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Neurobiological factors contributing to violence in humans remain poorly understood. One approach to this question is examining allelic variation in the X-linked monoamine oxidase A ( MAOA ) gene, previously associated with impulsive aggression in animals and humans. Here, we have studied the impact of a common functional polymorphism in MAOA on brain structure and function assessed with MRI in a large sample of healthy human volunteers. We show that the low expression variant, associated with increased risk of violent behavior, predicted pronounced limbic volume reductions and hyperresponsive amygdala during emotional arousal, with diminished reactivity of regulatory prefrontal regions, compared with the high expression allele. In men, the low expression allele is also associated with changes in orbitofrontal volume, amygdala and hippocampus hyperreactivity during aversive recall, and impaired cingulate activation during cognitive inhibition. Our data identify differences in limbic circuitry for emotion regulation and cognitive control that may be involved in the association of MAOA with impulsive aggression, suggest neural systems-level effects of X-inactivation in human brain, and point toward potential targets for a biological approach toward violence.

Numerous neuroimaging studies have examined the function of the dorsolateral prefrontal cortex in schizophrenia; although abnormalities usually are identified, it is unclear why some studies find too little activation and others too much. The authors' goal was to explore this phenomenon.They used the N-back working memory task and functional magnetic resonance imaging at 3 T to examine a group of 14 patients with schizophrenia and a matched comparison group of 14 healthy subjects.Patients' performance was significantly worse on the two-back working memory task than that of healthy subjects. However, there were areas within the dorsolateral prefrontal cortex of the patients that were more active and areas that were less active than those of the healthy subjects. When the groups were subdivided on the basis of performance on the working memory task into healthy subjects and patients with high or low performance, locales of greater prefrontal activation and locales of less activation were found in the high-performing patients but only locales of underactivation were found in the low-performing patients.These findings suggest that patients with schizophrenia whose performance on the N-back working memory task is similar to that of healthy comparison subjects use greater prefrontal resources but achieve lower accuracy (i.e., inefficiency) and that other patients with schizophrenia fail to sustain the prefrontal network that processes the information, achieving even lower accuracy as a result. These findings add to other evidence that abnormalities of prefrontal cortical function in schizophrenia are not reducible to simply too much or too little activity but, rather, reflect a compromised neural strategy for handling information mediated by the dorsolateral prefrontal cortex.

Objective: The identification of neurobiological intermediate phenotypes may hasten the search for susceptibility genes in complex psychiatric disorders such as schizophrenia. Earlier family studies have suggested that deficits in executive cognition and working memory may be related to genetic susceptibility for schizophrenia, but the biological basis for this behavioral phenotype has not been identified. Method: The authors used functional magnetic resonance imaging (fMRI) during performance of the N-back working memory task to assess working memoryrelated cortical physiology in nonschizophrenic, cognitively intact siblings of patients with schizophrenia. They compared 23 unaffected siblings of schizophrenic patients to 18 matched comparison subjects. As a planned replication, they studied another 25 unaffected siblings and 15 comparison subjects. Results: In both cohorts, there were no group differences in working memory performance. Nevertheless, both groups of siblings showed an exaggerated physiological response in the right dorsolateral prefrontal cortex that was qualitatively similar to results of earlier fMRI studies of patients with schizophrenia. Conclusions: These fMRI data provide direct evidence of a primary physiological abnormality in dorsolateral prefrontal cortex function in individuals at greater genetic risk for schizophrenia, even in the absence of a manifest cognitive abnormality. This exaggerated fMRI response implicates inefficient processing of memory information at the level of intrinsic prefrontal circuitry, similar to earlier findings in patients with schizophrenia. These data predict that inheritance of alleles that contribute to inefficient prefrontal information processing will increase risk for schizophrenia.

OBJECTIVE: Childhood onset of “adult” psychiatric disorders may be caused, in part, by more salient genetic risk. In this study, the rates of schizophrenia spectrum disorders among parents of patients with childhood-onset and adult-onset schizophrenia and parents of community comparison subjects were compared. METHOD: To assess the presence of axis I and axis II disorders associated with schizophrenia, parents of patients with childhood-onset schizophrenia (95 parents), patients with adult-onset schizophrenia (86 parents), and community comparison subjects (123 parents) were interviewed directly by using semistructured instruments. Information on 19 additional parents (parents of childhood-onset patients, N=2; parents of adult-onset patients, N=11; parents of community comparison subjects, N=6) was obtained by using a family history interview with the same instruments. Transcribed interviews were scored by a rater blind to group membership, and the morbid risks for schizophrenia spectrum disorders in the ...

Postmortem studies have implicated the central muscarinic acetylcholine system in schizophrenia. However, central muscarinic receptor availability has not previously been studied in vivo. Using [I-123]iodoquinuclidinyl benzilate ([(123)I]IQNB) single photon emission computed tomography (SPECT), the authors sought to compare the muscarinic receptor availability in vivo in unmedicated patients with schizophrenia and normal subjects.Twelve medication-free patients with schizophrenia underwent an [(123)I]IQNB SPECT scan during approximate-equilibrium conditions. A group of 10 age- and gender-matched normal comparison subjects were given the same kind of scan under similar conditions. Regions of interest were analyzed in the cortex, basal ganglia, thalamus, and pons. Binding data were analyzed as nCi/ml tissue per mCi injected dose.Muscarinic receptor availability was significantly less in patients with schizophrenia than in normal subjects in all regions of interest except the pons. Reductions ranged from -33% in the caudate to -20% in the occipital cortex. Positive symptoms of schizophrenia correlated negatively with muscarinic receptor availability in the striatum and the frontal cortex.These results indicate a reduction in muscarinic acetylcholine receptor availability in vivo in unmedicated patients with schizophrenia, confirming results from postmortem studies and adding further evidence that the muscarinic system is involved in the pathophysiology of schizophrenia.

Objective: Disturbed neuronal interactions may be involved in schizophrenia because it is without clear regional pathology. Aberrant connectivity is further suggested by theoretical formulations and neurochemical and neuroanatomical data. The authors applied to schizophrenia a recently available functional neuroimaging analytic method that permits characterization of cooperative action on the systems level. Method: Thirteen medication-free patients and 13 matched healthy comparison subjects performed a working memory (n-back) task and sensorimotor baseline task during positron emission tomography. “Functional connectivity” patterns, reflecting distributed correlated activity that differed most between groups, were extracted by a canonical variates analysis. Results: More than half the variance was explained by a single pattern showing inferotemporal, (para-)hippocampal, and cerebellar loadings for patients versus dorsolateral prefrontal and anterior cingulate activity for comparison subjects. Expression of this pattern perfectly separated all patient scans from comparison scans, thus showing promise as a trait marker. This result was validated prospectively by successfully classifying unrelated scans from the same patients and data from a new cohort. An additional 19% of variance corresponded to the pattern activated by the working memory task. Expression of this pattern was more variable in patients during working memory but not the control condition, suggesting inability to sustain a task-adequate neural network, consistent with the disconnection hypothesis. Conclusions: Pronounced disruptions of distributed cooperative activity in schizophrenia were found. A pattern showing disturbed frontotemporal interactions showed promise as a trait marker and may be useful for future investigations.

First-degree relatives of patients with schizophrenia appear to have subtle neurological signs, suggesting that these measures could serve as intermediate phenotypes in genetic studies of schizophrenia. The strength of a possible genetic component is unknown, however, leaving it uncertain whether such traits could increase the power to find schizophrenia susceptibility loci. The authors' goal was to investigate the strength of this possible genetic component.They estimated the relative risk of neurological impairments in a large group of siblings of patients with schizophrenia. Two standard neurological scales (the Neurological Evaluation Scale and the Woods Scale) were used to examine 115 patients, 185 of their siblings, and 88 normal comparison subjects.There were significant differences between the siblings of patients with schizophrenia and the normal comparison subjects only on the Woods Scale. Relative risk of neurological impairment was significantly increased in the sibling group, but the significance was weak to moderate. Neurological impairment was not redundant with several other intermediate phenotypic measures based on cognitive impairment.These data suggest that neurological signs cluster in patients with schizophrenia and their families and could possibly identify a unique component of genetic variance for risk of schizophrenia. However, the fairly low relative risk and the uncertain pathophysiology of such signs may limit their usefulness.

Certain cognitive, behavioral, and emotional deficits (so-called negative symptoms) in patients with schizophrenia have often been attributed to prefrontal cortical pathology, but direct evidence for a relationship between prefrontal neuronal pathology and negative symptoms has been lacking. The authors hypothesized that an in vivo measure of prefrontal neuronal pathology (N:-acetylaspartate [NAA] levels) in patients with schizophrenia would predict negative symptoms.Proton magnetic resonance spectroscopic imaging ((1)H-MRSI) and rating scales for negative and positive symptoms were used to study 36 patients with schizophrenia. Magnetic resonance spectra were analyzed as metabolite ratios, and parametric correlations were performed.A regionally selective negative correlation was found between prefrontal NAA-creatine ratio and negative symptom ratings in this group of patients with schizophrenia.Lower prefrontal NAA-and by inference greater neuronal pathology-predicted more severe negative symptoms in patients with schizophrenia. These data demonstrate a relationship between an intraneuronal measure of dorsolateral prefrontal cortex integrity and negative symptoms in vivo and represent further evidence for the involvement of the dorsolateral prefrontal cortex in negative symptoms associated with schizophrenia.

Impaired attention has frequently been observed in studies of unaffected siblings of patients with schizophrenia. To assess the suitability of impaired attention for use as an intermediate phenotype in genetic studies, the authors estimated the relative risk of impaired attention in a large group of siblings.The authors used the Continuous Performance Test, 1-9 version, with and without a distraction condition, to study 147 patients with schizophrenia, 193 of their siblings, and 47 normal comparison subjects. Relative risk (l) was estimated by using cutoff scores that were one, two, and three standard deviations below the mean sensitivity index value (d cent) of the normal comparison group in both Continuous Performance Test conditions.Patients but not their siblings performed worse than the normal comparison subjects in both conditions. Fifty percent of the patients, 24% of their siblings, and 18% of the normal comparison subjects scored one standard deviation below the mean score of the comparison group for the more difficult distraction version of the Continuous Performance Test. The patients with Continuous Performance Test scores one standard deviation below the mean score of the comparison group had a total of 97 siblings. Compared with the comparison group, this subgroup of siblings had significantly lower Continuous Performance Test scores. Relative risk was also significantly higher for the siblings of patients whose scores were one standard deviation (l=2. 1) and two standard deviations (l=3.3) below the mean of comparison subjects. Attempts to assess ascertainment bias suggest that this may be an underestimate.Poor performance on the Continuous Performance Test appears to be familial and, possibly, genetic. Relative risk estimates were in the moderate range. Given the ease of administering the Continuous Performance Test, the use of impaired attention as an intermediate phenotype could increase the power of genetic studies of schizophrenia.