Impact of neuroleptic medications on continuous performance test measures in schizophrenia

Severity in sustained attention impairment and clozapine-resistant schizophrenia: a retrospective study

BACKGROUND

Among patients with treatment-resistant schizophrenia (TRS), some exhibited further clozapine resistance (CR). This study aimed to investigate whether greater severity of treatment resistance in schizophrenia is associated with greater impairments in sustained attention.

METHODS

Patients with a DSM-IV-defined schizophrenia were recruited from a psychiatric center in northern Taiwan (April 2010 to October 2010). Both TRS and CR were determined retrospectively from participants' medical records following the consensus guidelines. The patients were divided into three groups: 102 non-TRS, 48 TRS without CR, and 54 TRS with CR. They underwent both undegraded and degraded Continuous Performance Tests (CPT), and their performance scores (d') were standardized against a community sample to derive age-, sex-, and education-adjusted z scores.

RESULTS

The TRS with CR group had significantly lower adjusted z scores of d' on both undegraded and degraded CPTs than the other two groups. Meanwhile, the differences between the TRS without CR group and the non-TRS group were not significant. Multivariable linear regression analyses with adjustment for covariates revealed a trend of gradient impairments on the degraded CPT from non-TRS to TRS without CR and to TRS with CR. The proportions of attentional deficits (an adjusted z score of ≤ - 2.5) on the degraded CPT also exhibited a significant trend, from 36.3% in the non-TRS group to 62.5% in the TRS without CR group and to 83.3% in the TRS with CR group.

CONCLUSIONS

Greater severity of treatment resistance in schizophrenia was associated with greater impairments in sustained attention, indicating some common vulnerability.

Not All Differences between Patients with Schizophrenia and Healthy Subjects Are Pathological: Performance on the Conners' Continuous Performance Test

OBJECTIVE

This study analyzed attentional performance in patients with schizophrenia during a continuous performance task requiring a high response rate.

METHOD

The Conners' Continuous Performance Test-II (CPT-II) was administered to 64 patients with schizophrenia and 64 healthy comparison subjects. A cross-sectional design was used in order to allow analysis of the means between patients and healthy subjects. Differences in performance were assessed for significance using ANCOVA. Percentiles were also analyzed in order to determine whether a participant showed normal or pathological performance. Pearson's correlation was used to detect possible relationships between attentional performance and psychopathology.

RESULTS

Of the 12 CPT-II measures, response style and slowing of reaction time (RT) between targets increased to similar extents between patients and healthy comparison subjects. Patients performed significantly less well than non-patient group on all other measures. Nevertheless, patient's performance on four of these measures remained within the normal range, and patient's performance on the remaining measures qualified as pathological only in the case of variability in hit RT. No significant correlations between attention performance and symptoms were found.

CONCLUSIONS

These results suggest that although patients may show lower attentional functioning than non-patients on tasks requiring a high response rate, their attentional performance remains within the normal range on most dimensions.

Dissociation of acute and chronic intermittent phencyclidine-induced performance deficits in the 5-choice serial reaction time task: influence of clozapine

BACKGROUND

Cognitive deficits are a core feature of schizophrenia that respond minimally to existing drugs. PCP is commonly used to model schizophrenia-like deficits preclinically although different dosing protocols may affect different domains. Here we characterise the acute, and chronic intermittent effects of PCP in the 5-choice serial reaction time task (5-CSRTT) in rats, and assess the effects of clozapine. In a novel approach, we also assess the effects of increased inhibitory load and conduct clinically relevant signal detection analysis (SDA).

MATERIALS AND METHODS

The effects of acute and repeated PCP (2.58 mg/kg) treatment on attentional processes and inhibitory control were assessed during and following the chronic treatment regime in the presence or absence of chronic clozapine (20 mg/kg/day).

RESULTS

Thirty minutes post-PCP injection, there was an increase in anticipatory responding which disappeared after 24 h. Although, acute PCP did not change accuracy of responding or processing speed, repeated PCP revealed delayed deficits in cognitive processing speed which were partly ameliorated by clozapine. Extended inter-trial intervals increased premature responding, while SDA revealed that clozapine modified persistent PCP-induced deficits in lnBeta (a composite measure of risk taking versus caution).

CONCLUSION

Acute NMDA receptor antagonism impairs inhibitory control, whereas repeated treatment produces delayed deficits in cognitive processing speed. The ability of clozapine partially to restore persistent PCP-induced deficits in processing speed and in lnBeta is consistent with clinical findings. This suggests that the enduring effects of repeated PCP treatment, combined with SDA, offers a useful, translational, approach to evaluate novel cognitive enhancers in the 5-CSRTT.

Deficits in visual sustained attention differentiate genetic liability and disease expression for schizophrenia from Bipolar Disorder

BACKGROUND

There is mounting evidence for shared genetic liability to psychoses, particularly with respect to Schizophrenia (SZ) and Bipolar Disorder (BD), which may also involve aspects of cognitive dysfunction. Impaired sustained attention is considered a cardinal feature of psychoses but its association with genetic liability and disease expression in BD remains to be clarified.

METHODS

Visual sustained attention was assessed using the Degraded Symbol Continuous Performance Test (DS-CPT) in a sample of 397 individuals consisting of 50 remitted SZ patients, 119 of their first degree relatives, 47 euthymic BD patients, 88 of their first degree relatives and 93 healthy controls. Relatives with a personal history of schizophrenia or bipolar spectrum disorders were excluded. Performance on the DS-CPT was evaluated based on the response criterion (the amount of perceptual evidence required to designate a stimulus as a target) and sensitivity (a signal-detection theory measure of signal/noise discrimination).

RESULTS

We found no effect of genetic risk or diagnosis for either disorder on response criterion. In contrast, impaired sensitivity was seen in SZ patients and to a lesser degree in their relatives but not in BD patients and their relatives. These findings were not attributable to IQ, medication, age of onset or duration of illness.

CONCLUSIONS

Our results argue for the specificity of visual sustained attention impairment in differentiating SZ from BD. They also suggest that compromised visual information processing is a significant contributor to these deficits in SZ.

Long-term effects of risperidone versus haloperidol on verbal memory, attention, and symptomatology in schizophrenia

There is evidence in the literature that cognitive functions in schizophrenia (SC) may be improved by atypical neuroleptics (NLPs) in contrast to typical medication, but there is still controversy regarding this apparent superiority of atypical drugs. In this study, we assessed the differential effects of risperidone and haloperidol on verbal memory, attention, and psychiatric symptoms in SC. The performance of 28 SC participants, randomly assigned to risperidone (2-6 mg/day) or haloperidol (2-40 mg/day), was compared with that of healthy controls. The California Verbal Learning Test (CVLT), the d2 Cancellation Test, and the Positive and Negative Symptoms Scale were administered at baseline and 3, 6, and 12 months. Relative to controls, all SC participants showed markedly impaired verbal memory and processing speed at each assessment period. There was no differential effect between the two NLPs on CVLT and d2 performance. However, risperidone was more effective than haloperidol in reducing psychiatric symptoms. Improvement in symptom severity was not associated with improvement in neurocognitive performance on these specific tests. Neither conventional nor atypical neuroleptic medications improved neurocognitive functioning over a 12-month follow-up, suggesting that psychopathological improvement under risperidone is independent of cognitive function.

More severe sustained attention deficits in nonpsychotic siblings of multiplex schizophrenia families than in those of simplex ones

Sustained attention deficits measured by the Continuous Performance Test (CPT) have been proposed as an endophenotype of schizophrenia. However, little is known about whether sustained attention deficits in first-degree relatives of schizophrenic patients are associated with familial loading for schizophrenia. We examined 107 parents and 84 siblings of simplex schizophrenia families as well as 72 parents and 56 siblings of multiplex schizophrenia families, all nonpsychotic, using the Diagnostic Interview for Genetic Studies and two sessions of the CPT (undegraded and degraded). The effect of perceptual load was assessed using the residual of the regression of the degraded score on the undegraded one. Statistical models that can adjust for familial correlations were used to compare the CPT performance of relatives between the two types of families. Siblings from multiplex families exhibited worse performance on the degraded CPT and less proficiency in processing the perceptual load than those from simplex families. No such difference was observed for the parents on either CPT version. We concluded that sustained attention along with perceptual load processing is more impaired in the siblings of schizophrenic patients with high familial loading and that this finding might be useful for future genetic dissection of schizophrenia.

A single nucleotide polymorphism fine mapping study of chromosome 1q42.1 reveals the vulnerability genes for schizophrenia, GNPAT and DISC1: Association with impairment of sustained attention

BACKGROUND

The marker D1S251 of chromosome 1q42.1 showed significant association with schizophrenia in a Taiwanese sample. We used single nucleotide polymorphism (SNP) fine mapping to search for the vulnerability genes of schizophrenia.

METHODS

We selected 120 SNPs covering 1 Mb around D1S251 from the public database. These selected SNPs were initially validated if allele frequency was >10%. Forty-seven validated SNPs were genotyped in 102 families with at least 2 siblings affected with schizophrenia.

RESULTS

Two SNP blocks showed significant association with schizophrenia. Block 1 (five-SNP), located between intron 2 and intron 13 of the glyceronephosphate O-acyltransferase (GNPAT) gene, showed the most significant associations using single-locus TDT (z = -2.07, p = .038, df = 1) and haplotype association analyses (z = -1.99, p = .046, df = 1). Block 2 (two-SNP), located between intron 4 and intron 5 of the disrupted-in-schizophrenia 1 (DISC1) gene, also showed the most significant results in both the single-locus (z = -3.22, p = .0013, df = 1) and haplotype association analyses (z = 3.35, p = .0008, df = 1). The association of the DISC1 gene with schizophrenia was mainly in the patient group with sustained attention deficits as assessed by the Continuous Performance Test.

CONCLUSIONS

Chromosome 1q42.1 harbors GNPAT and DISC1 as candidate genes for schizophrenia, and DISC1 is associated with sustained attention deficits.

Bilateral lesions of the habenula induce attentional disturbances in rats

The habenular nuclear complex is a major influence on brainstem cell groups that influence attention, but its role in attentional performance has not previously been explored. The present study investigated how habenula lesions affect attentional function as assessed by the 5-choice serial reaction time task (5-CSRTT) in male Lister-Hooded rats. Rats were pretrained in the 5-CSRTT before receiving discrete bilateral lesions of the habenula or a sham procedure. In test sessions immediately following recovery from surgery, lesioned rats showed a marked increase in premature responding. Over the course of testing this increase of premature responding declined in magnitude. In contrast, choice accuracy showed no impairment during the earliest postsurgery test sessions but progressively deteriorated over the course of testing. These opposite time courses strongly imply that different mechanisms mediate these two effects of the habenula lesion. Differential effects of drug treatment on these effects further supported this view. Thus, D-amphetamine (0.2 mg/kg s.c.) increased premature responding without affecting choice accuracy. On the other hand, haloperidol (0.01-0.03 mg/kg i.p.) decreased premature responding without significantly affecting choice accuracy. The results are consistent with the view that elevated premature responding in habenula-lesioned animals is mediated by increased dopaminergic activity, whereas impaired choice accuracy is not. Implications of these findings for the hypothesis that habenula dysfunction is involved in cognitive symptoms of schizophrenia are discussed.

Neurocognitive function in clinically stable men with bipolar I disorder or schizophrenia and normal control subjects

BACKGROUND

Patients with bipolar disorder and schizophrenia have been shown to have neurocognitive deficits when compared with control subjects. The degree and pattern of impairment between psychiatric groups have rarely been compared, especially when subjects are psychiatrically stable.

METHODS

Using a standard neurocognitive battery, we compared euthymic outpatients with bipolar disorder (n = 40), stable patients with schizophrenia (n = 20), and subjects with no psychiatric disorder (n = 22). The neurocognitive domains assessed included executive functioning, verbal memory, visual memory, procedural learning, visuoconstructive ability, and language functions. Effect sizes were calculated for each cognitive domain across groups.

RESULTS

Stable schizophrenic subjects demonstrated a generalized cognitive impairment across most domains compared with control subjects, with average effect sizes of .9. Euthymic bipolar subjects were significantly impaired compared with control subjects only in executive functioning (Wisconsin Card Sorting Task) and verbal memory (California Verbal Learning Test) domains (effect sizes in the .8-.9 range). Performance on the executive function measures was bimodal among bipolar subjects, suggesting two subgroups: one with relatively normal and one with impaired executive functioning. No significant differences between the bipolar patient group and control subjects were observed in visuoconstructive ability, procedural learning, or language function.

CONCLUSIONS

Both euthymic bipolar subjects and relatively stable schizophrenic subjects differed from control subjects in neurocognitive function. Among schizophrenic subjects, a generalized cognitive impairment was observed, and the degree of impairment was greater in the schizophrenic compared with the bipolar subjects. Subjects with bipolar disorder were impaired in two specific domains (verbal memory and executive function). Furthermore, within the bipolar group there was a subset with relatively normal executive functioning and a subset with significant impairment. Possible reasons for the persistence of these neurocognitive deficits in some subjects with bipolar disorder during periods of euthymia are reviewed.

Psychopharmacological approaches to modulating attention in the five-choice serial reaction time task: implications for schizophrenia

RATIONALE

In schizophrenia, attentional disturbance is a core feature which may not only accompany the disorder, but may precede the onset of psychiatric symptoms.

OBJECTIVES

The five-choice serial reaction time task (5CSRTT) is a test of visuo-spatial attention that has been used extensively in rats for measuring the effects of systemic and central neurochemical manipulations on various aspects of attentional performance, including selective attention, vigilance and executive control. These findings are relevant to our understanding of the neural systems that may be compromised in patients with schizophrenia.

METHODS

The 5CSRTT is conducted in an operant chamber that has multiple response locations, in which brief visual stimuli can be presented randomly. Performance is maintained using food reinforcers to criterion levels of accuracy. Various aspects of performance are measured, including attentional accuracy and premature responding, especially under different attentional challenges.

RESULTS

The effects of systemic and intra-cerebral infusions of selective dopamine, serotonin and cholinergic receptor agents on the 5CSRTT are reviewed with a view to identifying attention-enhancing effects that may be relevant to the treatment of cognitive deficits in schizophrenia. In addition, some novel agents such as modafinil and histamine receptor agents are also considered. Examining the effects of selective neurochemical lesions helped define the neural locus of attentional effects. Similarly, findings from microdialysis studies helped identify the extracellular changes in neurotransmitters and their metabolites in freely moving rats during performance of the 5CSRTT.

CONCLUSIONS

The monoaminergic and cholinergic systems have independent but complementary roles in attentional function, as measured by the 5CSRTT. These functions are predominantly under the control of the prefrontal cortex and striatum. These conclusions are considered in the context of their application towards therapeutic approaches for attentional disturbances that are typically observed in schizophrenic patients.

Sustained attention deficits in nonpsychotic relatives of schizophrenic patients: a recurrence risk ratio analysis

BACKGROUND

In nonpsychotic parents and siblings of schizophrenic patients, the recurrence risk ratios of sustained attention deficits, as measured by the continuous performance test (CPT), were examined with a series of cut-off points.

METHODS

Among 116 parents and 95 siblings of 91 schizophrenic probands in northern Taiwan, both undegraded and degraded sessions of the CPT were administered. Subjects' signal detection sensitivity of CPT performance (d') was standardized against a community sample without (unadjusted z score) or with (adjusted z score) adjustment for age, gender, and educational level.

RESULTS

Differences in the risk ratios between the parents and siblings that were based on the unadjusted z scores of CPT d' diminished markedly if the adjusted z scores were used. As the cut-off point in the adjusted z score decreased from -2.5 to -3.0, the risk ratio increased continually for both the undegraded (10.1-18.8 for parents, 10.0-16.7 for siblings) and degraded (12.4-102.7 for parents, 8.6-72.0 for siblings) test.

CONCLUSIONS

Stringent cut-off criteria of CPT deficits with adjustment for demographic features leads to recurrence risk ratios greater than those based on schizophrenia alone in both parents and siblings of schizophrenic patients.

Sustained attention deficits as markers of genetic susceptibility to schizophrenia

This article reviews recent evidence regarding the potential of the visual sustained attention deficits as measured by the Continuous Performance Test (CPT) as an endophenotype of the genetic susceptibility to schizophrenia. Findings in community subjects indicate that sustained attention develops during the primary school ages, reaches its maximum around early adolescence, and declines with age after adulthood. The assertion that CPT performance deficits, and especially on the more difficult versions, are reliable and valid genetic susceptibility indicators of schizophrenia is supported by the following results: 1) CPT deficits are present in schizophrenic patients, are particularly associated with negative and disorganized symptoms, and deficits on the more difficult CPT versions are not amenable to neuroleptic treatment; 2) subjects with schizotypal personality features also exhibit CPT deficits, which are specifically associated with the negative factor of schizotypy; 3) a substantial proportion of nonpsychotic relatives of schizophrenic patients (19-34%) have CPT deficits, which can also be predicted from their probands' CPT performance. Thus, using a CPT deficits as an endophenotype of schizophrenia would not only provide a valuable measure of genetic risk, but would also greatly enhance our understanding of etiology, and may help identify susceptibility genes for schizophrenia.

Comparison of the continuous performance test with and without working memory demands in healthy controls and patients with schizophrenia

The Penn Continuous Performance Test (PCPT), a measure of sustained visual attention developed for use in functional neuroimaging studies, was compared with a standard CPT developed by Gordon Diagnostic Systems (GDS; Vigilance subtest). The PCPT and the GDS CPT were administered with a standard neuropsychological battery to 68 healthy adults to assess reliability and construct validity. The test had adequate internal consistency, and convergent validity was established through significant correlations between measures of efficiency on the PCPT and the GDS CPT. With the exception of a significant correlation between efficiency measures on the GDS CPT and a measure of auditory sustained attention, neither version of the CPT correlated significantly with other measures in the battery. Factor analysis showed that the PCPT loaded with the GDS CPT. In 39 patients with schizophrenia and 39 matched, healthy controls, equivalent impairment was evident on the two CPT tasks. Neither version correlated significantly with symptom measurements. These results support previous conclusions that sustained visual attention in schizophrenia is a core information processing deficit, not directly related to symptomatology.

Information processing and attentional dysfunctions as vulnerability indicators in schizophrenia spectrum disorders

The schizotypal personality disorder is believed to be part of the schizophrenic spectrum of disorders including schizophrenic patients as well as some of their seemingly unaffected relatives with discreet symptoms. Spectrum-individuals are characterised by a genetic vulnerability for schizophrenia. The vulnerability is connected with neurocognitive deficits independent of clinical state. Some cognitive dysfunctions are unspecific and probably related to non-genetic brain damage. A consistent finding has, however, been poor performance in tasks involving information processing and attention. The findings point to the existence of specific sensory-perceptual deficits or a general attentional dysfunction. Identification of cognitive disturbances characteristic not only of schizophrenics, but also of schizotypal disordered and their relatives in the boundaries of schizophrenia, is relevant in order better to understand the pathogenetic mechanisms and treatment of schizophrenia. In the present review clinical data are analysed based on models of vulnerability and information processing with reference to a characterisation of the neuro-integrative deficits that form the core abnormalities of the spectrum.

Are there gender differences in neuropsychological performance in patients with first-episode schizophrenia?

To investigate gender differences in neuropsychological (NP) functioning in first episode (FE) schizophrenia, consecutively recruited patients with FE schizophrenia (37 males, 29 females) and a subsample of these patients (20 males, 20 females), individually matched for gender, age, and education to healthy controls (20 males, 20 females) were compared on a battery of standardized neuropsychological tests. Women performed better than men in tests of verbal memory and learning, and men performed better than women in spatial organization. However, no differences were present between schizophrenic patients and controls, except that male and female schizophrenic patients showed the most pronounced impairment in visual motor processing, attention and verbal memory and learning. Our data suggest that gender does not appear markedly to modify the cognitive impairment characteristic of schizophrenia. However, they underline the necessity of controlling confounding factors on NP performance such as gender and education.

Paranoid schizophrenia: non-specificity of neuropsychological vulnerability markers

During stages of remission, patients with paranoid schizophrenia seldom show severe attentional or information-processing dysfunctions, except in cases of long-term chronicity. The diagnostic specificity of four putative psychological vulnerability indicators of schizophrenia - the Span of Apprehension, the degraded stimulus Continuous Performance Test (dsCPT), the degraded stimulus visual backward masking task and the Wisconsin Card Sorting Test (WCST) - was examined in a group of patients with paranoid schizophrenia. Since no single test seems to identify all patients, the use of a combination of measures may be a useful strategy. Accordingly, the four tests were administered to 18 paranoid schizophrenic patients, 18 depressed patients and 18 normal subjects. Paranoid schizophrenic patients could be distinguished from normal subjects primarily on the basis of their performance on the backward masking task and secondarily by the dsCPT and the WCST. Paranoid schizophrenic and depressed patients could be differentiated to some extent by their performance on an information-mask condition of the backward masking task. Thus, of the four measures studied, only the degraded stimulus backward masking appeared to be a specific indicator of paranoid schizophrenia.

Attentional and eye tracking deficits correlate with negative symptoms in schizophrenia

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.