Carsten R. Bjarkam

Long-term meditation is associated with increased gray matter density in the brain stem

Extensive practice involving sustained attention can lead to changes in brain structure. Here, we report evidence of structural differences in the lower brainstem of participants engaged in the long-term practice of meditation. Using magnetic resonance imaging, we observed higher gray matter density in lower brain stem regions of experienced meditators compared with age-matched nonmeditators. Our findings show that long-term practitioners of meditation have structural differences in brainstem regions concerned with cardiorespiratory control. This could account for some of the cardiorespiratory parasympathetic effects and traits, as well as the cognitive, emotional, and immunoreactive impact reported in several studies of different meditation practices.

Neurite density from magnetic resonance diffusion measurements at ultrahigh field: Comparison with light microscopy and electron microscopy

Due to its unique sensitivity to tissue microstructure, diffusion-weighted magnetic resonance imaging (MRI) has found many applications in clinical and fundamental science. With few exceptions, a more precise correspondence between physiological or biophysical properties and the obtained diffusion parameters remain uncertain due to lack of specificity. In this work, we address this problem by comparing diffusion parameters of a recently introduced model for water diffusion in brain matter to light microscopy and quantitative electron microscopy. Specifically, we compare diffusion model predictions of neurite density in rats to optical myelin staining intensity and stereological estimation of neurite volume fraction using electron microscopy. We find that the diffusion model describes data better and that its parameters show stronger correlation with optical and electron microscopy, and thus reflect myelinated neurite density better than the more frequently used diffusion tensor imaging (DTI) and cumulant expansion methods. Furthermore, the estimated neurite orientations capture dendritic architecture more faithfully than DTI diffusion ellipsoids.

Evidence implicating BRD1 with brain development and susceptibility to both schizophrenia and bipolar affective disorder

Linkage studies suggest that chromosome 22q12–13 may contain one or more shared susceptibility genes for schizophrenia (SZ) and bipolar affective disorder (BPD). In a Faeroese sample, we previously reported association between microsatellite markers located at 22q13.31-qtel and both disorders. The present study reports an association analysis across five genes (including 14 single nucleotide and two microsatellite polymorphisms) in this interval using a case–control sample of 162 BPD, 103 SZ patients and 200 controls. The bromodomain-containing 1 gene (BRD1), which encodes a putative regulator of transcription showed association with both disorders with minimal P-values of 0.0046 and 0.00001 for single marker and overall haplotype analysis, respectively. A specific BRD1 2-marker ‘risk’ haplotype showed a frequency of ∼10% in the combined case group versus ∼1% in controls (P-value 2.8 × 10−7). Expression analysis of BRD1 mRNA revealed widespread expression in mammalian brain tissue, which was substantiated by immunohistochemical detection of BRD1 protein in the nucleus, perikaryal cytosol and proximal dendrites of the neurons in the adult rat, rabbit and human CNS. Quantitative mRNA analysis in developing fetal pig brain revealed spatiotemporal differences with high expression at early embryonic stages, with intense nuclear and cytosolar immunohistochemical staining of the neuroepithelial layer and early neuroblasts, whilst more mature neurons at later embryonic stages had less nuclear staining. The results implicate BRD1 with SZ and BPD susceptibility and provide evidence that suggests a role for BRD1 in neurodevelopment.

Chronic subthalamic high-frequency deep brain stimulation in Parkinson's disease – a histopathological study

This study describes the pathological findings in the brain of a patient with Parkinsons disease (PD) treated with bilateral subthalamic high‐frequency deep brain stimulation (STN DBS) for 29 months prior to death. After routine neuropathological examination, tissue blocks containing the electrode tracts, the subthalamic nucleus (STN), the substantia nigra and the pre‐frontal cortex were paraffin embedded and cut into 5‐μm‐thick serial sections and stained with several conventional staining methods and immunohistochemistry. Bilateral nigral depigmentation, cell loss and Lewy body formation confirmed the diagnosis of PD. Microscopic evaluation furthermore confirmed the location of the electrodes in the STN. The electrode tracts were surrounded by a 150‐μm‐wide glial fibrillary acidic protein (GFAP)‐positive capsule consisting of a thin collagen layer lining the lumen of the tract, whilst an area with few cells and axons constituted the capsule wall towards the surrounding normal brain tissue. The brain tissue appeared normal outside the capsule boundaries with no difference in areas of stimulation compared with areas of no stimulation. Our results correspond with previous studies performed after fewer months of STN DBS and indicate mild histopathological changes in the vicinity of the electrode tract, appearing to result from the electrode placement and not from the electrical stimulation.

Regional brain atrophy in primary fatigued patients with multiple sclerosis

OBJECTIVE To examine the relationship between fatigue, regional brain atrophy and normal appearing white matter damage in patients with multiple sclerosis. METHODS Primary fatigued (PF) (n, 17) and non-fatigued (NF) (n, 17) patients with relapsing remitting multiple sclerosis and moderate disability were grouped according to their subjective fatigue score. Also, they were examined with respect to processing speed and central motor activation during isometric contraction. Using 3 Tesla MRI quantitative analyses were performed on normal appearing brain tissue and of brain structure volumes with tensor based morphometry. RESULTS Between the PF and NF patients there was no significant differences in brain parenchymal fraction (81.5% vs. 82.4%), lesion load (0.53% vs. 0.36%) and NAA/Cr ratio (1.29 vs. 1.32 respectively). Eleven clusters of atrophy in PF versus NF involved gray and nearby white matter, the majority being located in areas functionally related to attentional control. Central motor activation was associated with atrophy in five regions in PF patients, three clusters involving the premotor and primary motor cortex. Normal appearing white matter did not differ between groups. CONCLUSION Primary fatigued patients with multiple sclerosis have extended regional atrophy of supratentorial brain parenchyma, involving the cerebral cortex, nearby white matter and the caudate head, areas which are functionally related to attentional control. We suggest that impaired central motor activation is due to interruption of the cortico-subcortical motor circuits involving the motor cortex.

Long-term Delivery of Nerve Growth Factor by Encapsulated Cell Biodelivery in the Göttingen Minipig Basal Forebrain

Nerve growth factor (NGF) prevents cholinergic degeneration in Alzheimers disease (AD) and improves memory in AD animal models. In humans, the safe delivery of therapeutic doses of NGF is challenging. For clinical use, we have therefore developed an encapsulated cell (EC) biodelivery device, capable of local delivery of NGF. The clinical device, named NsG0202, houses an NGF-secreting cell line (NGC-0295), which is derived from a human retinal pigment epithelial (RPE) cell line, stably genetically modified to secrete NGF. Bioactivity and correct processing of NGF was confirmed in vitro. NsG0202 devices were implanted in the basal forebrain of Göttingen minipigs and the function and retrievability were evaluated after 7 weeks, 6 and 12 months. All devices were implanted and retrieved without associated complications. They were physically intact and contained a high number of viable and NGF-producing NGC-0295 cells after explantation. Increased NGF levels were detected in tissue surrounding the devices. The implants were well tolerated as determined by histopathological brain tissue analysis, blood analysis, and general health status of the pigs. The NsG0202 device represents a promising approach for treating the cognitive decline in AD patients.

Distribution and morphology of serotonin-immunoreactive neurons in the brainstem of the New Zealand white rabbit

The aim of the present study was to demonstrate the morphology and distribution of the serotonergic neurons in the brainstem of the New Zealand white rabbit by using a highly specific immunocytochemical procedure. It was possible to divide the serotonergic neurons into a rostral group, which is situated in the mesencephalon and the rostral part of the pons containing four serotonergic nuclei, and a caudal group, which is located in the medulla and the caudal part of the pons containing five serotonergic nuclei. The localization of the serotonergic neurons is presented in a detailed brainstem atlas, and the distribution of the serotonergic neurons is in accordance with results obtained by other authors in different species.

A MRI-compatible stereotaxic localizer box enables high-precision stereotaxic procedures in pigs.

We present a nonmagnetic Plexiglas stereotaxic localizer box that can be fitted directly to the pig skull by aluminum screws, allowing stereotaxic MRI or ventriculography and subsequent high-precision stereotaxic procedures. The localizer box was used to target the subthalamic nucleus (STN) bilaterally in five female Göttingen minipigs. Stereotaxic markers were inserted in the pig skull, the head fixated in the localizer box by aluminum screws inserted bilaterally in the zygoma bone with the hard palate locked on a horizontal palate holder. MRI was obtained on a 3T-MR-imager revealing the relation between the inserted markers and the estimated STN-position, and thus the target coordinates. After the MRI, a stereotaxic frame with attached micromanipulator was locked on to the localizer box converting it into a stereotaxic device. The stereotaxic markers were exposed and used as starting point for the stereotaxic procedure, whereby a microelectrode for electrolytic lesioning was inserted in the STN. Postmortem histological analysis revealed 70% correct STN-targeting. The average distance from the lesion center to the STN center was 1.2 mm with a S.D. of 1.1 mm. The most displaced lesion being 3.6 mm from the STN center. We conclude that the described localizer box secure firm head fixation, allowing stereotaxic MRI and subsequent conversion into a stereotaxic device for high-precision stereotaxic procedures.

Pig brain stereotaxic standard space: Mapping of cerebral blood flow normative values and effect of MPTP-lesioning

The analysis of physiological processes in brain by position emission tomography (PET) is facilitated when images are spatially normalized to a standard coordinate system. Thus, PET activation studies of human brain frequently employ the common stereotaxic coordinates of Talairach. We have developed an analogous stereotaxic coordinate system for the brain of the Gottingen miniature pig, based on automatic co-registration of magnetic resonance (MR) images obtained in 22 male pigs. The origin of the pig brain stereotaxic space (0, 0, 0) was arbitrarily placed in the centroid of the pineal gland as identified on the average MRI template. The orthogonal planes were imposed using the line between stereotaxic zero and the optic chiasm. A series of mean MR images in the coronal, sagittal and horizontal planes were generated. To test the utility of the common coordinate system for functional imaging studies of minipig brain, we calculated cerebral blood flow (CBF) maps from normal minipigs and from minipigs with a syndrome of parkisonism induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-poisoning. These maps were transformed from the native space into the common stereotaxic space. After global normalization of these maps, an undirected search for differences between the groups was then performed using statistical parametric mapping. Using this method, we detected a statistically significant focal increase in CBF in the left cerebellum of the MPTP-lesioned group. We expect the present approach to be of general use in the statistical parametric mapping of CBF and other physiological parameters in living pig brain.

New strategies for embedding, orientation and sectioning of small brain specimens enable direct correlation to MR-images, brain atlases, or use of unbiased stereology

We present a newly developed brain slicing machine and technique for tissue embedding, which enable orientation of fresh or fixed brain tissue from small laboratory animals, in any given position, and subsequent tissue sectioning into slabs with an optional thickness between 0.5 and 20 mm. The oriented tissue slabs may be analysed directly, or processed further on a cryostat or vibratome, into thin stainable histological sections, and aligned to MR-images or brain atlases, depending on the reference used for the initial orientation. Additionally, we describe a new embedding medium (HistOmer) which is an alginate cold polymer ready for instant use after mixing with water. HistOmer allows accurate positioning of the tissue during embedding, and at the same time supports and protects the embedded tissue during sectioning. HistOmer is, therefore, described comprehensively and compared with other commonly used embedding media. This novel slicing technique may also, as illustrated, be used to perform isotropic random orientation of the embedded tissue, before sectioning into tissue slabs of the same thickness. The technique thereby fulfills the requirements for optimal tissue sampling and preparation needed for an unbiased stereologic analysis.