Increased basal ganglia volumes in velo-cardio-facial syndrome (deletion 22q11.2)

Neuroanatomical Correlates of Cognitive Dysfunction in 22q11.2 Deletion Syndrome

22q11.2 Deletion Syndrome (22q11.2DS), the most common chromosomal microdeletion, presents as a heterogeneous phenotype characterized by an array of anatomical, behavioral, and cognitive abnormalities. Individuals with 22q11.2DS exhibit extensive cognitive deficits, both in overall intellectual capacity and focal challenges in executive functioning, attentional control, perceptual abilities, motor skills, verbal processing, as well as socioemotional operations. Heterogeneity is an intrinsic factor of the deletion's clinical manifestation in these cognitive domains. Structural imaging has identified significant changes in volume, thickness, and surface area. These alterations are closely linked and display region-specific variations with an overall increase in abnormalities following a rostral-caudal gradient. Despite the extensive literature developing around the neurocognitive and neuroanatomical profiles associated with 22q11.2DS, comparatively little research has addressed specific structure-function relationships between aberrant morphological features and deficient cognitive processes. The current review attempts to categorize these limited findings alongside comparisons to populations with phenotypic and structural similarities in order to answer to what degree structural findings can explain the characteristic neurocognitive deficits seen in individuals with 22q11.2DS. In integrating findings from structural neuroimaging and cognitive assessments, this review seeks to characterize structural changes associated with the broad neurocognitive challenges faced by individuals with 22q11.2DS.

Neuroimaging Phenotypes Associated With Risk and Resilience for Psychosis and Autism Spectrum Disorders in 22q11.2 Microdeletion Syndrome

Identification of biological risk factors that contribute to the development of complex neuropsychiatric disorders such as psychosis and autism spectrum disorder (ASD) is key for early intervention and detection. Furthermore, parsing the biological heterogeneity associated with these neuropsychiatric syndromes will help us understand the neural mechanisms underlying psychiatric symptom development. The 22q11.2 microdeletion syndrome (22q11DS) is caused by a recurrent genetic mutation that carries significantly increased risk for developing psychosis and/or ASD. In this review, I provide an brief introduction to 22q11DS and discuss common phenotyping strategies that are used to assess psychosis and ASD in this population. I then summarize neuroimaging phenotypes associated with psychosis and ASD in 22q11.DS. Next, I discuss challenges within the field and provide practical suggestions to overcome these obstacles. Finally, I discuss future directions for moving 22q11DS risk and resilience research forward.

Impact of Cranial Base Abnormalities on Cerebellar Volume and the Velopharynx in 22q11.2 Deletion Syndrome

OBJECTIVE

The purpose of this study was to analyze the relationship between cranial base, cerebellar, craniofacial, and velopharyngeal (VP) variables in individuals with 22q11.2 deletion syndrome (22q11DS).

METHODS

Thirteen typically developing healthy children and 13 age- and sex-matched individuals with 22q11DS completed a magnetic resonance imaging scan, which was used to examine craniofacial and VP variables.

RESULTS

A statistically significant difference was noted in cerebellum volumes, F_1,24 = 7.947, P = .010, posterior nasal spine to posterior pharyngeal wall (PNS-PPW), F_1,24 = 4.878, P = .037, nasion-sella-basion (NSB) cranial base angles, F_1,24 = 7.253, P = .013, and sella-basion-opisthion (SBO) cranial base angles, F_1,24 = 9.134, P = .006, between children with 22q11DS and controls. The cerebellum volume was significantly reduced and cranial base angles were significantly more obtuse in individuals with 22q11DS. In the 22q11DS group, cerebellum volume was significantly correlated with sella-basion (SB) length, osseous pharyngeal depth, the PNS-PPW length, and velar length (P < .05). The PNS-PPW length was correlated with SB length, basion-opisthion length, NSB angle, SBO angle, and the VP ratio (P < .05).

CONCLUSION

This study supports previous findings on anatomical differences among individuals with 22q11DS and has expanded our current understanding of the potential relationship between craniofacial and VP variables in at least a subset of children with 22q11DS. Results provide preliminary insights into the potential relationship between a decrease in cerebellar volume, obtuse cranial base angles, and unfavorable VP dimensions.

Nosology and Phenomenology of Psychosis in Movement Disorders

Background

Psychotic symptoms, such as delusions and hallucinations, are part of the clinical picture of several conditions presenting movement disorders. Phenomenology and epidemiology of psychosis in Parkinson's disease have received wide attention; however, the presence of psychosis in other movement disorders is, comparatively, less well known.

Objectives

To review psychotic symptoms present in different movement disorders.

Methods

A comprehensive and structured literature search was performed to identify and analyze data on patients with movement disorders and comorbid psychosis.

Results

In monogenic parkinsonisms, such as PARK-GBA, PARK-LRRK2, and PARK-SNCA, visual hallucinations related to dopamine replacement therapy are frequent as well as are delusions in PARK-LRRK2 and PARK-SNCA, but not in PARK-GBA. Different types of delusions and hallucinations are found in Huntington's disease and other choreic disorders. In Tourette's syndrome, paranoid delusions as well as visual, olfactory, and auditory hallucinations have been described, which usually develop after an average of 10 years of disease. Delusions in ataxias are more frequent in ATX-TBP, ATX-ATN1, and ATX-ATXN3, whereas it is rare in Friedreich's ataxia. Psychosis is also a prominent and frequent clinical feature in Fahr's disease, Wilson's disease, neurodegeneration with brain iron accumulation, and some lysosomal storage disorders, whereas it is uncommon in atypical parkinsonisms and dystonia. Psychosis usually occurs at late disease stages, but may appear as onset symptoms of the disease, especially in Wilson's disease, Huntington's disease, late-onset Tays-Sachs, and Niemann-Pick.

Conclusion

Psychosis is a frequent comorbidity in most hyper- and hypokinetic movement disorders. Appropriate recognition is relevant both in the early and late disease stages.

Magnitude and heterogeneity of brain structural abnormalities in 22q11.2 deletion syndrome: a meta-analysis

The 22q11.2 deletion syndrome (22q11.2DS) is a neurodevelopmental disorder associated with a number of volumetric brain abnormalities. The syndrome is also associated with an increased risk for neuropsychiatric disorders including schizophrenia and autism spectrum disorder. An earlier meta-analysis showed reduced grey and white matter volumes in individuals with 22q11.2DS. Since this analysis was conducted, the number of studies has increased markedly, permitting more precise estimates of effects and more regions to be examined. Although 22q11.2DS is clinically heterogeneous, it is not known to what extent this heterogeneity is mirrored in neuroanatomy. The aim of this study was thus to investigate differences in mean brain volume and structural variability within regions, between 22q11.2DS and typically developing controls. We examined studies that reported measures of brain volume using MRI in PubMed, Web of Science, Scopus and PsycINFO from inception to 1 May 2019. Data were extracted from studies in order to calculate effect sizes representing case-control difference in mean volume, and in the variability of volume (as measured using the log variability ratio (lnVR) and coefficient of variation ratio (CVR)). We found significant overall decreases in mean volume in 22q11.2DS compared with control for: total brain (g = -0.96; p < 0.001); total grey matter (g = -0.81, p < 0.001); and total white matter (g = -0.81; p < 0.001). There was also a significant overall reduction of mean volume in 22q11.2DS subjects compared with controls in frontal lobe (g = -0.47; p < 0.001), temporal lobe (g = -0.84; p < 0.001), parietal lobe (g = -0.73; p = 0.053), cerebellum (g = -1.25; p < 0.001) and hippocampus (g = -0.90; p < 0.001). Significantly increased variability in 22q11.2DS individuals compared with controls was found only for the hippocampus (VR, 1.14; p = 0.036; CVR, 1.30; p < 0.001), and lateral ventricles (VR, 1.56; p = 0.004). The results support the notion that structural abnormalities in 22q11.2DS and schizophrenia are convergent, and also to some degree with findings in autism spectrum disorder. Finally, the increased variability seen in the hippocampus in 22q11.2DS may underlie some of the heterogeneity observed in the neuropsychiatric phenotype.

Attentional functioning in individuals with 22q11 deletion syndrome: insight from ERPs

The 22q11 deletion syndrome (22q11DS), or DiGeorge syndrome (DG), is one of the most common genetic deletion syndromes. DG also carries a high risk for psychiatric disorders, with learning disabilities frequently being reported. Impairments in specific cognitive domains, such as executive functioning and attention, have also been described. The aim of this study was to investigate attentional functioning in a group of subjects with DG using ERPs, and in particular the P300 and CNV components. We studied ten patients with DG and ten healthy subjects that performed a P300 Novelty task and a CNV motor task. P3b amplitude was significantly lower in patients than in controls, while P3b latency was comparable in patients and controls. The P3a parameters were similar in both groups. All CNV amplitudes were significantly lower in DG patients than in controls. DG patients displayed slower reaction times in the CNV motor task than healthy subjects. These results point to a cognitive dysfunction related above all to executive attentional processing in DG patients. In particular, a specific difficulty emerged in selective attention and in the ability to orient and to sustain the anticipatory attention required for an executive motor response.

Developmental coordination disorder, psychopathology and IQ in 22q11.2 deletion syndrome

BACKGROUND

22q11.2 deletion syndrome (22q11.2DS) is associated with high rates of neurodevelopmental disorder, however, the links between developmental coordination disorder (DCD), intellectual function and psychiatric disorder remain unexplored. Aims To establish the prevalence of indicative DCD in children with 22q11.2DS and examine associations with IQ, neurocognition and psychopathology.

METHOD

Neurocognitive assessments and psychiatric interviews of 70 children with 22q11.2DS (mean age 11.2, s.d. = 2.2) and 32 control siblings (mean age 11.5, s.d. = 2.1) were carried out in their homes. Nine children with 22q11.2DS and indicative DCD were subsequently assessed in an occupational therapy clinic.

RESULTS

Indicative DCD was found in 57 (81.4%) children with 22q11.2DS compared with 2 (6.3%) control siblings (odds ratio (OR) = 36.7, P < 0.001). Eight of nine (89%) children with indicative DCD met DSM-5 criteria for DCD. Poorer coordination was associated with increased numbers of anxiety, (P < 0.001), attention-deficit hyperactivity disorder (ADHD) (P < 0.001) and autism-spectrum disorder (ASD) symptoms (P < 0.001) in children with 22q11.2DS. Furthermore, 100% of children with 22q11.2DS and ADHD had indicative DCD (20 of 20), as did 90% of children with anxiety disorder (17 of 19) and 96% of children who screened positive for ASD (22 of 23). The Developmental Coordination Disorder Questionnaire score was related to sustained attention (P = 0.006), even after history of epileptic fits (P = 0.006) and heart problems (P = 0.009) was taken into account.

CONCLUSIONS

Clinicians should be aware of the high risk of coordination difficulties in children with 22q11.2DS and its association with risk of mental disorder and specific neurocognitive deficits. Declaration of interest None.

A supramodal role of the basal ganglia in memory and motor inhibition: Meta-analytic evidence

The ability to stop actions and thoughts is essential for goal-directed behaviour. Neuroimaging research has revealed that stopping actions and thoughts engage similar cortical mechanisms, including the ventro- and dorso-lateral prefrontal cortex. However, whether and how these abilities require similar subcortical mechanisms remains unexplored. Specifically of interest are the basal ganglia, subcortical structures long-known for their motor functions, but less so for their role in cognition. To investigate the potential common mechanisms in the basal ganglia underlying action and thought stopping, we conducted meta-analyses using fMRI data from the Go/No-Go, Stop-signal, and Think/No-Think tasks. All three tasks require active stopping of prepotent actions or thoughts. To localise basal ganglia activations, we performed high-resolution manual segmentations of striatal subregions. We found that all three tasks recovered clusters in the basal ganglia, although the specific localisation of these clusters differed. Although the Go/No-Go and Stop-signal tasks are often interchangeably used for measuring action stopping, their cluster locations in the basal ganglia did not significantly overlap. These different localised clusters suggest that the Go/No-Go and Stop-signal tasks may recruit distinct basal ganglia stopping processes, and therefore should not be treated equivalently. More importantly, the basal ganglia cluster recovered from the Think/No-Think task largely co-localised with that from the Stop-signal task, but not the Go/No-Go task, possibly indicating that the Think/No-Think and Stop-signal tasks share a common striatal circuitry involved in the cancellation of unwanted thoughts and actions. The greater similarity of the Think/No-Think task to the Stop-Signal rather than Go/No-Go task also was echoed at the cortical level, which revealed highly overlapping and largely right lateralized set of regions including the anterior DLPFC, VLPFC, Pre-SMA and ACC. Overall, we provide novel evidence suggesting not only that the basal ganglia are critical for thought stopping, but also that they are involved in specific stopping subprocesses that can be engaged by tasks in different domains. These findings raise the possibility that the basal ganglia may be part of a supramodal network responsible for stopping unwanted processes more broadly.

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Stopping actions and thoughts both consistently activate the basal ganglia.

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Action prevention and action cancellation engage distinct basal ganglia processes.

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Thought stopping co-localises with action cancellation, but not prevention.

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Basal ganglia may support a supramodal process cancellation mechanism.

Neuroradiographic findings in 22q11.2 deletion syndrome

22q11.2 deletion syndrome (22q11.2DS) is a common genetic disorder with enormous phenotypic heterogeneity. Despite the established prevalence of developmental and neuropsychiatric issues in this syndrome, its neuroanatomical correlates are not as well understood. A retrospective chart review was performed on 111 patients diagnosed with 22q11.2DS. Of the 111 patients, 24 with genetically confirmed 22q11.2 deletion and brain MRI or MRA were included in this study. The most common indications for imaging were unexplained developmental delay (6/24), seizures of unknown etiology (5/24), and unilateral weakness (3/24). More than half (13/24) of the patients had significant radiographic findings, including persistent cavum septi pellucidi and/or cavum vergae (8/24), aberrant cortical veins (6/24), polymicrogyria or cortical dysplasia (4/24), inner ear deformities (3/24), hypoplastic internal carotid artery (2/24), and hypoplastic cerebellum (1/24). These findings reveal the types and frequencies of brain malformations in this case series, and suggest that the prevalence of neuroanatomical abnormalities in 22q11.2DS may be underestimated. Understanding indications for imaging and frequently encountered brain malformations will result in early diagnosis and intervention in an effort to optimize patient outcomes.

Categorical versus dimensional approaches to autism-associated intermediate phenotypes in 22q11.2 microdeletion syndrome

BACKGROUND

22q11.2 Microdeletion syndrome (22q11DS) is associated with elevated rates of autism spectrum disorders (ASDs), although the diagnosis is controversial. In order to determine whether there is a biological substrate of ASD in 22q11DS, we examined neurocognitive and structural neuroanatomic differences between those with 22q11DS and an ASD diagnosis (22q11DS-ASD+) and those with 22q11DS without ASD (22q11DS-ASD-); we then determined whether these differences were better characterized within a categorical or dimensional framework.

METHODS

We collected multiple neurocognitive measures and high-resolution T1-weighted scans on 116 individuals (29 22q11DS-ASD+, 32 22q11DS-ASD-, 55 typically developing controls) between 6 and 26 years of age. Measures of subcortical volume, cortical thickness (CT), and surface area were extracted using the FreeSurfer image analysis suite. Group differences in neurocognitive and neuroanatomic measures were assessed; regression analyses were then performed to determine whether a categorical or dimensional measure of ASD was a better predictor of neurocognitive impairment and/or neuroanatomic abnormalities observed in 22q11DS-ASD+.

RESULTS

In comparison to 22q11DS-ASD-, 22q11DS-ASD+ participants exhibited decreased bilateral hippocampal CT and decreased right amygdala volumes. Those with 22q11DS-ASD+ also showed slowed processing speed and impairments in visuospatial and facial memory. Neurocognitive impairments fit a dimensional model of ASD, whereas reductions in parahippocampal CT were best explained by a categorical measure of ASD.

CONCLUSIONS

A combination of categorical and dimensional measures of ASD may provide the most comprehensive understanding of ASDs in 22q11DS.

Facial emotion perception by intensity in children and adolescents with 22q11.2 deletion syndrome

Difficulties in the recognition of emotions in expressive faces have been reported in people with 22q11.2 deletion syndrome (22q11.2DS). However, while low-intensity expressive faces are frequent in everyday life, nothing is known about their ability to perceive facial emotions depending on the intensity of expression. Through a visual matching task, children and adolescents with 22q11.2DS as well as gender- and age-matched healthy participants were asked to categorise the emotion of a target face among six possible expressions. Static pictures of morphs between neutrality and expressions were used to parametrically manipulate the intensity of the target face. In comparison to healthy controls, results showed higher perception thresholds (i.e. a more intense expression is needed to perceive the emotion) and lower accuracy for the most expressive faces indicating reduced categorisation abilities in the 22q11.2DS group. The number of intrusions (i.e. each time an emotion is perceived as another one) and a more gradual perception performance indicated smooth boundaries between emotional categories. Correlational analyses with neuropsychological and clinical measures suggested that reduced visual skills may be associated with impaired categorisation of facial emotions. Overall, the present study indicates greater difficulties for children and adolescents with 22q11.2DS to perceive an emotion in low-intensity expressive faces. This disability is subtended by emotional categories that are not sharply organised. It also suggests that these difficulties may be associated with impaired visual cognition, a hallmark of the cognitive deficits observed in the syndrome. These data yield promising tracks for future experimental and clinical investigations.

The development of cognitive control in children with chromosome 22q11.2 deletion syndrome

Chromosome 22q11.2 Deletion Syndrome (22q11.2DS) is caused by the most common human microdeletion, and it is associated with cognitive impairments across many domains. While impairments in cognitive control have been described in children with 22q11.2DS, the nature and development of these impairments are not clear. Children with 22q11.2DS and typically developing children (TD) were tested on four well-validated tasks aimed at measuring specific foundational components of cognitive control: response inhibition, cognitive flexibility, and working memory. Molecular assays were also conducted in order to examine genotype of catechol-O-methyltransferase (COMT), a gene located within the deleted region in 22q11.2DS and hypothesized to play a role in cognitive control. Mixed model regression analyses were used to examine group differences, as well as age-related effects on cognitive control component processes in a cross-sectional analysis. Regression models with COMT genotype were also conducted in order to examine potential effects of the different variants of the gene. Response inhibition, cognitive flexibility, and working memory were impaired in children with 22q11.2DS relative to TD children, even after accounting for global intellectual functioning (as measured by full-scale IQ). When compared with TD individuals, children with 22q11.2DS demonstrated atypical age-related patterns of response inhibition and cognitive flexibility. Both groups demonstrated typical age-related associations with working memory. The results of this cross-sectional analysis suggest a specific aberration in the development of systems mediating response inhibition in a sub-set of children with 22q11.2DS. It will be important to follow up with longitudinal analyses to directly examine these developmental trajectories, and correlate neurocognitive variables with clinical and adaptive outcome measures.

Neuroanatomical phenotypes in a mouse model of the 22q11.2 microdeletion

Recurrent deletions at the 22q11.2 locus have been established as a strong genetic risk factor for the development of schizophrenia and cognitive dysfunction. Individuals with 22q11.2 deletions have a range of well-defined volumetric abnormalities in a number of critical brain structures. A mouse model of the 22q11.2 deletion (Df(16)A(+/-)) has previously been utilized to characterize disease-associated abnormalities on synaptic, cellular, neurocircuitry, and behavioral levels. We performed a high-resolution MRI analysis of mutant mice compared with wild-type littermates. Our analysis revealed a striking similarity in the specific volumetric changes of Df(16)A(+/-) mice compared with human 22q11.2 deletion carriers, including in cortico-cerebellar, cortico-striatal and cortico-limbic circuits. In addition, higher resolution magnetic resonance imaging compared with neuroimaging in human subjects allowed the detection of previously unknown subtle local differences. The cerebellar findings in Df(16)A(+/-) mice are particularly instructive as they are localized to specific areas within both the deep cerebellar nuclei and the cerebellar cortex. Our study indicates that the Df(16)A(+/-)mouse model recapitulates most of the hallmark neuroanatomical changes observed in 22q11.2 deletion carriers. Our findings will help guide the design and interpretation of additional complementary studies and thereby advance our understanding of the abnormal brain development underlying the emergence of 22q11.2 deletion-associated psychiatric and cognitive symptoms.

Hippocampal malrotation is associated with chromosome 22q11.2 microdeletion

BACKGROUND

Patients with chromosome 22q11.2 deletion syndrome (22q11DS) are at a seven fold increased risk of developing seizures. However, only a fraction of these patients exhibit structural abnormalities such as polymicrogyria (PMG) and periventricular nodular heterotopia (PNH) that are known to cause seizures and to be associated with 22q11DS. In this study we used a dedicated seizure imaging protocol to look for additional structural abnormalities in these individuals that may explain the elevated risk of seizure disorder in this patient group.

METHODS

Nineteen consecutive adult subjects with 22q11DS underwent a 3 Tesla MRI with a dedicated high-resolution seizure protocol. Neurological exam was performed in all patients. Genome-wide analysis excluded the presence of other pathogenic microdeletions or duplications.

RESULTS

Structural abnormalities were found in 11 of 14 subjects with sufficient image quality. These included three patients with PNH, one of whom had associated PMG. In addition, there was a surprisingly high prevalence of unilateral hippocampal malrotation (HIMAL), observed in 9 of 14 cases (64%). EEG findings showed interictal epileptiform discharges with focal distribution in four patients and generalized discharges in one patient.

CONCLUSION

The results suggest that, in addition to other known structural abnormalities, 22q11DS is associated with HIMAL. It has been suggested that this developmental abnormality of the hippocampus may predispose or otherwise contribute to epileptogenesis. However in this study we observed HIMAL in a large proportion of patients, with and without epilepsy. Therefore, other as yet unknown factors may contribute to the high prevalence of epilepsy in this population.

Action simulation in hallucination-prone adolescents

Theoretical and empirical accounts suggest that impairments in self-other discrimination processes are likely to promote the expression of hallucinations. Studies using a variety of paradigms involving self-performed actions argue in favor of perspective taking confusion in hallucination-prone subjects. However, our understanding of such processes during adolescence is still at an early stage. The present study thus aims (1) to delineate the neural correlates sustaining mental simulation of actions involving self-performed actions (first-person perspective; 1PP) and other-performed actions (third-person perspective; 3PP) during adolescence (2) to identify atypical activation patterns during 1PP/3PP mental simulation of actions in hallucination-prone adolescents (3) to examine whether differential risk for schizophrenia (clinical vs. genetic) is also associated with differential impairments in the 1PP/3PP mental simulation of actions during adolescence. Twenty-two typically developing controls (Control group; 6 females), 12 hallucination-prone adolescents [auditory hallucination (AH) group; 7 females] and 13 adolescents with 22q11.2 Deletion Syndrome (22q11.2DS group; 4 females) were included in the study. During the fMRI task, subjects were presented with a cue (self-other priming cues) indicating to perform the task using either a first person perspective (“you”-1PP) or a third person perspective (“best friend”-3PP) and then they were asked to mentally simulate actions based on the type of cue. Hallucination-proneness was assessed using a self-report questionnaire [Cardiff Anomalous Perception Scale (CAPS)]. Our results indicated that atypical patterns of cerebral activation, particularly in the key areas of self-other distinction, were found in both groups at risk for auditory hallucinations (AHs and 22q11.2DS). More precisely, adolescents in the AH group presented decreased activations in the right middle occipital gyrus BA19, left cingulate gyrus BA31, and right precuneus BA31 for the 3PP > 1PP contrast. Adolescents in the 22q11.2DS group presented decreased activations in the right superior occipital gyrus BA19, left caudate tail and left precuneus BA7 for the 3PP > 1PP contrast. In comparison to the Control group, only the 22q11.2DS adolescents showed a decreased activation for other-related cues (prime other > prime self contrast) in areas of visual imagery, episodic memory and social cognition. This study characterizes the neural correlates of mental imagery for actions during adolescence, and suggests that a differential risk for hallucination-proneness (clinical vs. genetic) is associated to similar patterns of atypical activations in key areas sustaining self-other discrimination processes. These observations may provide relevant information for future research and prevention strategies with regards to hallucination-proneness during adolescence.

A cross-sectional analysis of the development of response inhibition in children with chromosome 22q11.2 deletion syndrome

Chromosome 22q11.2 deletion syndrome (22q11.2DS) is a neurogenetic disorder that is associated with cognitive impairments and significantly elevated risk for developing schizophrenia. While impairments in response inhibition are central to executive dysfunction in schizophrenia, the nature and development of such impairments in children with 22q11.2DS, a group at high risk for the disorder, are not clear. Here we used a classic Go/No-Go paradigm to quantify proactive (anticipatory stopping) and reactive (actual stopping) response inhibition in 47 children with 22q11.2DS and 36 typically developing (TD) children, all ages 7-14. A cross-sectional design was used to examine age-related associations with response inhibition. When compared with TD individuals, children with 22q11.2DS demonstrated typical proactive response inhibition at all ages. By contrast, reactive response inhibition was impaired in children with 22q11.2DS relative to TD children. While older age predicted better reactive response inhibition in TD children, there was no age-related association with reactive response inhibition in children with 22q11.2DS. Closer examination of individual performance data revealed a wide range of performance abilities in older children with 22q11.2DS; some typical and others highly impaired. The results of this cross-sectional analysis suggest an impaired developmental trajectory of reactive response inhibition in some children with 22q11.2DS that might be related to atypical development of neuroanatomical systems underlying this cognitive process. As part of a larger study, this investigation might help identify risk factors for conversion to schizophrenia and lead to early diagnosis and preventive intervention.

Clues to the foundations of numerical cognitive impairments: evidence from genetic disorders

Several neurodevelopmental disorders of known genetic etiology generate phenotypes that share the characteristic of numerical and mathematical cognitive impairments. This article reviews some of the main findings that suggest a possible key role that spatial and temporal information processing impairments may play in the atypical development of numerical cognitive competence. The question of what neural substrate might underlie these impairments is also addressed, as are the challenges for interpreting neural structure/cognitive function mapping in atypically developing populations.

Adaptive strategy for the statistical analysis of connectomes

We study an adaptive statistical approach to analyze brain networks represented by brain connection matrices of interregional connectivity (connectomes). Our approach is at a middle level between a global analysis and single connections analysis by considering subnetworks of the global brain network. These subnetworks represent either the inter-connectivity between two brain anatomical regions or by the intra-connectivity within the same brain anatomical region. An appropriate summary statistic, that characterizes a meaningful feature of the subnetwork, is evaluated. Based on this summary statistic, a statistical test is performed to derive the corresponding p-value. The reformulation of the problem in this way reduces the number of statistical tests in an orderly fashion based on our understanding of the problem. Considering the global testing problem, the p-values are corrected to control the rate of false discoveries. Finally, the procedure is followed by a local investigation within the significant subnetworks. We contrast this strategy with the one based on the individual measures in terms of power. We show that this strategy has a great potential, in particular in cases where the subnetworks are well defined and the summary statistics are properly chosen. As an application example, we compare structural brain connection matrices of two groups of subjects with a 22q11.2 deletion syndrome, distinguished by their IQ scores.

The 22q11.2 microdeletion: fifteen years of insights into the genetic and neural complexity of psychiatric disorders

Over the last fifteen years it has become established that 22q11.2 deletion syndrome (22q11DS) is a true genetic risk factor for schizophrenia. Carriers of deletions in chromosome 22q11.2 develop schizophrenia at rate of 25-30% and such deletions account for as many as 1-2% of cases of sporadic schizophrenia in the general population. Access to a relatively homogeneous population of individuals that suffer from schizophrenia as the result of a shared etiological factor and the potential to generate etiologically valid mouse models provides an immense opportunity to better understand the pathobiology of this disease. In this review we survey the clinical literature associated with the 22q11.2 microdeletions with a focus on neuroanatomical changes. Then, we highlight results from work modeling this structural mutation in animals. The key biological pathways disrupted by the mutation are discussed and how these changes impact the structure and function of neural circuits is described.

Regional cortical volumes and congenital heart disease: a MRI study in 22q11.2 deletion syndrome

Children with congenital heart disease (CHD) who survive surgery often present impaired neurodevelopment and qualitative brain anomalies. However, the impact of CHD on total or regional brain volumes only received little attention. We address this question in a sample of patients with 22q11.2 deletion syndrome (22q11DS), a neurogenetic condition frequently associated with CHD. Sixty-one children, adolescents, and young adults with confirmed 22q11.2 deletion were included, as well as 80 healthy participants matched for age and gender. Subsequent subdivision of the patients group according to CHD yielded a subgroup of 27 patients with normal cardiac status and a subgroup of 26 patients who underwent cardiac surgery during their first years of life (eight patients with unclear status were excluded). Regional cortical volumes were extracted using an automated method and the association between regional cortical volumes, and CHD was examined within a three-condition fixed factor. Robust protection against type I error used Bonferroni correction. Smaller total cerebral volumes were observed in patients with CHD compared to both patients without CHD and controls. The pattern of bilateral regional reductions associated with CHD encompassed the superior parietal region, the precuneus, the fusiform gyrus, and the anterior cingulate cortex. Within patients, a significant reduction in the left parahippocampal, the right middle temporal, and the left superior frontal gyri was associated with CHD. The present results of global and regional volumetric reductions suggest a role for disturbed hemodynamic in the pathophysiology of brain alterations in patients with neurodevelopmental disease and cardiac malformations.

Reduced NoGo-anteriorisation during continuous performance test in deletion syndrome 22q11.2

Deletion syndrome 22q11.2 (DS22q11.2) is a high-risk factor for psychiatric disorders. Alterations in brain morphology and function including the anterior cingulate cortex (ACC) are suggested to underlie the increased psychiatric disposition. We assessed response-inhibition in patients with DS22q11.2 (n=13) and healthy controls (n=13) matched for age, sex, and handedness by means of a Go-NoGo-Task during recording of a multi-channel electroencephalography (EEG). Analysis of event-related potentials (P300) resulted in an aberrant topographical pattern and NoGo-anteriorisation (NGA) as a parameter of medial prefrontal function was significantly reduced in patients with DS22q11.2 compared to controls. Differences in IQ between groups did not account for the findings. Source localization analysis (LORETA) revealed diminished left temporal brain activation during the Go-condition, but no altered ACC activation in DS22q11 during the NoGo-condition. Despite recent reports of structural alterations of the ACC in DS22q11.2 our findings suggest that response-inhibition mediated by the ACC is not impaired in DS22q11.2.

[Time processing in the velo-cardio-facial syndrome (22q11) and its link with the caudate nucleus]

INTRODUCTION

Velocardiofacial syndrome (VCFS) is a neurogenetic disorder caused by a microdeletion on chromosome 22q11. Among other cognitive impairments and learning difficulties, affected individuals show difficulties in estimating time intervals (Debbané et al., 2005). Interestingly, neuroimaging studies have found an increased volume of the basal ganglia of people with VCFS (Eliez et al., 2002; Kates et al., 2004; Campbell et al., 2006). Given that the caudate nucleus represents a central component of the cerebral network underlying temporal perception skills, the present report proposes to examine potential relationships between cerebral alteration to the caudate nucleus and time estimation in individuals with VCFS.

METHODS

A group of 30 patients with VCFS and 38 age-matched healthy individuals participated in time perception and time reproduction tasks. In the time perception task, individuals listened to two sequential stimuli and had to choose the longer of both stimuli by pressing a button. In the time reproduction task, subjects listened to a succession of sounds and once this succession had stopped they had to reproduce the same rhythm with their dominant index. Cerebral MRI images were also obtained for each participant. A manual tracing procedure was performed to measure the basal ganglia volume.

RESULTS

Participants with VCFS demonstrated significantly poorer performances during the time perception and time reproduction tasks in comparison to the control participants. Further, increased volume of the caudate nucleus was found in individuals with VCFS. Correlational analyses revealed a significant relationship between the caudate nucleus's volume and the performances obtained in the time perception task for control participants. This correlation was not found for individuals with VCFS.

CONCLUSION

The present results suggest that cerebral alterations to the caudate nucleus in VCFS may alter the temporal perception function it sustains.

22q11.2 microdeletions: linking DNA structural variation to brain dysfunction and schizophrenia

Recent studies are beginning to paint a clear and consistent picture of the impairments in psychological and cognitive competencies that are associated with microdeletions in chromosome 22q11.2. These studies have highlighted a strong link between this genetic lesion and schizophrenia. Parallel studies in humans and animal models are starting to uncover the complex genetic and neural substrates altered by the microdeletion. In addition to offering a deeper understanding of the effects of this genetic lesion, these findings may guide analysis of other copy-number variants associated with cognitive dysfunction and psychiatric disorders.

Bridging the gene-behavior divide through neuroimaging deletion syndromes: Velocardiofacial (22q11.2 Deletion) and Williams (7q11.23 Deletion) syndromes

Investigating the relationship between genes and the neural substrates of complex human behavior promises to provide essential insight into the pathophysiology of mental disorders. One approach to this inquiry is through neuroimaging of individuals with microdeletion syndromes that manifest in specific neuropsychiatric phenotypes. Both Velocardiofacial syndrome (VCFS) and Williams syndrome (WS) involve haploinsufficiency of a relatively small set of identified genes on the one hand and association with distinct, clinically relevant behavioral and cognitive profiles on the other hand. In VCFS, there is a deletion in chromosomal region 22q11.2 and a resultant predilection toward psychosis, poor arithmetic proficiency, and low performance intelligence quotients. In WS, there is a deletion in chromosomal region 7q11.23 and a resultant predilection toward hypersociability, non-social anxiety, impaired visuospatial construction, and often intellectual impairment. Structural and functional neuroimaging studies have begun not only to map these well-defined genetic alterations to systems-level brain abnormalities, but also to identify relationships between neural phenotypes and particular genes within the critical deletion regions. Though neuroimaging of both VCFS and WS presents specific, formidable methodological challenges, including comparison subject selection and accounting for neuroanatomical and vascular anomalies in patients, and many questions remain, the literature to date on these syndromes, reviewed herein, constitutes a fruitful "bottom-up" approach to defining gene-brain relationships.

Evidence of gray matter reduction and dysfunction in chromosome 22q11.2 deletion syndrome

Chromosome 22q11.2 deletion syndrome (22q11DS) is associated with cognitive deficits and morphometric brain abnormalities in childhood and a markedly elevated risk of schizophrenia in adolescence/early adulthood. Determining the relationship between neurocognition and neuroimaging findings would yield crucial information about childhood neurodevelopment and provide a basis for the study of the trajectory that occurs on the pathway to psychosis. We compared morphometric brain findings between non-psychotic children with 22q11DS (n = 22) and healthy controls (n = 16), and examined the association between neurocognitive functioning and morphometric brain findings. Volumetric regional gray matter differences between the 22q11DS and control subjects were measured, and correlations of the regional gray matter volumes and neurocognition were performed. Children with 22q11DS demonstrated reductions in gray matter in several brain regions, chiefly the frontal cortices, the cingulate gyrus and the cerebellum. The volumetric reductions in these salient areas were associated with poor performance in sustained attention, executive function and verbal memory; however, the relation of brain volume with cognitive performance did not differ between the patient and control groups. Thus, children with 22q11DS demonstrate gray matter reductions in multiple brain regions that are thought to be relevant to schizophrenia. The correlation of these volumetric reductions with poor neurocognition indicates that these brain regions may mediate higher neurocognitive functions implicated in schizophrenia.

Meta-analysis of magnetic resonance imaging studies in chromosome 22q11.2 deletion syndrome (velocardiofacial syndrome)

OBJECTIVES

22q11.2 deletion syndrome (22q11.2DS), also known as velocardiofacial syndrome (VCFS) or DiGeorge Syndrome, is a genetic disorder due to a micro deletion on chromosome 22q11.2. VCFS is associated with abnormalities in brain structure and with an increased risk of psychiatric disorders, particularly schizophrenia. The aim of this review was to statistically summarize the structural imaging literature on VCFS which due to the relatively rarity of the disorder tends to consider small sample sizes.

METHOD

A systematic review and meta-analysis of region of interest (ROI) studies comparing VCFS with healthy controls was carried out. Significant heterogeneity was explored using meta-regression.

RESULTS

Subjects with VCFS were characterised by global brain volumetric reduction including several cortical regions, cerebellum and hippocampus. The area of the corpus callosum was increased.

CONCLUSIONS

Many regions extensively studied in schizophrenia were not covered in the existing VCFS literature. However, the studies considered support volumetric abnormalities which may help explain why VCFS is associated with a greatly increased risk of psychosis and other psychiatric disorders.

Velo-Cardio-Facial Syndrome

Velocardiofacial syndrome (VCFS) also known as DiGeorge, conotruncal anomaly face and Cayler syndromes is caused by a microdeletion in the long arm of chromosome 22. We review the history of the syndrome from the first clinical reports almost half a century ago to the current intriguing molecular findings associating genes from the microdeletion region and the physical and neuropsychiatric phenotype of the syndrome. Velocardiofacial syndrome has a wide spectrum of more than 200 physical manifestations including palate and cardiac anomalies. Yet, the most challenging manifestations of VCFS are the learning disabilities and neuropsychiatric disorders. As VCFS is relatively common and as up to one third of the subjects with VCFS develop schizophrenia like psychotic disorder the syndrome is the most commonly known genetic risk factor to schizophrenia. Identifying the genetic, cognitive and psychiatric risk factors for VCFS-schizophrenia is under the focus of intensive research.

Genes, brain development and psychiatric phenotypes in velo-cardio-facial syndrome

Velo-cardio-facial syndrome (VCFS) has been in the focus of intensive research over the last 15 years. The syndrome represents a homogeneous model for studying the effect of a decreased dosage of genes on the development of brain structure and function and, consequently, on the emergence of schizophrenia-like psychotic disorder. In this review, we describe the psychiatric phenotype of children, adolescents, and young adults with VCFS. We redefine the concept of "behavioral phenotype" and suggest that psychosis fulfills the criteria of a behavioral phenotype of the syndrome. Identifying the risk factors for the emergence of psychosis in VCFS is a major goal of several large-scale longitudinal studies that are currently underway. We review the knowledge gained so far about risk factors for psychosis in VCFS, including early neuropsychiatric symptoms, development of brain structure and function, and the effect of a reduced dosage of genes from the 22q11 deletion region. Although the brain structure in subjects with VCFS is not drastically different from typically developing controls, newer imaging modalities that measure white matter tracts, cortical thickness, and cortical gyrification are likely to identify more subtle and specific neuroanatomical substrates of the syndrome. Among the 24 genes within the deletion region, the role of catechol-O-methyltransferase (COMT) on the VCFS phenotype has been investigated in depth. The findings suggest that because of haploinsufficiency of the COMT gene individuals with VCFS are exposed to a high level of prefrontal dopamine, and this interferes with their prefrontal cognitive functioning and may contribute to their high rate of psychosis and other psychiatric disorders. The other genes and environmental factors that shape the unique neuropsychiatric phenotype of VCFS are yet to be discovered.

Neural phenotypes of common and rare genetic variants

Neuroimaging methods offer a powerful way to bridge the gaps between genes, neurobiology and behavior. Such investigations may be further empowered by complementary strategies involving chromosomal abnormalities associated with particular neurobehavioral phenotypes, which can help to localize causative genes and better understand the genetics of complex traits in the general population. Here we review the evidence from studies using these convergent approaches to investigate genetic influences on brain structure: (1) studies of common genetic variations associated with particular neuroanatomic phenotypes, and (2) studies of possible 'genetic subtypes' of neuropsychiatric disorders with very high penetrance, with a focus on neuroimaging studies using novel computational brain mapping algorithms. Finally, we discuss the contribution of behavioral neurogenetics research to our understanding of the genetic basis of neuropsychiatric disorders in the broader population.

A new account of the neurocognitive foundations of impairments in space, time and number processing in children with chromosome 22q11.2 deletion syndrome

In this article, I present an updated account that attempts to explain, in cognitive processing and neural terms, the nonverbal intellectual impairments experienced by most children with deletions of chromosome 22q11.2. Specifically, I propose that this genetic syndrome leads to early developmental changes in the structure and function of clearly delineated neural circuits for basic spatiotemporal cognition. This dysfunction then cascades into impairments in basic magnitude and then numerical processes, because of the central role that representations of space and time play in their construction. I propose that this takes the form of "spatiotemporal hypergranularity"; the increase in grain size and thus reduced resolution of mental representations of spatial and temporal information. The result is that spatiotemporal processes develop atypically and thereby produce the characteristic impairments in nonverbal cognitive domains that are a hallmark feature of chromosome 22q11.2 deletion syndrome. If this hypothesis driven account is supported by future research, the results will create a neurocognitive explanation of spatiotemporal and numerical impairments in the syndrome that is specific enough to be directly translated into the development of targeted therapeutic interventions.

Developmental trajectories of brain structure in adolescents with 22q11.2 deletion syndrome: a longitudinal study

The 22q11.2 deletion syndrome (22q11.2DS) is associated with very high rates of schizophrenia-like psychosis and cognitive deficits. Here we report the results of the first longitudinal study assessing brain development in individuals with 22q11.2DS. Twenty-nine children with 22q11.2DS and 29 age and gender matched controls were first assessed during childhood or early adolescence; Nineteen subjects with 22q11.2DS and 18 controls underwent follow-up during late adolescence-early adulthood. The 22q11.2DS subjects showed greater longitudinal increase in cranial and cerebellar white matter, superior temporal gyrus, and caudate nucleus volumes. They also had a more robust decrease in amygdala volume. Verbal IQ (VIQ) scores of the 22q11.2DS group that developed psychotic disorders declined significantly between assessments. Decline in VIQ in 22q11.2DS was associated with more robust reduction of left cortical grey matter volume. No volumetric differences were detected between psychotic and nonpsychotic subjects with 22q11.2DS. Brain maturation associated with verbal cognitive development in 22q11.2DS varies from that observed in healthy controls. Further longitudinal studies are likely to elucidate brain developmental trajectories in 22q11.2DS and their association to psychotic disorders and cognitive deficits in this population.

From genes to brain: understanding brain development in neurogenetic disorders using neuroimaging techniques

For almost two decades, a considerable amount of work has been devoted to the accurate delineation of normal and abnormal brain development using cerebral MRI. In the broad field of neuroimaging research, specific genetic conditions associated with impaired cognitive performances or with psychiatric symptoms have received increased attention because of their potential for revealing insight on the biologic correlates of behavior. First delineated by volumetric measurements of cerebral lobes or regions of interest, new image processing techniques are currently defining cerebral phenotypes associated with neurogenetic disorders with increasing precision. In this article the authors review the contribution of structural brain imaging in advancing our understanding of the pathogenic processes underlying altered brain development in Down, fragile X, and velocardiofacial (22q11DS) syndromes.

Velocardiofacial syndrome

Velocardiofacial syndrome (VCFS) is the most common known microdeletion in humans. It is also the most common known genetic risk factor for schizophrenia. The aim of this article is to describe the clinical characteristics of the syndrome, with emphasis on the myriad psychiatric disorders and abnormal behaviors from a developmental perspective. In addition, the possible pathways that lead to the psychotic symptoms and cognitive deficits are discussed. Guidelines are suggested to alert clinicians to the possibility of the presence of VCFS, and the cumulative clinical experience and limited research on psychiatric treatments for VCFS are presented. There is an urgent need to conduct treatment trials in this high-risk population.

Domain specific attentional impairments in children with chromosome 22q11.2 deletion syndrome

One of the defining cognitive characteristics of the chromosome 22q deletion syndrome (DS22q11.2) is visuospatial processing impairments. The purpose of this study was to investigate and extend the specific attentional profile of children with this disorder using both an object-based attention task and an inhibition of return task. A group of children with the disorder was compared in these tasks with a group of age-matched typically developing children. The children with DS22q11.2 demonstrated impaired spatially based orienting which is consistent with previous findings in this group. Strikingly, the children with DS22q11.2 also demonstrated an improved ability to use object-based cues, relative to the typically developing group. Finally, the children with DS22q11.2 demonstrated an intact inhibition of return system, however, it appears to be delayed developmentally.

Gender-Moderated Dorsolateral Prefrontal Reductions in 22q11.2 Deletion Syndrome: Implications for Risk for Schizophrenia

To investigate the impact of the microdeletion on morphology of the prefrontal cortex in 22q11.2 Deletion Syndrome (22q11.2 DS), high-resolution, anatomic magnetic resonance imaging was performed on 19 children and adolescents with 22q11.2 DS (11 females, 8 males) and 18 unaffected controls (10 females, 8 males). Tissue volumes of the dorsolateral, dorsomedial, orbitolateral, and orbitomedial prefrontal cortex were measured. Tasks of executive function and working memory were administered to investigate the association between anatomy and function. Whole brain volume and frontal lobe tissue volume were preserved in girls but reduced in boys with 22q11.2 DS relative to age-matched controls. Dorsolateral prefrontal cortex (DLPFC) volumes were reduced in participants with 22q11.2 DS, although the gender-by-diagnosis effect found for frontal lobe was not as robust for DLPFC. DLPFC volumes were associated with performance on tasks of planning and emotional facial recognition. Longitudinal studies are needed to clarify whether gender differences in frontal lobe and DLPFC persist with development, and whether the volumes of the DLPFC are associated with eventual deterioration in adaptive/psychosocial function that may presage the onset of schizophrenia, for which individuals with 22q11.2 DS are at a disproportionately high risk.

Neuropsychological Profile and Neuroimaging in Patients with 22Q11.2 Deletion Syndrome: A Review Keywords:

22q11.2 Deletion Syndrome is associated with cognitive, behavioural, and psychiatric problems and is known to affect brain structure. Recently, 22q11.2 Deletion Syndrome has been proposed as a disease model for a genetic subtype of schizophrenia. In this paper we discuss the currently available literature on neurocognitive functioning and brain anatomy in patients with 22q11.2 Deletion Syndrome, and how this contributes to our understanding of the neurobiology of schizophrenia. Research on cognitive functioning in 22q11.2 Deletion Syndrome patients suggests a specific cognitive profile with impairments on arithmetical, visuo-spatial, and executive tasks and relatively preserved language skills. Prominent findings of neuroimaging studies in 22q11.2 Deletion Syndrome patients are: reduction of overall brain volume, midline defects, structural alterations of cerebellum and frontal lobe, white matter abnormalities, and decreased grey matter volumes in parietal and temporal areas. We describe how brain abnormalities in patients with 22q11.2 Deletion Syndrome may contribute to the understanding of the clinical syndrome including cognitive impairments, psychotic symptoms, and social and communication problems.

Corpus callosum morphology and ventricular size in chromosome 22q11.2 deletion syndrome

In this paper, novel methods were used to map the corpus callosum morphology of children with chromosome 22q11.2 deletion syndrome in order to further investigate changes to that structure and to examine their possible effects on cognitive function. The callosal profiles were extracted from the centermost MRI midsagittal slice by supervised thresholding and the structure's boundary and midline were computed automatically. Difference analysis was based on non-rigid registration, in which a template image is warped to conform to the shape of each corpus callosum in the sample. Boundaries and midlines were registered to a template and the results used to determine the average callosal shapes for children with the deletion and for controls. Pointwise registration also enabled the detailed evaluation of callosal curvature, width, area and length. Significant differences between the two groups were found in shape, size and bending angle. Results showed group differences that were concentrated in the anterior part of the structure, more specifically in the rostrum, which was larger and longer in the group with the syndrome. Correlation analyses showed that ventricular enlargement does not fully account for callosal morphology differences in children with the deletion. However, areal measurements did reveal important relationships between changes in callosal morphology and cognitive function. These novel findings reveal intricate relationships between genetic and disease-specific factors in the callosal anatomy and the potential impact of those changes on cognitive functions.

Hippocampal volume reduction in 22q11.2 deletion syndrome

Hippocampal volume reduction and decreased memory skills form a characteristic neurofunctional alteration observed in schizophrenia. Individuals affected with 22q11.2 deletion syndrome (22q11DS), while exhibiting memory deficits throughout development, are also at high risk for developing schizophrenia. The present study sought to investigate hippocampal volume reduction as separate of global grey matter reduction in a large, independent sample of individuals with 22q11DS. Volumetric data from structural magnetic resonance imaging was obtained for 43 individuals affected with 22q11DS, aged 6-39 years of age, as well as for 40 healthy individuals matched for age and gender. Drawing of the amygdala was included to enhance the delineation of the hippocampus, and circumscription of both the amygdala and the hippocampus were executed using an increased resolution matrix. After controlling for total grey volume reductions observed in affected individuals, a significant decrease in hippocampus volume was observed in the 22q11DS group, driven by significant bilateral volumetric reduction of the body of the hippocampus. These results are discussed in reference to memory and cerebral alterations already reported in 22q11DS. Further, the specific implications of hippocampus body volume reduction are outlined in light of its anatomical relationships and its function in memory. Finally, reduction of hippocampal volume in 22q11DS is examined in the context of psychiatric risk status associated to the deletion.

The contribution of novel brain imaging techniques to understanding the neurobiology of mental retardation and developmental disabilities

Studying the biological mechanisms underlying mental retardation and developmental disabilities (MR/DD) is a very complex task. This is due to the wide heterogeneity of etiologies and pathways that lead to MR/DD. Breakthroughs in genetics and molecular biology and the development of sophisticated brain imaging techniques during the last decades have facilitated the emergence of a field called Behavioral Neurogenetics. Behavioral Neurogenetics focuses on studying genetic diseases with known etiologies that are manifested by unique cognitive and behavioral phenotypes. In this review, we describe the principles of magnetic resonance imaging (MRI) techniques, including structural MRI, functional MRI, and diffusion tensor imaging (DTI), and how they are implemented in the study of Williams (WS), velocardiofacial (VCFS), and fragile X (FXS) syndromes. From WS we learn that dorsal stream abnormalities can be associated with visuospatial deficits; VCFS is a model for exploring the molecular and brain pathways that lead to psychiatric disorders for which subjects with MR/DD are at increased risk; and finally, findings from multimodal imaging techniques show that aberrant frontal-striatal connections are implicated in the executive function and attentional deficits of subjects with FXS. By deciphering the molecular pathways and brain structure and function associated with cognitive deficits, we will gain a better understanding of the pathophysiology of MR/DD, which will eventually make possible more specific treatments for this population.

Basal ganglia calcification and psychosis in 22q11.2 deletion syndrome

Intracerebral calcifications are a facultative symptom of hypoparathyreoidism in 22q11.2 deletion syndrome (22qDS). We describe a patient with 22qDS, basal ganglia calcification (BGC) and psychotic symptoms and discuss the etiological connection of BGC with psychiatric symptoms. Future work needs to determine the prevalence of BGC in 22qDS and psychiatric disorders.

22q11.2 deletion syndrome: genetics, neuroanatomy and cognitive/behavioral features keywords

This paper presents a conceptual review of the genetic underpinnings of 22q11.2 Deletion Syndrome. The neuroanatomical, neuropsychological, behavioral, and psychiatric phenotype associated with 22q11.2 Deletion Syndrome is also explored, including variables that are thought to affect symptom expression. The history of the deletion syndrome is described, and future directions for continued research are discussed.

Enlarged striatum in abstinent methamphetamine abusers: a possible compensatory response

BACKGROUND

Little is known about structural brain abnormalities associated with methamphetamine (METH) abuse; therefore, we aimed: 1) to evaluate possible morphometric changes, especially in the striatum of recently abstinent METH-dependent subjects; 2) to evaluate whether morphometric changes are related to cognitive performance; and 3) to determine whether there are sex-by-METH interactions on morphometry.

METHODS

Structural MRI was performed in 50 METH and 50 comparison subjects with the same age range and sex proportion; quantitative morphometric analyses were performed in the subcortical gray matter, cerebellum and corpus callosum. Neuropsychological tests were also performed in 44 METH and 28 comparison subjects.

RESULTS

METH users showed enlarged putamen (left: + 10.3%, p = .0007; right: + 9.6%, p = .001) and globus pallidus (left: + 9.3%, p = .002; right: + 6.6%, p = .01). Female METH subjects additionally showed larger mid-posterior corpus callosum (+ 9.7%, p = .05). Although METH users had normal cognitive function, those with smaller striatal structures had poorer cognitive performance and greater cumulative METH usage.

CONCLUSIONS

Since METH subjects with larger striatal structures had relatively normal cognitive performance and lesser cumulative METH usage, the enlarged putamen and globus pallidus might represent a compensatory response to maintain function. Possible mechanisms for the striatal enlargement include glial activation and inflammatory changes associated with METH-induced injury.

Volumetric, connective, and morphologic changes in the brains of children with chromosome 22q11.2 deletion syndrome: an integrative study

Chromosome 22q11.2 deletion syndrome is a highly prevalent genetic disorder whose manifestations include developmental disability and sometimes mental retardation. The few studies that have examined brain morphology in different samples from this population have found similar general patterns, mostly using region of interest measures. We employed voxel-based techniques to concurrently examine specific morphologic changes in multiple brain tissue measures. Results were similar to previous findings of volumetric reductions in the posterior brain. They also extended them in two ways. First, our methods provided greater specificity in the localization of changes detected. Second, the combination of our measures of gray and white matter along with cerebrospinal fluid volume and fractional anisotropy, which indicates the structure of white matter, showed a posterior displacement of and morphologic changes to the corpus callosum in affected children.

Temporal perception in velo-cardio-facial syndrome

Temporal perception abilities refer to timing mechanisms used in daily life, such as the ability to reproduce and judge time, previously associated with the basal ganglia and the cerebellum, respectively. In individuals affected by velo-cardio-facial (VCFS), both the basal ganglia and the cerebellum have been shown to be particularly vulnerable to abnormal brain development, though related temporal perception abilities have yet to be investigated. In this study, our goal was to characterize time perception and reproduction abilities in individuals with VCFS. Compared to controls, we hypothesized that individuals with VCFS would be less accurate and show more variability when reproducing a fixed-interval series of auditory beeps; furthermore, we predicted that they would show a higher perceptive acuity threshold when discriminating between subtle time differences. Forty-two subjects with VCFS and 35 matched controls participated in temporal perception evaluations. In the reproduction of time finger-tapping task, subjects were asked to press a button in cadence with a series of fixed interval beeps, and then to hold the same tempo when the beeps stopped. Overall, the VCFS group showed less accuracy and more variability in reproduction ability when compared to controls. In the second experiment, subjects were tested on auditory and visual time perception tasks. Subjects were presented with a fixed interval stimulus and a stimulus of varying duration, and were asked to determine the longer of the two. The VCFS group required a greater discrepancy between tones to accurately discriminate the two stimuli. The results point to an alteration in temporal perception associated with VCFS. Implications of altered temporal perception abilities and their relationship to the VCFS phenotype are discussed.

Thalamic reductions in children with chromosome 22q11.2 deletion syndrome

Children with chromosome 22q11.2 deletion syndrome (22q) suffer from physical and behavioral dysfunctions, including neuroanatomical anomalies, visuo-spatial processing deficits, and increased risk for psychopathology. Reduced total brain volume, parietal lobe volume, and cerebellar volumes, enlarged ventricles, and increased basal ganglia volumes have been reported. Since previous literature has related the pulvinar nucleus of the thalamus to visuo-spatial processing, we compared the thalamic volume in children with 22q to typically developing controls. Children with 22q showed a significant reduction of the thalamus compared with normally developing children, specifically in the posterior portion of the thalamus, including the pulvinar nucleus. These results provide the first evidence for a potential relationship between posterior thalamic reductions and the characteristic visuo-spatial deficits demonstrated in this group.