Corpus callosum shape and morphology in youth across the psychosis Spectrum.

The corpus callosum is the largest white matter tract in the human brain connecting and coordinating homologous regions of the right and left hemispheres and has been strongly implicated in the pathogenesis of psychosis. We investigated corpus callosum morphology in a large community cohort of 917 individuals (aged 8-21), including 267 endorsing subsyndromal or threshold psychotic symptoms (207 on the psychosis spectrum and 60 with limited psychosis based on previously published criteria) and 650 non-psychotic volunteers. We used a highly reliable and previously published algorithm to automatically identify the midsagittal plane and to align the corpus callosum along the anterior and posterior commissures for segmentation, thereby eliminating these sources of error variance in dependent measures, which included perimeter, length, mean thickness and shape (circularity). The parcellation scheme divided the corpus callosum into 7 subregions that consisted of the rostrum, genu, rostral body, anterior midbody, posterior midbody, isthmus, and splenium. Both individuals endorsing psychotic symptoms and those with limited psychosis had significantly (p<.05) smaller area and lower thickness measures compared to healthy volunteers, but did not differ significantly from each other. Findings were relatively widespread indicating a relatively global effect not circumscribed to any particular corpus callosum subregion. These data are consistent with the hypothesis that corpus callosum abnormalities may be evident early in the course of illness and predate the onset of frank psychosis. Given that these measures can be easily obtained and are highly reliable they may assist in the identification of individuals at future risk for psychosis.

Greater extracellular free-water in first-episode psychosis predicts better neurocognitive functioning.

Free Water Imaging is a novel diffusion magnetic resonance (MR) imaging method that is able to separate changes affecting the extracellular space from those that reflect changes in neuronal cells and processes. A previous Free Water Imaging study in schizophrenia identified significantly greater extracellular water volume in the early stages of the disorder; however, its clinical and functional sequelae have not yet been investigated. Here, we applied Free Water Imaging to a larger cohort of 63 first-episode patients with psychosis and 70 healthy matched controls to better understand the functional significance of greater extracellular water. We used diffusion MR imaging data and the Tract-Based Spatial Statistics analytic pipeline to first analyze fractional anisotropy (FA), the most commonly employed metric for assessing white matter. This comparison was then followed by Free Water Imaging analysis, where two parameters, the fractional volume of extracellular free-water (FW) and cellular tissue FA (FA-t), were estimated and compared across the entire white matter skeleton between groups, and correlated with cognitive measures at baseline and following 12 weeks of antipsychotic treatment. Our results indicated lower FA across the whole brain in patients compared with healthy controls that overlap with significant increases in FW, with only limited decreases in FA-t. In addition, higher FW correlated with better neurocognitive functioning following 12 weeks of antipsychotic treatment. We believe this is the first study to suggest that an extracellular water increase during the first-episode of psychosis, which may be indicative of an acute neuroinflammatory process, and/or cerebral edema may predict better functional outcome.

A phenome-wide examination of neural and cognitive function.

This data descriptor outlines a shared neuroimaging dataset from the UCLA Consortium for Neuropsychiatric Phenomics, which focused on understanding the dimensional structure of memory and cognitive control (response inhibition) functions in both healthy individuals (130 subjects) and individuals with neuropsychiatric disorders including schizophrenia (50 subjects), bipolar disorder (49 subjects), and attention deficit/hyperactivity disorder (43 subjects). The dataset includes an extensive set of task-based fMRI assessments, resting fMRI, structural MRI, and high angular resolution diffusion MRI. The dataset is shared through the OpenfMRI project, and is formatted according to the Brain Imaging Data Structure (BIDS) standard.

The relationship between temperament and character and psychotic-like experiences in healthy children and adolescents.

BACKGROUND: Prior work by our group identified personality profiles associated with psychotic-like experiences (PLE's) in healthy adults that were strikingly similar to those found in schizophrenia patients, with the exception of two key differences. Specifically, higher levels of PLE's were linked to higher persistence and cooperativeness, suggesting that these characteristics might represent personality-based resilience factors. Notably, age and personality were significantly correlated in these data, raising questions about whether healthy children and adolescents would show similar results. To date, no study has examined personality profiles associated with both positive and negative PLE's in healthy children and adolescents using Cloninger's Temperament and Character Inventory (TCI). Thus, this study examined the relationship between TCI dimensions and PLE's in healthy children and adolescents. METHOD: The TCI and the Community Assessment of Psychic Experiences (CAPE) were administered to 123 healthy children and adolescents aged 8-18. Multiple regression models were used to examine personality dimensions associated with overall severity of PLE's as well as severity of positive and negative PLE's separately. RESULTS: Positive, negative, and overall PLE severity were all associated with a personality pattern of higher harm avoidance and lower self-directedness. Negative PLE severity was also associated with lower persistence. CONCLUSIONS: Personality correlates of PLE's in healthy children and adolescents were largely consistent with our past work on PLE's in healthy adults. However, our previously identified resilience factors were notably absent in this sample. These findings may suggest that these personality characteristics have not yet crystallized or emerged to aid in coping with PLE's.

Recognition deficits in mice carrying mutations of genes encoding BLOC-1 subunits pallidin or dysbindin.

Numerous studies have implicated DTNBP1, the gene encoding dystrobrevin-binding protein or dysbindin, as a candidate risk gene for schizophrenia, though this relationship remains somewhat controversial. Variation in dysbindin, and its location on chromosome 6p, has been associated with cognitive processes, including those relying on a complex system of glutamatergic and dopaminergic interactions. Dysbindin is one of the seven protein subunits that comprise the biogenesis of lysosome-related organelles complex 1 (BLOC-1). Dysbindin protein levels are lower in mice with null mutations in pallidin, another gene in the BLOC-1, and pallidin levels are lower in mice with null mutations in the dysbindin gene, suggesting that multiple subunit proteins must be present to form a functional oligomeric complex. Furthermore, pallidin and dysbindin have similar distribution patterns in a mouse and human brain. Here, we investigated whether the apparent correspondence of pallid and dysbindin at the level of gene expression is also found at the level of behavior. Hypothesizing a mutation leading to underexpression of either of these proteins should show similar phenotypic effects, we studied recognition memory in both strains using the novel object recognition task (NORT) and social novelty recognition task (SNRT). We found that mice with a null mutation in either gene are impaired on SNRT and NORT when compared with wild-type controls. These results support the conclusion that deficits consistent with recognition memory impairment, a cognitive function that is impaired in schizophrenia, result from either pallidin or dysbindin mutations, possibly through degradation of BLOC-1 expression and/or function.

Neural substrates of inhibitory control deficits in 22q11.2 deletion syndrome.

22q11.2 deletion syndrome (22q11DS) is associated with elevated levels of impulsivity, inattention, and distractibility, which may be related to underlying neurobiological dysfunction due to haploinsufficiency for genes involved in dopaminergic neurotransmission (i.e. catechol-O-methyltransferase). The Stop-signal task has been employed to probe the neural circuitry involved in response inhibition (RI); findings in healthy individuals indicate that a fronto-basal ganglia network underlies successful inhibition of a prepotent motor response. However, little is known about the neurobiological substrates of RI difficulties in 22q11DS. Here, we investigated this using functional magnetic resonance imaging while 45 adult participants (15 22q11DS patients, 30 matched controls) performed the Stop-signal task. Healthy controls showed significantly greater activation than 22q11DS patients within frontal cortical and basal ganglia regions during successful RI, whereas 22q11DS patients did not show increased neural activity relative to controls in any regions. Using the Barratt Impulsivity Scale, we also investigated whether neural dysfunction during RI was associated with cognitive impulsivity in 22q11DS patients. RI-related activity within left middle frontal gyrus and basal ganglia was associated with severity of self-reported cognitive impulsivity. These results suggest reduced engagement of RI-related brain regions in 22q11DS patients, which may be relevant to characteristic behavioral manifestations of the disorder.

A schizophrenia risk gene, ZNF804A, is associated with brain white matter microstructure.

Genome-wide association studies have provided strong evidence for association of the SNP rs1344706 in the ZNF804A gene with schizophrenia and bipolar disorder. Neuroimaging studies have suggested that variation at rs1344706 may be associated with neural endophenotypes such as white matter volumes and densities. However, analyses of white matter microstructure using diffusion tensor imaging (DTI) have produced conflicting results. We examined the association between rs1344706 and white matter microstructure in 107 healthy individuals using tract-based spatial statistics (TBSS). TBSS analysis showed significant association between the risk allele and lower fractional anisotropy in the corpus callosum, left forceps minor, and right parietal white matter (p<.05; FWE corrected). Post-hoc analyses indicated that this association was largely driven by alterations in radial diffusivity, consistent with an effect of genotype on myelination. In light of the strong DTI evidence for white matter microstructural abnormalities in schizophrenia, the current results implicate a potential mechanism for schizophrenia risk formation by ZNF804A rs1344706 genotype.

Disrupted working memory circuitry and psychotic symptoms in 22q11.2 deletion syndrome.

22q11.2 deletion syndrome (22q11DS) is a recurrent genetic mutation that is highly penetrant for psychosis. Behavioral research suggests that 22q11DS patients exhibit a characteristic neurocognitive phenotype that includes differential impairment in spatial working memory (WM). Notably, spatial WM has also been proposed as an endophenotype for idiopathic psychotic disorder, yet little is known about the neurobiological substrates of WM in 22q11DS. In order to investigate the neural systems engaged during spatial WM in 22q11DS patients, we collected functional magnetic resonance imaging (fMRI) data while 41 participants (16 22q11DS patients, 25 demographically matched controls) performed a spatial capacity WM task that included manipulations of delay length and load level. Relative to controls, 22q11DS patients showed reduced neural activation during task performance in the intraparietal sulcus (IPS) and superior frontal sulcus (SFS). In addition, the typical increases in neural activity within spatial WM-relevant regions with greater memory load were not observed in 22q11DS. We further investigated whether neural dysfunction during WM was associated with behavioral WM performance, assessed via the University of Maryland letter-number sequencing (LNS) task, and positive psychotic symptoms, assessed via the Structured Interview for Prodromal Syndromes (SIPS), in 22q11DS patients. WM load activity within IPS and SFS was positively correlated with LNS task performance; moreover, WM load activity within IPS was inversely correlated with the severity of unusual thought content and delusional ideas, indicating that decreased recruitment of working memory-associated neural circuitry is associated with more severe positive symptoms. These results suggest that 22q11DS patients show reduced neural recruitment of brain regions critical for spatial WM function, which may be related to characteristic behavioral manifestations of the disorder.

Effects of acute cortisol and cocaine administration on attention, recall and recognition task performance in individuals with cocaine dependence.

This study investigated the effects of acute cocaine administration on cognition, and whether these can be modeled using exogenous hydrocortisone, because cocaine-induced cortisol elevations may influence its cognitive effects. Twelve cocaine-dependent individuals received an intravenous bolus of cortisol (0.5 or 0.2 mg/kg) and cocaine (0.2 mg/kg) in a double-blind randomized placebo-controlled and counterbalanced fashion. Cognitive testing included verbal tasks of vigilance attention, free recall and recognition memory before the boluses and at 20, 60 and 100 min thereafter. The statistical analysis investigated dose response effects while accounting for all sources of variance in the design. No effects of low dose cocaine were found on any variables. Low dose cortisol enhanced and high dose impaired vigilance attention, and a trend was found for the same dose response profile on twice-heard words. An opposite trend, inconsistent with prior research on cortisol and cognition, was observed for recognition: low dose impaired and high dose enhanced recognition of once-heard words, and a very weak trend was found for recognition of new words. These findings, though tempered by design limitations, suggest a complex non-linear cortisol attention/recognition dose-response relationship and call for further research to elucidate cortisol's effects on cognition and their role in the pathophysiology of cocaine dependence.

Gender differences in cocaine craving among non-treatment-seeking individuals with cocaine dependence.

The purpose of this pilot study was to evaluate potential gender differences in cocaine craving among non-treatment seekers with cocaine dependence. We examined 10 female and 11 male individuals matched by demographic characteristics and severity of drug use; we used a multidimensional questionnaire that assesses various aspects of craving: (a) current intensity, (b) projected intensity, (c) resistance to use cocaine, (d) responsiveness to drug-related conditioned stimuli, and (e) imagined likelihood of use if in a setting with access to drugs. Other instruments utilized were the Hamilton Rating Scale for Depression and Addiction Severity Index. Female subjects had higher total craving scores (p < .05), with post hoc tests showing more present desire to use cocaine and responsivity to drug-conditioned stimuli, along with lower scores on the desire not to use cocaine. In exploratory analyses, we found greater depressive symptomatology (p = .02) and severity of family/social problems (p = .02) in females than their males counterparts. These results suggest that gender may influence different aspects of cocaine craving. As estrogen is purported to modulate craving-related dopaminergic systems, further studies will be needed to confirm these observed gender differences and to investigate their possible mechanisms, particularly estrogen-dopamine interactions and their effect on craving and mood.