Clozapine but not haloperidol Re-establishes normal task-activated rCBF patterns in schizophrenia within the anterior cingulate cortex

Effects of acute antipsychotic treatment on brain activation in first episode psychosis: an fMRI study

This study aimed to assess the neurophysiological effects of acute atypical antipsychotic treatment on cognitive functioning in subjects presenting with a first episode of psychosis. We used functional MRI to examine the modulatory effects of acute psychopharmacological intervention on brain activation during four different cognitive tasks: overt verbal fluency, random movement generation, n-back and a spatial object memory task. Treatment with atypical antipsychotics was associated with alterations in regional activation during each task and also when task demands were manipulated within paradigms. The initial treatment of psychosis with atypical antipsychotics thus appears to be associated with modifications of the neurofunctional correlates of executive and mnemonic functions. These effects need to be considered when interpreting group differences in activation between medicated patients and controls.

Fine-tuning of awake prefrontal cortex neurons by clozapine: comparison with haloperidol and N-desmethylclozapine

BACKGROUND

Mechanisms underlying clozapine's better clinical efficacy in schizophrenia remain poorly understood. The prefrontal cortex (PFC) has been implicated as a primary site for the therapeutic effects of clozapine; however, evidence for how clozapine influences the activity of PFC neurons in behaviorally relevant contexts is lacking.

METHODS

Ensemble single unit recording in awake rats was used to measure the activity of PFC neurons in response to clozapine, its main metabolite N-desmethylclozapine (DMClz), and the typical antipsychotic drug haloperidol during baseline conditions and after treatment with the N-methyl-D-aspartate antagonist MK801. Behavioral stereotypy was scored during recording.

RESULTS

Clozapine and DMClz but not haloperidol had an activity-dependent influence on spontaneous firing rate of PFC cells: they increased the activity of neurons with low baseline firing rates and decreased the activity of neurons with higher firing rates. Clozapine and DMClz but not haloperidol also reversed the effect of MK801 on PFC neuronal firing. This reversal was strongly correlated with blockade of MK801-induced behavioral stereotypy.

CONCLUSIONS

These findings indicate that clozapine has the capacity to fine-tune spontaneous and disrupted activity of PFC neurons. This effect might contribute, in part, to the therapeutic efficacy of clozapine in schizophrenia.

Patterns of anterior cingulate activation in schizophrenia: a selective review

BACKGROUND

Anterior cingulate cortex (ACC) dysfunction is implicated in schizophrenia by numerous strands of scientific investigation. Functional neuroimaging studies of the ACC in schizophrenia have shown task-related hypo-activation, hyper-activation, and normal activation relative to comparison subjects. Interpreting these results and explaining their inconsistencies has been hindered by our ignorance of the healthy ACC's function. This review aims to clarify the site and magnitude of ACC activations in schizophrenia, and sources of their variation.

METHOD

48 studies of mnemonic and executive task-related activations in schizophrenia using both positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) were analyzed.

RESULTS

Abnormal activations in schizophrenia were not restricted to the "cognitive" part of the ACC. Hypoactivations were most common, and were found in all types of tasks. Hyperac-tivations when found, were largely in n-back tasks.

CONCLUSIONS

Hypoactivations cannot be explained by poor performance, more demanding control conditions or chronicity of illness alone. Patients on anti-psychotic medication tended to show both greater ACC activation and better performance, although whether this is directly due to their medication or the resultant reduction in symptoms is unclear. The relationship between ACC rCBF and task performance is not straightforward. Future research should better control confounding factors and incorporate different levels of difficulty.

Deficit in schizophrenia to recruit the striatum in implicit learning: a functional magnetic resonance imaging investigation

In schizophrenia, explicit learning deficits have been well established although it is less clear whether these patients have deficits in implicit learning (IL). IL is thought to depend on intact striatal functioning. This study examined the hypothesis that schizophrenia patients show deficient recruitment of striatal activation during an IL paradigm, relative to performance-matched healthy comparison subjects. Ten subjects with schizophrenia on atypical antipsychotic medication and 10 age, gender, education, and performance matched healthy comparison subjects underwent fMRI while performing an IL task. On the basis of whole-brain and striatal region-of-interest analyses, we found a relative lack of striatal activation in schizophrenia patients. This result is consistent with convergent evidence of striatal dysfunction in schizophrenia.

Use of magnetic resonance imaging in tracking the course and treatment of schizophrenia

Confirming the early conceptualization of Bleuler (1911) and Kraepelin (1919), magnetic resonance imaging (MRI) studies have demonstrated structural and functional brain abnormalities, predominantly involving the frontal and temporal lobes, in schizophrenia. Most of the abnormalities are already present at illness onset. However, there is, growing evidence for treatment-related neural changes in schizophrenia, such as enlargement of the caudate nucleus (neurotoxic effect) with the use of typical antipsychotics and increases in cortical volumes and improved functional responses (neurotrophic effect) with the use of atypical antipsychotics. More recently, brain changes during the prodrome and transition-to-illness stages of schizophrenia have begun to be characterized. Another area of importance is the use of MRI, as a biological marker, to monitor and define partial or full resistance to medication. Understanding the trait- and state-related influences of brain abnormalities during the course of the illness is critical for developing effective treatment and possibly prevention strategies in schizophrenia.

Imaging genomics and response to treatment with antipsychotics in schizophrenia

Recent important advancements in genomic research have opened the way to new strategies for public health management. One of these questions pertains to how individual genetic variation may be associated with individual variability in response to drug treatment. The field of pharmacogenetics may have a profound impact on treatment of complex psychiatric disorders like schizophrenia. However, pharmacogenetic studies in schizophrenia have produced conflicting results. The first studies examined potential associations between clinical response and drug receptor genes. Subsequent studies have tried to use more objective phenotypes still in association with drug receptor genes. More recently, other studies have sought the association between putative causative or modifier genes and intermediate phenotypes. Thus, conflicting results may be at least in part explained by variability and choice of the phenotype, by choice of candidate genes, or by the relatively little knowledge about the neurobiology of this disorder. We propose that choosing intermediate phenotypes that allow in vivo measurement of specific neuronal functions may be of great help in reducing several of the potential confounds intrinsic to clinical measurements. Functional neuroimaging is ideally suited to address several of these potential confounds, and it may represent a powerful strategy to investigate the relationship between behavior, brain function, genes, and individual variability in the response to treatment with antipsychotic drugs in schizophrenia. Preliminary evidence with potential susceptilibity genes such as COMT, DISC1, and GRM3 support these assumptions.

Do psychotherapies produce neurobiological effects?

BACKGROUND

An area of recent interest in psychiatric research is the application of neuroimaging techniques to investigate neural events associated with the development and the treatment of symptoms in a number of psychiatric disorders.

OBJECTIVE

To examine whether psychological therapies modulate brain activity and, if so, to examine whether these changes similar to those found with relevant pharmacotherapy in various mental disorders.

METHODS

Relevant data were identified from Pubmed and PsycInfo searches up to July 2005 using combinations of keywords including 'psychological therapy', 'behaviour therapy', 'depression', 'panic disorder', 'phobia', 'obsessive compulsive disorder', 'schizophrenia', 'psychosis', 'brain activity', 'brain metabolism', 'PET', 'SPECT' and 'fMRI'.

RESULTS

There was ample evidence to demonstrate that psychological therapies produce changes at the neural level. The data, for example in depression, panic disorder, phobia and obsessive compulsive disorder (OCD), clearly suggested that a change in patients' symptoms and maladaptive behaviour at the mind level with psychological techniques is accompanied with functional brain changes in relevant brain circuits. In many studies, cognitive therapies and drug therapies achieved therapeutic gains through the same neural pathways although the two forms of treatment may still have different mechanisms of action.

CONCLUSIONS

Empirical research indicates a close association between the 'mind' and the 'brain' in showing that changes made at the mind level in a psychotherapeutic context produce changes at the brain level. The investigation of changes in neural activity with psychological therapies is a novel area which is likely to enhance our understanding of the mechanisms for therapeutic changes across a range of disorders.

Correlations between rCBF and symptoms in two independent cohorts of drug-free patients with schizophrenia

We report on the correlations between whole brain rCBF and the positive and negative symptoms of schizophrenia in two cohorts of patients who were scanned while free of antipsychotic medication. We hypothesized that positive symptoms would correlate with rCBF in limbic and paralimbic regions, and that negative symptoms would correlate with rCBF in frontal and parietal regions. Both cohorts of patients with schizophrenia (Cohort 1: n=32; Cohort 2: n=23) were scanned using PET with H(2)(15)O while free of antipsychotic medication for an average of 21 and 15 days, respectively. Both groups were scanned during a resting state. Using SPM99, we conducted pixel by pixel linear regression analyses between BPRS scores and whole brain rCBF. As hypothesized, positive symptoms correlated with rCBF in the anterior cingulate cortex (ACC) in a positive direction and with the hippocampus/parahippocampus in a negative direction in both patient groups. When the positive symptoms were further divided into disorganization and hallucination/delusion scores, similar positive correlations with ACC and negative correlations with hippocampus rCBF were found. In both cohorts, the disorganization scores correlated positively with rCBF in Broca's area. As expected, negative symptoms correlated inversely with rCBF in frontal and parietal regions. This study provides evidence that limbic dysfunction may underlie the production of positive symptoms. It suggests that abnormal function of Broca's area may add a specific language-related dimension to positive symptoms. This study also provides further support for an independent neurobiological substrate of negative symptoms distinct from positive symptoms. The involvement of both frontal and parietal regions is implicated in the pathophysiology of negative symptoms.

Beneficial effect of atypical antipsychotics on prefrontal brain function in acute psychotic disorders

Disturbance of prefrontal brain functions is assumed to be responsible for prominent psychopathological symptoms in psychotic disorders. Treatment with atypical, in contrast to typical antipsychotics is considered as a possible strategy for an improvement of prefrontal brain function. In the present study, response control as a specific prefrontal brain function was assessed by means of the Nogo-anteriorization (NGA) derived from the event-related potentials elicited during a Go-NoGo task in a consecutive sample of 39 patients suffering from acute psychotic disorders (brief psychotic disorders, 298.8, n = 34 and schizoaffective disorders, 295.70, n = 5; cycloid psychoses according to the Leonhard classification). A highly significant positive correlation between the amount of antipsychotic medication in terms of chlorpromazine equivalents per day and the NGA as a measure of prefrontal response control was only found in the subgroup of patients treated exclusively or predominantly with atypical antipsychotics but not for those treated with typical antipsychotics. These results are in line with the notion that atypical antipsychotics may exert a beneficial effect on prefrontal brain function.

Functional effects of single dose first- and second-generation antipsychotic administration in subjects with schizophrenia

Using PET with (15)O water, we characterized the time course of functional brain changes following the acute administration of a first- and a second-generation antipsychotic. Volunteers with schizophrenia were scanned while drug-free (baseline) and after single dose administration of haloperidol (n=6) or olanzapine (n=6) during a time course adapted to their plasma kinetics. To obtain brain location information, we contrasted each post-drug scan to baseline-acquired scans. We plotted the regional cerebral blood flow (rCBF) extracted in these locations and calculated the kinetic characteristics of the curves. Further, we compared and contrasted the rCBF changes induced by the drugs over the first 4 h post-drug administration. Dorsal and ventral striatum, thalamus and anterior cingulate cortex were activated with haloperidol, while frontal, temporal and cerebellum regions evidenced reduced flow. With olanzapine, ventral striatum, anterior cingulate and temporal cortices evidenced increases, and thalamus and lingual cortex decreases, in rCBF. Both drugs activated the caudate nucleus. Haloperidol induced greater activation of the dorsal striatum than did olanzapine. These data reveal important differences in patterns of brain activation between the drugs. Differences in the involvement in basal ganglia parallel known differences between the drugs in the emergence of acute EPS upon emergency administration.

Cerebral metabolic changes induced by clozapine in schizophrenia and related to clinical improvement

RATIONALE

The study of the different effects on brain metabolism between typical and atypical antipsychotics would aid in understanding their mechanisms of action. Clozapine is of special interest, since it is one of the most effective antipsychotic drugs and demonstrates a distinctive mechanism of action in pre-clinical studies with respect to typical neuroleptics.

OBJECTIVE

To study the differences in cerebral activity induced by clozapine as compared to those produced by haloperidol.

METHODS

[18F]Fluoro-deoxy-glucose (FDG)-positron emission tomography (PET) scans were obtained in the resting condition before and after 6 months of treatment with clozapine in 22 treatment-resistant patients with schizophrenia. Before inclusion, patients had been chronically treated with classical drugs, and all of them received haloperidol during the last month. Data were analyzed with statistical parametric mapping (SPM'99) methods, comparing pre-treatment and post-treatment conditions. The association between the changes in symptom scores and metabolism was also assessed to corroborate the functional relevance of possible metabolic changes.

RESULTS

Clozapine decreased prefrontal and basal ganglia activity, and increased occipital metabolism, including primary and association visual areas. The change in negative symptoms was related with the decrease of basal ganglia activity; the improvement in disorganization related to the metabolic decrease in the motor area, and the change in positive symptoms was associated to the increase of activity in the visual area.

CONCLUSIONS

These results show that haloperidol and clozapine produce different patterns of metabolic changes in schizophrenia. Compared to the haloperidol baseline, clozapine inhibited the metabolic activity of the prefrontal and motor cortical regions and basal ganglia and induced a higher activation of the visual cortex. The improvement in disorganization, negative and positive syndromes with clozapine may be respectively associated with metabolic changes in the motor area, basal ganglia, and visual cortex.

Plasticity at hippocampal to prefrontal cortex synapses is impaired by loss of dopamine and stress: importance for psychiatric diseases

The direct hippocampal to prefrontal cortex pathway and its changes in synaptic plasticity is a useful framework for investigating the functional operations of hippocampal-prefrontal cortex communication in cognitive functions. Synapses on this pathway are modifiable and synaptic strength can be turned up or down depending on specific patterns of activity in the pathway. The objective of this review will be to summarize the different studies carried out on this topic including very recent data and to underline the importance of animal models for the development of new and effective medications in psychiatric diseases. We have shown that long-term potentiation (LTP) of hippocampal-prefrontal synapses is driven by the level of mesocortical dopaminergic (DA) activity and more recently that stress is also an environmental determinant of LTP at these cortical synapses. Stimulation of the ventral tegmental area at a frequency known to evoke DA overflow in the prefrontal cortex produces a long-lasting enhancement of the magnitude of hippocampal-prefrontal cortex LTP whereas a depletion of cortical DA levels generates a dramatic decrease in this LTP. Moreover, hippocampal stimulation induces a transient but significant increase in DA release in the prefrontal cortex and an optimal level of D1 receptor activation is essential for LTP expression. We recently investigated the impact of stress on hippocampal-prefrontal LTP and demonstrated that exposure to an acute stress causes a remarkable and long-lasting inhibition of LTP. Furthermore, we demonstrated that tianeptine, an antidepressant which has a unique mode of action, and clozapine an atypical antipsychotic when administered at doses normally used in human testing are able to reverse the impairment in LTP. Stressful life events have a substantial causal association with psychiatric disorders like schizophrenia and depression and recent imaging studies have shown an important role of the limbic-cortical circuit in the pathophysiology of these illnesses. Therefore, we proposed that agents capable of reversing the impairment of plasticity at hippocampal to prefrontal cortex synapses have the potential of becoming new therapeutic classes of antidepressant or antipsychotic drugs.