Processing speed and working memory span: their differential role in superficial and deep memory processes in schizophrenia.

Previous work has suggested that decrement in both processing speed and working memory span plays a role in the memory impairment observed in patients with schizophrenia. We undertook a study to examine simultaneously the effect of these two factors. A sample of 49 patients with schizophrenia and 43 healthy controls underwent a battery of verbal and visual memory tasks.

Does intravenous Δ9-tetrahydrocannabinol increase dopamine release? A SPET study.

Intravenous (IV) Δ9-tetrahydrocannabinol (THC) induces transient psychotic symptoms in healthy subjects and in schizophrenic patients, but the psychotomimetic mechanism is unknown. One possibility is that THC stimulates dopamine (DA) release in the striatum. In this study we tested whether IV THC led to an increase in striatal DA release compared to placebo.

Serial and semantic encoding of lists of words in schizophrenia patients with visual hallucinations.

Previous research has suggested that visual hallucinations in schizophrenia are associated with abnormal salience of visual mental images. Since visual imagery is used as a mnemonic strategy to learn lists of words, increased visual imagery might impede the other commonly used strategies of serial and semantic encoding. We had previously published data on the serial and semantic strategies implemented by patients when learning lists of concrete words with different levels of semantic organisation (Brébion et al.

Production of atypical category exemplars in patients with schizophrenia.

Previous studies have revealed semantic memory impairments in patients with schizophrenia, and suggested that certain of these impairments were related to thought disorganization. One explanation offered for this is a broadening of the boundaries of semantic categories in schizophrenia. We selected 16 semantic categories, and required a sample of 41 schizophrenia patients and 43 healthy control subjects to produce one exemplar from each category.

Depression, avolition, and attention disorders in patients with schizophrenia: associations with verbal memory efficiency.

The authors undertook a study of the clinical correlates of verbal memory deficits in schizophrenia. The first purpose was to replicate the finding of a significant association between depression and impairment in the deep encoding memory processes. The second purpose was to test the hypothesis that certain clinical symptoms--avolition, disorders of attention--also play a role in verbal memory impairment, distinct from a global negative symptomatology score.

Working memory span and motor and cognitive speed in schizophrenia.

Objective: The aim of this study was to investigate the verbal working memory deficit and decrease of motor and cognitive speed in patients with schizophrenia, and to clarify their associations with negative and depressive symptomatology.

Methods: Forty patients with schizophrenia and 41 healthy control individuals were administered the backward digit span to assess the working memory capacity, along with 3 tests of processing speed.

Results: Patients demonstrated reduced backward digit span, as well as decreased motor and cognitive speed.

Role of processing speed and premorbid IQ on visual recognition in patients with schizophrenia.

Previous research had shown that processing speed and premorbid IQ are predictors of verbal-memory efficiency in patients with schizophrenia. We investigated whether the same factors are involved in visual memory. A total of 49 patients with schizophrenia and 43 healthy controls were administered a picture recognition task.

Visual hallucinations in schizophrenia: confusion between imagination and perception.

Objective: An association between hallucinations and reality-monitoring deficit has been repeatedly observed in patients with schizophrenia. Most data concern auditory/verbal hallucinations. The aim of this study was to investigate the association between visual hallucinations and a specific type of reality-monitoring deficit, namely confusion between imagined and perceived pictures.

Cortical dopamine D2/D3 receptors are a common site of action for antipsychotic drugs--an original patient data meta-analysis of the SPECT and PET in vivo receptor imaging literature.

Subject numbers in neuroreceptor imaging studies of antipsychotic treatment in schizophrenia are generally insufficient to directly test the relationship of regional D(2)/D(3) and 5HT(2A) receptor binding to clinical efficacy. We selected positron emission tomography (PET) and single photon emission computed tomography (SPECT) studies of antipsychotic dose vs occupancy at both temporal cortex and striatal D(2)/D(3) receptors. We selected corresponding SPECT and PET studies of 5HT(2A) receptor occupancy.

Relationship between ketamine-induced psychotic symptoms and NMDA receptor occupancy: a [(123)I]CNS-1261 SPET study.

Rationale: Ketamine induces effects resembling both positive and negative psychotic symptoms of schizophrenia. These are thought to arise through its action as an uncompetitive antagonist of the N-methyl-D-aspartate (NMDA) receptor.

Objectives: We used [(123)I]CNS-1261 to study ketamine binding to NMDA receptors in healthy human controls in vivo and its relationship to positive and negative psychotic symptom induction.

Visual memory errors in schizophrenic patients with auditory and visual hallucinations.

Hallucinations have been found associated with false detection or false recognition of acoustic/verbal material in several studies. We investigated whether they were also linked with false recognition of pictures. Furthermore, an association between hallucinations and deficits in remembering temporal context was observed in previous research on schizophrenia.

Sexual function and gonadal hormones in patients taking antipsychotic treatment for schizophrenia or schizoaffective disorder.

Objective: To determine rates of sexual dysfunction and hypogonadism and establish the relationship between gonadal hormone levels and sexual function in patients taking antipsychotic treatment for schizophrenia or schizoaffective disorder.

Method: We studied 103 patients with schizophrenia or schizoaffective disorder (mean age = 46.2 (SD = 12.

Glutamate and dopamine dysregulation in schizophrenia--a synthesis and selective review.

The dopamine hypothesis of schizophrenia is the principal explanatory model of antipsychotic drug action. Recent discoveries extend our understanding of the neurochemistry of schizophrenia, with increasing evidence of dysfunction in glutamate and GABA as well as dopamine systems. In this review, we study the evidence for dopaminergic dysfunction in schizophrenia, drawing data from neurochemical imaging studies.

Schizophrenia: more evidence for less glutamate.

Evaluation of: Hahn CJ, Hoau-Yan W, Dan-Sung C et al. Altered neuregulin 1-erbB4 signaling contributes to NMDA receptor hypofunction in schizophrenia. Nat.

Role of processing speed and depressed mood on encoding, storage, and retrieval memory functions in patients diagnosed with schizophrenia.

The role of various types of slowing of processing speed, as well as the role of depressed mood, on each stage of verbal memory functioning in patients diagnosed with schizophrenia was investigated. Mixed lists of high- and low-frequency words were presented, and immediate and delayed free recall and recognition were required. Two levels of encoding were studied by contrasting the relatively automatic encoding of the high-frequency words and the more effortful encoding of the low-frequency words.

The relationship between prolactin levels and glucose homeostasis in antipsychotic-treated schizophrenic patients.

Objectives: To determine if prolactin levels are associated with glucose-insulin homeostasis in antipsychotic-treated patients with schizophrenia.

Method: Prolactin levels and glucose homeostasis (quantified using oral glucose tolerance testing, insulin measurement, and homeostasis model assessment) were measured in 15 patients with elevated prolactin levels secondary to antipsychotic treatment of schizophrenia (mean age, 30.4 years; SD, 5.

Temporal context discrimination in patients with schizophrenia: associations with auditory hallucinations and negative symptoms.

Background: A deficit in remembering the temporal context of events (a type of source memory) has been observed in schizophrenia, and suggested to be associated with positive symptoms.

Methods: In order to investigate memory for temporal context, we administered a list discrimination task to a sample of schizophrenia patients and a sample of healthy controls. Participants were required to learn two lists of mixed high- and low-frequency words separated by 10 min, then to remember whether each word had been presented in the first or in the second list.

Towards NR2B receptor selective imaging agents for PET-synthesis and evaluation of N-[11C]-(2-methoxy)benzyl (E)-styrene-, 2-naphthyl- and 4-trifluoromethoxyphenylamidine.

Three potent and selective 11C-labelled NR2B antagonists have been synthesized and evaluated as PET ligands. The brain uptake of the compounds in mice varied substantially and was dominated by metabolism. One compound was found to have favourable uptake and retention in the brain, as well as a binding pattern consistent with the expression of the target receptor as measured by in vitro autoradiography.

[123I]TPCNE--a novel SPET tracer for the sigma-1 receptor: first human studies and in vivo haloperidol challenge.

[123I]TPCNE (1(trans-[123I]iodopropen-2-yl)-4-[(4-cyanophenoxy)methyl] piperidine; Ki = 0.67 nM; log P = 3.36) is a novel sigma-1 receptor SPET ligand.

Closing in on the AMPA receptor: synthesis and evaluation of 2-acetyl-1-(4'-chlorophenyl)-6-methoxy-7-[11C]methoxy-1,2,3,4-tetrahydroisoquinoline as a potential PET tracer.

2-Acetyl-1-(4'-chlorophenyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline, one of the most potent non-competitive AMPA antagonists described to date, has been labelled with carbon-11 and tritium and evaluated as a potential ligand for in vivo imaging of AMPA receptors using PET. The carbon-11 labelled compound showed good initial brain uptake in rats, but with rapid clearance and relatively homogenous distribution. In saturation binding studies, the tritiated racemic ligand was found to be highly potent with a Kd of 14.

Processing speed: a strong predictor of verbal memory performance in schizophrenia.

The role of slowing of processing speed in verbal memory impairment in patients with schizophrenia was investigated. Forty-one patients with schizophrenia and 41 healthy control subjects were administered a verbal memory task involving free recall of three lists of words, which varied in their degree of semantic organization. Standard processing speed tests were administered as well.

Ketamine displaces the novel NMDA receptor SPET probe [(123)I]CNS-1261 in humans in vivo.

[(123)I]CNS-1261 [N-(1-naphthyl)-N'-(3-iodophenyl)-N-methylguanidine] is a high-affinity SPET ligand with selectivity for the intra-channel PCP/ketamine/MK-801 site of the N-methyl-d-aspartate (NMDA) receptor. This study evaluated the effects of ketamine (a specific competitor for the intra-channel PCP/ketamine/MK-801 site) on [(123)I]CNS-1261 binding to NMDA receptors in vivo. Ten healthy volunteers underwent 2 bolus-plus-infusion [(123)I]CNS-1261 scans, one during placebo and the other during a ketamine challenge.

Antipsychotic drug action: targets for drug discovery with neurochemical imaging.

Schizophrenia is a serious lifelong mental illness for which current treatments may only be partially effective. All antipsychotic medications available at present are thought to exert their main antipsychotic effect through antagonism of dopamine D2 receptors. Clozapine is the most effective antipsychotic drug currently available, but it can cause serious side effects, including agranulocytosis and diabetes.

Hallucinations, negative symptoms, and response bias in a verbal recognition task in schizophrenia.

Several studies have reported an association between hallucinations and tendency to make false alarms in acoustic signal detection tasks. Previous work on patients with schizophrenia has suggested that false recognitions and other types of memory error were positively associated with hallucinations and inversely associated with certain negative symptoms of withdrawal. In this study, 40 patients with schizophrenia were administered a word recognition task.