Home About us Contact
|
Home About us Contact | ||
|
|
||
Ganglia
Kinds of Ganglia Terms modified by Ganglia Selected AbstractsReview of animal models for autism: implication of thyroid hormoneCONGENITAL ANOMALIES, Issue 1 2006Miyuki Sadamatsu ABSTRACT,, Autism is a behaviorally defined disorder associated with characteristic impairments in social interactions and communication, as well as restricted and repetitive behaviors and interest. Its prevalence was once thought to be 2/10 000, but recently several large autism prevalence reviews revealed that the rate of occurrence was roughly 30/10 000. While it has been considered a developmental disorder, little is certain about its etiology. Neuroanatomical studies at the histological level in the brains of autistic patients provide many arguments in the etiology of autism. Results from postmortem and imaging studies have implicated many major structures of the brain including the limbic system, cerebellum, corpus callosum, basal ganglia and brainstem. There is no single biological or clinical marker for autism. While several promising candidate genes have been presented, the critical loci are yet unknown. Environmental influences such as rubella virus, valproic acid, and thalidomide exposure during pregnancy are also considered important, as concordance in monozygotic twins is less than 100% and the phenotypic expression of the disorder varies widely. It is thus hypothesized that non-genetic mechanisms contribute to the onset of autistic syndrome. In light of these ambiguities, hope is held that an animal model of autism may help elucidate matters. In this article, we overview most of the currently available animal models for autism, and propose the rat with mild and transient neonatal hypothyroidism as a novel model for autism. [source] A young woman with visual hallucinations, delusions of persecution and a history of performing arson with possible three-generation Fahr diseaseACTA PSYCHIATRICA SCANDINAVICA, Issue 1 2010M. Shirahama Objective:, Fahr disease (FD) is a rare neurological and psychiatric disorder. The disease is classified by intracranial calcification of the basal ganglia with the globus pallidus region being particularly affected. We examined a young woman with visual hallucinations, delusions of persecution and a history of performing arson with possible third-generation FD. Method:, Case report of third-generation FD. Results:, A 23-year-old woman was arrested for two arsons: i) The patient exhibited progressive psychotic symptoms, including visual hallucinations, delusion of injury, irritability, lability of mood, mental retardation and visual disorders and ii) Computed tomography (CT) imaging demonstrated bilateral calcifications of the basal ganglia (globus pallidus) in the patient, her mother and her grandmother. Conclusion:, We found a family with a three-generation history of FD who exhibited calcification in the brain and mental retardation. Compared to her mother, the patient described here displayed anticipation of disease onset. [source] Turner syndrome: Neuroimaging findings: Structural and functionalDEVELOPMENTAL DISABILITIES RESEARCH REVIEW, Issue 4 2009Ronan Mullaney Abstract Neuroimaging studies of Turner syndrome can advance our understanding of the X chromosome in brain development, and the modulatory influence of endocrine factors. There is increasing evidence from neuroimaging studies that TX individuals have significant differences in the anatomy, function, and metabolism of a number of brain regions; including the parietal lobe; cerebellum, amygdala, hippocampus; and basal ganglia; and perhaps differences in "connectivity" between frontal and parieto-occipital regions. Finally, there is preliminary evidence that genomic imprinting, sex hormones and growth hormone have significant modulatory effects on brain maturation in TS. © 2009 Wiley-Liss, Inc. Dev Disabil Res Rev 2009;15:279,283. [source] Brain dysmorphology in individuals with severe prenatal alcohol exposureDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 3 2001Sarah L Archibald MA Our previous studies revealed abnormalities on structural MRI (sMRI) in small groups of children exposed to alcohol prenatally. Microcephaly, disproportionately reduced basal ganglia volume, and abnormalities of the cerebellar vermis and corpus callosum were demonstrated. The present study used sMRI to examine in detail the regional pattern of brain hypoplasia resulting from prenatal exposure to alcohol using a higher resolution imaging protocol and larger sample sizes than reported previously. Fourteen participants (mean 11.4 years; eight females, six males) with fetal alcohol syndrome (FAS) and 12 participants (mean 14.8 years; four females, eight males) with prenatal exposure to alcohol (PEA) but without the facial features of FAS were compared to a group of 41 control participants (mean 12.8 years, 20 females, 21 males). Findings of significant microcephaly and disproportionately reduced basal ganglia volumes in the FAS group were confirmed. Novel findings were that in FAS participants, white matter volumes were more affected than gray matter volumes in the cerebrum, and parietal lobes were more affected than temporal and occipital lobes. Among subcortical structures, in contrast to the disproportionate effects on caudate nucleus, the hippocampus was relatively preserved in FAS participants. Differences between the PEA group and controls were generally non-significant; however, among a few of the structures most affected in FAS participants, there was some evidence for volume reduction in PEA participants as well, specifically in basal ganglia and the parietal lobe. There were no group differences in cerebral volume asymmetries. Severe prenatal alcohol exposure appears to produce a specific pattern of brain hypoplasia. [source] Transcranial magnetic stimulation in child psychiatry: disturbed motor system excitability in hypermotoric syndromesDEVELOPMENTAL SCIENCE, Issue 3 2002Gunther H. Moll Normal development and dysfunctions of motor system excitability can be investigated in vivo by means of single- and paired-pulse transcranial magnetic stimulation (TMS). While different TMS-parameters show different developmental time courses between 8 and 16 years of age, distinct dysfunctional patterns of motor system excitability can be demonstrated in child psychiatric disorders with hypermotoric behavior: in tic disorder, a shortened cortical silent period can be stated providing evidence for deficient inhibitory mechanisms within the sensorimotor loop, probably primarily at the level of the basal ganglia. In attention deficit hyperactivity disorder (ADHD), a decreased intracortical inhibition indicates deficient inhibitory mechanisms within the motor cortex (but enhancement of intracortical inhibition after oral intake of 10 mg methylphenidate). In children with comorbid ADHD and tic disorder, the findings of a reduced intracortical inhibition as well as a shortened cortical silent period provide evidence for additive effects at the level of motor system excitability. Thus, TMS allows us to obtain substantial insight into both the normal development and the neurobiological basis of hypermotoric syndromes in child psychiatry. [source] Presynaptic diadenosine polyphosphate receptors: Interaction with other neurotransmitter systemsDRUG DEVELOPMENT RESEARCH, Issue 1-2 2001M. Teresa Miras-Portugal Abstract Diadenosine polyphosphates (ApnA n = 2,6) are natural compounds that can play a neurotransmitter role in the synaptic terminals of the central nervous system. Microfluorimetric studies of [Ca2+]i in single synaptic terminals have shown the presence of specific ionotropic receptors for nucleotides and dinucleotides. These dinucleotide receptors may or may not coexist at the same terminal. Aminergic terminals from rat basal ganglia have been immunologically characterised by the presence of the vesicular monoamine transporter 2 after the functional studies. Fifty-eight percent of these terminals respond to nucleotides, and of these, 17% respond only to Ap5A. Cholinergic terminals from rat midbrain were immunologically characterised by the vesicular acetylcholine transporter. Sixty-three percent of these terminals responded to nucleotides, and of these, 22% responded only to Ap5A. The presynaptic ionotropic dinucleotide receptors can coexist not only with the ATP receptors, but also with various subtypes of nicotinic receptors. GABAergic terminals from rat midbrain were immunologically characterised by the vesicular inhibitory amino acid transporter. Fifty-nine percent of these terminals responded to nucleotides, and of these, 17% responded only to Ap5A. The presynaptic dinucleotide receptors, when stimulated, are able to induce the GABA release from synaptosomal preparations. These data clearly show the broad interaction of nucleotides and dinucleotides with other neurotransmitter systems. Drug Dev. Res. 52:239,248, 2001. © 2001 Wiley-Liss, Inc. [source] A brainlike learning system with supervised, unsupervised, and reinforcement learningELECTRICAL ENGINEERING IN JAPAN, Issue 1 2008Takafumi Sasakawa Abstract According to Hebb's cell assembly theory, the brain has the capability of function localization. On the other hand, it is suggested that in the brain there are three different learning paradigms: supervised, unsupervised, and reinforcement learning, which are related deeply to the three parts of brain: cerebellum, cerebral cortex, and basal ganglia, respectively. Inspired by the above knowledge of the brain in this paper we present a brainlike learning system consisting of three parts: supervised learning (SL) part, unsupervised learning (UL) part, and reinforcement learning (RL) part. The SL part is a main part learning input,output mapping; the UL part is a competitive network dividing input space into subspaces and realizes the capability of function localization by controlling firing strength of neurons in the SL part based on input patterns; the RL part is a reinforcement learning scheme, which optimizes system performance by adjusting the parameters in the UL part. Numerical simulations have been carried out and the simulation results confirm the effectiveness of the proposed brainlike learning system. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(1): 32,39, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20600 [source] Movement-Induced Focal Motor Seizures and Choreoathetosis As- sociated with Nonketotic Hyperglycemia: A Case ReportEPILEPSIA, Issue 2000Hisashi Tanaka Case Report: We report the case of a diabetic woman who developed right-sided reflex seizures and bilateral choreoathetosis during an episode of nonketotic hyperglycemia. The patient was a 67-year-old woman with a 14-year history of HCV-related liver cirrhosis who experienced polydipsia and polyuria in January 1998. She began to have episodes of abnormal hyperkinetic movements of the right upper extremity and tonic-clonic seizures in the right arm triggered by voluntary movements of right or bilateral arms in the beginning of March 1998. The seizures increased in frequency and consequently left her disabled. She was admitted to our hospital with complaints of these abnormal motor phenomena on March 9, 1998. Neurological examinations revealed that she was alert, well-oriented, and that cranial nerve functions were normal. Slight motor weakness of the right upper limb and deep tendon hyporeflexes were observed in all extremities. Sensations and cerebellar functions were intact. Choreic or athetotic involuntary movements were seen in the bilateral upper limbs and neck. These involuntary movements were increased by voluntary movement or posturing of the upper limbs. The focal tonic-clonic seizures were easily triggered by voluntary movements such as knotting a cord. This seizure suddenly began by tonic movements in the right upper limb and gradually progressed to the right hemi-face and neck without loss of consciousness. The average duration of seizures was about one minute. The laboratory data demonstrated mild leukocytopenia, thrombocytopenia, hepatic dysfunction, and hyperglycemia without ketosis. Fasting blood glucose was 41 I mg/dl, and HbAlc was 14.5%. Blood ammonia was within normal levels. Cranial CT revealed no abnormalities. Brain MRI on T I-weighted images demonstrated bilateral high signal intensity in the putamen. An interictal EEG revealed a symmetrical slow background activity of 7,8 Hz. An ictal EEG recording showed a 2.5 4 Hz irregular sharp and slow wave discharge in the bilateral frontal-central regions. Treatment with carbamazepine was ineffective for the seizures. However, the seizures completely disappeared after the administration of insulin on March 17. Under good control of the hyperglycemia, the abnormal involuntary movements decreased gradually and then completely disappeared; the patient became neurologically asymptomatic by March 30. The follow-tip EEG demonstrated 9-Hz alpha background activity without any epileptic discharges. Conclusions: Nonketotic hyperglycemia has been rarely reported to cause stimulus-induced seizures or hyperkinetic involuntary movements such as hemichorea-ballism. To our knowledge, this is the first reported case of both induced seizures and involuntary movements simultaneously caused by hyperglycemia. Movement-induced seizures and choreoathetoid movements in this patient can be considered to result from transiently-increased activity in the basal ganglia and/or cerebral cortex associated with metaholic disorders. [source] An exploration of anger phenomenology in multiple sclerosisEUROPEAN JOURNAL OF NEUROLOGY, Issue 12 2009U. Nocentini Background and purpose:, Multiple sclerosis (MS) patients are often emotionally disturbed. We investigated anger in these patients in relation to demographic, clinical, and mood characteristics. Patients and methods:, About 195 cognitively unimpaired MS patients (150 relapsing,remitting and 45 progressive) were evaluated with the State Trait Anger Expression Inventory, the Chicago Multiscale Depression Inventory, and the State Trait Anxiety Inventory. The patients' anger score distribution was compared with that of the normal Italian population. Correlation coefficients among scale scores were calculated and mean anger scores were compared across different groups of patients by analysis of variance. Results:, Of the five different aspects of anger, levels of withheld and controlled Anger were respectively higher and lower than what is expected in the normal population. Although anger was correlated with anxiety and depression, it was largely independent from these mood conditions. Mean anger severity scores were not strongly influenced by individual demographic characteristics and were not higher in more severe patients. Conclusions:, The presence of an altered pattern of anger, unrelated to the clinical severity of MS, suggests that anger is not an emotional reaction to disease stress. An alteration of anger mechanisms might be a direct consequence of the demyelination of the connections among the amygdale, the basal ganglia and the medial prefrontal cortex. [source] Cerebral hemiatrophy with superficial siderosis and PLEDs due to a germ cell tumor of the basal gangliaEUROPEAN JOURNAL OF NEUROLOGY, Issue 8 2006N. Kumar The diagnosis of basal ganglia germ cell tumors may be delayed due to slow progression and minimal early changes on magnetic resonance imaging (MRI). The cystic nature of some tumors may lead to non-diagnostic biopsies. We describe the clinical, imaging, laboratory, and postmortem findings of a basal ganglia germ cell tumor in a 19-year-old man. Clues to an early antemortem diagnosis based on MRI findings and determination of tumor markers are discussed. An early diagnosis and accurate characterization of basal ganglia germ cell tumors is essential for optimal therapy. The presence of cerebral hemiatrophy and hemorrhagic or cystic components is suggestive. Measurement of serum and cerebrospinal fluid markers such as human chorionic gonadotropin may suggest the diagnosis. [source] Thiethylperazine-induced parkinsonism: in vivo demonstration of dopamine D2 receptors blockadeEUROPEAN JOURNAL OF NEUROLOGY, Issue 10 2004C. Briani Thiethylperazine (Torecan®) is a piperazine phenothiazine employed to relieve vertigo. Its use may be associated with extrapyramidal side effects (dystonia, akathisia, tardive dyskinesia) (Sulkava, 1984), but parkinsonism has rarely been described. We describe a woman who, 1 month after the onset of thiethylperazine treatment, developed parkinsonism that disappeared 2 months after withdrawal of the drug. However, cerebral single-photon emission computed tomography (SPECT) with the dopamine (DA) D2 receptors ligand 123I-iodobenzamide (123I-IBZM) revealed a persistent reduced DA D2 receptors activity (by 45%) in the basal ganglia (BG), which may be clinically not effective. [source] Striatal infarcts mimicking frontotemporal dementia: a case reportEUROPEAN JOURNAL OF NEUROLOGY, Issue 4 2003Y. Nishio We described a patient with bilateral striatal infarcts, in whom stereotyped and disinhibited behaviors were insidiously emerged over 2 years mimicking frontotemporal dementia (FTD). A positron emission tomography with 18-fluorodeoxy glucose showed a hypometabolism in the frontal lobes, basal ganglia, and thalami. The peculiar behavioral alterations remained unchanged for the following 7 years, suggesting that the disease is not degenerative but of vascular origin. A disruption of the fronto-subcortical circuits at the level of the striatum or the anterior thalamic peduncle is attributable to the FTD-like behavioral and cognitive syndrome. [source] Early-onset Alzheimer's disease with presenilin-1 M139V mutation: clinical, neuropsychological and neuropathological studyEUROPEAN JOURNAL OF NEUROLOGY, Issue 3 2003A. J. Larner The clinical, neuropsychological and neuropathological features of a patient with early-onset Alzheimer's disease as a result of the M139V presenilin-1 (PSEN-1) mutation are presented, and compared with previous reports of patients with the same mutation. Similarities, such as the age at onset and the relative preservation of naming skills, and differences, such as the significant basal ganglia, thalamic and cerebellar pathology, are noted. This clinical and pathological heterogeneity in patients with the same PSEN-1 mutation suggests phenotype modulation by genetic and/or epigenetic factors. [source] Natural killer cell proliferation and circulating cytokines in patients with bilateral basal ganglia calcificationEUROPEAN JOURNAL OF NEUROLOGY, Issue 5 2002T. Morishima Ten adult patients with symmetrical calcifications in the bilateral basal ganglia (diagnosed as physiological calcifications) were analyzed for lymphocyte subsets and cytokines. Increased number of natural killer (NK) cells were identified in the peripheral blood of seven patients by lymphocyte subset analysis. Tumor necrosis factor- , was detected in the sera of five patients and interferon- , was detected in one patient. In summary, NK cell propagation and circulating cytokines, particularly tumor necrosis factor- ,, may be involved in the etiology of basal ganglia calcification. [source] Basal ganglia and frontal involvement in self-generated and externally-triggered finger movements in the dominant and non-dominant handEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2009Félix-Etienne François-Brosseau Abstract Although there are a number of functional neuroimaging studies that have investigated self-initiated and externally-triggered movements, data directly comparing right and left hands in this context are very scarce. The goal of this study was to further understand the role of the basal ganglia and prefrontal cortex in the realm of self-initiated and externally-triggered right and left hand movements. Young healthy right-handed adults performed random, follow and repeat conditions of a finger moving task with their right and left hands, while being scanned with functional magnetic resonance imaging. Significant activation of the dorsolateral prefrontal cortex was observed when comparing the self-initiated movements with the repeated control and externally-triggered movements when using either hand in agreement with its role in monitoring. The caudate nucleus activation was found during self-initiated conditions compared with the control condition when either hand was used, showing that it is particularly involved when a new movement needs to be planned. Significant putamen activation was observed in all within-hand contrasts except for the externally-triggered vs. control condition when using the left hand. Furthermore, greater putaminal activation was found for the left vs. the right hand during the control condition, but for the right vs. the left hand subtraction for the self-initiated condition. Our results show that the putamen is particularly involved in the execution of non-routine movements, especially if those are self-initiated. Furthermore, we propose that, for right-handed people performing fine movements, as far as putamen involvement is concerned, the lack of proficiency of the non-dominant hand may prevail over other task demands. [source] Gamma activity and reactivity in human thalamic local field potentialsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2009Florian Kempf Abstract Depth recordings in patients with Parkinson's disease on dopaminergic therapy have revealed a tendency for oscillatory activity in the basal ganglia that is sharply tuned to frequencies of ,70 Hz and increases with voluntary movement. It is unclear whether this activity is essentially physiological and whether it might be involved in arousal processes. Here we demonstrate an oscillatory activity with similar spectral characteristics and motor reactivity in the human thalamus. Depth signals were recorded in 29 patients in whom the ventral intermediate or centromedian nucleus were surgically targeted for deep brain stimulation. Thirteen patients with four different pathologies showed sharply tuned activity centred at ,70 Hz in spectra of thalamic local field potential (LFP) recordings. This activity was modulated by movement and, critically, varied over the sleep,wake cycle, being suppressed during slow wave sleep and re-emergent during rapid eye movement sleep, which physiologically bears strong similarities with the waking state. It was enhanced by startle-eliciting stimuli, also consistent with modulation by arousal state. The link between this pattern of thalamic activity and that of similar frequency in the basal ganglia was strengthened by the finding that fast thalamic oscillations were lost in untreated parkinsonian patients, paralleling the behaviour of this activity in the basal ganglia. Furthermore, there was sharply tuned coherence between thalamic and pallidal LFP activity at ,70 Hz in eight out of the 11 patients in whom globus pallidus and thalamus were simultaneously implanted. Subcortical oscillatory activity at ,70 Hz may be involved in movement and arousal. [source] Neuronal activity in the subthalamic nucleus modulates the release of dopamine in the monkey striatumEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2009Yasushi Shimo Abstract The primate subthalamic nucleus (STN) is commonly seen as a relay nucleus between the external and internal pallidal segments, and as an input station for cortical and thalamic information into the basal ganglia. In rodents, STN activity is also known to influence neuronal activity in the dopaminergic substantia nigra pars compacta (SNc) through inhibitory and excitatory mono- and polysynaptic pathways. Although the anatomical connections between STN and SNc are not entirely the same in primates as in rodents, the electrophysiologic and microdialysis experiments presented here show directly that this functional interaction can also be demonstrated in primates. In three Rhesus monkeys, extracellular recordings from SNc during microinjections into the STN revealed that transient pharmacologic activation of the STN by the acetylcholine receptor agonist carbachol substantially increased burst firing of single nigral neurons. Transient inactivation of the STN with microinjections of the GABA-A receptor agonist muscimol had the opposite effect. While the firing rates of individual SNc neurons changed in response to the activation or inactivation of the STN, these changes were not consistent across the entire population of SNc cells. Permanent lesions of the STN, produced in two animals with the fiber-sparing neurotoxin ibotenic acid, reduced burst firing and firing rates of SNc neurons, and substantially decreased dopamine levels in the primary recipient area of SNc projections, the striatum, as measured with microdialysis. These results suggest that activity in the primate SNc is prominently influenced by neuronal discharge in the STN, which may thus alter dopamine release in the striatum. [source] Drifting grating stimulation reveals particular activation properties of visual neurons in the caudate nucleusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2008Attila Nagy Abstract The role of the caudate nucleus (CN) in motor control has been widely studied. Less attention has been paid to the dynamics of visual feedback in motor actions, which is a relevant function of the basal ganglia during the control of eye and body movements. We therefore set out to analyse the visual information processing of neurons in the feline CN. Extracellular single-unit recordings were performed in the CN, where the neuronal responses to drifting gratings of various spatial and temporal frequencies were recorded. The responses of the CN neurons were modulated by the temporal frequency of the grating. The CN units responded optimally to gratings of low spatial frequencies and exhibited low spatial resolution and fine spatial frequency tuning. By contrast, the CN neurons preferred high temporal frequencies, and exhibited high temporal resolution and fine temporal frequency tuning. The spatial and temporal visual properties of the CN neurons enable them to act as spatiotemporal filters. These properties are similar to those observed in certain feline extrageniculate visual structures, i.e. in the superior colliculus, the suprageniculate nucleus and the anterior ectosylvian cortex, but differ strongly from those of the primary visual cortex and the lateral geniculate nucleus. Accordingly, our results suggest a functional relationship of the CN to the extrageniculate tecto-thalamo-cortical system. This system of the mammalian brain may be involved in motion detection, especially in velocity analysis of moving objects, facilitating the detection of changes during the animal's movement. [source] Prior pallidotomy reduces and modifies neuronal activity in the subthalamic nucleus of Parkinson's disease patientsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2008A. Zaidel Abstract Parkinson's disease (PD) patients with prior radio-frequency lesions in the internal segment of the globus pallidus (GPi, pallidotomy), whose symptoms have deteriorated, may be candidates for further invasive treatment such as subthalamic deep brain stimulation (STN DBS). Six patients with prior pallidotomy (five unilaterally; one bilaterally) underwent bilateral STN DBS. The microelectrode recordings (MERs, used intraoperatively for STN verification), ipsilateral and contralateral to pallidotomy, and MERs from 11 matched PD patients who underwent bilateral STN DBS without prior pallidotomy were compared. For each trajectory, average, variance and mean successive difference (MSD, a measure of irregularity) of the root mean square (RMS) of the STN MER were calculated. The RMS in trajectories ipsilateral to pallidotomy showed significant reduction of the mean average and MSD of STN activity when compared with trajectories from patients without prior pallidotomy. The RMS parameters contralateral to pallidotomy tend to lie between those ipsilateral to pallidotomy and those without prior pallidotomy. The average STN power spectral density of oscillatory activity was notably lower ipsilateral to pallidotomy than contralateral, or without prior pallidotomy. The finding that pallidotomy reduces STN activity and changes firing characteristics, in conjunction with the effectiveness of STN DBS despite prior pallidotomy, calls for reappraisal and modification of the current model of the basal ganglia (BG) cortical network. It highlights the critical role of direct projections from the BG to brain-stem structures and suggests a possible GPi,STN reciprocal positive-feedback mechanism. [source] Cholinergic modulation of visuospatial responding in central thalamusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2007Lori A. Newman Abstract Central thalamus has extensive connections with basal ganglia and frontal cortex that are thought to play a critical role in sensory-guided goal-directed behavior. Central thalamic activity is influenced by cholinergic projections from mesopontine nuclei. To elucidate this function we trained rats to respond to lights in a reaction time (RT) task and compared effects of muscarinic (2.4, 7.3, 22 nmol scopolamine) and nicotinic (5.4, 16, 49, 98 nmol mecamylamine) antagonists with the GABAA agonist muscimol (0.1, 0.3, 1.0 nmol) in central thalamus. We compared this with subcutaneous (systemic) effects of mecamylamine (3.2, 9.7, 29 µmol/kg) and scopolamine (0.03, 0.09, 0.26 µmol/kg). Subcutaneous scopolamine increased omissions (failure to respond within a 3-s response window) at the highest dose tested. Subcutaneous mecamylamine increased omissions at the highest dose tested while impairing RT and per cent correct at lower doses. Intrathalamic injections of muscimol and mecamylamine decreased per cent correct at doses that did not affect omissions or RT. Intrathalamic scopolamine increased omissions and RT at doses that had little effect on per cent correct. Anatomical controls indicated that the effects of mecamylamine were localized in central thalamus and those of scopolamine were not. Drug effects did not interact with attention-demanding manipulations of stimulus duration, proximity of stimulus and response locations, or stimulus array size. These results are consistent with the hypothesis that central thalamus mediates decisional processes linking sensory stimuli with actions, downstream from systems that detect sensory signals. They also provide evidence that this function is specifically influenced by nicotinic cholinergic receptors. [source] Nigrostriatal lesion induces D2-modulated phase-locked activity in the basal ganglia of ratsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2007Camila L. Zold Abstract There is a debate as to what modifications of neuronal activity underlie the clinical manifestations of Parkinson's disease and the efficacy of antiparkinsonian pharmacotherapy. Previous studies suggest that release of GABAergic striatopallidal neurons from D2 receptor-mediated inhibition allows spreading of cortical rhythms to the globus pallidus (GP) in rats with 6-hydroxydopamine-induced nigrostriatal lesions. Here this abnormal spreading was thoroughly investigated. In control urethane-anaesthetized rats most GP neurons were excited during the active part of cortical slow waves (,direct-phase' neurons). Two neuronal populations having opposite phase relationships with cortical and striatal activity coexisted in the GP of 6-hydroxydopamine-lesioned rats. ,Inverse-phase' GP units exhibited reduced firing coupled to striatal activation during slow waves, suggesting that this GP oscillation was driven by striatopallidal hyperactivity. Half of the pallidonigral neurons identified by antidromic stimulation exhibited inverse-phase activity. Therefore, spreading of inverse-phase oscillations through pallidonigral axons might contribute to the abnormal direct-phase cortical entrainment of basal ganglia output described previously. Systemic administration of the D2 agonist quinpirole to 6-hydroxydopamine-lesioned rats reduced GP inverse-phase coupling with slow waves, and this effect was reversed by the D2 antagonist eticlopride. Because striatopallidal hyperactivity was only slightly reduced by quinpirole, other mechanisms might have contributed to the effect of quinpirole on GP oscillations. These results suggest that antiparkinsonian efficacy may rely on other actions of D2 agonists on basal ganglia activity. However, abnormal slow rhythms may promote enduring changes in functional connectivity along the striatopallidal axis, contributing to D2 agonist-resistant clinical signs of parkinsonism. [source] Biochemical and electrophysiological changes of substantia nigra pars reticulata driven by subthalamic stimulation in patients with Parkinson's diseaseEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2006Salvatore Galati Abstract To understand the events underlying the clinical efficacy of deep brain stimulation (DBS) of the subthalamic nucleus (STN), electrophysiological recordings and microdialysis evaluations were carried out in the substantia nigra pars reticulata (SNr), one of the two basal ganglia (BG) nuclei targeted by STN output, in patients with Parkinson's disease (PD). Clinically effective STN-DBS caused a significant increase of the SNr firing rate. The poststimulus histogram (PSTH) showed an excitation peak at 1.92,3.85 ms after the STN stimulus. The spontaneous discharge of SNr neurons was driven at the frequency of the stimulation (130 Hz), as shown in the autocorrelograms (AutoCrl). The fast Fourier transform (FFT) analysis showed a peak at 130 Hz, and a less pronounced second one at 260 Hz. Accordingly, in the distribution of the interspike intervals (ISIs), the mode was earlier, and skewness more asymmetric. Biochemically, the increased excitatory driving from the STN was reflected by a clear-cut increase in cyclic guanosine 3',5'-monophosphate (cGMP) levels in the SNr. These results indicate that the beneficial effect of DBS in PD patients is paralleled with a stimulus-synchronized activation of the STN target, SNr. Our findings suggest that, during STN-DBS, a critical change towards a high-frequency oscillatory discharge occurs. [source] Deficits in the mid-brain raphe nuclei and striatum of the AS/AGU rat, a protein kinase C-, mutantEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2005M. Al-Fayez Abstract The AS/AGU rat carries a recessive mutation (agu) in the gene coding for the gamma isoform of protein kinase C. The rat is characterized by disordered locomotion and progressive dysfunction of the nigrostriatal dopaminergic (DA) system. This dysfunction begins with a failure to release DA within the striatum and culminates in cell loss within the substantia nigra pars compacta. The present study examines another midbrain aminergic system with input to the basal ganglia, the serotonergic (5-HT) raphe,striatal system originating in the dorsal raphe nucleus. By 3 months after birth, there is a very substantial reduction in the extracellular levels of 5-HT in the dorsal caudate-putamen of the mutants compared with controls (c. 70%). This is accompanied by a proportional increase in the levels of the 5-HT metabolite 5-hydroxyindole acetic acid (5-HIAA). At a later age, there are reductions in whole tissue 5-HT (and increases in 5-HIAA) in both the striatum and the region containing the dorsal raphe nucleus, as well as numbers of 5-HT-immunoreactive cells in the dorsal raphe nucleus. The median raphe appears to be unaffected. The results are seen in terms of an initial dysfunction in transmitter release leading to cell death, perhaps through the formation of free radicals or neurotoxins. [source] Lesions to the subthalamic nucleus decrease impulsive choice but impair autoshaping in rats: the importance of the basal ganglia in Pavlovian conditioning and impulse controlEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2005Catharine A. Winstanley Abstract Although the subthalamic nucleus (STN) is involved in regulating motor function, and inactivation of this structure relieves the motor symptoms in Parkinsonian patients, recent data indicate that corticosubthalamic connections are involved in both the regulation of attention and the ability to withhold from responding. Considerable evidence suggests that the neural circuitry underlying such behavioural disinhibition or impulsive action can be at least partially dissociated from that implicated in impulsive decision-making and it has been suggested that the tendency to choose impulsively is related to the ability to form and use Pavlovian associations. To explore these hypotheses further, STN-lesioned rats were tested on the delay-discounting model of impulsive choice, where impulsivity is defined as the selection of a small immediate over a larger delayed reward, as well as in a rodent autoshaping paradigm. In contrast to previous reports of increased impulsive action, STN lesions decreased impulsive choice but dramatically impaired the acquisition of the autoshaping response. When the STN was lesioned after the establishment of autoshaping behaviour, lesioned subjects were more sensitive to the omission of reward, indicative of a reduction in the use of Pavlovian associations to control autoshaping performance. These results emphasize the importance of the STN in permitting conditioned stimulus,unconditioned stimulus associations to regulate goal-seeking, a function which may relate to the alterations in impulsive choice observed in the delay-discounting task. These data bear a striking similarity to those observed after lesions of the orbitofrontal cortex and are suggestive of an important role for corticosubthalamic connections in complex cognitive behaviour. [source] Forebrain projections to the hypothalamus are topographically organized in anurans: conservative traits as compared with amniotesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2005Nerea Moreno Abstract The organization of the forebrain in amphibians (anamniotes) is currently being re-evaluated in terms of evolution and several evidences have corroborated numerous traits shared by amphibians and amniotes, such as the organization of the basal ganglia and the amygdaloid complex. In the present study we have analysed the organization of forebrain afferent systems to the hypothalamus of the frog Rana perezi. In vivo and in vitro tract-tracing techniques with dextran amines and immunohistochemistry for localizing nitric oxide synthase (NOS) in a series of single or combined experiments were used as NOS labelling reveals hypothalamic afferents arising from the lateral amygdala and the combination allowed analysis of the relationship between fibers of different origins in the same section. The results showed a large segregation of afferents in the hypothalamic region depending on their site of origin in the forebrain. Four highly topographically organized prosencephalic tracts reaching the anuran hypothalamus were observed: (i) the medial forebrain bundle, from the medial pallium and septal complex; (ii) the caudal branch of the stria terminalis formed by fibers arising in the lateral and medial amygdala; (iii) part of the lateral forebrain bundle with fibers from the central amygdala and (iv) the dorsal thalamo-hypothalamic tract. Fibers coursing in each tract reach the hypothalamus and terminate in distinct fields. The resemblance in pattern of forebrain-hypothalamic organization between amphibians and amniotes suggests that this feature represents an important trait conserved in the evolution of all tetrapods and therefore essential for the hypothalamic function. [source] Distribution and signaling of TREM2/DAP12, the receptor system mutated in human polycystic lipomembraneous osteodysplasia with sclerosing leukoencephalopathy dementiaEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2004Giuseppina Sessa Abstract Together with its adaptor protein, the adaptor protein of 12 kDa also known as KARAP and TYROBP (DAP12), triggering r (TREM2) is a stimulatory membrane receptor of the immunoglobulin/lectin-like superfamily, well known in myeloid cells. In humans, however, loss-of-function mutations of TREM2/DAP12 leave myeloid cells unaffected but induce an autosomal recessive disease characterized, together with bone cysts, by a spectrum of pathological lesions in the cortex, thalamus and basal ganglia with clinical symptoms of progressive dementia (polycystic lipomembraneous osteodysplasia with sclerosing leukoencephalopathy). Nothing was known about the role of TREM2/DAP12 in brain cell biology and physiology. By confocal immunocytochemistry we demonstrate that, in both human and mouse cerebral cortex, TREM2/DAP12, strongly expressed by microglia, is also present in a fraction of neurons but not in astrocytes and oligodendrocytes. In contrast, in the hippocampal cortex TREM2-expressing neurons are rare. Both in neurons and microglia the receptor appears to be located mostly intracellularly in a discrete compartment(s) partially coinciding with (or adjacent to) the Golgi complex/trans-Golgi network. Four nerve cell lines were identified as expressing the intracellular receptor system. In living human microglia CHME-5 and glioblastoma T98G cells, activation of TREM2 by its specific antibody induced [Ca2+]i responses, documenting its surface expression and functioning. Surface expression of TREM2, low in resting CHME-5 and T98G cells, increases significantly and transiently (60 min) when cells are stimulated by ionomycin, as revealed by both surface biotinylation and surface immunolabeling. Our results provide the first information about the expression, distribution (mostly intracellular) and functioning of TREM2/DAP12 system in nerve cells, a necessary step in the understanding of the cellular mechanisms affected in polycystic lipomembraneous osteodysplasia with sclerosing leukoencephalopathy. [source] Prefrontal-subcortical dissociations underlying inhibitory control revealed by event-related fMRIEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2004A. M. Clare Kelly Abstract Using event-related fMRI, this study investigated the neural dynamics of response inhibition under fluctuating task demands. Fourteen participants performed a GO/NOGO task requiring inhibition of a prepotent motor response to NOGO events that occurred as part of either a Fast or Slow presentation stream of GO stimuli. We compared functional activations associated with correct withholds (Stops) required during the Fast presentation stream of stimuli to Stops required during the Slow presentation stream. A predominantly right hemispheric network was activated across conditions, consistent with previous studies. Furthermore, a functional dissociation of activations between conditions was observed. Slow Stops elicited additional activation in anterior dorsal and polar prefrontal cortex and left inferior parietal cortex. Fast Stops showed additional activation in a network that included right dorsolateral prefrontal cortex, insula and dorsal striatum. These results are discussed in terms of our understanding of the impact of preparation on the distributed network underlying response inhibition and the contribution of subcortical areas, such as the basal ganglia, to executive control processes. [source] Cortical mechanisms of smooth pursuit eye movements with target blanking.EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2004An fMRI study Abstract Smooth pursuit eye movements are evoked by retinal image motion of visible moving objects and can also be driven by the internal representation of a target due to extraretinal mechanisms (e.g. efference copy). To delineate the corresponding neuronal correlates, functional magnetic resonance imaging at 1.5 T was applied during smooth pursuit at 10 °/s with continuous target presentation and target blanking for 1 s to 16 right-handed healthy males. Eye movements were assessed during scanning sessions by infra-red reflection oculography. Smooth pursuit performance was optimal when the target was visible but decreased to a residual velocity of about 30% of the velocity observed during continuous target presentation. Random effects analysis of the imaging data yielded an activation pattern for smooth pursuit in the absence of a visual target (in contrast to continuous target presentation) which included a number of cortical areas in which extraretinal information is available such as the frontal eye field, the superior parietal lobe, the anterior and the posterior intraparietal sulcus and the premotor cortex, and also the supplementary and the presupplementary eye field, the supramarginal gyrus, the dorsolateral prefrontal cortex, cerebellar areas and the basal ganglia. We suggest that cortical mechanisms such as prediction, visuo-spatial attention and transformation, multimodal visuomotor control and working memory are of special importance for maintaining smooth pursuit eye movements in the absence of a visible target. [source] Disruption of self-organized actions in monkeys with progressive MPTP-induced parkinsonism: II.EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2004Effects of reward preference Abstract The motor and cognitive symptoms of Parkinson's disease (PD) are well documented, but little is known about the functionality of motivational processes mediated by the limbic circuits of basal ganglia. The aim of this study was to test the ability of motivational processes to direct and to urge behaviour, in four vervet monkeys (Cercopithecus aethiops) progressively intoxicated with systemic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) injections (0.3,0.4 mg/kg every 4,7 days). In the food preference task, the monkeys had to retrieve two types of directly visible food, simultaneously available in the wells of a reward board. At all stages of MPTP-induced parkinsonism, the monkeys continued to take their favourite food first. In the symbol discrimination task, the wells were covered with sliding plaques cued by symbols indicating the absence or presence of a reward, and the different types of food were blocked in separate sessions. Monkeys with mild or moderate parkinsonism made fewer attempts and took longer to retrieve non-preferred compared with preferred rewards. These results indicate that motivational processes are still able to direct (food preference task) and to urge (symbol discrimination task) behaviour in MPTP-lesioned monkeys. Such a functional preservation may be related to the relatively spared dopaminergic innervation of the limbic circuits that we found in our monkeys, in agreement with the literature on humans. Furthermore, the frequency of executive disorders (such as hesitations and freezing) appeared to be much lower with the preferred rewards. Thus, the preserved motivational processes may help to overcome executive dysfunction in the early stages of human PD. [source] Substantia nigra pars reticulata neurons code initiation of a serial pattern: implications for natural action sequences and sequential disordersEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2002Melanie Meyer-Luehmann Abstract Sequences of movements are initiated abnormally in neurological disorders involving basal ganglia dysfunction, such as Parkinson's disease or Tourette's syndrome. The substantia nigra pars reticulata (SNpr) is one of the two primary output structures of the basal ganglia. However, little is known about how substantia nigra mediates the initiation of normal movement sequences. We studied its role in coding initiation of a sequentially stereotyped but natural movement sequence by recording neuronal activity in SNpr during behavioural performance of ,syntactic grooming chains'. These are rule-governed sequences of up to 25 grooming movements emitted in four predictable (syntactic) phases, which occur spontaneously during grooming behaviour by rats and other rodents. Our results show that neuronal activation in central SNpr codes the onset of this entire rule-governed sequential pattern of grooming actions, not elemental grooming movements. We conclude that the context of sequential pattern may be more important than the elemental motor parameters in determining SNpr neuronal activation. [source] | ||||||||||||||||||||||||||||||||||