The effect of second-generation antipsychotics on basal ganglia and thalamus in first-episode psychosis patients.

Patients who have recently experienced a first of episode psychosis (FEP) exhibit considerable heterogeneity in subcortical brain volumes. These results become even more divergent when exploring the effect of antipsychotic medication among other clinical and cognitive features. We aimed to contrast volumetric measures in basal ganglia and thalamus in patients with a FEP treated with different second-generation antipsychotics. T1-weighted magnetic resonance images were obtained and subcortical structures were extracted with MAGeT-Brain. Relationships with cognitive functioning were also explored with a Global Cognitive Index obtained, on average, within one month from the scan. Subgroups included: risperidone (n = 26), aripiprazole (n = 22), olanzapine (n = 19) and controls (n = 80). The olanzapine subgroup displayed significant enlargement of the right globus pallidus volume compared with all other groups. Moreover, despite not exhibiting poorer cognitive capacity than the rest of patients, results from a stepwise multiple-regression linear regression analysis identified a significant negative association between right globus pallidus volume and scores on the Global Cognitive Index among these patients. To our knowledge, this is the first study to associate treatment with olanzapine with an increase in globus pallidus volume in a sample of FEP patients with a relatively short time of antipsychotic monotherapy. Such enlargement was also found to be associated with poorer global cognitive functioning. Exploration of the biological underpinnings of this early medication-induced enlargement should be the focus of future investigations since it may lend insight towards achieving a better clinical outcome for these patients.

Does an integrated outreach intervention targeting multiple stages of early psychosis improve the identification of individuals at clinical high risk?

AIMS: To explore the impact of a targeted case identification intervention, with training and education regarding first-episode psychosis and clinical high-risk syndromes, on the referral and identification of those at high risk. METHODS: Using a historical control design, referral information from pre-intervention and post-intervention periods was collected via administrative data and clinician notes from a catchment-based early psychosis service. RESULTS: A significant increase in the number of referrals sent to the service's clinical high-risk unit was observed following the intervention (P = 0.01). The proportion of referrals eligible was significantly higher post-intervention (P = 0.03), with the majority (26/44, 59.1%) referred via the first-episode psychosis service unit. CONCLUSIONS: An integrated outreach intervention for both first-episode psychosis and the clinical high-risk state was effective in increasing referrals of eligible cases to the service's at-risk unit. Rather than being stage-specific, targeted case identification strategies and service integration should span across the early stages of psychosis.

Evaluating accuracy of striatal, pallidal, and thalamic segmentation methods: Comparing automated approaches to manual delineation.

Accurate automated quantification of subcortical structures is a greatly pursued endeavour in neuroimaging. In an effort to establish the validity and reliability of these methods in defining the striatum, globus pallidus, and thalamus, we investigated differences in volumetry between manual delineation and automated segmentations derived by widely used FreeSurfer and FSL packages, and a more recent segmentation method, the MAGeT-Brain algorithm. In a first set of experiments, the basal ganglia and thalamus of thirty subjects (15 first episode psychosis [FEP], 15 controls) were manually defined and compared to the labels generated by the three automated methods. Our results suggest that all methods overestimate volumes compared to the manually derived "gold standard", with the least pronounced differences produced using MAGeT. The least between-method variability was noted for the striatum, whereas marked differences between manual segmentation and MAGeT compared to FreeSurfer and FSL emerged for the globus pallidus and thalamus. Correlations between manual segmentation and automated methods were strongest for MAGeT (range: 0.51 to 0.92; p<0.01, corrected), whereas FreeSurfer and FSL showed moderate to strong Pearson correlations (range 0.44-0.86; p<0.05, corrected), with the exception of FreeSurfer pallidal (r=0.31, p=0.10) and FSL thalamic segmentations (r=0.37, p=0.051). Bland-Altman plots highlighted a tendency for greater volumetric differences between manual labels and automated methods at the lower end of the distribution (i.e. smaller structures), which was most prominent for bilateral thalamus across automated pipelines, and left globus pallidus for FSL. We then went on to examine volume and shape of the basal ganglia structures using automated techniques in 135 FEP patients and 88 controls. The striatum and globus pallidus were significantly larger in FEP patients compared to controls bilaterally, irrespective of the method used. MAGeT-Brain was more sensitive to shape-based group differences, and uncovered widespread surface expansions in the striatum and globus pallidus bilaterally in FEP patients compared to controls, and surface contractions in bilateral thalamus (FDR-corrected). By contrast, after using a recommended cluster-wise thresholding method, FSL only detected differences in the right ventral striatum (FEP>Control) and one cluster of the left thalamus (Control>FEP). These results suggest that different automated pipelines segment subcortical structures with varying degrees of variability compared to manual methods, with particularly pronounced differences found with FreeSurfer and FSL for the globus pallidus and thalamus.

Prepulse inhibition (PPI) of tactile startle response in recombinant congenic strains of mice: QTL mapping and comparison with acoustic PPI.

Prepulse inhibition (PPI) of the startle response is a psychophysiological measure of sensorimotor gating believed to be cross-modal between different sensory systems. We analyzed the tactile startle response (TSR) and PPI of TSR (tPPI), using light as a prepulse stimulus, in the mouse strains A/J and C57BL/6J and 36 recombinant congenic strains derived from them. Parental strains were significantly different for TSR, but were comparable for tPPI. Among the congenic strains, variation for TSR was significant in both genetic backgrounds, but that of tPPI was significant only for the C57BL/6J background. Provisional mapping for loci modulating TSR and tPPI was carried out. Using mapping data from our previous study on acoustic startle responses (ASR) and PPI of ASR (aPPI), no common markers for aPPI and tPPI were identified. However, some markers were significantly associated with both ASR and TSR, at least in one genetic background. These results indicate cross-modal genetic regulation for the startle response but not for PPI, in these mouse strains.

Effects of clozapine on behavioral and metabolic traits relevant for schizophrenia in two mouse strains.

RATIONALE: Schizophrenia is a heterogeneous syndrome both at the etiological and clinical levels. In particular, patients with schizophrenia exhibit important variability in their therapeutic and metabolic responses to clozapine, an antipsychotic medication. OBJECTIVE: Here, we determine whether two mouse strains show differing clozapine responses with respect to weight gain, enhancement of prepulse inhibition of acoustic startle, and reversal of amphetamine-induced locomotion. Observed between-strain differences may be partly due to genetic factors that can be subsequently mapped using quantitative genetic approaches. METHODS: We treated the A/J and C57BL/6J inbred mouse strains with clozapine for 22 days. Prepulse inhibition and amphetamine-induced locomotion were measured after 3-4 days of clozapine treatment and again after 21-22 days of treatment. Weight gain was also monitored during treatment. RESULTS. Three-day treatment with clozapine increased prepulse inhibition in both strains. Four-day clozapine treatment reduced amphetamine-induced locomotion only in the C57BL/6J strain. Long-term (21-22 days) clozapine treatment did not affect these behaviors in either strain. After an initial weight loss during the first 5 days, clozapine (4 mg/kg) induced a significant weight gain in both strains. CONCLUSIONS: The reversal of schizophrenia-related behaviors after short-term, but not long-term, clozapine treatment is consistent with other rodent studies. Although short-term clozapine treatment reduced amphetamine-induced locomotion only in the C57BL/6J strain, strain differences in amphetamine responses confound the interpretation of these results; therefore, quantitative genetic approaches may be difficult to carry out with this trait. In contrast, enhancement of prepulse inhibition after three days of clozapine treatment and weight gain induced by clozapine are relatively straightforward to quantify, making these trait more amenable to quantitative genetic approaches.

Molecular cloning and characterization of human RAI1, a gene associated with schizophrenia.

Schizophrenia is a common neuropsychiatric disorder of uncertain etiology that is believed to result from the interaction of environmental factors and multiple genes. To identify new genes predisposing to schizophrenia, numerous groups have focused on CAG-repeat-containing genes. We previously reported a CAG repeat polymorphism that was shown to be associated with both the severity of the phenotype and the response to medication in schizophrenic patients. In this article, we now report the genomic structure of this gene, the retinoic acid inducible-1 gene (RAI1), and present its characterization. This gene, located on chromosome 17p11.2, comprises six exons coding for a 7.6-kb mRNA. The RAI1 gene is highly homologous to its mouse counterpart and it is expressed at high levels mainly in neuronal tissues.

Provisional mapping of quantitative trait loci modulating the acoustic startle response and prepulse inhibition of acoustic startle.

Prepulse inhibition (PPI) of the acoustic startle response (ASR) is a form of sensorimotor gating, defined as an inhibition of the startle response when a low intensity stimulus, the prepulse, precedes the startling stimulus. Deficits in PPI have been reported in schizophrenia and other psychiatric/neurological disorders, and correlate with symptom severity in schizophrenia, suggesting that deficient PPI per se or abnormalities in neural circuits regulating PPI may cause some symptoms of schizophrenia. If so, then genes conferring reduced PPI may contribute toward genetic vulnerability to schizophrenia. Studies with selectively bred rodent strains indicate that PPI is under genetic control; however, the identity of the relevant genes is unknown. The current study used recombinant congenic mouse strains derived from C57BL/6J and A/J parents to assess genetic variability in PPI and in ASR and to identify provisional quantitative trait loci (QTLs) modulating these phenotypes. Significant between-strain differences in ASR and in PPI at each of several prepulse intensities (75, 80, 85, 90, 95 dB) were found. Correlations between PPI at the various prepulse intensities were highly significant, suggesting appreciable overlap in genetic regulation of PPI across prepulse intensities. Five QTLs (chromosomes 3, 5, 7, 16) associated with PPI across all prepulse intensities, but not with ASR, were identified. Two additional QTLs (chromosomes 2, 11) associated with both PPI and ASR were found. Fifteen QTLs were associated with ASR alone. Data on genotypes of informative congenic strains were used to support probable involvement of loci modulating PPI and to narrow the probable chromosomal location of QTLs. If confirmed, these QTLs may suggest candidate genes directing novel mechanisms for regulation of PPI