Hp Burmeister

Default mode network activity in schizophrenia studied at resting state using probabilistic ICA

Alterations in brain function in schizophrenia and other neuropsychiatric disorders are evident not only during specific cognitive challenges, but also from functional MRI data obtained during a resting state. Here we apply probabilistic independent component analysis (pICA) to resting state fMRI series in 25 schizophrenia patients and 25 matched healthy controls. We use an automated algorithm to extract the ICA component representing the default mode network (DMN) as defined by a DMN-specific set of 14 brain regions, resulting in z-scores for each voxel of the (whole-brain) statistical map. While goodness of fit was found to be similar between the groups, the region of interest (ROI) as well as voxel-wise analysis of the DMN showed significant differences between groups. Healthy controls revealed stronger effects of pICA-derived connectivity measures in right and left dorsolateral prefrontal cortices, bilateral medial frontal cortex, left precuneus and left posterior lateral parietal cortex, while stronger effects in schizophrenia patients were found in the right amygdala, left orbitofrontal cortex, right anterior cingulate and bilateral inferior temporal cortices. In patients, we also found an inverse correlation of negative symptoms with right anterior prefrontal cortex activity at rest and negative symptoms. These findings suggest that aberrant default mode network connectivity contributes to regional functional pathology in schizophrenia and bears significance for core symptoms.

Anosmia Leads to a Loss of Gray Matter in Cortical Brain Areas

Chronic olfactory disorders, including the complete loss of the sense of smell (anosmia), are common. Using voxel-based morphometry (VBM) in magnetic resonance imaging (MRI), structural changes in the cerebral gray matter (GM) of a group of patients with anosmia compared with a normosmic, healthy control group were evaluated. Patients with anosmia presented a significant decrease of GM volume mainly in the nucleus accumbens with adjacent subcallosal gyrus, in the medial prefrontal cortex (MPC) including the middle and anterior cingulate cortices, and in the dorsolateral prefrontal cortex (dlPFC). These areas are part of the limbic loop of the basal ganglia and except the dlPFC secondary olfactory areas. They also play an important role in many neurological diseases. Furthermore, volume decreases in smaller areas like the piriform cortex, insular cortex, orbitofrontal cortex, hippocampus, parahippocampal gyrus, supramarginal gyrus, and cerebellum could be seen. Longer disease duration was associated with a stronger atrophy in the described areas. No local increases in the GM volume could be observed. A comparison with results of an additionally executed functional MRI study on olfaction in healthy subjects was performed to evaluate the significance of the observed atrophy areas in cerebral olfactory processing. To our knowledge, this is the first study on persisting structural changes in cortical GM volume after complete olfactory loss.

Gray and white matter reduction in hyposmic subjects — A voxel-based morphometry study

The absence of olfactory input causes structural brain remodelling in humans. Mainly, the olfactory bulb and cortical olfactory areas are involved in this process. The aim of our study was to investigate volume changes of the gray and white matter in a group of subjects with an impaired but not complete loss of olfaction (hyposmia). Magnetic resonance images of hyposmic subjects and an age- and sex-matched control group were acquired on a 3T scanner. Voxel-based morphometry (VBM) was performed using VBM8 toolbox and SPM8 in a Matlab environment. The analysis revealed significant gray matter volume loss in the insular cortex, anterior cingulate cortex, orbitofrontal cortex, cerebellum, fusiform gyrus, precuneus, middle temporal gyrus and piriform cortex. In the VBM white matter analysis areas of volume loss were found underneath the insular cortex, in the cerebellum and middle frontal gyrus. All areas of white matter atrophy were spatially connected to areas of gray matter volume loss except the middle frontal gyrus alterations. No significant gray or white matter volume increases could be observed. The pattern of gray matter alterations was similar to that known from anosmic subjects with a lower extent. To our knowledge, we report here for the first time on white matter volume alterations in patients with olfactory deficit.

Functional deactivations: multiple ipsilateral brain areas engaged in the processing of somatosensory information.

Somatosensory signals modulate activity throughout a widespread network in both of the brain hemispheres: the contralateral as well as the ipsilateral side of the brain relative to the stimulated limb. To analyze the ipsilateral somatosensory brain areas that are engaged during limb stimulation, we performed functional magnetic resonance imaging (fMRI) in 12 healthy subjects during electrical median nerve stimulation using both a block‐ and an event‐related fMRI design. Data were analyzed through the use of model‐dependent (SPM) and model‐independent (ICA) approaches. Beyond the well‐known positive blood oxygenation level‐dependent (BOLD) responses, negative deflections of the BOLD response were found consistently in several ipsilateral brain areas, including the primary somatosensory cortex, the supplementary motor area, the insula, the dorsal part of the posterior cingulate cortex, and the contralateral cerebellum. Compared to their positive counterparts, the negative hemodynamic responses showed a different time course, with an onset time delay of 2.4 s and a peak delay of 0.7 s. This characteristic delay was observed in all investigated areas and verified by a second (purely tactile) event‐related paradigm, suggesting a systematic difference for brain areas involved in the processing of somatosensory information. These findings may indicate that the physiological basis of these deactivations differs from that of the positive BOLD responses. Therefore, an altered model for the negative BOLD response may be beneficial to further model‐dependent fMRI analyses. Hum Brain Mapp, 2010.

Clinical MR Mammography: Impact of Hormonal Status on Background Enhancement and Diagnostic Accuracy

PURPOSE Hormonal stimulation can induce background enhancement (BE) in MR mammography (MRM). This fact has been assumed to decrease the accuracy of MRM. Consequently, this report investigates: 1. The prevalence of BE in postmenopausal vs. premenopausal women in correlation to hormonal cycle phase (CP). 2. The impact of hormonal status (HS) and BE on diagnostic accuracy. MATERIALS AND METHODS Consecutive patients over 22 months with complete HS information (week of CP or postmenopausal) were included in this prospective investigation. Exclusion criteria were any hormonal therapy, hysterectomy as well as cancer proven by biopsy. The standard of reference was histopathology. All MRM scans were acquired using the same protocol (1.5 T, dynamic T 1w GRE after 0.1 mmol/kg bw Gd-DTPA i. v.). Two radiologists rated all examinations in consensus according to BI-RADS. BE was defined as: 0 = missing, 1 = moderate, 2 = distinct. RESULTS 224 patients (150 postmenopausal, 74 premenopausal, 45 in the second week of CP) were included in this study (83 benign and 141 malignant findings). BE was more frequent in premenopausal women (p = 0.006), but did not differ between CP (p = 0.460). Neither HS nor BE had a significant impact on the diagnostic parameters of MRM (p ≥ 0.375). However, regarding BE, the relative number of false positive (FP) findings was highest (5 / 10; 50 %) in the distinct BE group. Regarding HS, 17 % more FP findings were observed in premenopausal women examined outside the second week of CP. CONCLUSION In premenopausal women, HS leads to increased BE of breast tissue, independent of CP. Distinct BE and less pronounced, non-optimal CP may lead to an increased number of false positive findings.

Cortical reorganization in Bell's palsy

PURPOSE Bells palsy, a unilateral, idiopathic facial nerve palsy, is a common disorder that is generally followed by a good recovery of function. The aim of this study was to investigate the impact of such a transiently decreased motor control (without deafferentation) on the functional reorganization of the brain. METHODS To address this issue, functional MRI was applied to 10 patients in the acute state of Bells palsy and after their complete clinical recovery. The functional paradigm consisted of unilateral facial movements with the affected as well as the non-affected side. RESULTS We found an overactivity of several brain areas contralateral to the palsy that are related to error detection and sensory-motor integration in the acute stage and motor integration and control in the follow-up. Functional connectivity was disrupted in the affected cortical motor system during the acute stage of Bells palsy compared to the follow-up. This altered connectivity was found mostly between motor areas in the hemisphere contralateral to the paretic side, whereas the interhemispherical connectivity remained largely stable. CONCLUSION Our results indicate that a transient peripheral deefferentation causes functional reorganization in the brain that partly persists even after an apparently complete clinical recovery.

Gray matter alterations in parosmia.

Parosmia is a common olfactory disorder. In this condition, odors are perceived in a different quality than usual. This distorted olfactory percept is typically reported to be unpleasant. Little is known about the pathophysiology of this phenomenon. Previous studies demonstrated smaller volumes of the olfactory bulbs in patients with parosmia compared to subjects without parosmia. In order to investigate structural brain alterations in areas beyond the olfactory bulb, in the current study voxel-based morphometry was applied. A group of 22 parosmic patients was compared with control subjects matched for age- and sex, who exhibited a similar performance in olfactory tests. Performing a whole brain analysis, we found profound gray matter volume loss in the left anterior insula in parosmic patients. In an additional volume of interest analysis including primary and secondary olfactory areas, we also found volume loss in the right anterior insula, the anterior cingulate cortex, the hippocampus bilaterally, and the left medial orbitofrontal cortex. Many of these areas are critically involved in olfactory quality discrimination and odor memory. The present results indicate that reduced gray matter volume in brain regions supporting odor discrimination and memory is related to disturbed olfactory sensation in parosmia.

Time Course of Cortical Plasticity After Facial Nerve Palsy A Single-Case Study

Background. Functional connectivity is defined as the temporal correlation between spatially remote neurophysiological events. This method has become particularly useful for studying neuroplasticity to detect changes in the collaboration of brain areas during cortical reorganization. Methods. In this article, the authors longitudinally studied voxel-based morphometry and resting state functional magnetic resonance imaging 10 times in 1 patient during the course of Bell palsy (idiopathic facial nerve palsy) up to complete clinical recovery. Results. Morphometric analysis revealed a significant alteration in the face area of the primary motor cortex (M1) contralateral to the paretic face, with an initial increase in gray matter concentration. Functional connectivity analysis between the M1 and other parts of the facial motor network revealed acutely disrupted intrahemispheric connectivity but unaltered interhemispheric connectivity. The disrupted functional connectivity was most pronounced on the day of the onset of symptoms, with a subsequent return toward normal during the course of recovery. This time course was found to differ between the selected parts of the facial motor network. However, the increase in functional connectivity strength preceded clinical recovery in all areas and reached a stable level before the patient fully recovered. Conclusion. These results demonstrate that recovery from facial nerve palsy is complemented by cortical reorganization, with pronounced changes of functional connectivity that precede clinical recovery.

Visual Grading Characteristics (VGC) Analysis of Diagnostic Image Quality for High Resolution 3 Tesla MRI Volumetry of the Olfactory Bulb

RATIONALE AND OBJECTIVES The aim of this study was to evaluate the suitability of 3-T magnetic resonance imaging (MRI) for olfactory bulb volumetry, comparing image quality obtained using different sequences on the basis of physical characteristics in combination with observer performance. MATERIALS AND METHODS Twenty-two healthy volunteers (11 men, 11 women; mean age, 25 years) underwent 3-T MRI of the frontal skull base in this prospective study. Imaging was performed using a constructive interference in steady state (CISS) three-dimensional Fourier transformation sequence, a three-dimensional T2-weighted (3D-T2w) sequence, and a two-dimensional T2-weighted (2D-T2w) sequence. The relative performance of sequences was assessed using visual grading characteristic analysis. Interobserver agreement was assessed using κ statistics. For evaluation of physical image quality characteristics, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated and compared using Wilcoxons test. SNR and CNR measurements were correlated with visual grading results. RESULTS Visual grading characteristic analysis showed significantly better image quality ratings for the CISS sequence compared to the 3D-T2w and 2D-T2w sequence, and the 2D-T2w sequence performed significantly better compared to the 3D-T2w sequence (P < .001). Interobserver agreement was substantial (κ = 0.66-0.73). Wilcoxons test revealed significantly higher SNR and CNR values for the 2D-T2w sequence compared to the 3D-T2w and CISS sequences, and SNR and CNR values for the 3D-T2w sequence were significantly higher compared to those for the CISS sequence (P < .001 for each). Significant correlation between SNR and CNR and visual grading was found for the 3D-T2w sequence (SNR: ρ = 0.510, P = .015; CNR: ρ = 0.546, P = .009). CONCLUSIONS High-resolution 3-T MRI resulted in excellent values for SNR and CNR, suggesting the appropriateness of the sequences for olfactory bulb MRI volumetry. Visual grading characteristic analysis revealed the CISS sequence to be the most suitable for olfactory bulb volumetry.

Antipsychotic drug effects on left prefrontal phospholipid metabolism: A follow-up 31P-2D-CSI study of haloperidol and risperidone in acutely ill chronic schizophrenia patients

INTRODUCTION ³¹Phosphorous magnetic resonance spectroscopy (2D chemical shift imaging, CSI) allows multiregional study of membrane phospholipids and high-energy phosphates in vivo. Increased membrane lipid turnover and impaired energy supply have repeatedly been shown in first-episode schizophrenia patients, and might be a target of drug actions other than dopamine receptors. Here, we explored differential metabolic effects of a typical vs. an atypical antipsychotic on brain phospholipids. METHODS We applied 2D-CSI MR spectroscopy in 17 recurrent-episode schizophrenia patients off antipsychotics at baseline and at follow-up after 6 weeks, during which 7 patients were treated with haloperidol (10-16 mg/d) and 10 with risperidone (4-6 mg/d). Psychopathology changes were assessed using PANSS, BPRS and CGI scores. RESULTS Follow-up analysis using repeated measure ANOVA revealed different effects of both antipsychotic agents: while risperidone generally increased metabolite levels, haloperidol showed a tendency to decrease them. This diverging effect was significant for ATP levels in the left lateral frontal cortex. Furthermore, risperidone increased ATP in the left dorsolateral prefrontal cortex, left anterior temporal cortex and left insular cortex, basal ganglia, and anterior cerebellum, along with left frontal and prefrontal increase of PCr, PDE and PME in these brain regions. CONCLUSION Risperidone seems to stimulate neuronal and synaptic phospholipid remodeling in left frontal and prefrontal regions, and to a lesser extent also in temporal and insular cortices. We discuss these effects with respect to clinical effects on negative and cognitive symptoms, as well as interaction of phospholipid metabolism with glutamatergic neurotransmission.