-evoked gamma band response and saccade measures of inhibitory abilities are the most valid behavioral measures of schizophrenia's neuropathological correlates. The extant data suggest that psychophysiological studies of schizophrenia can provide consistent and theoretically meaningful information for localizing neuropathology and for assessing the genetics of this complex disorder.

Multiple site evaluation of P50 suppression among schizophrenia and normal comparison subjects

Normally, when two brief, non-startling auditory stimuli are presented 500 ms apart, with long (e.g., 10 s) interpair intervals, the positive potential occurring approx. 50 ms after the first stimulus (P50) is relatively large, and the P50 to the second stimulus is smaller. In schizophrenia patients, however, the P50 to the second stimulus is larger than normal. In this study, 36 schizophrenia and 36 normal comparison subjects were tested in a two-click paradigm. Data were recorded from six electrode locations (F3, Fz, F4, C3, Cz, C4). The results support the hypothesis that schizophrenia patients have poor P50 suppression that is not an artifact of differential P50 wave morphology or differences in the number of usable trials between groups. In addition, the vertex location alone (Cz) was equal to, if not better than, any combination of sites for differentiating between groups. These results support the use of the Cz site alone in most investigations of P50 suppression deficits among schizophrenia spectrum patients. Further work investigating the neuropathological correlates of poor P50 suppression among schizophrenia patients by recording from multiple electrode locations, however, could be helpful.

The gamma band response may account for poor P50 suppression in schizophrenia

The relationship between gamma band response (GBR) and P50 suppression was investigated among 10 DSM-IV schizophrenia patients and 10 normal comparison subjects using neuromagnetic and electrical recordings. In a paired-click paradigm, the neuromagnetic GBR and M100 suppression data improved schizophrenia-normal group separations over the typical electrical, vertex-recorded P50 suppression measure. The neuromagnetic GBR was also superior to the magnetic equivalent of P50 (M50) for discriminating schizophrenia and normal subjects. Our data are consistent with the hypothesis that P50 may be a subcomponent of the GBR, and that P50 suppression may be a proxy for GBR suppression. Measurement of the GBR should be given consideration as another, and perhaps better, means for evaluating auditory-evoked response abnormalities among schizophrenia patients.

The effect of fixation condition manipulations on antisaccade performance in schizophrenia: studies of diagnostic specificity

This series of studies evaluated (1) hypotheses that poor antisaccade performance is attributable to confounding variables (e.g., visual attention deficits, incomplete understanding of task demands) and (2) the specificity of poor antisaccade performance to schizophrenia. In addition to self-correcting errors before being cued to do so, schizophrenia patients also showed the expected saccadic reaction time changes to fixation condition manipulations: decreased latencies for gap and increased latencies for overlap trials. These data suggest that schizophrenia patients are adequately engaged in and understand the antisaccade task. Schizophrenia patients made fewer correct antisaccade responses than other psychiatric patients (obsessive-compulsive and bipolar disorder) and normal subjects. The first-degree relatives of schizophrenia patients also generated a decreased proportion of correct antisaccade responses compared with normal subjects. For schizophrenia patients who performed below the range of normal subjects, 26% of their relatives also performed below the normal range. Conversely, patients who performed normally did not have a single poor-performing relative. These data suggest that increased antisaccade error rates may index a liability for schizophrenia within a subset of families.

P50 suppression among schizophrenia and normal comparison subjects: a methodological analysis

The present report investigated the relationship between P50 suppression and habituation among 20 schizophrenia and 20 normal comparison subjects. Subjects were presented with clicks delivered over headphones in a S1-S2 paradigm (clicks were separated by 500 msec; average intertrial interval was 8 sec). There were 60 total trials; the data were analyzed separately for the first and second 30 trials. The groups did not differ either on the number of usable trials or on the morphology of their P50 responses. Consistent with previous reports, schizophrenia patients demonstrated deficient P50 suppression. The overall suppression effect was not due to a group difference on S1 P50 amplitudes, but was associated with schizophrenia patients having smaller S1-S2 P50 amplitude difference scores than normal comparison subjects. Furthermore, the suppression effect appears to be more pronounced during the first than during the second block of trials. Thus, it may be important to evaluate changes in P50 responses over time among schizophrenia and normal comparison subjects.

Season of birth and electroencephalogram power abnormalities in schizophrenia

To determine the association between season of birth and electroencephalogram (EEG) power abnormalities in schizophrenia, this study examined the resting EEGs of 28 winter-born and 81 nonwinter-born schizophrenia patients. Eighteen winter-born and 58 nonwinter-born nonschizophrenic psychosis patients (e.g., bipolar disorder patients with psychotic features), and 97 normal subjects were also studied. Compared to normal subjects, nonwinter-born schizophrenia patients had augmented low-frequency power and diminished alpha band power, but winter-born schizophrenia patients failed to have any EEG power abnormalities. Nonwinter-born nonschizophrenic psychosis patients had the same low-frequency and alpha band power abnormalities as nonwinter-born schizophrenia patients. The winter-born non-schizophrenic psychosis group failed to show any EEG power abnormalities. The results of this study indicate that in psychosis the functional characteristics of the brain vary depending on the season in which a person is born. Low-frequency and alpha band EEG power abnormalities may help distinguish psychosis stemming from a seasonally varying pathogen from psychosis of other etiologies.

Characteristics of open- and closed-loop smooth pursuit responses among obsessive-compulsive disorder, schizophrenia, and nonpsychiatric individuals

Twenty obsessive-compulsive disorder patients and comparison samples of 20 schizophrenia and 20 nonpsychiatric individuals were presented with (a) a step-ramp task designed to measure smooth pursuit initiation and (b) a regular ramp task designed to measure steady-state tracking performance. Obsessive-compulsive disorder and non-psychiatric individuals had statistically similar pursuit reaction time and average eye accelerations during the open-loop interval. They also had similar closed-loop performance. Schizophrenia patients, however, had delayed pursuit reaction times and reduced eye acceleration during the last 60 ms of the open-loop interval. These findings suggest that brain regions supporting smooth pursuit performance are unimpaired among obsessive-compulsive disorder patients. Furthermore, the deficits found in the schizophrenia patients replicate and extend the results of previous smooth pursuit studies.

Saccades to moving targets in schizophrenia: evidence for normal posterior cortex functioning

People diagnosed with schizophrenia have abnormalities of smooth pursuit eye movement initiation that could be attributable to dysfunction of posterior cortical areas and/or the smooth pursuit regions of frontal cortex. To evaluate whether schizophrenia patients' pursuit initiation performance is most consistent with pre- or postrolandic neuropathology, 25 schizophrenia patients and 25 nonpsychiatric individuals were presented step-ramp stimuli moving either away from or toward the fovea. Schizophrenia and nonpsychiatric individuals did not differ on position error of saccades to moving targets, suggesting that the schizophrenia patients did not have general difficulty with motion perception. During the initial 100 ms of smooth pursuit, however, schizophrenia patients had significantly slower eye velocities than did nonpsychiatric individuals. These results suggest that schizophrenia patients' smooth pursuit abnormalities are not associated with neuropathology of posterior cortical areas.

The ability to produce express saccades as a function of gap interval among schizophrenia patients

The ability to produce "express saccades" is associated with adequate functioning of saccadic burst cells in the superior colliculus. Saccadic burst cells appear to be under the inhibitory control of both the collicular and the dorsolateral frontal fixation systems. Twenty schizophrenia patients and 20 nonpsychiatric subjects were presented a saccade task that included five different gap intervals (0, 100, 200, 300, and 400 ms) between fixation point offset and peripheral target onset (at +/-4 degrees). All subjects generated the highest frequency of express saccades in trials with a gap interval of 200 ms. Schizophrenia patients had an increased frequency of express saccades across gap intervals, especially for targets presented in the right visual field. The groups did not differ in the percentages of anticipatory saccades or saccadic amplitudes. These results suggest that schizophrenia patients' saccadic burst cells in the superior colliculus are functioning adequately, but may be consistent with dysfunction of dorsolateral frontal cortex and/or its interconnecting subcortical circuitry.

Timing and amplitude of saccades during predictive saccadic tracking in schizophrenia

Schizophrenia patients have ocular motor abnormalities. It has been hypothesized that these abnormalities are associated with frontal eye field pathology. If so, schizophrenia patients should have difficulties decreasing saccadic reaction times in response to predictably moving targets. To evaluate the frontal eye field hypothesis, 25 schizophrenic and 26 nonpsychiatric subjects completed predictive saccadic tracking tasks. The groups demonstrated equivalent decreases in saccadic reaction times over consecutive trials. Schizophrenia patients, however, had faster reaction times and shorter amplitude saccades than nonpsychiatric subjects. The shorter amplitude saccades were made regardless of reaction time, perhaps an antipsychotic medication effect. The reaction time results are unlikely to be an effect of treatment with antipsychotic medication and are inconsistent with the hypothesis that schizophrenia patients have frontal eye field pathology.

Ocular motor responses to unpredictable and predictable smooth pursuit stimuli among patients with obsessive-compulsive disorder

This study was conducted to evaluate the smooth pursuit system functioning of patients with obsessive-compulsive disorder (OCD). For Study 1, 12 subjects with OCD and 12 nonpsychiatric subjects were administered 9-deg-per-sec ramp stimuli to elicit smooth pursuit eye movements. Consistent with a previous report, patients with OCD did not significantly differ from nonpsychiatric subjects on pursuit gain, or frequency of corrective and intrusive saccades. Patients with OCD, however, had smaller catch-up saccades during smooth pursuit than nonpsychiatric subjects. For Study 2, 12 subjects with OCD and 12 nonpsychiatric subjects were administered 2 different triangle wave stimuli with target velocities of 12 (0.2 Hz) deg per sec and 24 (0.4 Hz) deg per sec. Subjects with OCD and nonpsychiatric subjects did not significantly differ on any variable in the slow target velocity condition. When following 24-deg-per-sec targets, however, patients with OCD had significantly lower pursuit gain than the nonpsychiatric subjects. Results from Study 1 and 2 are consistent with the hypothesis that patients with OCD have a modest smooth pursuit deficit that is elicited only while following faster velocity targets.

Ocular-motor delayed-response task performance among schizophrenia patients

Twenty schizophrenia patients and 20 nonpsychiatric subjects were presented with an ocular-motor delayed-response task. Schizophrenia patients generated fewer memory-guided saccades which were characterized by increased latency and decreased gain relative to the nonpsychiatric subjects. In addition, the patients generated an increased frequency of reflexive (made to the initial cue) and anticipatory (made during the delay period) errors. The results are most consistent with hypothesized pathology of prefrontal cortex among schizophrenia patients.

Abnormality of smooth pursuit eye movement initiation: specificity to the schizophrenia spectrum?

Schizophrenia patients have a deficiency of smooth pursuit eye movement initiation. We addressed whether this deficit is specifically related to a predisposition for schizophrenia. Thirty-two relatives of schizophrenia patients, eight schizotypals, 13 psychiatric comparison, and 33 nonpsychiatric subjects were assessed on smooth pursuit initiation. The nonpsychiatric subjects had significantly higher eye accelerations than did subjects in the other three groups, who did not significantly differ. The relatives were subdivided into three groups: (a) those with a schizophrenia spectrum disorder (n = 4) performed similarly to the schizotypals; (b) those with a major depression history (n = 7) were similar to the psychiatric comparison subjects; and (c) those with no psychiatric history differed from the nonpsychiatric subjects only on 30 degrees/s targets. There was also a significant relationship between offspring and parent eye accelerations to 30 degrees/s targets (r = .476). These results suggest that pursuit initiation deficits may be associated with a nonspecific, genetically transmitted neurological abnormality among schizophrenia spectrum disorder subjects.

Internal consistency reliability of resting EEG power spectra in schizophrenic and normal subjects

The reliability of resting electroencephalogram (EEG) power spectra was assessed for 49 normal and 44 schizophrenic subjects. We specifically examined internal consistency reliability to determine how much EEG data are necessary to ensure small measurement error. Twenty-one 8-s epochs of resting EEG were collected from each subject from site Cz. Epochs containing artifacts or blinks were eliminated. Power was computed in the bands delta (0.125-3 Hz), theta (3.125-8 Hz), alpha (8.125-13 Hz), beta1 (13.125-20 Hz) beta 2 (20.125-25 Hz) and beta 3 (25.125-30 Hz). Internal consistency was computed using coefficient alpha (Cronbach, 1951). Results for both groups indicated that eight artifact-free epochs of data were sufficient to give a coefficient alpha value of around .9. The schizophrenic and normal groups did not differ with respect to coefficient alpha. The proportion of artifacts in the data from the schizophrenics indicated that to obtain eight artifact-free epochs from members of each group, 40% more data would be required from the schizophrenics.

Resting EEG in first-episode schizophrenia patients, bipolar psychosis patients, and their first-degree relatives

We evaluated the resting electroencephalogram (EEG) of 50 first-episode schizophrenia patients and 55 of their relatives, 31 first-episode bipolar patients and 35 of their relatives, and 113 nonpsychiatric subjects and 42 of their relatives. The frequency characteristics of the EEG showed moderate stability for a subgroup of these subjects (n = 106) who were tested twice, approximately 9 months apart. Both the schizophrenia and bipolar patients showed a generalized pattern of increased delta and theta and decreased alpha activity. The bipolar patients demonstrated additional right hemisphere activity that was not present among the schizophrenia patients and nonpsychiatric subjects, a finding consistent with hypotheses concerning nondominant hemisphere involvement in the regulation of elated mood. The schizophrenia patients' female relatives and/or relatives with affective disorders and the bipolar patients had significantly reduced peak alpha frequencies. This finding may be related to reduced information processing capacity among these subjects.

Eye tracking dysfunction in schizophrenia: characterization of component eye movement abnormalities, diagnostic specificity, and the role of attention

To characterize oculomotor components and diagnostic specificity of eye tracking abnormalities in schizophrenia, we examined a large consecutively admitted series of psychotic patients and matched controls. The most common abnormality in schizophrenic patients was low gain (slow) pursuit eye movements (47% of cases). Pursuit and saccadic eye movement abnormalities were no more severe in schizophrenic Ss than in those with affective psychoses, except that high rates of catch-up saccades were unique to schizophrenic Ss (17% of cases). These findings indicate that impaired pursuit eye movements are a major cause of eye tracking impairments in schizophrenia, that tracking dysfunctions commonly occur in affective psychoses, and that markedly high rates of catch-up saccades during eye tracking may be specific to schizophrenia.

Eye tracking dysfunction in schizophrenia: characterization of component eye movement abnormalities, diagnostic specificity, and the role of attention

To characterize oculomotor components and diagnostic specificity of eye tracking abnormalities in schizophrenia, we examined a large consecutively admitted series of psychotic patients and matched controls. The most common abnormality in schizophrenic patients was low gain (slow) pursuit eye movements (47% of cases). Pursuit and saccadic eye movement abnormalities were no more severe in schizophrenic Ss than in those with affective psychoses, except that high rates of catch-up saccades were unique to schizophrenic Ss (17% of cases). These findings indicate that impaired pursuit eye movements are a major cause of eye tracking impairments in schizophrenia, that tracking dysfunctions commonly occur in affective psychoses, and that markedly high rates of catch-up saccades during eye tracking may be specific to schizophrenia.

Saccadic system functioning among schizophrenia patients and their first-degree biological relatives

In Study 1, 30 schizophrenia Ss and 27 nonpsychiatric comparison Ss were presented with a fixation task, a visually guided reflexive saccade (prosaccade) task, a predictive tracking task (0.4-Hz square wave), and an antisaccade task. The 2 groups did not differ on either the fixation or prosaccade tasks. Schizophrenia Ss had an increased number of errors on the antisaccade task and had decreased rightward visually guided saccade amplitudes during the predictive tracking task. In Study 2, 13 psychiatric comparison Ss and 32 first-degree biological relatives of the schizophrenia Ss were compared with the schizophrenia Ss and a larger and older sample of nonpsychiatric Ss (n = 33) on the predictive tracking and antisaccade tasks. The groups did not differ on predictive saccadic tracking. The schizophrenia Ss and their first-degree biological relatives made more errors on the antisaccade task than both the nonpsychiatric and psychiatric comparison groups (who did not significantly differ). Results are consistent with the notion that dysfunction of dorsolateral prefrontal cortex, caudate nucleus, or both is related to liability for schizophrenia.

Handedness in first-episode psychotic patients and their first-degree biological relatives

We evaluated the handedness of 58 schizophrenia patients and 54 of their relatives, 23 patients with major depression with psychosis and 24 of their relatives, 36 patients with bipolar psychosis and 33 of their relatives, and 119 nonpsychiatric subjects and 42 of their relatives. Computerized tomography measures were also available for a subset of the psychotic patients. The schizophrenia patients were significantly more left-handed than any of the other groups, and increased sinistrality was also associated with larger lateral ventricle to brain area ratios. The relatives of the schizophrenia patients did not significantly differ on handedness from either the relatives of the affective psychosis patients or the nonpsychiatric subjects. Our findings do not support the notion that left-handedness in schizophrenia is genetically influenced. More research with larger family member data sets is warranted to further explore this possibility.

Smooth pursuit in schizophrenia: abnormalities of open- and closed-loop responses

A sample of 29 schizophrenia patients and 27 nonpsychiatric subjects were tested on measures of open- and closed-loop smooth-pursuit performance. Rashbass step-ramps were used to measure pursuit latency and open-loop gain. Regular ramps were used to calculate frequency and amplitude of both catch-up saccades and square-wave jerks, frequency of anticipatory saccades, and steady-state gain. Schizophrenia patients demonstrated lower open-loop gain than did nonpsychiatric subjects, an effect that was accentuated at faster target velocities. They also showed reduced steady-state gain, but only to 30 degrees/s right-moving targets. There was no evidence of saccadic abnormalities during smooth pursuit among the schizophrenia patients. These patients generated fewer square-wave jerks than did nonpsychiatric subjects for 10 degrees /s left-moving targets. These results suggest an abnormality of smooth-pursuit initiation among patients with schizophrenia.

Resting EEG in first-episode and chronic schizophrenia

We examined the frequency characteristics of the electroencephalogram (EEG) in 102 schizophrenic patients (44 first-episode and 58 chronic patients) and 102 normal comparison subjects. EEGs of schizophrenic patients had more delta (1-3 Hz) and theta (3.125-8 Hz) activity and less alpha (8.125-13 Hz) activity than normal comparison subjects. There were no significant differences in the EEG frequency composition of first-episode and chronic patients. Because first-episode and chronic patients were characterized by different disorder durations and treatment histories, the similarity of their EEGs suggests that EEG abnormalities are stable characteristics of schizophrenia and are not treatment-related epiphenomena. A principal components analysis of EEG power bands identified an augmented low frequency-diminished alpha component and a beta component. Schizophrenic patients had significantly higher scores on the augmented low frequency-diminished alpha component than did normal comparison subjects, and there was no significant group difference in scores on the beta component. The findings of this investigation suggest that EEG abnormalities in schizophrenia reflect aspects of brain dysfunction.

Mixture analysis of pursuit eye-tracking dysfunction in schizophrenia

Results of two recent studies suggest that a distinct subgroup of schizophrenic patients and their relatives have particularly deviant eye tracking. Such heterogeneity could be of considerable importance, as it may indicate significant pathophysiologic or etiologic heterogeneity in schizophrenia. An analysis of 101 consecutive-admission schizophrenic patients confirmed the existence of two distinct subgroups of patients with higher and lower levels of spatial [root mean square (RMS)] eye-tracking error. However, there was no heterogeneity in the disturbance of pursuit eye movements. Anticipatory saccades, which by definition add very large amounts of spatial tracking error, were more frequent in the "high" RMS error group. Rates of anticipatory saccades were similar in the "low" RMS error patient group and normal controls, and there was no heterogeneity in the expression of anticipatory saccades. Apparent heterogeneity in global indices of eye-tracking impairment in schizophrenia appears to be a measurement artifact reflecting the powerful influence of anticipatory saccades on global performance indices, rather than true heterogeneity in the expression of any specific eye movement abnormality.

Personality and clinical characteristics in patients with trichotillomania

BACKGROUND

Trichotillomania, a disorder of self-directed hair pulling, has been the subject of few systematic studies. Although personality characteristics and disorders are often noted to coexist with trichotillomania, no thorough assessment of comorbidity with DSM-III-R Axis II disorders has been published. The present study was conducted to evaluate personality disorders and other personality characteristics in a large outpatient population of trichotillomanics and to compare these findings with those in a nontrichotillomanic comparison group.

METHOD

Forty-eight outpatient female trichotillomanics were evaluated with the Structured Interview for DSM-III-R Personality Disorders (SIDP-R) and the revised version of the Minnesota Multiphasic Personality Inventory (MMPI-2). Personality disorders and personality cluster symptom scores from the SIDP-R and MMPI-2 scales were compared with those derived from a comparison group of 48 age-matched female outpatient psychiatric patients.

RESULTS

Forty-two percent of the trichotillomanic group met criteria for a personality disorder. The only statistically significant difference in frequency of diagnoses between the trichotillomanic and comparison groups was a greater frequency of borderline personality disorder in the comparison group. Trichotillomanics demonstrated significantly less SIDP-R cluster A personality symptoms as well as less depression and better psychological adjustment on the MMPI-2.

CONCLUSION

Our study suggests that no particular personality disorder or trait characterizes female trichotillomanics. Female trichotillomanics seeking psychiatric intervention appear to have better psychological adjustment and less psychopathology in general than other psychiatric outpatients.

Smooth pursuit ocular motor dysfunction in schizophrenia: evidence for a major gene

OBJECTIVE

Evidence suggests that poor eye tracking relates to genetically transmitted vulnerability for schizophrenia. The authors tested competing models for the genetic transmission of poor eye tracking in a search for major gene effects.

METHOD

Samples from three studies (conducted in Minneapolis, New York, and Vancouver, B.C.) were pooled. Probands (N = 92) were diagnosed as schizophrenic by DSM-III criteria. Of the comparison subjects (N = 171), Vancouver patients were an epidemiologic first-episode group; at other sites unselected admitted patients were studied. First-degree relatives (N = 146) of 65 probands were also studied. Eye tracking was measured while subjects followed a horizontally moving, sinusoidally driven (0.4 Hz) spot of light on a screen. Performance was quantified by root mean square error. Data analysis was by complex segregation analysis (Bonney's class D regressive models).

RESULTS

A single major gene is needed to account for poor eye tracking in schizophrenic patients and their relatives. This gene alone can explain about two-thirds of the variance in eye tracking performance. A single gene alone (regardless of dominance) will, however, not account for the data; polygenic factors are also required.

CONCLUSIONS

Results support postulation of a single gene for ocular motor dysfunction, which may be a risk factor for schizophrenia. Eye tracking may be useful as a gene carrier test in genetic studies of schizophrenia.

A family study of nailfold plexus visibility in psychotic disorders

It has been proposed that the nailfold subpapillary plexus visibility score (PVS) may be a marker of susceptibility to schizophrenia. To further investigate this hypothesis, we evaluated plexus visibility in a sample of 61 chronic schizophrenics, a large sample of first-episode psychotic patients and their first-degree relatives (50 with schizophrenia, and 51 of their relatives; 29 with schizophreniform disorder, 30 of their relatives; 32 with major depression with psychotic features, 35 of their relatives; 33 with a bipolar disorder with psychotic features, 32 of their relatives), and 169 normal control subjects. Group comparisons demonstrated that (1) the probands with chronic schizophrenia, first episode schizophrenia, and schizophreniform disorder did not differ from one another on PVS; (2) these subjects combined had higher PVS ratings than the other two proband groups and normal subjects combined (who did not differ); and (3) none of the relative groups significantly differed from either one another or the normal subjects. On the other hand, relatives of schizophrenia spectrum probands with high PVS (greater than or equal to 10.0) had higher PVS ratings than the relatives of such probands with low PVS. Patterns of familial correlations suggested that PVS was moderately heritable (0.40). There was no evidence that nonadditive genetic variation influenced the trait.

Smooth-pursuit eye movement dysfunction and liability for schizophrenia: Implications for genetic modeling

Forty-one nonpsychiatric subjects, 38 probands with schizophrenia, and 99 of their relatives were studied. Oculomotor functioning was bimodally distributed for probands and relatives. Oculomotor dysfunction was not present in all families with a schizophrenic proband. In those families in which it was present, there were significant phenotypic correlations between oculomotor functioning and schizophrenia-related characteristics. The patterns of familial resemblance in the families in whom oculomotor dysfunction was present were consistent with nonadditive genetic variance contributing both to oculomotor dysfunction and to the relationship between oculomotor dysfunction and clinical symptoms. These results suggest that schizophrenia may be etiologically heterogeneous and that oculomotor dysfunction may help to identify nonadditive genetic variance for this disorder.

Psychometric detection of schizotypy: perceptual aberration and physical anhedonia in relatives of schizophrenics

We administered scales of Perceptual Aberration (PERAB) and Physical Anhedonia (PHYSAN), traits that may be related to risk for schizophrenia, to 54 schizophrenics, 146 of their first-degree relatives (evaluated for schizophrenia-related disorders), and 178 normal subjects (screened for psychotic disorders in them or their relatives). For both scales, there was a significant effect of group membership. For the PERAB scale, the schizophrenics had higher scores than the normal subjects, who had higher scores than the relatives. For the PHYSAN scale, schizophrenics had higher scores than their relatives, who had higher scores than the normal subjects. Patterns of familial correlations also suggested that physical anhedonia, but not perceptual aberration, may be familial among schizophrenics and their relatives. The PHYSAN scale, but not the PERAB one, may be a useful indicator of liability for schizophrenia among the relatives of affected probands.

Phenotypic correlations between oculomotor functioning and schizophrenia-related characteristics in relatives of schizophrenic probands

Abnormalities of visual pursuit tracking are frequent in the first-degree relatives of probands with schizophrenia. The relationship between oculomotor abnormalities and schizophrenia-related characteristics in those family members, however, has received little attention. Fifty-three first-degree relatives of 24 probands with schizophrenia were evaluated for the presence of schizophrenia-related characteristics using both interview (Schedule for Schizotypal Personalities) and questionnaire (Chapman scales). The family members also had their eye movements recorded during pursuit tracking tasks and scored for gain in both the frequency and time domains, and saccadic intrusions. Social-interpersonal schizophrenia-related features were significantly related to both time- and frequency-domain gain calculations. It appears that abnormalities in the smooth-pursuit oculomotor system may be associated with symptoms conjectured to be most closely related to a genetic diathesis for schizophrenia. These findings provide further evidence that oculomotor abnormalities may be related to risk for this disorder.

Familial prevalence and coaggregation of schizotypy indicators: a multitrait family study

Schizophrenic probands (n = 17), their first-degree relatives (n = 61), and medically and psychiatrically screened normal control subjects (n = 18) were studied with structured interviews for DSM-III Axis I disorders and schizotypal personality disorder, questionnaire measures of schizotypy, measures of smooth-pursuit eye movement dysfunction, and attention dysfunction. Schizophrenic subjects scored abnormally on essentially all measures. Relatives differed significantly from control subjects on most measures. Correlational analyses indicate that many characteristics tested in these measures run together in families. The data are consistent with the hypothesis that a single vulnerability dimension or typology, presumably in part genetically transmitted, may account for phenotypically distinct abnormalities. These traits, taken together, may have joint usefulness for identifying persons with a predisposition to schizophrenia.

Psychometric detection of schizotypy: Perceptual aberration and physical anhedonia in relatives of schizophrenics

We administered scales of Perceptual Aberration (PERAB) and Physical Anhedonia (PHYSAN), traits that may be related to risk for schizophrenia, to 54 schizophrenics, 146 of their first-degree relatives (evaluated for schizophrenia-related disorders), and 178 normal subjects (screened for psychotic disorders in them or their relatives). For both scales, there was a significant effect of group membership. For the PERAB scale, the schizophrenics had higher scores than the normal subjects, who had higher scores than the relatives. For the PHYSAN scale, schizophrenics had higher scores than their relatives, who had higher scores than the normal subjects. Patterns of familial correlations also suggested that physical anhedonia, but not perceptual aberration, may be familial among schizophrenics and their relatives. The PHYSAN scale, but not the PERAB one, may be a useful indicator of liability for schizophrenia among the relatives of affected probands.

Familial prevalence and coaggregation of schizotypy indicators: A multitrait family study

Schizophrenic probands (n = 17), their first-degree relatives (n = 61), and medically and psychiatrically screened normal control subjects (n = 18) were studied with structured interviews for DSM-III Axis I disorders and schizotypal personality disorder, questionnaire measures of schizotypy, measures of smooth-pursuit eye movement dysfunction, and attention dysfunction. Schizophrenic subjects scored abnormally on essentially all measures. Relatives differed significantly from control subjects on most measures. Correlational analyses indicate that many characteristics tested in these measures run together in families. The data are consistent with the hypothesis that a single vulnerability dimension or typology, presumably in part genetically transmitted, may account for phenotypically distinct abnormalities. These traits, taken together, may have joint usefulness for identifying persons with a predisposition to schizophrenia.

Pursuit gain and saccadic intrusions in first-degree relatives of probands with schizophrenia

Oculomotor functioning of 26 probands with schizophrenia, 12 spectrum and 46 nonspectrum first-degree relatives, and 38 nonpsychiatric control subjects was evaluated. Spectrum relatives had more anticipatory saccades (ASs) and lower pursuit gain than nonspectrum relatives, who had more ASs and lower pursuit gain than control subjects. Probands also had lower pursuit gain than nonspectrum relatives and control subjects but did not differ from other groups on AS frequency. Control subjects had more globally accurate pursuit tracking (root mean square [RMS] error deviation) than both relative groups, whereas probands had the poorest RMS scores. Square wave jerk frequency did not differentiate the groups. Attention enhancement affected the frequency of ASs but did not affect either the other intrusive saccadic event or RMS scores. These results offer evidence that eye-movement dysfunction may serve as a biological marker for schizophrenia.

Is eye movement dysfunction a biological marker for schizophrenia? A methodological review

There is a high prevalence of eye movement dysfunction (EMD) in persons with schizophrenia and their first-degree relatives. Studies addressing the prevalence, stability, familial transmission, and psychological correlates of EMD in persons from both psychiatric and general populations offer suggestive evidence that this abnormality may serve as a biological marker for schizophrenia. Although these findings are promising, their significance for elucidating the diagnostic bandwidth, pathophysiology, and genetics of this disorder remains to be determined. More precise characterization of ocular motility, perhaps when used in conjunction with global measures of pursuit adequacy, may be essential for clarifying the pathophysiological and genetic significance of EMD for schizophrenia. Recent research efforts are beginning to identify particular abnormalities that could serve as more specific biological markers for schizophrenia.