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Background: Cognitive processing deficits have been identified as an abnormality that schizotypal personality disorder (SPD) individuals share with schizophrenic patients. It has been hypothesized that impaired working memory may be a critical component of several of the more complex cognitive deficits found in schizophrenia spectrum patients., Method: 18 DSM-III-R SPD patients, and 17 normal comparison subjects were compared on a pen and paper visuospatial working memory task. Moreover, we identified a second psychiatric comparison group comprised of nine patients with other, non-odd cluster personality disorder diagnoses who met no more than one of the SPD criteria and were also tested on the same task. Each person was given 14 immediate recall trials and 10 trials using a 10 s delay., Results: SPD patients performed significantly worse than normal control subjects on the working memory task. SPD patients also performed significantly worse compared to the non-schizophrenia-related personality disorder psychiatric comparison group., Conclusions: Like schizophrenic patients, SPD patients demonstrate working memory impairment compared to normal controls. This impairment may be specific to the schizophrenia-related personality disorders.

Thirty patients with a DSM-III-R diagnosis of schizophrenia were assessed for severity of schizophrenic symptoms using the Brief Psychiatric Rating Scale (BPRS) and were tested on a Continuous Performance Test (CPT) and a smooth pursuit eye tracking task. Negative symptoms were significantly correlated with eye tracking impairment (r = 0.43, p < 0.01) and CPT deficits (r = 0.67, p < 0.001), but performance on neither task was correlated with positive symptoms. CPT performance and eye tracking performance were modestly correlated with each other (r = 0.39, p < 0.01) and CPT performance was found to be a stronger predictor of negative symptoms than eye tracking performance. These data indicate that neurocognitive markers of vulnerability to schizophrenia are associated with negative rather than positive symptoms.

Human and nonhuman primate data suggest that visuospatial working memory is mediated by a neural network that includes the prefrontal cortex. Simple working memory tasks are less complex than standard neuropsychological tests of frontal dysfunction. As such, they are less vulnerable to general performance factors such as amotivation and uncooperativeness in schizophrenic patients. These tasks thus hold promise as potential measures of frontal dysfunction in schizophrenia. However, the specific parameters of visuospatial working memory deficit in schizophrenia have not been established. This study assessed working memory functions in 18 schizophrenic patients and 28 controls using a pen-and-paper analogue of a monkey prefrontal cortex activation task. Schizophrenic patients and controls performed similarly on a sensory-guided task that did not require working memory functions, yet schizophrenic patients performed significantly worse than controls on tasks that required subjects to retain visuospatial information for delay periods of 10 and 20 s. These data suggest that the working memory deficits in patients with schizophrenia begin to appear less than 10 s following encoding of visuospatial information and that these working memory deficits can be assessed with easily administered pen-and-paper tasks.

Objective: Previous research has shown biological, phenomenological, and cognitive similarities between schizophrenic patients and individuals with schizophrenia-related personality disorders and features. Evidence further suggests that of these common dysfunctions, abnormal attention is one of the most promising indicators of a biological susceptibility to schizophrenia-related disorders. Although attentional dysfunctions have been reliably detected in schizophrenic patients as well as in a variety of populations at risk for schizophrenia, few studies have investigated attention in clinical patients with schizotypal personality disorder. In this study, the extent of attentional impairment was assessed in subjects with schizotypal personality disorder, normal comparison subjects, patients with other personality disorders, and schizophrenic patients., Method: Thirty subjects with schizotypal personality disorder, 35 subjects with other personality disorders (i.e., clinic patients with non-odd cluster personality disorders), 36 subjects with schizophrenia, and 20 comparison subjects who did not meet criteria for any axis I or axis II disorder participated in this study. All subjects were diagnosed according to DSM-III criteria. Attention was assessed by using the Continuous Performance Test, Identical Pairs Version., Results: Analyses indicated that subjects with schizotypal personality disorder, like schizophrenic subjects, performed significantly worse than comparison subjects on both the verbal and spatial tasks of the Continuous Performance Test, Identical Pairs Version. In contrast, patients with other personality disorders performed similarly to comparison subjects across conditions., Conclusions: These results suggest that patients with schizotypal personality disorder are impaired in their attentional functioning relative to normal comparison subjects and that they display deficits that are similar to the pattern characterizing schizophrenic patients.

Background: Biological relatives of patients with schizophrenia demonstrate an increased prevalence of schizotypal personality disorder symptoms, eye tracking deficits, and attentional disturbances. We investigated whether these hypothesized components of a schizophrenia-related phenotype are associated with one another or are independent in nonpsychotic relatives of patients with schizophrenia., Methods: Eighty-three nonpsychotic first-degree relatives of 38 patients with schizophrenia and 45 control subjects without a psychiatric diagnosis underwent clinical evaluation, eye tracking evaluation, and the Continuous Performance Test (CPT) of visual attention., Results: Eye tracking qualitative rating was more powerful than quantitative eye tracking measures or CPT measures in discriminating relatives of patients with schizophrenia from control subjects. Correlations between neurocognitive variables and DSM-III-R schizotypal personality disorder symptom clusters suggested that CPT errors of omission are associated with positive schizotypal symptoms. Eye tracking measures were not significantly correlated with schizotypal symptoms or CPT errors in relatives of patients with schizophrenia., Conclusions: Eye tracking deficits in the relatives of patients with schizophrenia are unrelated to CPT deficits and schizotypal symptoms. Eye tracking deficits and disturbances in visual attention may be separate components of a schizophrenia-related phenotype and should be considered as independent factors in genetic studies of schizophrenia.

In order to pursue the hypothesis that the dorsolateral prefrontal cortex is a source of cognitive deficit in schizophrenia, we developed an easily administered pen-and-paper human analogue of a visuospatial working memory task that in non-human primates activates the neurons of Walker area 46 (Goldman-Rakic, 1987). Compared to normal controls, schizophrenic patients made significantly greater errors in identifying where a visuospatial stimulus had been presented to them 30 and 60 seconds earlier, and these differences were significantly greater than in an immediate recall condition. These data suggest that schizophrenic patients have visuospatial working memory deficits that are sensitive to pen-and-paper versions of the tasks that activate the Walker area 46 in non-human primates. The availability of an easily administered test that may be associated with the functioning of the prefrontal cortex may enable more specific assessment of this brain region in humans.

We tested 54 nonpsychotic first degree relatives of 23 schizophrenic probands and 18 control subjects matched for age and education on several neuropsychological tests. The tests were selected to assess overall intellectual ability or because previous work indicated that they are particularly sensitive measures of cognitive dysfunction in schizophrenic patients. The relatives of schizophrenic patients performed significantly worse than the control subjects on tests of verbal fluency and on Trailmaking, part B. Each of these tests contributed unique variance to the discrimination between groups. The groups did not differ significantly on the number of perseverative errors on the Wisconsin Card Sorting Test, Wechsler Adult Intelligence Scale-Revised block design or vocabulary, or Trailmaking, part A. Eight relatives who met DSM-III-R criteria for schizotypal personality disorder were more impaired than the remaining 46 relatives on letter fluency, but otherwise their performance was similar to that of nonschizotypal relatives. These data suggest that close relatives of schizophrenic patients may have subtle neuropsychological impairments that are not necessarily associated with clinical symptoms of schizophrenia spectrum disorders.