Cerebellum

Nitric oxide mediates vascular relaxing effects of endothelial cells, cytotoxic actions of macrophages and neutrophils, and influences of excitatory amino acids on cerebellar cyclic GMP. Its enzymatic formation from arginine by a soluble enzyme associated with stoichiometric production of citrulline requires NADPH and Ca2 . We show that nitric oxide synthetase

Nitric oxide (NO), apparently identical to endothelium-derived relaxing factor in blood vessels, is also formed by cytotoxic macrophages, in adrenal gland and in brain tissue, where it mediates the stimulation by glutamate of cyclic GMP formation in the cerebellum. Stimulation of intestinal or anococcygeal nerves liberates NO, and the resultant muscle relaxation is blocked by arginine derivatives that inhibit NO synthesis. It is, however, unclear whether in brain or intestine, NO released following nerve stimulation is formed in neurons, glia, fibroblasts, muscle or blood cells, all of which occur in proximity to neurons and so could account for effects of nerve stimulation on cGMP and muscle tone. We have now localized NO synthase protein immunohistochemically in the rat using antisera to the purified enzyme. We demonstrate NO synthase in the brain to be exclusively associated with discrete neuronal populations. NO synthase is also concentrated in the neural innervation of the post...

40. In the alternative arrangement, p53 finger 2 spans a 4-bp subsite (3Ј-ACAG-5Ј) and finger 3 recognizes the adjacent 3Ј-GGT-5Ј subsite. A similar spacing occurs at one point in the GLI-DNA complex (12). 41. We thank E. Rebar for support, encouragement, reagents, and advice that made this project possible; M. Elrod-Erickson for sharing refined coordinates of the Zif268-DNA complex and for advice on purification of zinc finger peptides; L. Nekludova for extensive discussions about modeling studies with these new zinc finger proteins and for help with computer graphics; W. El-Deiry for providing sequences before publication; and J. Pomerantz, S.

YMPHOCYTIC hypophysitis is a rare, idiopathic intrasellar lesion that presents with a mass effect and pituitary dysfunction; fewer than 400 cases have been reported to date. 5 Lymphocytic hypophysitis has a marked female predominance and most commonly becomes symptomatic during pregnancy or the postpartum period. The lesion usually presents as a compressive lesion of the anterior pituitary, hypothalamus, or optic apparatus, or appears as endocrinological dysfunction including diabetes insipidus and hormone deficiency. The hypophysitis is hypothesized to be autoimmune in nature, with florid B-cell, T-cell, and plasma cell infiltration of the adenohypophysis.

Anatomical, physiological and functional neuroimaging studies suggest that the cerebellum participates in the organization of higher order function, but there are very few descriptions of clinically relevant cases that address this possibility. We performed neurological examinations, bedside mental state tests, neuropsychological studies and anatomical neuroimaging on 20 patients with diseases confined to the cerebellum, and evaluated the nature and severity of the changes in neurological and mental function. Behavioural changes were clinically prominent in patients with lesions involving the posterior lobe of the cerebellum and the vermis, and in some cases they were the most noticeable aspects of the presentation. These changes were characterized by: impairment of executive functions such as planning, set-

A consensus conference on multiple system atrophy (MSA) in 1998 established criteria for diagnosis that have been accepted widely. Since then, clinical, laboratory, neuropathologic, and imaging studies have advanced the field, requiring a fresh evaluation of diagnostic criteria. We held a second consensus conference in 2007 and present the results here. Experts in the clinical, neuropathologic, and imaging aspects of MSA were invited to participate in a 2-day consensus conference. Participants were divided into five groups, consisting of specialists in the parkinsonian, cerebellar, autonomic, neuropathologic, and imaging aspects of the disorder. Each group independently wrote diagnostic criteria for its area of expertise in advance of the meeting. These criteria were discussed and reconciled during the meeting using consensus methodology. The new criteria retain the diagnostic categories of MSA with predominant parkinsonism and MSA with predominant cerebellar ataxia to designate the predominant motor features and also retain the designations of definite, probable, and possible MSA. Definite MSA requires neuropathologic demonstration of CNS alpha-synuclein-positive glial cytoplasmic inclusions with neurodegenerative changes in striatonigral or olivopontocerebellar structures. Probable MSA requires a sporadic, progressive adult-onset disorder including rigorously defined autonomic failure and poorly levodopa-responsive parkinsonism or cerebellar ataxia. Possible MSA requires a sporadic, progressive adult-onset disease including parkinsonism or cerebellar ataxia and at least one feature suggesting autonomic dysfunction plus one other feature that may be a clinical or a neuroimaging abnormality. These new criteria have simplified the previous criteria, have incorporated current knowledge, and are expected to enhance future assessments of the disease.

During ischemic brain injury, glutamate accumulation leads to overstimulation of postsynaptic glutamate receptors with intracellular Ca 2+ overload and neuronal cell death. Here we show that glutamate can induce either early necrosis or delayed apoptosis in cultures of cerebellar granule cells. During and shortly after exposure to glutamate, a subpopulation of neurons died by necrosis. In these cells, mitochondrial membrane potential collapsed, nuclei swelled, and intracellular debris were scattered in the incubation medium. Neurons surviving the early necrotic phase recovered mitochondrial potential and energy levels. Later, they underwent apoptosis, as shown by the formation of apoptotic nuclei and by chromatin degradation into high and low molecular weight fragments. These results suggest that mitochondrial function is a critical factor that determines the mode of neuronal death in excitotoxicity.

The traditional view that the basal ganglia and cerebellum are simply involved in the control of movement has been challenged in recent years. One of the pivotal reasons for this reappraisal has been new information about basal ganglia and cerebellar connections with the cerebral cortex. In essence, recent anatomical studies have revealed that these connections are organized into discrete circuits

Stem cells are a valuable resource for treating disease, but limited access to stem cells from tissues such as brain restricts their utility. Here, we injected marrow stromal cells (MSCs) into the lateral ventricle of neonatal mice and asked whether these multipotential mesenchymal progenitors from bone marrow can adopt neural cell fates when exposed to the brain microenvironment. By 12 days postinjection, MSCs migrated throughout the forebrain and cerebellum without disruption to the host brain architecture. Some MSCs within the striatum and the molecular layer of the hippocampus expressed glial fibrillary acidic protein and, therefore, differentiated into mature astrocytes. MSCs also populated neuron rich regions including the Islands of Calleja, the olfactory bulb, and the internal granular layer of the cerebellum. A large number of MSCs also were found within the external granular layer of the cerebellum. In addition, neurofilament positive donor cells were found within the reticular formation of the brain stem, suggesting that MSCs also may have differentiated into neurons. Therefore, MSCs are capable of producing differentiated progeny of a different dermal origin after implantation into neonatal mouse brains. These results suggest that MSCs are potentially useful as vectors for treating a variety of central nervous system disorders.

Background The cerebral mechanisms underlying the behaviours that lead to pathological overeating and obesity are poorly understood. Dopamine, a neurotransmitter that modulates rewarding properties of food, is likely to be involved. To test the hypothesis that obese individuals have abnormalities in brain dopamine activity we measured the availability of dopamine D 2 receptors in brain. Methods Brain dopamine D 2 receptor availability was measured with positron emission tomography (PET) and [C-11]raclopride (a radioligand for the dopamine D 2 receptor). Bmax/Kd (ratio of the distribution volumes in striatum to that in cerebellum minus 1) was used as a measure of dopamine D 2 receptor availability. Brain glucose metabolism was also assessed with 2-deoxy-2[ 18 F]fluoro-D-glucose (FDG). Findings Striatal dopamine D 2 receptor availability was significantly lower in the ten obese individuals (2•47 [SD 0•36]) than in controls (2•99 [0•41]; p0•0075). In the obese individuals body mass index (BMI) correlated negatively with the measures of D 2 receptors (r =0•84; pр0•002); the individuals with the lowest D 2 values had the largest BMI. By contrast, neither whole brain nor striatal metabolism differed between obese individuals and controls, indicating that striatal reductions in D 2 receptors were not due to a systematic reduction in radiotracer delivery. Interpretation The availability of dopamine D 2 receptor was decreased in obese individuals in proportion to their BMI. Dopamine modulates motivation and reward circuits and hence dopamine deficiency in obese individuals may perpetuate pathological eating as a means to compensate for decreased activation of these circuits. Strategies aimed at improving dopamine function may be beneficial in the treatment of obese individuals.

Group functional connectivity magnetic resonance imaging (fcMRI) studies have documented reliable changes in human functional brain maturity over development. Here we show that support vector machine-based multivariate pattern analysis extracts sufficient information from fcMRI data to make accurate predictions about individuals’ brain maturity across development. The use of only 5 minutes of resting-state fcMRI data from 238 scans of typically developing volunteers (ages 7 to 30 years) allowed prediction of individual brain maturity as a functional connectivity maturation index. The resultant functional maturation curve accounted for 55% of the sample variance and followed a nonlinear asymptotic growth curve shape. The greatest relative contribution to predicting individual brain maturity was made by the weakening of short-range functional connections between the adult brain’s major functional networks.

Leptin is the primary signal through which the hypothalamus senses nutritional state and modulates food intake and energy balance. Leptin reduces food intake by upregulating anorexigenic (appetite-reducing) neuropeptides, such as α-melanocyte-stimulating hormone, and downregulating orexigenic (appetite-stimulating) factors, primarily neuropeptide Y. Genetic defects in anorexigenic signalling, such as mutations in the melanocortin-4 (ref. 5) or leptin receptors, cause obesity. However, alternative orexigenic pathways maintain food intake in mice deficient in neuropeptide Y. CB1 cannabinoid receptors and the endocannabinoids anandamide and 2-arachidonoyl glycerol are present in the hypothalamus, and marijuana and anandamide stimulate food intake. Here we show that following temporary food restriction, CB1 receptor knockout mice eat less than their wild-type littermates, and the CB1 antagonist SR141716A reduces food intake in wild-type but not knockout mice. Furthermore, defective leptin signalling is associated with elevated hypothalamic, but not cerebellar, levels of endocannabinoids in obese db/db and ob/ob mice and Zucker rats. Acute leptin treatment of normal rats and ob/ob mice reduces anandamide and 2-arachidonoyl glycerol in the hypothalamus. These findings indicate that endocannabinoids in the hypothalamus may tonically activate CB1 receptors to maintain food intake and form part of the neural circuitry regulated by leptin.

Nitric oxide, which mediates influences of numerous neurotransmitters and modulators on vascular smooth muscle and leukocytes, can be formed in the brain from arginine by an enzymatic activity that stoichiometrically generates citrulline. We show that glutamate and related amino acids, such as N-methyl-D-aspartate, markedly stimulate arginine-citrulline transformation in cerebellar slices stoichiometrically with enhancement of cGMP levels. N'-monomethyl-L-arginine blocks the augmentation both of citrulline and cGMP with identical potencies. Arginine competitively reverses both effects ofN0-monomethyl-L-arginine with the same potencies. Hemoglobin, which complexes nitric oxide, prevents the stimulation by N-methyl-D-aspartate of cGMP levels, and superoxide dismutase, which elevates nitric oxide levels, increases cGMP formation. These data establish that nitric oxide mediates the stimulation by glutamate of cGMP formation.

A sensitive immunofluorescene technique was used to describe systematically the distribution of dopamine-β-hydroxylase (DBH)-containing cell bodies, non-terminal fiber pathways, and terminal fields in the brain of the male albino rat. DBH is the enzyme that catalyzes the conversion of dopamine to noradrenaline, and as such is useful as an anatomical marker for noradrenaline and possibly adrenaline neurons. The enzyme is not present in dopamine- or indolamine-containing neurons. Ten micron frozen sections (1-in-20 series) were prepared in the frontal, sagittal, and horizontal planes from the olfactory bulb to the upper cervical segments of the spinal cord; adjacent sections in each plane were stained for DBH and for cells (toluidine blue-azure II). An atlas consisting of 40 projection drawings of selected frontal sections illustrates the results of the investigation. DBH perikarya are confined to three groups in the pons and medulla: the well defined locus coeruleus, a more diffuse but continuous subcoeruleus group that arches through the pons and ventral medulla, and a third dorsal medullary group centered in the dorsal motor nucleus of the vagus. A single principal adrenergic fiber system distributes a great many of the axons from these neuron groups to a majority of nuclear areas in the brain. In the pons and medulla two components of the fiber system may be distinguished. A medullary branch may be followed from the posterior aspect of the subcoeruleus group dorsally and then anteriorly through the lateral tegmental field and ventral aspect of the vestibular complex to a position subjacent to the locus coeruleus, where it is joined by a subcoeruleus branch consisting of a large number of fibers coursing among cells along the length of the subcoeruleus group, and by fibers arising from the locus coeruleus. Anterior to the locus coeruleus the principal adrenergic bundle courses as a single fiber tract immediately ventrolateral to the central gray in the mesencephalon and in the zona incerta and substantia innominata in the diencephalon. At the level of the septal area separate bundles reach the cortex dorsally over the genu of the corpus callosum via the medial septal-diagonal band nuclei and the lateral septum and ventrally between the olfactory tubercle and caudate-putamen. In the medulla and pons adrenergic fibers undoubtedly course in both directions. Anterior to the most rostral pontine cell bodies, however, all fibers presumably ascend. Along the course of the bundle distinct branches emerge to innervate circumscribed terminal fields. In addition, certain regions of the brain such as the reticular formation and pontine gray receive diffuse DBH innervation derived from less clearly defined pathways. A small number of areas in the brain contain little or no detectable DBH. These include the caudate-putamen, nucleus accumbens, globus pallidus, olfactory tubercle, subthalamic nucleus, substantia nigra, pretectal area, third, fourth and sixth cranial nerve nuclei, and the trapezoid body nucleus.

Nitric oxide (NO) has been linked to numerous physiological and pathophysiological events that are not readily explained by the well established effects of NO on soluble guanylyl cyclase. Exogenous NO S-nitrosylates cysteine residues in proteins, but whether this is an important function of endogenous NO is unclear. Here, using a new proteomic approach, we identify a population of proteins that are endogenously S-nitrosylated, and demonstrate the loss of this modification in mice harbouring a genomic deletion of neuronal NO synthase (nNOS). Targets of NO include metabolic, structural and signalling proteins that may be effectors for neuronally generated NO. These findings establish protein S-nitrosylation as a physiological signalling mechanism for nNOS.

The heterogeneity of neural gene expression and the spatially limited expression of many low-abundance messenger RNAs in the brain has made cloning and analysis of such messages difficult. To generate amounts of nucleic acids sufficient for use in standard cloning strategies, we have devised a method for producing amplified heterogeneous populations of RNA from limited quantities of cDNA. Whole cerebellar RNA was primed with a synthetic oligonucleotide containing the T7 RNA polymerase promoter sequence 5' to a polythymidyate region. After second-strand cDNA synthesis, T7 RNA polymerase was used to generate amplified antisense RNA (aRNA). Up to 80-fold molar amplification has been achieved from nanogram quantities of cDNA. The amplified material is similar in size distribution to the parent cDNA and shows sequence heterogeneity as assessed by Southern and Northern blot analysis. Specific messages for moderateabundance mRNAs for actin and guanine nucleotide-binding protein (G-protein) a subunits have been detected in the amplified material. By using in situ transcription to generate cONA, sequences for cyclophilin have been detected in aRNA derived from single cerebellar tissue sections. cDNA derived from a single cerebellar Purkinje cell also has been amplified and yields material that hybridizes to cognate whole RNA and mRNA but not to Escherichia coli RNA.

Does the cerebellum influence nonmotor behavior? Recent anatomical studies demonstrate that the output of the cerebellum targets multiple nonmotor areas in the prefrontal and posterior parietal cortex, as well as the cortical motor areas. The projections to different cortical areas originate from distinct output channels within the cerebellar nuclei. The cerebral cortical area that is the main target of each output channel is a major source of input to the channel. Thus, a closed-loop circuit represents the major architectural unit of cerebro-cerebellar interactions. The outputs of these loops provide the cerebellum with the anatomical substrate to influence the control of movement and cognition. Neuroimaging and neuropsychological data supply compelling support for this view. The range of tasks associated with cerebellar activation is remarkable and includes tasks designed to assess attention, executive control, language, working memory, learning, pain, emotion, and addiction. These data, along with the revelations about cerebro-cerebellar circuitry, provide a new framework for exploring the contribution of the cerebellum to diverse aspects of behavior. 413 Annu. Rev. Neurosci. 2009.32:413-434. Downloaded from arjournals.annualreviews.org by University of Pittsburgh on 09/21/09. For personal use only.

GABA (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the mammalian central nervous system, where it exerts its effects through ionotropic (GABA(A/C)) receptors to produce fast synaptic inhibition and metabotropic (GABA(B)) receptors to produce slow, prolonged inhibitory signals. The gene encoding a GABA(B) receptor (GABA(B)R1) has been cloned; however, when expressed in mammalian cells this receptor is retained as an immature glycoprotein on intracellular membranes and exhibits low affinity for agonists compared with the endogenous receptor on brain membranes. Here we report the cloning of a complementary DNA encoding a new subtype of the GABAB receptor (GABA(B)R2), which we identified by mining expressed-sequence-tag databases. Yeast two-hybrid screening showed that this new GABA(B)R2-receptor subtype forms heterodimers with GABA(B)R1 through an interaction at their intracellular carboxy-terminal tails. Upon expression with GABA(B)R2 in HEK293T cells, GABA(B)R1...

When we look at our hands, we immediately know that they are part of our own body. This feeling of ownership of our limbs is a fundamental aspect of selfconsciousness. We have studied the neuronal counterparts of this experience. A perceptual illusion was used to manipulate feelings of ownership of a rubber hand presented in front of healthy subjects while brain activity was measured by functional magnetic resonance imaging. The neural activity in the premotor cortex reflected the feeling of ownership of the hand. This suggests that multisensory integration in the premotor cortex provides a mechanism for bodily self-attribution.

Four monoclonal antibodies are characterized that have been obtained from a fusion of mouse myeloma P3-NSl/l-Ag4-1 with spleen cells from BALB/c mice immunized with white matter from bovine corpus callosum. The corresponding antigens (0 antigens) are designated 01,02,03, and 04. The localization

Background: Reelin (RELN) is a glycoprotein secreted preferentially by cortical ␥-aminobutyric acidergic (GABAergic) interneurons (layers I and II) that binds to integrin receptors located on dendritic spines of pyramidal neurons or on GABAergic interneurons of layers III through V expressing the disabled-1 gene product (DAB1), a cytosolic adaptor protein that mediates RELN action. To replicate earlier findings that RELN and glutamic acid decarboxylase (GAD) 67 , but not DAB1 expression, are down-regulated in schizophrenic brains, and to verify whether other psychiatric disorders express similar deficits, we analyzed, blind, an entirely new cohort of 60 postmortem brains, including equal numbers of patients matched for schizophrenia, unipolar depression, and bipolar disorder with nonpsychiatric subjects.

A sensitive immunohistochemical technique was used, along with highly specific affinity-purified antibodies to brain-derived neurotrophic factor (BDNF), to generate a detailed mapping of BDNF immunoreactivity (BDNF-ir) throughout the adult rat CNS. A parallel analysis of sites of BDNF synthesis was performed with in situ hybridization techniques using a cRNA probe to the exon encoding mature rat BDNF protein. These combined data revealed (1) groups of cell bodies containing diffuse BDNF-ir throughout the CNS that were strongly correlated with fields of cells containing BDNF mRNA; (2) varying degrees of BDNF-ir outside of cell bodies, in what appeared to be fibers and/or terminals; and (3) many regions containing extremely heavy BDNF-immunoreactive fiber/terminal labeling that lacked BDNF mRNA (e.g., medial habenula, central nu-cleus of the amygdala, bed nucleus of stria terminalis, lateral septum, and spinal cord). The latter observation suggested that in these regions BDNF was derived from anterograde axonal transport by afferent systems. In the two cases in which this hypothesis was tested by the elimination of select afferents, BDNF immunostaining was completely eliminated. These data, along with the observation that BDNF-ir was rarely found within dendrites or fibers en passage, suggest that BDNF protein produced in adult CNS neurons is polarized primarily along axonal processes and is preferentially stored in terminals within the innervation target.

Anterior cingulate cortex (ACC) may play a key role in cognitive control by monitoring for the occurrence of response conflict (i.e. simultaneous activation of incompatible response tendencies). Low-frequency responding might provide a minimal condition for eliciting such conflict, as a result of the need to overcome a prepotent response tendency. We predicted that ACC would be selectively engaged during low-frequency responding, irrespective of the specific task situation. To test this hypothesis, we examined ACC activity during the performance of simple choice-discrimination tasks, using rapid event-related functional magnetic resonance imaging. Subjects were scanned while performing three tasks thought to tap different cognitive processes: 'Go/No-go' (response inhibition), 'oddball' (target detection), and two-alternative forcedchoice (response selection). Separate conditions manipulated the frequency of relevant task events. Consistent with our hypothesis, the same ACC region was equally responsive to low-frequency events across all three tasks, but did not show differential responding when events occurred with equal frequency. Subregions of the ACC were also identified that showed heightened activity during the response inhibition condition, and on trials in which errors were committed. Task-sensitive activity was also found in right prefrontal and parietal cortex (response inhibition), left superior temporal and tempoparietal cortex (target detection), and supplementary motor area (response selection). Taken together, the results are consistent with the hypothesis that the ACC serves as a generic detector of processing conflict arising when low-frequency responses must be executed, but also leave open the possibility that further functional specialization may occur within ACC subregions.

The density and distribution of brain damage after 2–10 min of cerebral ischemia was studied in the rat. Ischemia was produced by a combination of carotid clamping and hypotension, followed by 1 week recovery. The brains were perfusion-fixed with formaldehyde, embedded in paraffin, subserially sectioned, and stained with acid fuchsin/cresyl violet. The number of necrotic neurons in the cerebral cortex, hippocampus, and caudate nucleus was assessed by direct visual counting. Somewhat unexpectedly, mild brain damage was observed in some animals already after 2 min, and more consistently after 4 min of ischemia. This damage affected CA4 and CA1 pyramids in the hippocampus, and neurons in the subiculum. Necrosis of neocortical cells began to appear after 4 min and CA3 hippocampal damage after 6 min of ischemia, while neurons in the caudoputamen were affected first after 8–10 min. Selective neuronal necrosis of the cerebral cortex worsened into infarction after higher doses of insult. Damage was worst over the superolateral convexity of the hemisphere, in the middle laminae of the cerebral cortex. The caudate nucleus showed geographically demarcated zones of selective neuronal necrosis, damage to neurons in the dorsolateral portion showing an all-or-none pattern. Other structures involved included the amygdaloid, the thalamic reticular nucleus, the septal nuclei, the pars reticularis of the substantia nigra, and the cerebellar vermis.

THE int-1 proto-oncogene was first identified as a gene activated in virally induced mouse mammary tumours 1,2 . Expression studies, however, suggest that the normal function of this gene may be in spermatogenesis and in the development of the central nervous system 3–5 . Genes ...

The distributions of the mRNAs encoding the L-glutamate transporters GLTl and GLAST were examined in the rat brain by in situ hybridization using 35S-labelled oligonucleotide probes. Probes directed to GLTl produced dense labelling in the hippocampus, neocortex and neostriatum, and weak labelling in the cerebellum. In contrast, GLAST mRNA appeared to be greatly enriched in the cerebellum compared to other brain regions. While the intensity of the labelling for G U S T and GLTl varied among different regions, their cellular distributions appeared to coincide inasmuch as both mRNAs were mainly expressed by glial cells. Labelling occurred, inter aka, in glial cells throughout the hippocampus, and in Golgi epithelial cells in the Purkinje cell layer of the cerebellum.

These experiments use functional magnetic resonance imaging (fMRI) to reveal neural activity uniquely associated with perception of biological motion. We isolated brain areas activated during the viewing of point-light figures, then compared those areas to regions known to be involved in coherent-motion perception and kinetic-boundary perception. Coherent motion activated a region matching previous reports of human MT/MST complex located on the temporo-parieto-occipital junction. Kinetic boundaries activated a region posterior and adjacent to human MT previously identified as the kinetic-occipital (KO) region or the lateral-occipital (LO) complex. The pattern of activation during viewing of biological motion was located within a small region on the ventral bank of the occipital extent of the superior-temporal sulcus (STS). This region is located lateral and anterior to human MT/MST, and anterior to KO. Among our observers, we localized this region more frequently in the right hemisp...

Methamphetamine is a popular drug of abuse that is neurotoxic to dopamine (DA) terminals when administered to laboratory animals. Studies in methamphetamine abusers have also documented significant loss of DA transporters (used as markers of the DA terminal) that are associated with slower motor function and decreased memory. The extent to which the loss of DA transporters predisposes methamphetamine abusers to neurodegenerative disorders such as Parkinsonism is unclear and may depend in part on the degree of recovery. Here we assessed the effects of protracted abstinence on the loss of DA transporters in striatum, in methamphetamine abusers using positron emission tomography and [ 11 C]d-threo-methylphenidate (DA transporter radioligand). Brain DA transporters in five methamphetamine abusers evaluated during short abstinence (Ͻ6 months) and then retested during protracted abstinence (12-17 months) showed significant increases with protracted abstinence (caudate, ϩ19%; putamen, ϩ16%). Although performance in some of the tests for which we observed an association with DA transporters showed some improvement, this effect was not significant. The DA transporter increases with abstinence could indicate that methamphetamine-induced DA transporter loss reflects temporary adaptive changes (i.e., downregulation), that the loss reflects DA terminal damage but that terminals can recover, or that remaining viable terminals increase synaptic arborization. Because neuropsychological tests did not improve to the same extent, this suggests that the increase of the DA transporters was not sufficient for complete function recovery. These findings have treatment implications because they suggest that protracted abstinence may reverse some of methamphetamine-induced alterations in brain DA terminals.

The cerebellum is known to project via the thalamus to multiple motor areas of the cerebral cortex. In this study, we examined the extent and anatomical organization of cerebellar input to multiple regions of prefrontal cortex. We first used conventional retrograde tracers to map the origin of thalamic projections to five prefrontal regions: medial area 9 (9m), lateral area 9

Vascular permeability factor (VPF)/vascular endothelial growth factor (VEGF) is unique in its ability to promote vascular permeability and endothelial cell growth, and its role in tumor development has received considerable attention. In this report, we describe the elevation of VIM-/ VEGF transcript expression in human hepatocellular carcinoma. Surgical samples of 23 patients with hepatocellular carcinoma were studied using reverse transcription-PCR analysis. The oligonucleotide primers were designed to amplify all four known splicing variants that could be ex pressed in the samples studied. Sixteen cases showed VPF/VEGF tran script expression in the tumor (16/23, 69.6%), whereas only 9 of the 23 patients showed it in the corresponding nontumoral part. There was no difference between the pattern of expression of VPF/VEGF isoforms in tumoral and nontumoral tissues. VPF/VEGF mRNA expression in the liver tumors was associated with fibrous capsule formation and septal formation (/' < 0.05 respectively, Fisher's exact /' test). In situ hybridiza tion confirmed the presence of VPF/VEGF mRNA expression in tumor cells and less intensely in hepatocytes of nontumoral liver. We also found that VPF/VEGF expression in the tumor cell was increased in the area adjacent to necrotic regions (presumably hypoxic regions). As a regulator of vascular permeability and endothelial cell growth factor, VPF/VEGF may play an important role in the development of hepatocellular carci noma.

Trisomy 21, the chromosomal condition responsible for Down syndrome (DS, OMIM #190685), is the most common identifiable genetic cause of intellectual disability. Approximately half of all children with DS are born with a significant congenital heart defect (CHD), the most common of which is an atrioventricular septal defect (AVSD). As children with comorbid DS and CHD increasingly survive cardiac surgery, characterization of their early developmental trajectories is critical for designing early interventions to maximize individual potential. Herein, the developmental domains (cognitive, language, and motor) of children with DS and AVSD (DS + AVSD, n=12) were compared to children with DS and a structurally normal heart (DS -CHD, n=17) using the Bayley Scales of Infant and Toddler Development III. The DS + AVSD cohort mean age was relatively the same as controls with DS -CHD, 14.5 ±7.3 months compared with 14.1 ± 8.4 months, respectively. Although the motor domain was the only domain that showed a statistically significant difference between groups (p < .05), both cognitive standard scores (p = 0.63) and language composite standard scores (p = 0.10) were lower in the DS + AVSD cases compared with the DS -CHD controls although it is not statistically significant. Since this is the first study to examine the early developmental outcomes of children with DS + AVSD, the findings may be useful for clinicians in providing anticipatory guidance.

Neural activity increases local blood flow in the CNS, which is the basis of BOLD and PET functional imaging techniques1-3. Blood flow is assumed to be regulated by precapillary arterioles, because capillaries lack smooth muscle. However, most (65%) noradrenergic innervation of CNS blood vessels is of capillaries rather than arterioles4, and in muscle and brain a dilatory signal propagates from vessels near metabolically active cells to precapillary arterioles5,6, suggesting that blood flow control is initiated at the capillary level. Pericytes, which are apposed to CNS capillaries and contain contractile proteins7, could initiate such signalling. Here we show that pericytes can control capillary diameter in whole retina and cerebellar slices. Electrical stimulation of retinal pericytes evoked a localised capillary constriction, which propagated at 2μm/sec to constrict distant pericytes. Superfused ATP in retina, or noradrenaline in cerebellum, made pericytes constrict capillaries, and glutamate reversed the constriction produced by noradrenaline. Electrical stimulation or puffing GABA receptor blockers in the inner retina also evoked pericyte constriction. In simulated ischaemia, some pericytes constricted capillaries. Pericytes are likely modulators of blood flow in response to changes in neural activity, which may contribute to functional imaging signals and to CNS vascular disease.

This review paper focuses on studies in healthy human subjects that examined the functional neuroanatomy and cerebral plasticity associated with the learning, consolidation and retention phases of motor skilled behaviors using modern brain imaging techniques. Evidence in support of a recent model proposed by Doyon and Ungerleider [Functional Anatomy of Motor Skill Learning. In: Squire LR, Schacter DL, editors. Neuropsychology of Memory. New York: Guilford Press, 2002.] is also discussed. The latter suggests that experience-dependent changes in the brain depend not only on the stage of learning, but also on whether subjects are required to learn a new sequence of movements (motor sequence learning) or learn to adapt to environmental perturbations (motor adaptation). This model proposes that the cortico-striatal and cortico-cerebellar systems contribute differentially to motor sequence learning and motor adaptation, respectively, and that this is most apparent during the slow learning phase (i.e. automatization) when subjects achieve asymptotic performance, as well as during reactivation of the new skilled behavior in the retention phase.

The composite structure of the mammalian skull, which forms predominantly via intramembranous ossification, requires precise pre-and post-natal growth regulation of individual calvarial elements. Disturbances of this process frequently cause severe clinical manifestations in humans. Enhanced DNA binding by a mutant MSX2 homeodomain results in a gain of function and produces craniosynostosis in humans 1,2 . Here we show that Msx2-deficient mice have defects of skull ossification and persistent calvarial foramen. This phenotype results from defective proliferation of osteoprogenitors at the osteogenic front during calvarial morphogenesis, and closely resembles that associated with human MSX2 haploinsufficiency in parietal foramina 3 (PFM). Msx2 -/mice also have defects in endochondral bone formation. In the axial and appendicular skeleton, post-natal deficits in Pth/Pthrp receptor (Pthr) signalling and in expression of marker genes for bone differentiation indicate that Msx2 is required for both chondrogenesis and osteogenesis. Consistent with phenotypes associated with PFM, Msx2-mutant mice also display defective tooth, hair follicle and mammary gland development, and seizures, the latter accompanied by abnormal development of the cerebellum. Most Msx2-mutant phenotypes, including calvarial defects, are enhanced by genetic combination with Msx1 loss of function, indicating that Msx gene dosage can modify expression of the PFM phenotype. Our results provide a developmental basis for PFM and demonstrate that Msx2 is essential at multiple sites during organogenesis.

This review summarizes recent investigations of temporal processing. We focus on motor and perceptual tasks in which crucial events span hundreds of milliseconds. One key question concerns whether the representation of temporal information is dependent on a specialized system, distributed across a network of neural regions, or computed in a local task-dependent manner. Consistent with the specialized system framework, the cerebellum is associated with various tasks that require precise timing. Computational models of timing mechanisms within the cerebellar cortex are beginning to motivate physiological studies. Emphasis has also been placed on the basal ganglia as a specialized timing system, particularly for longer intervals. We outline an alternative hypothesis in which this structure is associated with decision processes.

Anatomical, clinical and imaging findings suggest that the cerebellum is engaged in cognitive and affective functions as well as motor control. Evidence from converging modalities also indicates that there is a functional topography in the human cerebellum for overt control of movement vs. higher functions, such that the cerebellum can be divided into zones depending on connectivity with sensorimotor vs. multimodal association cortices. Using functional MRI, we show that regions active during overt movement differ from those involved in higher-level language, spatial processing and working memory tasks. Nine healthy participants each completed five tasks in order to determine the relative activation patterns for the different paradigms. Right-handed finger-tapping activated right cerebellar lobules IV-V and VIII, consistent with descriptions of the cerebellar homunculi. Verb generation engaged right cerebellar lobules VI-Crus I and a second cluster in lobules VIIB-VIIIA. Mental rotation activation peaks were localized to medial left cerebellar lobule VII (Crus II). A 2-back working memory task activated bilateral regions of lobules VI-VII. Viewing arousing vs. neutral images did not reliably activate the cerebellum or cerebral limbic areas in this study. The cerebellar functional topography identified in this study reflects the involvement of different cerebro-cerebellar circuits depending on the demands of the task being performed: overt movement activated sensorimotor cortices along with contralateral cerebellar lobules IV-V and VIII, whereas more cognitively demanding tasks engaged prefrontal and parietal cortices along with cerebellar lobules VI and VII. These findings provide further support for a cerebellar role in both motor and cognitive tasks, and better establish the existence of functional subregions in the cerebellum. Future studies are needed to determine the exact contribution of the cerebellumand different cerebro-cerebellar circuitsto task performance.

1. To investigate the origin and functional significance of a recently described tonic GABAA receptor-mediated conductance in cerebellar granule cells we have made recordings from cells in cerebellar slices from rats of different ages (postnatal days P4 to P28). 2. During development there was a dramatic change in the properties of GABA-mediated synaptic transmission. The contribution to GABAA receptor-mediated charge transfer from the tonic conductance (GGABA), relative to that resulting from discrete spontaneous postsynaptic currents (sPSCs), was increased from 5% at P7 to 99% at P21. GGABA was reduced by bicuculline, tetrodotoxin and by lowering extracellular Ca2+, and was initially present only in those cells which exhibited sPSCs. 3. At P7 sPSCs were depolarizing, occasionally triggering a single action potential. By P18 the GABA reversal potential was shifted close to the resting potential and GGABA produced a shunting inhibition. Removal of GGABA by bicuculline increased gran...