Waxholm Space atlas of the rat brain: a 3D atlas supporting data analysis and integration.

Volumetric brain atlases are increasingly used to integrate and analyze diverse experimental neuroscience data acquired from animal models, but until recently a publicly available digital atlas with complete coverage of the rat brain has been missing. Here we present an update of the Waxholm Space rat brain atlas, a comprehensive open-access volumetric atlas resource. This brain atlas features annotations of 222 structures, of which 112 are new and 57 revised compared to previous versions. It provides a detailed map of the cerebral cortex, hippocampal region, striatopallidal areas, midbrain dopaminergic system, thalamic cell groups, the auditory system and main fiber tracts. We document the criteria underlying the annotations and demonstrate how the atlas with related tools and workflows can be used to support interpretation, integration, analysis and dissemination of experimental rat brain data.

The intralaminar thalamus: a review of its role as a target in functional neurosurgery.

The intralaminar thalamus, in particular the centromedian-parafascicular complex, forms a strategic node between ascending information from the spinal cord and brainstem and forebrain circuitry that involves the cerebral cortex and basal ganglia. A large body of evidence shows that this functionally heterogeneous region regulates information transmission in different cortical circuits, and is involved in a variety of functions, including cognition, arousal, consciousness and processing of pain signals. Not surprisingly, the intralaminar thalamus has been a target area for (radio)surgical ablation and deep brain stimulation (DBS) in different neurological and psychiatric disorders. Historically, ablation and stimulation of the intralaminar thalamus have been explored in patients with pain, epilepsy and Tourette syndrome. Moreover, DBS has been used as an experimental treatment for disorders of consciousness and a variety of movement disorders. In this review, we provide a comprehensive analysis of the underlying mechanisms of stimulation and ablation of the intralaminar nuclei, historical clinical evidence, and more recent (experimental) studies in animals and humans to define the present and future role of the intralaminar thalamus as a target in the treatment of neurological and psychiatric disorders.

On the pathophysiology and treatment of akinetic mutism.

Akinetic mutism (AM) is a rare neurological disorder characterized by the presence of an intact level of consciousness and sensorimotor capacity, but with a simultaneous decrease in goal-directed behavior and emotions. Patients are in a wakeful state of profound apathy, seemingly indifferent to pain, thirst, or hunger. It represents the far end within the spectrum of disorders of diminished motivation. In recent years, more has become known about the functional roles of neurocircuits and neurotransmitters associated with human motivational behavior. More specific, there is an increasing body of behavioral evidence that links specific damage of functional frontal-subcortical organization to the occurrence of distinct neurological deficits. In this review, we combine evidence from lesion studies and neurophysiological evidence in animals, imaging studies in humans, and clinical investigations in patients with AM to form an integrative theory of its pathophysiology. Moreover, the specific pharmacological interventions that have been used to treat AM and their rationales are reviewed, providing a comprehensive overview for use in clinical practice.

Mesencephalic dopamine neurons interfacing the shell of nucleus accumbens and the dorsolateral striatum in the rat.

Parallel corticostriatonigral circuits have been proposed that separately process motor, cognitive, and emotional-motivational information. Functional integration requires that interactions exist between neurons participating in these circuits. This makes it imperative to study the complex anatomical substrate underlying corticostriatonigral circuits. It has previously been proposed that dopaminergic neurons in the ventral mesencephalon may play a role in this circuit interaction. Therefore, we studied in rats convergence of basal ganglia circuits by depositing an anterograde neuroanatomical tracer into the ventral striatum together with a retrograde fluorescent tracer ipsilaterally in the dorsolateral striatum. In the mesencephalon, using confocal microscopy, we looked for possible appositions of anterogradely labeled fibers and retrogradely labeled neurons, "enhancing" the latter via intracellular injection of Lucifer Yellow. Tyrosine hydroxylase (TH) immunofluorescence served to identify dopaminergic neurons. In neurophysiological experiments, we combined orthodromic stimulation in the medial ventral striatum with recording from ventral mesencephalic neurons characterized by antidromic stimulation from the dorsal striatum. We observed terminal fields of anterogradely labeled fibers that overlap populations of retrogradely labeled nigrostriatal cell bodies in the substantia nigra pars compacta and lateral ventral tegmental area (VTA), with numerous close appositions between boutons of anterogradely labeled fibers and nigrostriatal, TH-immunopositive neurons. Neurophysiological stimulation in the medial ventral striatum caused inhibition of dopaminergic nigrostriatal neurons projecting to the ventrolateral striatal territory. Responding nigrostriatal neurons were located in the medial substantia nigra and adjacent VTA. Our results strongly suggest a functional link between ventromedial, emotional-motivational striatum, and the sensorimotor dorsal striatum via dopaminergic nigrostriatal neurons.

Heterogeneous neuronal activity in the lateral habenula after short- and long-term cocaine self-administration in rats.

Cocaine addiction is thought to be the result of drug-induced functional changes in a neural network implicated in emotions, learning and cognitive control. Recent studies have implicated the lateral habenula (LHb) in drug-directed behavior, especially its aversive aspects. Limited cocaine exposure has been shown to alter neuronal activity in the LHb, but the impact of long-term drug exposure on habenula function has not been determined. Therefore, using c-fos as a marker, we here examined neuronal activity in LHb in rats that self-administered cocaine for either 10 or 60 days. Both the density of labeled cells and the cellular labeling intensity were measured in the lateral (LHbL) and medial (LHbM) parts of LHb. After 10 days of cocaine self-administration, both the density and intensity of c-fos-positive cells were significantly increased in LHbL, but not LHbM, while after 60 days, an increased density (but not intensity) of labeled neurons in both LHbL and LHbM was observed. Most c-fos-labeled neurons were glutamatergic. In addition, we found increased GAD65 expression after 10 but not 60 days of cocaine self-administration in the rostral mesencephalic tegmental nucleus. These data shed light on the complex temporal dynamics by which cocaine self-administration alters activity in LHb circuitry, which may play an important role in the descent to compulsive drug use as a result of prolonged cocaine-taking experience.

Damaged fiber tracts of the nucleus basalis of Meynert in Parkinson's disease patients with visual hallucinations.

Damage to fiber tracts connecting the nucleus basalis of Meynert (NBM) to the cerebral cortex may underlie the development of visual hallucinations (VH) in Parkinson's disease (PD), possibly due to a loss of cholinergic innervation. This was investigated by comparing structural connectivity of the NBM using diffusion tensor imaging in 15 PD patients with VH (PD + VH), 40 PD patients without VH (PD - VH), and 15 age- and gender-matched controls. Fractional anisotropy (FA) and mean diffusivity (MD) of pathways connecting the NBM to the whole cerebral cortex and of regional NBM fiber tracts were compared between groups. In PD + VH patients, compared to controls, higher MD values were observed in the pathways connecting the NBM to the cerebral cortex, while FA values were normal. Regional analysis demonstrated a higher MD of parietal (p = 0.011) and occipital tracts (p = 0.027) in PD + VH, compared to PD - VH patients. We suggest that loss of structural connectivity between the NBM and posterior brain regions may contribute to the etiology of VH in PD. Future studies are needed to determine whether these findings could represent a sensitive marker for the hypothesized cholinergic deficit in PD + VH patients.

Organization of the Anterior Limb of the Internal Capsule in the Rat.

Dysfunction of the orbitofrontal (OFC) and anterior cingulate (ACC) cortices has been linked with several psychiatric disorders, including obsessive-compulsive disorder, major depressive disorder, posttraumatic stress disorder, and addiction. These conditions are also associated with abnormalities in the anterior limb of the internal capsule, the white matter (WM) bundle carrying ascending and descending fibers from the OFC and ACC. Furthermore, deep-brain stimulation (DBS) for psychiatric disorders targets these fibers. Experiments in rats provide essential information on the mechanisms of normal and abnormal brain anatomy, including WM composition and perturbations. However, whereas descending prefrontal cortex (PFC) fibers in primates form a well defined and topographic anterior limb of the internal capsule, the specific locations and organization of these fibers in rats is unknown. We address this gap by analyzing descending fibers from injections of an anterograde tracer in the rat ACC and OFC. Our results show that the descending PFC fibers in the rat form WM fascicles embedded within the striatum. These bundles are arranged topographically and contain projections, not only to the striatum, but also to the thalamus and brainstem. They can therefore be viewed as the rat homolog of the primate anterior limb of the internal capsule. Furthermore, mapping these projections allows us to identify the fibers likely to be affected by experimental manipulations of the striatum and the anterior limb of the internal capsule. These results are therefore essential for translating abnormalities of human WM and effects of DBS to rodent models.SIGNIFICANCE STATEMENT Psychiatric diseases are linked to abnormalities in specific white matter (WM) pathways, and the efficacy of deep-brain stimulation relies upon activation of WM. Experiments in rodents are necessary for studying the mechanisms of brain function. However, the translation of results between primates and rodents is hindered by the fact that the organization of descending WM in rodents is poorly understood. This is especially relevant for the prefrontal cortex, abnormal connectivity of which is central to psychiatric disorders. We address this gap by studying the organization of descending rodent prefrontal pathways. These fibers course through a subcortical structure, the striatum, and share important organization principles with primate WM. These results allow us to model primate WM effectively in the rodent.

Circuit-Based Corticostriatal Homologies Between Rat and Primate.

BACKGROUND: Understanding the neural mechanisms of psychiatric disorders requires the use of rodent models; however, frontal-striatal homologies between rodents and primates are unclear. In contrast, within the striatum, the shell of the nucleus accumbens, the hippocampal projection zone, and the amygdala projection zone (referred to as the striatal emotion processing network [EPN]) are conserved across species. We used the relationship between the EPN and projections from the anterior cingulate cortex (ACC) and orbitofrontal cortex (OFC) to assess network similarities across rats and monkeys. METHODS: We first compared the location and extent of each major component of the EPN in rats and macaques. Next, we used anatomic cases with anterograde injections in ACC/OFC to determine the extent to which corticostriatal terminal fields overlapped with these components and with each other. RESULTS: The location and size of each component of the EPN were similar across species, containing projections primarily from infralimbic cortex in rats and area 25 in monkeys. Other ACC/OFC terminals overlapped extensively with infralimbic cortex/area 25 projections, supporting cross-species similarities in OFC topography. However, dorsal ACC had different connectivity profiles across species. These results were used to segment the monkey and rat striata according to ACC/OFC inputs. CONCLUSIONS: Based on connectivity with the EPN, and consistent with prior literature, the infralimbic cortex and area 25 are likely homologues. We also see evidence of OFC homologies. Along with segmenting the striatum and identifying striatal hubs of overlapping inputs, these results help to translate findings between rodent models and human pathology.

Compensatory fronto-parietal hyperactivation during set-shifting in unmedicated patients with Parkinson's disease.

Patients with Parkinson's disease (PD) often suffer from impairments in executive functions, such as mental rigidity, which can be measured as impaired set-shifting. Previous studies have shown that set-shifting deficits in patients with PD result from hypo-excitation of the caudate nucleus and lateral prefrontal cortices. The results of these studies may have been influenced by the inclusion of patients on dopaminergic medication, and by choosing set-shifting paradigms in which performance also depends on other cognitive mechanisms, such as matching-to-sample. To circumvent these potential confounding factors, we tested patients with PD that were not on dopamine replacement therapy, and we developed a new feedback-based paradigm to measure the cognitive construct set-shifting more accurately. In this case-control study, 18 patients with PD and 35 well-matched healthy controls performed the set-shifting task, while task-related neural activation was recorded using functional magnetic resonance imaging. Behaviourally, PD patients, compared with healthy controls, made more errors during repeat trials, but not set-shift trials. The patients, compared with controls, showed increased task-related activation of the bilateral inferior parietal cortex, and the right superior frontal gyrus, and decreased activation of the right ventrolateral prefrontal cortex during set-shift trials. Our findings suggest that, despite decreased task-related activation of the right ventrolateral prefrontal cortex, these early-stage unmedicated patients with PD do not yet suffer from set-shifting deficits due to compensatory hyperactivation in the inferior parietal cortex and the superior frontal gyrus.

Stage-dependent nigral neuronal loss in incidental Lewy body and Parkinson's disease.

To gain a better understanding of the significance of α-synuclein pathological conditions during disease progression in Parkinson's disease, we investigated whether 1) nigral neuronal loss in incidental Lewy body disease and Parkinson's disease donors is associated with the local burden α-synuclein pathological conditions during progression of pathological conditions; 2) the burden and distribution of α-synuclein pathological conditions are related to clinical measures of disease progression. Post-mortem tissue and medical records of 24 Parkinson's disease patients, 20 incidental Lewy body disease donors, and 12 age-matched controls were obtained from the Netherlands Brain Bank for morphometric analysis. We observed a 20% decrease in nigral neuronal cell density in incidental Lewy body disease compared with controls. Nigral neuronal loss (12%) was already observed before the appearance α-synuclein aggregates. The progression from Braak α-synuclein stage 3 to 4 was associated with a significant decline in neuronal cell density (46%). Nigral neuronal loss increased with later Braak α-synuclein stages but did not vary across consecutive Braak α-synuclein stages. We observed a negative correlation between neuronal density and local α-synuclein burden in the substantia nigra of Parkinson's disease patients (ρ = -0.54), but no relationship with Hoehn & Yahr stage or disease duration. In conclusion, our findings cast doubt on the pathogenic role of α-synuclein aggregates in elderly, but do suggest that the severity of neurodegeneration and local burden of α-synuclein pathological conditions are closely coupled during disease progression in Parkinson's disease.

Cerebrospinal fluid and plasma clusterin levels in Parkinson's disease.

Clusterin is a multifunctional chaperone protein that has repeatedly been linked to Alzheimer's disease (AD) pathogenesis and, more recently, also to Parkinson's disease (PD) by both genetic and proteomic analyses. Although clusterin is detectable in cerebrospinal fluid (CSF) and plasma, studies comparing clusterin levels in PD patients and controls have been scarce and yielded conflicting data. The aim of the present study was to determine whether CSF and/or plasma clusterin levels differ between PD patients and controls and are related to disease severity. We measured CSF and plasma clusterin levels in a group of 52 PD patients and in 50 age-matched neurologically healthy controls and found that clusterin levels in CSF and plasma were not different between the two groups. Furthermore, clusterin levels in CSF and plasma were not associated with disease duration, stage or severity. CSF clusterin levels did, however, correlate with CSF levels of total tau, phospho-tau and amyloid-ß-42. We elaborate on the identified correlations between levels of clusterin and AD related proteins and on possible explanations for the discrepant findings in clusterin studies in PD so far.

The rat prefrontostriatal system analyzed in 3D: evidence for multiple interacting functional units.

Previous studies in monkeys disclosed a specific arrangement of corticostriatal projections. Prefrontal and premotor areas form dense projection fields surrounded by diffuse terminal areas extending outside the densely innervated region and overlapping with projections from other areas. In this study, the mode of prefrontostriatal innervation was analyzed in rats using a 3D approach. Following injections of tracers in defined cortical areas, 3D maps from individual cases were elaborated and combined into a global 3D map allowing us to define putative overlaps between projection territories. In addition to providing a detailed 3D mapping of the topographic representation of prefrontal cortical areas in the rat striatum, the results stress important similarities between the rodent and primate prefrontostriatal projections. They share the dual pattern of focal and diffuse corticostriatal projections. Moreover, besides segregated projections consistent with parallel processing, the interweaving of projection territories establishes specific patterns of overlaps spatially organized along the dorsoventral, mediolateral, and anteroposterior striatal axis. In particular, the extensive striatal projection fields from the prelimbic and anterior cingulate areas, which partly overlap the terminal fields from medial, orbital, and lateral prefrontal cortical areas, provide putative domains of convergence for integration between reward, cognitive, and motor processes.

Limbic and motor circuits involved in symmetry behavior in Tourette's syndrome.

OBJECTIVE: The need for symmetry and ordering objects related to a "just right"-feeling is a common symptom in Tourette's syndrome (TS) and resembles symmetry behavior in obsessive-compulsive disorder, but its pathophysiology is unknown. We used a symptom provocation paradigm to investigate the neural correlates of symmetry behavior in TS and hypothesized the involvement of frontal-striatal and limbic brain areas. METHODS: Pictures of asymmetrically and symmetrically arranged objects were presented in randomized blocks (4 blocks of each condition) to 14 patients with TS and 10 matched healthy controls (HC). A H2 15O positron emission tomography scan was acquired during each stimulus block, resulting in 8 scans per subject. After each scan, state anxiety and symmetry behavior (the urge to rearrange objects) were measured using a visual analogue scale. RESULTS: During the asymmetry condition, TS patients showed increased regional cerebral blood flow (rCBF) in the anterior cingulate cortex, supplementary motor area, and inferior frontal cortex, whereas HC showed increased rCBF in the visual cortex, primary motor cortex, and dorsal prefrontal cortex. Symmetry ratings during provocation correlated positively with orbitofrontal activation in the TS group and sensorimotor activation in the HC group, and negatively with dorsal prefrontal activity in HC. CONCLUSIONS: Results suggest that both motor and limbic circuits are involved in symmetry behavior in TS. Motor activity may relate to an urge to move or perform tics, and limbic activation may indicate that asymmetry stimuli are salient for TS patients. In contrast, symmetry provocation in HC resulted in activation of brain regions implicated in sensorimotor function and cognitive control.

The proteome of the locus ceruleus in Parkinson's disease: relevance to pathogenesis.

The locus ceruleus is among the earliest affected brain regions in Parkinson's disease (PD) showing Lewy body pathology and neuronal loss. To improve our understanding of the pathogenesis of PD, we performed the first proteomic analysis ever of post-mortem locus ceruleus tissue of six pathologically confirmed PD patients, and six age- and gender-matched non-neurological controls. In total 2495 proteins were identified, of which 87 proteins were differentially expressed in the locus ceruleus of PD patients compared with controls. The majority of these differentially expressed proteins are known to be involved in processes that have been implicated in the pathogenesis of PD previously, including mitochondrial dysfunction, oxidative stress, protein misfolding, cytoskeleton dysregulation and inflammation. Several individual proteins were identified that have hitherto not been associated with PD, such as regucalcin, which plays a role in maintaining intracellular calcium homeostasis, and isoform 1 of kinectin, which is involved in transport of cellular components along microtubules. In addition, pathway analysis suggests a pathogenetic role for aminoacyl-tRNA-biosynthesis. These findings indicate that the proteome of the locus ceruleus of PD patients and non-neurological controls provides data that are relevant to the pathogenesis of PD, reflecting both known and potentially novel pathogenetic pathways.

Density gradients of vesicular glutamate- and GABA transporter-immunoreactive boutons in calbindinand µ-opioid receptor-defined compartments in the rat striatum.

Cortical and subcortical inputs to the striatum are functionally highly organized and they obey to some extent striatal patch-matrix topography. Whether this organization is reflected in the density of various glutamatergic endings is unknown. We therefore mapped boutons expressing the vesicular glutamate transporters VGluT1 and VGluT2, together with boutons immunoreactive for vesicular γ-aminobutyric acid (GABA) transporter (VGAT) in patch and matrix throughout the striatum. We used triple-immunofluorescence staining followed by multichannel, high-magnification confocal laser scanning and 3D object recognition. Densities of VGluT1 and VGluT2 boutons were on average higher in matrix than in patches in all striatal sectors. The dorsal one-third of the striatum contained the highest densities of VGluT1 boutons. Subsequent 3D surface plotting revealed patterns of density "valleys" in the dorsomedial striatum coinciding with patch locations in the patch-matrix mapping. The density of VGluT1 boutons increased along three axes: ventrolateral-to-dorsomedial, ventral-to-dorsal, and lateral-to-medial. In contrast, VGluT2 showed a global increase in density from lateral to medial and a relatively high density in the ventral striatum. VGAT appeared more evenly distributed in the striatal patch-matrix than the VGluTs, with a tendency of bouton density to increase from medial to lateral. We noted a good correlation between the high VGluT1 bouton density dorsomedially with inputs from dorsal medial prefrontal cortex and related thalamic regions, and the enhanced VGluT2 input ventromedially with input from ventral medial prefrontal cortex and thalamic, amygdaloid, and hippocampal sources.

Diagnostic cerebrospinal fluid biomarkers for Parkinson's disease: a pathogenetically based approach.

The inaccuracy of the early diagnosis of Parkinson's disease (PD) has been a major incentive for studies aimed at the identification of biomarkers. Brain-derived cerebrospinal fluid (CSF) proteins are potential biomarkers considering the major role that proteins play in PD pathogenesis. In this review, we discuss the current hypotheses about the pathogenesis of PD and identify the most promising candidate biomarkers among the CSF proteins studied so far. The list of potential markers includes proteins involved in various pathogenetic processes, such as oxidative stress and protein aggregation. This list will undoubtedly grow in the near future by application of CSF proteomics and subsequent validation of identified proteins. Probably a single biomarker will not suffice to reach high sensitivity and specificity, because PD is pathogenetically heterogeneous and shares etiological factors with other neurodegenerative diseases. Furthermore, identified candidate biomarkers will have to be thoroughly validated before they can be implemented as diagnostic aids.

A 3D multi-modal and multi-dimensional digital brain model as a framework for data sharing.

Computer based three-dimensional reconstruction and co-registration of experimental data provide powerful tools for integration of observation derived from various technical approaches leading to better understanding of brain functions. Here we describe a method to build a 3D multi-modal and multi-dimensional model of brain structures providing framework for data sharing. All image processing, registration and 3D reconstruction were performed using open source software IMOD package software and ImageJ. The reconstruction procedure is based on series of AChE and Nissl stained sections aligned to blockface pictures. Integration of experimental data into the reference model is achieved by co-registration of Nissl sections of experimental brain cases by positioning landmarks on corresponding anatomical structures. To overcome the challenge of comparing for experimental sections with those of the reference model, adjustment of experimental model to the brain model was done section by section and limited to the structures of interest. For this adjustment we stress the use of cytoarchitectural criteria for accurate registration of anatomical structures and co-registration procedures.

Frontal-striatal abnormalities underlying behaviours in the compulsive-impulsive spectrum.

In this paper, we tentatively bring together the psychiatric, neurological and addiction perspectives on the impulsive-compulsive spectrum of neuropsychiatric disorders, in order to understand the pathophysiology of impulse control disorders (ICDs) in Parkinson's disease. In an attempt to try to pool the various levels of information we will therefore focus on three disorders within the impulse-compulsive spectrum, i.e., obsessive-compulsive disorder (OCD), ICDs in Parkinson's disease, and cocaine seeking behaviour. Whereas there are large differences between these three domains, each with their own nomenclature, hypotheses and study results, they share the focus on an imbalance within and between the frontal-striatal circuits as underlying substrate for the behaviours. For each disorder, we summarize the results from recent studies in order to describe in which way alterations in the frontal-striatal circuits contribute to the phenotype. The phenomenological overlap between ICDs in Parkinson's disease, addiction and OCD needs further investigation, since better understanding of the overlapping and differentiating characteristics will contribute to our understanding of the pathophysiology of the disturbances and treatment alternatives.

[Give attention to war in medical education]. / Schenk aandacht aan oorlog in het medisch onderwijs.

Medical consequences of war are prominent in the media. The United Nations and the World Medical Association have called for medical curricula to permanently include consideration of human rights, in particular human rights in war time. Information on the medical consequences of war and weapon systems is valuable knowledge. Courses on this subject are popular amongst medical students, a considerable number of whom are willing to spend a period working for organisations as the Red Cross, Doctors without Borders or the Military Health Service. In spite of this, none of the Dutch medical faculties has given the subject a permanent place in its curriculum. Gathering knowledge on the medical consequences of war depends completely on the efforts of individuals.