Cognitive Function In Schizophrenic Patients Research Articles

Effects of Cigarette Smoking and Nicotine Nasal Spray on Psychiatric Symptoms and Cognition In Schizophrenia

Schizophrenic patients have among the highest rates of smoking of any group of patients. Previous studies have identified psychophysiological and potential nicotinic receptor abnormalities which may be associated with this phenomenon. The effects of acute smoking or acute administration of nicotine nasal spray, after smoking abstinence, on negative symptoms and neurocognitive function have been less extensively studied in experimental designs. This study investigated the effects of smoking of high nicotine or denicotinized cigarettes, and receiving active or placebo nicotine nasal sprays, on positive and negative symptoms and cognitive functions in schizophrenic patients. The study utilized a placebo controlled crossover experimental design with pre- and post-drug evaluations on each experimental day. Smoking high nicotine cigarettes decreased negative symptoms more than denicotinized cigarettes, but smoking neither cigarette changed scores of positive symptoms, anxiety, or depression. Active nicotine nasal spray did not differentially decrease negative symptoms compared with placebo, but did improve performance on a spatial organization task, and tended to improve some measures of verbal memory and two-choice reaction time in schizophrenic patients. Both high and denicotinized cigarettes improved performance on the spatial processing task, but there was no statistically significant differential drug (Cigarette type) effect. These results suggest that acute smoking of cigarettes may transiently decrease negative symptoms in patients with schizophrenia, but it is unclear whether this effect is attributable to nicotine, other components of cigarettes, or the act of smoking. Nicotine nasal spray may modestly improve some selected aspects of cognitive function in schizophrenia.

The effects of benzodiazepines on event-related potential indices of automatic and controlled processing in schizophrenia: A preliminary report

The effects of benzodiazepines on cognitive function in schizophrenic patients were investigated using event-related potential (ERP) measurement during an auditory selective attention task. In this study, the authors compared the mismatch negativity (MMN) and N2b components between two subgroups of schizophrenic patients: one is comprised of patients who received no benzodiazepines (NT group, n=7) and the other is comprised of those administered benzodiazepines in the daytime (T group, n=7). There were no significant differences in MMN and N2b amplitudes between the two subgroups, whereas the N2b latency was significantly prolonged in the T group relative to the NT group. This suggested that benzodiazepines induce delayed stimulus classification processing in schizophrenic patients.

Executive/attentional cognitive functions in schizophrenic patients and their parents: a preliminary study

The aim of this study was to determine whether executive/attentional cognitive performances could be considered as markers of vulnerability to schizophrenia. The Stroop Color Word and fluency tests were significantly impaired in schizophrenic patients and their parents compared to controls matched on age and sex while performances on Nelson's Modified Card Sorting Test and the Trail Making Test did not differ. The impairments on the Stroop and fluency could be considered as endophenotypic markers of schizophrenia.

Effects of risperidone on information processing and attention in first-episode schizophrenia

Risperidone appears to have a beneficial effect in several areas of cognitive function in schizophrenic patients. In previous studies, however, the clinical characteristics of the subjects differed between studies, and were heterogenous even in single study. Most of the subjects were previously exposed to different kinds of neuroleptics and some of them were treatment-resistant. The aim of this study is to evaluate the effect of risperidone on attention and information processing in a homogenous subgroup of schizophrenic patients, i.e. drug-naı̈ve first-episode inpatients. In the patient group ( n=17), cognitive tests and clinical assessments were performed before and after 8 weeks of risperidone treatment. The same cognitive tests were administered to the control group ( n=24). The delay between test and retest was 8 weeks. Before treatment, the patient group performed significantly worse than control group on the tests measuring continuous attention, vigilance, and the speed of information processing. After treatment (the average dose of risperidone was 7.3 mg/day), in spite of significant improvement of the clinical symptoms, the patients did not show any significant improvement or worsening in most of the items of these tests. The control group did not show any practice effect. These results suggest that first-episode schizophrenic patients have deficits in sustained attention and vigilance to visual stimuli, as well as the speed of information processing to visual and auditory stimuli, and these deficits are unrelated to clinical symptoms and remain stable during the early phase of treatment. This study did not receive pharmaceutical company financial support.

Multilevel Modeling of Cognitive Function in Schizophrenic Patients and Their First Degree Relatives

We describe multilevel modeling of cognitive function in subjects with schizophrenia, their healthy first degree relatives and controls. The purpose of the study was to compare mean cognitive performance between the three groups after adjusting for various covariates, as well as to investigate differences in the variances. Multilevel models were required because subjects were nested within families and some of the measures were repeated several times on the same subject. The following four methodological issues that arose during the analysis of the data are discussed. First, when the random effects distribution was not normal, non-parametric maximum likelihood (NPML) was employed, leading to a different conclusion than the conventional multilevel model regarding one of the main study hypotheses. Second, the between-subject (within-family) variance was allowed to differ between the three groups. This corresponded to the variance at level 1 or level 2 depending on whether repeated measures were analyzed. Third, a positively skewed response was analyzed using a number of different generalized linear mixed models. Finally, penalized quasilikelihood (PQL) estimates for a binomial response were compared with estimates obtained using Gaussian quadrature. A small simulation study was carried out to assess the accuracy of the latter.

Serotonin 6 Receptor Polymorphism in Schizophrenia: Frequency, Age at Onset and Cognitive Function

The relative abundance of serotonin 6 receptor (5HT6) in some limbic regions and the high affinity of some antipsychotics for 5HT6 suggest that the 5HT6 gene might play a role in the pathogenesis of schizophrenic disorders. A recent study reported an association between a C267T polymorphism of the 5HT6 gene and schizophrenia. In order to test whether the 5HT6 gene plays a role in the pathogenesis of schizophrenic disorders, patients (n = 148) and control subjects (n = 160) were genotyped for 5HT6. We also investigated the relationship between genotypes and patients’ age at onset and cognitive function in schizophrenic patients. Cognitive function in the patients was evaluated by the Mini-Mental State Examination (MMSE). The results demonstrated no significant differences in genotype or allele frequencies between controls and patients. In the patient group, age at onset and MMSE score did not differ significantly among the three 5HT6 genotpyes. The results of this study suggest that the 5HT6 C267T polymorphism plays no major role in susceptibility to the development of schizophrenia and is not related to cognitive impairment or age at onset in schizophrenic patients. Further studies of the relation between 5HT6 polymorphism and the symptoms and the therapeutic response in schizophrenic patients may help to elucidate the role of 5HT6 in the pathogenesis of schizophrenia.

Sex differences in neuropsychological functioning of first-episode and chronically ill schizophrenic patients.

The purpose of this study was to determine whether men and women with schizophrenia demonstrate differences in cognitive abilities. Two cohorts of patients with schizophrenia, an acute first-episode and a chronically hospitalized group, were evaluated with a neuropsychological battery and compared with a normal group of subjects. After adjustment for age, age at onset, and premorbid IQ, male chronic patients performed worse than female chronic patients on measures of visual memory. These differences were eliminated after control for symptom severity. No other differences were found in cognitive function between men and women in either cohort. Sex differences in cognitive function in schizophrenic patients are not robust findings.

Heterogeneity in cognitive functioning of schizophrenic patients evaluated by a lexical decision task.

The disorganization pattern in schizophrenia, which involves formal thought disorders, is thought to be correlated with a deficit in integrative processes of contextual information. We tested the hypothesis that thought disordered schizophrenics, unlike non-though disordered schizophrenics, would present a deficit in the processing of the context during a task which involves these integrative processes. A group of 22 schizophrenic patients diagnosed in accordance with DSM-III-R criteria and a group of 11 control subjects were compared using a semantic priming version of the lexical decision task. The experimental design used low-level structuration of verbal material to reveal the difficulty that schizophrenic patients encounter in using semantic regularities. A significant difference in priming effect was found between the three groups. Control subjects and non-thought disordered schizophrenics exhibit a priming effect for related word pairs when compared with unrelated pairs (respectively F(1,10) = 17.7; P < 0.002 and f(1,10) = 14.5; P > 0.003) but thought disordered schizophrenics did not (F(1,10) < 1; NS). This finding provides evidence for the cognitive heterogeneity of schizophrenic subjects. This absence of priming effect in thought-disordered schizophrenic subjects supports the hypothesis that these patients present a deficit in the post-lexical controlled information processing that permits the integration of semantic information.

Absence of ketamine effects on memory and other cognitive functions in schizophrenic patients

Glutamatergic dysfunction may play an important role in both the pathophysiology of schizophrenia, and impaired memory commonly observed in that disorder. NMDA receptor antagonists impair learning/memory in animal models, putatively based on its ability to block long-term potentiation (LTP) in the hippocampus. Although well studied in animal models, research in humans is limited and confounded by administration of NMDA antagonists before the learning experience. Based on presumed glutamatergic dysfunction, it was predicted that the NMDA antagonist ketamine would not effect memory in schizophrenic subjects. Bolus injections of ketamine (0.5 mg/kg) or placebo were given to seven patients with schizophrenia in this double-blind cross-over study. Immediately prior to injection, subjects were administered verbal and figural memory tests. Delayed recalls were obtained 30–45 min postinjection. In order to rule out drug-induced generalized cognitive impairments, other cognitive tasks were administered pre- and postinjection. The results indicate no differences between the drug and placebo conditions for either memory task, and no changes on the other cognitive tasks observed.

Cognitive function in schizophrenia: association with negative and positive symptoms.

20 schizophrenic patients were classified as having either predominantly negative (n = 11) or predominantly positive symptoms (n = 9), utilizing the Scale for the Assessment of Negative Symptoms and the Scale for the Assessment of Positive Symptoms. Cognitive functioning was evaluated in these participants and 10 nonpatient controls using a word-fluency test and word-generation task. Finally, all participants were evaluated using the Coglab Card Sort Test, a computerized version of the Wisconsin Card Sort Test. The only reliable difference in performance among groups was on perseverative errors on the Coglab Card Sort Test. Schizophrenic participants made significantly more perseverative errors than controls and those classified as having primarily negative symptoms made more perseverative errors than those classified as having predominantly positive symptoms. These findings confirm previous reports with respect to cognitive functioning of schizophrenic patients and are consistent with the hypotheses regarding frontal lobe dysfunction in schizophrenia. These data encourage research with larger samples.

The relationship between psychosocial and cognitive functioning in schizophrenic patients and expressed emotion and communication deviance in their parents

The relationship between the family variables of expressed emotion (EE) and communication deviance (CD) and patient attributes of cognitive functions and clinical symptoms were examined. Eleven schizophrenic patients and their parents were evaluated at the beginning and the end of a 2-year treatment programme. The test battery for the patients included the Global Assessment Scale (GAS), Brief Psychiatric Rating Scale and a cognitive test battery. Parents' CD was evaluated with the Communication Conflict Situation and their EE level with Camberwell Family Interview. A significant correlation between patients' GAS score and mother's criticism score was found. The cognitive variable of backward masking was the measure that most consistently showed a close relationship to parent's EE level. The masking measure also differentiated significantly between parents who improved and parents who did not improve on EE during the 2-year treatment period. An empirical basis for a link between patients' cognitive functioning and parents' style of communication was not found.

Neuropsychological performance in schizophrenic inpatients as a function of medication status

Previous research has been unclear with respect to neuroleptie medication effects on cognitive functioning in schizophrenic patients. The present study compared the neuropsychological functioning of three groups of schizophrenic inpatients who differed in with regard to medication status. 19 medication stabilized (clinically determined doses of Thiothixene), 10 medication naive, and 21 medication washed-out inpatient schizophrenics meeting SADS/RDC criteria were given extensive neuropsychological testing as well as a number of clinical rating scales. There were no statistical differences between groups in education, total scores on the Brief Psychiatric Rating Scale (BPRS), BPRS Positive Symptom factor or negative symptoms (SANS) at baseline. As expected, there was a trend toward younger subjects in the medication naive group (mean age = 25.4 + 6.8) as compared with the medicated (mean age 28.9 + 8.8) and the medication washed.out (mean age 32.8 + 8.7) groups. A statistical difference (p-.048) in dominant hand fmger oscillation was noted with the medication stabilized patients performing faster. A trend toward better delayed memory for designs on the Wechsler Memory Scale in the medication naive group was also observed (p-.06). There were no significant differences or trends between groups on measures of executive functioning, verbal memory, and speech/language functioning. Examination of standardized scores suggested overall poorer performance of all three groups on measures of executive functioning, attention/concentration, psychomotor speed, and verbal memory when compatld to normals. The current study confirms the presence of cognitive deficits in schizophrenics which are apparent at the time of the onset of their first psychotic break and remain relatively unaffected by pharmacotherapy.

Cognitive functions in schizophrenic patients with tardive dyskinesia.

Cognitive functions in schizophrenic patients with tardive dyskinesia.