Volume reduction of the right anterior limb of the internal capsule in patients with schizotypal disorder

Developmental trajectories of subcortical structures in relation to dimensional schizotypy expression along adolescence

Morphological abnormalities of subcortical structures have been consistently reported along the schizophrenia clinical spectrum, and they may play an important role in the pathophysiology of psychosis. However, the question arises whether these subcortical features are consequences of medication and illness chronicity, or if they contribute to the vulnerability to develop schizophrenia spectrum disorders. If some of the subcortical abnormalities could be evidenced in community adolescents expressing higher schizotypal traits (psychometric schizotypy), they could potentially shed light on vulnerability markers. To date, very few studies have examined the link between psychometric schizotypy and volumes of subcortical regions, and none of them have used a longitudinal design. This study sets out to investigate developmental trajectories of subcortical volumes in 110 community adolescents (12 to 20 years old), for whom MRI-scans were acquired over a period of 5 years, reaching a total of 297 scans. Analyses were conducted using Freesurfer, and schizotypal traits were measured with the Schizotypal Personality Questionnaire (SPQ). Using mixed model regression analyses following a region-of-interest approach, we observed differential linear developmental trajectories in four subcortical structures when comparing higher versus lower scorers on the disorganized schizotypy dimension (bilateral hippocampus, left-lateral ventricle and left-pallidum) and the negative schizotypy dimension (bilateral pallidum, and right-thalamus). All results survived a threshold of p < .05 (FDR-corrected) while covarying for the effect of other psychological problems (externalized and internalized psychopathology). These results indicate that expression of higher levels of negative and disorganized schizotypy during adolescence was associated with neural markers linking schizotypy personality features to schizophrenia spectrum disorders.

The anterior limb of the internal capsule: Anatomy, function, and dysfunction

The last two decades have seen a re-emergence of neurosurgery for severe, refractory psychiatric diseases, largely due to the advent of more precise and safe operative techniques. Nevertheless, the optimal targets for these surgeries remain a matter of debate, and are often grandfathered from experiences in the late 20th century. To better explore the rationale for one target in particular - the anterior limb of the internal capsule (ALIC) - we comprehensively reviewed all available literature on its role in the pathophysiology and treatment of mental illness. We first provide an overview of its functional anatomy, followed by a discussion on its role in several prevalent psychiatric diseases. Given its structural integration into the limbic system and involvement in a number of cognitive and emotional processes, the ALIC is a robust target for surgical treatment of refractory psychiatric diseases. The advent of novel neuroimaging techniques, coupled with image-guided therapeutics and neuromodulatory treatments, will continue to enable study on the ALIC in mental illness.

Characterization of the Fiber Connectivity Profile of the Cerebral Cortex in Schizotypal Personality Disorder: A Pilot Study

Schizotypal personality disorder (SPD) is considered one of the classic disconnection syndromes. However, the specific cortical disconnectivity pattern has not been fully investigated. In this study, we aimed to explore significant alterations in whole-cortex structural connectivity in SPD individuals (SPDs) by combining the techniques of brain surface morphometry and white matter tractography. Diffusion and structural MR data were collected from 20 subjects with SPD (all males; age, 19.7 ± 0.9 years) and 18 healthy controls (all males; age, 20.3 ± 1.0 years). To measure the structural connectivity for a given unit area of the cortex, the fiber connectivity density (FiCD) value was proposed and calculated as the sum of the fractional anisotropy of all the fibers connecting to that unit area in tractography. Then, the resultant whole-cortex FiCD maps were compared in a vertex-wise manner between SPDs and controls. Compared with normal controls, SPDs showed significantly decreased FiCD in the rostral middle frontal gyrus (crossing BA 9 and BA 10) and significantly increased FiCD in the anterior part of the fusiform/inferior temporal cortex (P < 0.05, Monte Carlo simulation corrected). Moreover, the gray matter volume extracted from the left rostral middle frontal cluster was observed to be significantly greater in the SPD group (P = 0.02). Overall, this study identifies a decrease in connectivity in the left middle frontal cortex as a key neural deficit at the whole-cortex level in SPD, thus providing insight into its neuropathological basis.

Genetic and Neuroimaging Features of Personality Disorders: State of the Art

Personality disorders often act as a common denominator for many psychiatric problems, and studies on personality disorders contribute to the etiopathology, diagnosis, and treatment of many mental disorders. In recent years, increasing evidence from various studies has shown distinctive features of personality disorders, and that from genetic and neuroimaging studies has been especially valuable. Genetic studies primarily target the genes encoding neurotransmitters and enzymes in the serotoninergic and dopaminergic systems, and neuroimaging studies mainly focus on the frontal and temporal lobes as well as the limbic-paralimbic system in patients with personality disorders. Although some studies have suffered due to unclear diagnoses of personality disorders and some have included few patients for a given personality disorder, great opportunities remain for investigators to launch new ideas and technologies in the field.

Orbitofrontal sulcogyral pattern and olfactory sulcus depth in the schizophrenia spectrum

Morphological changes in the orbitofrontal cortex (OFC), such as an altered sulcogyral pattern of the 'H-shaped' orbital sulcus and a shallow olfactory sulcus, have been demonstrated in schizophrenia, possibly reflecting deviations in early neurodevelopment. However, it remains unclear whether patients with schizotypal features exhibit similar OFC changes. This magnetic resonance imaging study examined the OFC sulcogyral pattern (Types I, II, III, and IV) and olfactory sulcus morphology in 102 patients with schizophrenia, 47 patients with schizotypal disorder, and 84 healthy controls. The OFC sulcogyral pattern distribution between the groups was significantly different on the right hemisphere, with the schizophrenia patients showing a decrease in Type I (vs controls and schizotypal patients) and an increase in Type III (vs controls) expression. However, the schizotypal patients and controls did not differ in the OFC pattern. There were significant group differences in the olfactory sulcus depth bilaterally (schizophrenia patients < schizotypal patients < controls). Our findings suggest that schizotypal disorder, a milder form of schizophrenia spectrum disorders, partly shares the OFC changes (i.e., altered depth of the olfactory sulcus) with schizophrenia, possibly reflecting a common disease vulnerability. However, altered distribution of the OFC pattern specific to schizophrenia may at least partly reflect neurodevelopmental pathology related to a greater susceptibility to overt psychosis.

Different patterns of white matter disruption among amnestic mild cognitive impairment subtypes: relationship with neuropsychological performance

Amnestic mild cognitive impairment (aMCI) is recognized as the prodromal phase of Alzheimer's disease (AD). Evidence showed that patients with multiple-domain (MD) aMCI were at higher risk of converting to dementia and exhibited more severe gray matter atrophy than single-domain (SD) aMCI. The investigation of the microstructural abnormalities of white matter (WM) among different subtypes of aMCI and their relations with cognitive performances can help to understand the variations among aMCI subtypes and to construct potential imaging based biomarkers to monitor the progression of aMCI. Diffusion-weighted MRI data were acquired from 40 patients with aMCI (aMCI-SD: n = 19; aMCI-MD: n = 21) and 37 healthy controls (HC). Voxel-wise and atlas-based analyses of whole-brain WM were performed among three groups. The correlations between the altered diffusion metrics of the WM tracts and the neuropsychological scores in each subtype of aMCI were assessed. The aMCI-MD patients showed disrupted integrity in multiple WM tracts across the whole-brain when compared with HCs or with aMCI-SD. In contrast, only few WM regions with diffusion changes were found in aMCI-SD as compared to HCs and with less significance. For neuropsychological correlations, only aMCI-MD patients exhibited significant associations between disrupted WM connectivity (in the body of the corpus callosum and the right anterior internal capsules) and cognitive impairments (MMSE and Digit Symb-Coding scores), whereas no such correlations were found in aMCI-SD. These findings indicate that the degeneration extensively exists in WM tracts in aMCI-MD that precedes the development of AD, whereas underlying WM pathology in aMCI-SD is imperceptible. The results are consistent with the view that aMCI is not a uniform disease entity and presents heterogeneity in the clinical progression.

Neuroimaging findings in schizotypal personality disorder: a systematic review

BACKGROUND

Schizotypal personality disorder is the prototypical schizophrenia-spectrum condition, sharing similar phenomenological, cognitive, genetic, physiological, neurochemical, neuroanatomical and neurofunctional abnormalities with schizophrenia. Investigations into SPD circumvent many confounds inherent to schizophrenia such as medication and institutionalization. Hence, SPD offers a unique vantage point from which to study schizophrenia-spectrum conditions.

METHODS

We systematically reviewed the neuroimaging literature in SPD to establish: (1) whether there are concordant findings in SPD and schizophrenia, possibly reflective of core pathology between the two conditions and (2) whether there are discordant findings in SPD and schizophrenia, possibly reflecting protective factors in the former. The findings are synthesized across structural and functional neuroimaging domains.

RESULTS

A total of 54 studies were identified. Medial temporal lobe structures seem to be compromised in both SPD and schizophrenia. In schizophrenia prefrontal structures are further compromised, whereas in SPD these seem to be larger-than-normal, possibly reflecting a compensatory mechanism. Additional pathology is discussed, including evidence of aberrant subcortical dopaminergic functioning.

CONCLUSIONS

SPD is a schizophrenia-spectrum condition that shares pathology with schizophrenia, but is distinct in showing unique neural findings. Future studies are needed to confirm and localize regions of common and disparate pathology between SPD and schizophrenia.

Anterior limb of the internal capsule in schizotypal personality disorder: fiber-tract counting, volume, and anisotropy

Mounting evidence suggests that white matter abnormalities and altered subcortical-cortical connectivity may be central to the pathology of schizophrenia (SZ). The anterior limb of the internal capsule (ALIC) is an important thalamo-frontal white-matter tract shown to have volume reductions in SZ and to a lesser degree in schizotypal personality disorder (SPD). While fractional anisotropy (FA) and connectivity abnormalities in the ALIC have been reported in SZ, they have not been examined in SPD. In the current study, magnetic resonance (MRI) and diffusion tensor imaging (DTI) were obtained in age- and sex-matched individuals with SPD (n=33) and healthy controls (HCs; n=38). The ALIC was traced bilaterally on five equally spaced dorsal-to-ventral axial slices from each participant's MRI scan and co-registered to DTI for the calculation of FA. Tractography was used to examine tracts between the ALIC and two key Brodmann areas (BAs; BA10, BA45) within the dorsolateral prefrontal cortex (DLPFC). Compared with HCs, the SPD participants exhibited (a) smaller relative volume at the mid-ventral ALIC slice level but not the other levels; (b) normal FA within the ALIC; (c) fewer relative number of tracts between the most-dorsal ALIC levels and BA10 but not BA45 and (d) fewer dorsal ALIC-DLPFC tracts were associated with greater symptom severity in SPD. In contrast to prior SZ studies that report lower FA, individuals with SPD show sparing. Our findings are consistent with a pattern of milder thalamo-frontal dysconnectivity in SPD than schizophrenia.

A review of structural MRI and diffusion tensor imaging in schizotypal personality disorder

Individuals with schizotypal personality disorder (SPD) share genetic, phenomenologic, and cognitive abnormalities with people diagnosed with schizophrenia. To date, 15 structural MRI studies of the brain have examined size, and 3 diffusion tensor imaging studies have examined white matter connectivity in SPD. Overall, both types of structural neuroimaging modalities have shown temporal lobe abnormalities similar to those observed in schizophrenia, while frontal lobe regions appear to show more sparing. This intriguing pattern suggests that frontal lobe sparing may suppress psychosis, which is consistent with the idea of a possible neuroprotective factor. In this paper, we review these 18 studies and discuss whether individuals with SPD who both resemble and differ from schizophrenia patients in their phenomenology, share some or all of the structural brain imaging characteristics of schizophrenia. We attempt to group the MRI abnormalities in SPD into three patterns: 1) a spectrum of severity-abnormalities are similar to those observed in schizophrenia but not so severe; 2) a spectrum of region-abnormalities affecting some, but not all, brain regions affected in schizophrenia; and 3) a spectrum of compensation-abnormalities reflecting greater-than-normal white matter volume, possibly serving as a buffer or compensatory mechanism protecting the individual with SPD from the frank psychosis observed in schizophrenia.

Anterior internal capsule volumes increase in patients with schizophrenia switched from typical antipsychotics to olanzapine

Abnormalities in connectivity are thought to contribute to the symptoms of schizophrenia. Accumulating evidence suggests that antipsychotic medication affects both subcortical and cortical grey and white matter volumes. The goal of this study was to investigate the effects of antipsychotic medication on two white matter tracts: a subcortical-cortical tract, the anterior and posterior limbs of the internal capsule; and a cortical-cortical tract, the corpus callosum. Magnetic resonance imaging was conducted on 10 chronic schizophrenia patients treated with typical antipsychotics and 20 healthy controls at baseline. Patients were switched to olanzapine and both groups were rescanned after 1 year. At baseline, the volume of the anterior limb of the internal capsule was 24% smaller in typical-treated patients than controls (p = 0.009). Patients treated with greater amounts of chlorpromazine-equivalent daily dosage had smaller anterior internal capsule volumes at baseline (r = -0.65, p = 0.04). At follow-up, after being switched to olanzapine, there were no significant differences between patients and controls. Patients with schizophrenia had a significant 25% increase in anterior internal capsule volume from baseline to follow-up compared with controls (p = 0.04). These effects were most prominent in the anterior limb of the internal capsule, which consists of fronto-thalamic pathways, and were not statistically significant in the posterior limb of the internal capsule or corpus callosum. Olanzapine may be effective in normalizing fronto-thalamic structural connectivity in schizophrenia.

Feasibility of prefronto-caudate pathway tractography using high resolution diffusion tensor tractography data at 3T

Mapping the human brain frontostriatal pathways using noninvasive diffusion tensor imaging (DTI) has been hampered by the inadequate imaging sensitivity, poor spatial resolution, lower tensor anisotropy within gray matter, increased partial volume averaging effects and poor signal-to-noise ratio. We investigated for the first time the utility of high spatial resolution DTI-based fiber-tractography using the fiber assignment by continuous tracking (FACT) to reconstruct and quantify bilaterally the prefronto-caudo-thalamic connections within the human brain at 3T. Five healthy right-handed men (age range 24-37 years) were studied. We traced the anterior thalamic radiation and prefronto-caudo-thalamic pathways bilaterally and measured the volume of each tract and the corresponding diffusion tensor metrics in all subjects. The anterior thalamic radiation tract volume and corresponding fractional anisotropy (FA) were significantly larger bilaterally than prefronto-caudate pathway, whereas the mean diffusivity (D(av)) values were similar (p>0.7). For both anterior thalamic radiation and prefronto-caudate pathway the tract volume and corresponding DTI metrics (FA, D(av)) were not significantly different between the two hemispheres (p>0.2). Our DTI acquisition protocol and analysis permitted the reconstruction of the connectivity of the caudate with the thalamus as well as with the prefrontal cortex and allowed tracking of the whole trajectory of the prefronto-caudo-thalamic pathway.

The role of early life stress in development of the anterior limb of the internal capsule in nonhuman primates

Deep brain stimulation (DBS) of the anterior limb of the internal capsule (ALIC) may be effective in treating depression. Parental verbal abuse has been linked to decreased fractional anisotropy (FA) of white matter and reduced FA correlated with depression and anxiety scores. Utilizing a nonhuman primate model of mood and anxiety disorders following disrupted mother-infant attachment, we examined whether adverse rearing conditions lead to white matter impairment of the ALIC. We examined white matter integrity using Diffusion Tensor Imaging (DTI) on a 3T-MRI. Twenty-one adult male Bonnet macaques participated in this study: 12 were reared under adverse [variable foraging demand (VFD)] conditions whereas 9 were reared under normative conditions. We examined ALIC, posterior limb of the internal capsule (PLIC) and occipital white matter. VFD rearing was associated with significant reductions in FA in the ALIC with no changes evident in the PLIC or occipital cortex white matter. Adverse rearing in monkeys persistently impaired frontal white matter tract integrity, a novel substrate for understanding affective susceptibility.

Diffusion tensor imaging in studying white matter complexity: a gap junction hypothesis

The role of the prefrontal cortex as an executive oversight of posterior brain regions raises the question of the extent to which the anterior regions of the brain interconnect with the posterior regions. The aim of this study is to test the complexity of rostral white matter tracts, which connect anterior and posterior brain regions, in comparison to caudal white matter tracts and the corpus callosum. Diffusion tensor imaging (DTI) is a modality that measures fractional anisotropy (FA). Higher white matter complexity could result in a decrease of FA, possibly through denser intersection of fiber tracts. DTI was used to determine regional FA in 9 healthy bonnet macaques (Macaca radiata). Four regions of interest were included: anterior and posterior limbs of the internal capsule, the occipital lobe white matter, and the corpus callosum. FA of the anterior limbs of the internal capsule was lowest compared to all other regions of interest (Newman-Keuls (N-K); p<0.0001), whereas FA of the corpus callosum was highest (N-K; p<0.0001). The posterior limbs of the internal capsule and the occipital white matter were not distinguishable but exhibited intermediate FA in comparison to the former (N-K; p<0.0001) and the latter (N-K; p<0.0001). The current study demonstrates that FA, a measure of white matter complexity, can vary markedly as a function of region of interest. Moreover, validation of these findings using neurohistological studies and replication in human samples appears warranted.

Increased pituitary volume in schizophrenia spectrum disorders

While hypothalamic-pituitary-adrenal (HPA) axis hyperactivity has been implicated in psychotic disorders, previous magnetic resonance imaging (MRI) studies of the pituitary gland volume in schizophrenia have yielded controversial results. It is also unknown whether patients with schizophrenia spectrum such as schizotypal disorder exhibit pituitary volume changes. In this study, we investigated the pituitary volume using MRI in 47 schizotypal disorder patients (29 males, mean age=25.0 years), 72 schizophrenia patients (38 males, mean age=26.2 years), and 81 age and gender matched healthy controls (46 males, mean age=24.5 years). Both patient groups had a larger pituitary volume compared with controls, but no difference was found between the schizophrenia and schizotypal patients. The pituitary volume was larger in females than in males for all diagnostic groups. There was no association between the pituitary volume and type (typical versus atypical), daily dosage, or duration of antipsychotic medication in either patient group. These findings are consistent with a stress-diathesis model of schizophrenia and further suggest that the schizotypal patients share HPA axis hyperactivity with young established schizophrenia patients reflecting a common vulnerability to stress within the schizophrenia spectrum.

Schizotypal personality: neurodevelopmental and psychosocial trajectories

Schizotypal personality research holds the promise of critically important insights into the etiology and ultimate prevention of schizophrenia. This article provides a critical overview of diagnostic, developmental, demographic, psychosocial, genetic, neurodevelopmental, psychophysiological, neurochemical, neurocognitive, brain imaging, and prevention-treatment issues pertaining to this personality disorder. It is argued that genetic and early environmental influences act in concert to alter brain structure/function throughout development, resulting in disturbances to basic cognitive and affective processes that give rise to three building blocks of schizotypy-cognitive-perceptual, interpersonal, and disorganized features. Two clinical subtypes are hypothesized: (a) neurodevelopmental schizotypy, which has its roots in genetic, prenatal, and early postnatal factors, is relatively stable, has genetic affinity to schizophrenia, and may benefit preferentially from pharmacological intervention, and (b) pseudoschizotypy, which is unrelated to schizophrenia, has its roots in psychosocial adversity, shows greater symptom fluctuations, and may be more responsive to psychosocial intervention.

Diffusion tensor imaging in schizophrenia

BACKGROUND

Alignment of white matter axons as inferred from diffusion tensor imaging has indicated changes in schizophrenia in frontal and frontotemporal white matter.

METHODS

Diffusion tensor anisotropy and anatomical magnetic resonance images were acquired in 64 patients with schizophrenia and 55 normal volunteers. Anatomical images were acquired with a magnetization prepared rapid gradient echo sequence, and diffusion tensor images used a pulsed gradient spin-echo acquisition. Images were aligned and warped to a standard brain, and anisotropy in normal volunteers and patients was compared using significance probability mapping.

RESULTS

Patients showed widespread areas of reduced anisotropy, including the frontal white matter, the corpus callosum, and the frontal longitudinal fasciculus.

CONCLUSIONS

These findings, which are consistent with earlier reports of frontal decreases in anisotropy, demonstrate that the effects are most prominent in frontal and callosal areas and are particularly widespread in frontal white matter regions.

Diffusion tensor imaging of frontal lobe white matter tracts in schizophrenia

We acquired diffusion tensor and structural MRI images on 103 patients with schizophrenia and 41 age-matched normal controls. The vector data was used to trace tracts from a region of interest in the anterior limb of the internal capsule to the prefrontal cortex. Patients with schizophrenia had tract paths that were significantly shorter in length from the center of internal capsule to prefrontal white matter. These tracts, the anterior thalamic radiations, are important in frontal-striatal-thalamic pathways. These results are consistent with findings of smaller size of the anterior limb of the internal capsule in patients with schizophrenia, diffusion tensor anisotropy decreases in frontal white matter in schizophrenia and hypothesized disruption of the frontal-striatal-thalamic pathway system.

Temporal lobe gray matter in schizophrenia spectrum: a volumetric MRI study of the fusiform gyrus, parahippocampal gyrus, and middle and inferior temporal gyri

Although several brain morphologic studies have suggested abnormalities in the temporal regions to be a common indicator of vulnerability for the schizophrenia spectrum, less attention has been paid to temporal lobe structures other than the superior temporal gyrus or the medial temporal region. In this study, we investigated the volume of gray matter in the fusiform gyrus, the parahippocampal gyrus, the middle temporal gyrus, and the inferior temporal gyrus using magnetic resonance imaging in 39 schizotypal disorder patients, 65 schizophrenia patients, and 72 age and gender matched healthy control subjects. The anterior fusiform gyrus was significantly smaller in the schizophrenia patients than the control subjects but not in the schizotypal disorder patients, while the volume reduction of the posterior fusiform gyrus was common to both disorders. Volumes for the middle and inferior temporal gyri or the parahippocampal gyrus did not differ between groups. These findings suggest that abnormalities in the posterior region of the fusiform gyrus are, as have been suggested for the superior temporal gyrus or the amygdala/hippocampus, prominent among the temporal lobe structures as a common morphologic substrate for the schizophrenia spectrum, whereas more widespread alterations involving the anterior region might be associated with the development of full-blown schizophrenia.

Reduced anterior internal capsule and thalamic volumes in first-episode psychosis

BACKGROUND

The thalamus is the gateway for sensory and motor information en route to the cortex. Information is processed via thalamocortical and corticothalamic pathways coursing through the internal capsules. In this study, we investigated the relationship between the anterior limb of the internal capsule, posterior limb of the internal capsule, and thalamus in first-episode psychosis (FEP).

METHODS

Twenty-nine FEP subjects (26 DSM-IV schizophrenia, 2 schizoaffective disorder, 1 psychosis not otherwise specified) and 22 healthy volunteers participated in this study. Anterior limb of the internal capsule (AIC), posterior limb of the internal capsule (PIC), and the thalamus volumes were manually determined from MRI scans.

RESULTS

FEP subjects had reduced AIC volumes (F(1,45)=6.18, p=0.017) and thalamic volumes (F(1,45)=8.00, p=0.007) compared to healthy volunteers. PIC volumes did not differ. Significant correlations between AIC volumes and thalamic volumes were observed in subjects with FEP, but not in healthy volunteers. Negative relationships between thalamic volumes and symptom severity were also observed.

CONCLUSIONS

The AIC and thalamic volumes were reduced in subjects with FEP compared to healthy volunteers. Abnormalities in thalamocortical and orticothalamic pathways may contribute to functional disruption of neural circuits in psychosis.

Reduction of caudate nucleus volumes in neuroleptic-naïve female subjects with schizotypal personality disorder

BACKGROUND

The caudate nucleus might contribute to the psychopathological and cognitive deficits observed in schizotypal personality disorder (SPD), a schizophrenia spectrum disorder. Here we focused on female patients, because this group is underrepresented in studies of SPD and schizophrenia, and we might learn more about the caudate and clinical and cognitive impairments that are unique to female patients diagnosed with SPD.

METHODS

Magnetic resonance imaging scans, obtained on a 1.5-T magnet with 1.5-mm contiguous slices, were used to measure the caudate in 32 neuroleptic-naïve women with SPD and in 29 female normal comparison subjects. Subjects were group-matched for age, parental socioeconomic status, and intelligence quotient.

RESULTS

We found significantly reduced left and right caudate relative volume (8.3%, 7.7%) in female SPD subjects compared with normal comparison subjects. In female SPD subjects, we found significant correlations between smaller total caudate relative volume and worse performance on the Wisconsin Card Sorting test (nonperseverative errors) and on the California Verbal Learning Test (verbal memory and learning), and significant correlations between smaller total caudate relative volume and both positive and negative symptoms on the Structured Interview for Schizotypy.

CONCLUSIONS

These findings demonstrate that, for female SPD subjects, smaller caudate volume is associated with poorer cognitive performance and more schizotypal symptomatology.

Morphologic alterations of the parcellated superior temporal gyrus in schizophrenia spectrum

Morphologic abnormalities of the superior temporal gyrus (STG) as well as its sub-regions such as Heschl's gyrus (HG) or planum temporale (PT) have been reported in schizophrenia patients, but have not been extensively studied in schizotypal subjects. In the present study, magnetic resonance images were acquired from 65 schizophrenia patients, 39 schizotypal disorder patients, and 72 healthy controls. Volumetric analyses were performed using consecutive 1-mm coronal slices on the temporal pole (TP) and superior temporal sub-regions [planum polare (PP), HG, PT, rostral STG, and caudal STG]. The HG was significantly smaller in schizophrenia patients compared with controls but not in schizotypal patients, while volume reductions of the left PT and bilateral caudal STG were common to both disorders. The TP gray matter was larger in female schizotypal patients compared with female schizophrenia patients. There were no significant group differences in the PP and rostral STG volume. In the subgroup of early phase schizophrenia patients (illness duration <1.0 year), smaller volumes for the left PP and rostral STG were correlated with hallucinations and delusions. Our findings suggest that morphologic changes in the posterior regions of the STG are common to the schizophrenia spectrum, whereas less involvement of the HG, and possibly the PP and rostral STG might be related to the sparing of schizotypal patients from developing overt psychosis.

Differential contributions of prefrontal and temporolimbic pathology to mechanisms of psychosis

Common abnormalities within the schizophrenia spectrum may be essential for the pathogenesis of schizophrenia, but additional pathological changes may be required for the development of full-blown schizophrenia. Clarifying the neurobiological similarities and differences between established schizophrenia and a milder form of schizophrenia spectrum disorder would potentially discriminate the pathophysiological mechanisms underlying the core features of the schizophrenia spectrum from those associated with overt psychosis. High-resolution MRIs were acquired from 25 patients with schizotypal disorder, 53 patients with schizophrenia and 59 healthy volunteers matched for age, gender, handedness and parental education. Volumetric measurements of the medial temporal structures and the prefrontal cortex subcomponents were performed using consecutive 1-mm thick coronal slices. Parcellation of the prefrontal cortex into subcomponents was performed according to the intrinsic anatomical landmarks of the frontal sulci/gyri. Compared with the controls, the bilateral volumes of the amygdala and the hippocampus were reduced comparably in the schizotypal and schizophrenia patients. The parahippocampal gyrus volume did not differ significantly between diagnostic groups. Total prefrontal grey matter volumes were smaller bilaterally in the schizophrenia patients than in the controls and the schizotypal patients, whereas the schizotypal patients had larger prefrontal grey matter than the controls in the right hemisphere. In the schizophrenia patients, grey matter volumes of the bilateral superior frontal gyrus, left middle frontal gyrus, bilateral inferior frontal gyrus and bilateral straight gyrus were smaller than those in the controls. The schizophrenia patients also had reduced grey matter volumes in the right superior frontal gyrus, bilateral middle frontal gyrus and right inferior frontal gyrus relative to the schizotypal patients. Compared with the controls, the schizotypal patients had larger volumes of the bilateral middle frontal gyrus and smaller volumes of the right straight gyrus. There were no significant between-group differences in volumes of the ventral medial prefrontal cortex or the orbitofrontal cortex. These findings suggest that volume reductions in the amygdala and hippocampus are the common morphological substrates for the schizophrenia spectrum, which presumably represent the vulnerability. Additional widespread involvement of the prefrontal cortex in schizophrenia may lead to the loss of inhibitory control in other brain regions and suggests (although it is not specifically be related to) its critical role in the manifestation of overt psychosis.

Volumetric MRI study of the short and long insular cortices in schizophrenia spectrum disorders

We have previously reported volume reductions of the insular cortex in schizophrenia, but it is still not clear whether insular cortex volume loss preferentially involves the anterior (short insular cortex) or posterior (long insular cortex) portion. On the other hand, no volumetric studies of the brain have examined changes in insular cortex volume in subjects with schizotypal features. In this study, we separately investigated the volumes of the short and long insular cortex portions using magnetic resonance imaging in 37 schizotypal disorder patients (24 males, 13 females), 62 schizophrenia patients (32 males, 30 females), and 69 healthy controls (35 males, 34 females). While the volumes of the short and long insular cortex were significantly reduced in schizophrenia patients compared with schizotypal disorder patients and control subjects, there was no difference between schizotypal disorder patients and control subjects. These results suggest that the volume reduction of the insular cortex may be specific to overt schizophrenia without topographically specific localization.

Neuroimaging and personality disorders

Within the past several years, neuroimaging research on personality disorders has begun to develop. Personality disorders can be thought of as trait-like dysfunctional patterns in cognitive, affective, impulse control, and interpersonal domains. These domains of dysfunction have been linked to specific neural circuits. Developments in brain imaging techniques have allowed researchers to examine the neural integrity of these circuits in personality-disordered individuals. This article reviews the neuroimaging literature on borderline personality disorder, antisocial personality disorder (including psychopathy) and schizotypal personality disorder. Functional and structural studies provide support for dysfunction in fronto-limbic circuits in borderline and antisocial personality disorder, whereas temporal lobe and basal striatal-thalamic compromise is evident in schizotypal personality disorder.

Structural brain differences in patients with schizophrenia and schizotypal disorder demonstrated by voxel-based morphometry

Brain abnormalities of schizophrenia probably consist of deviation related to the vulnerability and pathological changes in association with overt psychosis. We conducted a cross-sectional comparison in brain morphology between patients with overt schizophrenia and schizotypal disorder, a schizophrenia-spectrum disorder without florid psychotic episode. Voxelbased morphometry was applied to assess gray matter volume in 25 patients with schizophrenia, 25 patients with schizotypal disorder, and 50 healthy control subjects. In comparison with controls, schizophrenia patients showed gray matter reductions in the bilateral medial frontal, inferior frontal, medial temporal, and septal regions, and the left middle frontal, orbitofrontal, insula, and superior temporal regions, and an increased gray matter in the left basal ganglia. Schizotypal disorder patients showed reductions in the left inferior frontal, insula, superior temporal, and medial temporal regions. There was a significant reduction in the left orbitofrontal region of schizophrenia compared with schizotypal disorder. Gray matter reductions that are common to both patient groups such as those in the left medial temporal and inferior frontal regions may represent vulnerability to schizophrenia, and additional involvement of several frontal regions may be crucial to florid psychosis.