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PubMed2002

Dopamine-dependent changes in the functional connectivity between basal ganglia and cerebral cortex in humans.

We test the hypothesis that interaction between the human basal ganglia and cerebral cortex involves activity in multiple functional circuits characterized by their frequency of oscillation, phase characteristics, dopamine dependency and topography. To this end we took recordings from macroelectrodes (MEs) inserted into the subthalamic nucleus (STN) in eight awake patients following functional neurosurgery for Parkinson's disease. An EEG was also recorded, as were the signals from MEs in the globus pallidus interna (GPi) in two of the cases. Coherence between EEG and ME potentials was apparent in three major frequency bands, 2-10 Hz, 10-30 Hz and 70-85 Hz. These rhythmic activities differed in their cortical topography, although coherence was always strongest over the midline. Coherence between EEG and ME potentials in the 70-85 Hz band was only recorded in patients treated with levodopa. Cortical activity phase led that in the basal ganglia in those oscillatory activities with frequencies <30 Hz. In contrast, STN and GPi phase led cortex in the 70-85 Hz band. The temporal differences in the way in which cortical activity led or lagged behind that in STN/GPi were similar, around 20 ms, regardless of the overall direction of information flow and frequency band. We conclude that the basal ganglia may receive multiple cortical inputs at frequencies <30 Hz and, in the presence of dopaminergic activity, produce a high frequency drive back to the cerebral cortex, in particular the supplementary motor area (SMA).

Adult↗
PubMed1998

Distribution of calbindin D-28k and parvalbumin neurons and fibers in the rat basal ganglia.

This review deals with the distribution of immunoreactivity for calbindin D-28k (CB) and parvalbumin (PV) in the different nuclei of the rodent basal ganglia analyzed with the data available after the use of single and double antigen procedures applied to single sections. These findings reveal that CB and PV are distributed according to a highly heterogeneous pattern in the caudate putamen complex (CPu), globus pallidus (GP), entopeduncular nucleus (EP), subthalamic nucleus (STh) and substantia nigra (SN) of the rat. In each basal ganglia structure, the two calcium-binding proteins label different neuronal subsets. Therefore, the use of CB and PV immunohistochemistry may be considered as an excellent tool to define distinct chemoarchitectonic and functional domains within the complex organization of the basal ganglia. Double immunohistochemical methods are also useful to illustrate the relationships between the different chemical subdivisions of the CPu, GP, EP, STh and SN and the chemically characterized connections with each other and with other forebrain and brainstem structures. However, specific rules should be followed when combining single and double immunostaining procedures, and the results of such studies must be evaluated with caution. When they are used properly, these methods can reveal hitherto unknown principles of organization of the basal ganglia and thus shed new light on the anatomical and functional organization of this set of subcortical structures involved in the control of motor behavior.

Animals↗
PubMed2004

Basal ganglia--hippocampal interactions support the role of the hippocampal formation in sensorimotor integration.

Experiments were carried out to evaluate whether neural activity in the basal ganglia is functionally related to the neural activity underlying mechanisms of theta band oscillation and synchrony in the hippocampal formation. Experiment 1 demonstrated that electrical stimulation administered to the substantia nigra, globus pallidus (GP) and caudate-putamen (CPu) in urethane anesthetized rats elicited theta field activity in the hippocampal formation. Subsequent microinfusion of the local anesthetic procaine hydrochloride into the medial septum reversibly abolished this effect. In Experiment 2, single cell discharge profiles established for 152 cells recorded in nuclei of the basal ganglia resulted in 101 (66%) being classified as theta-related and 51 (34%) classified as nonrelated. Theta-related cells were further subclassified as tonic theta-ON cells (n = 79) and tonic theta-OFF (n = 22). Tonic theta-ON and tonic theta-OFF cells displayed irregular or regular (tonic) discharge patterns. Rhythmic discharge patterns did not occur in any theta-related cells in the nuclei of the basal ganglia. However, analyses using Kaneoke and Vitek's [J. Neurosci. Methods 68, (1996) 211] algorithms revealed that 51/101 (50%) theta-related cells displayed periodicity in their discharge patterns whereas 27/51 (53%) of the nonrelated cells displayed periodicity in their discharge patterns. The periodicities in the majority of cells were in frequency ranges above that of theta band oscillation and synchrony. The results support the following conclusions: (1) the cellular activity of the basal ganglia, composed of nuclei traditionally associated with motor functions, is functionally connected with the neural circuitry involved in the generation of theta band oscillation and synchrony in the hippocampal formation; (2) the observed functional connectivity provides support for the role of the hippocampal formation in sensorimotor integration.

Animals↗
PubMed1992

Excitatory amino acid binding sites in the basal ganglia of the rat: a quantitative autoradiographic study.

Quantitative receptor autoradiography was used to determine the distribution of excitatory amino acid binding sites in the basal ganglia of rat brain. alpha-Amino-3-hydroxy-5-methylisoxazole-4-propionic acid, N-methyl-D-aspartate, kainate, quisqualate-sensitive metabotropic and non-N-methyl-D-aspartate, non-kainate, non-quisqualate glutamate binding sites had their highest density in striatum, nucleus accumbens, and olfactory tubercle. Kainate binding was higher in the lateral striatum but there was no medial-lateral striatal gradient for other binding sites. N-Methyl-D-aspartate and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid binding sites were most dense in the nucleus accumbens and olfactory tubercle. There was no dorsal-ventral gradient within the striatal complex for the other binding sites. Other regions of the basal ganglia had lower densities of ligand binding. To compare binding site density within non-striatal regions, binding for each ligand was normalized to the striatal binding density. When compared to the striatal complex, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid and metabotropic binding sites had higher relative density in the globus pallidus, ventral pallidum, and subthalamic nucleus than other binding sites. Metabotropic binding also had a high relative density in the substantia nigra. Non-N-methyl-D-aspartate, non-kainate, non-quisqualate glutamate binding sites had a high relative density in globus pallidus, ventral pallidum, and substantia nigra. N-Methyl-D-aspartate binding sites had a low relative density in pallidum, subthalamic nucleus, substantia nigra and ventral tegmental area. Our data indicate heterogeneous distribution of excitatory amino acid binding sites within rat basal ganglia and suggest that the character of excitatory amino acid-mediated neurotransmission within the basal ganglia is also heterogeneous.

Animals↗
PubMed1997

Re-evaluation of the functional anatomy of the basal ganglia in normal and Parkinsonian states.

In the late 1980s, a functional and anatomical model of basal ganglia organization was proposed in order to explain the clinical syndrome of Parkinson's disease. According to this model, the pathological overactivity observed in the subthalamic nucleus and the output station of the basal ganglia plays a crucial role in the pathophysiology of the motor signs of Parkinson's disease. The hyperactivity of subthalamic neurons in Parkinsonism is viewed as a direct consequence of a pathological hypoactivity of the external segment of the pallidum. This article reviews recent data from different experimental approaches that challenge the established model of basal ganglia organization by reinterpreting the functional interaction between the external segment of the pallidum and the subthalamic nucleus in both the normal and pathological state. Indeed, recent neurobiochemical studies have rather unexpectedly shown that the GABAergic and metabolic activities of the external pallidum are not decreased in human and non-human primates with Parkinsonism. This absence of any decrease in activity might be explained by the functionally antagonistic influences of the striatal and subthalamic afferences within the external pallidum, as suggested by several anatomical studies. In addition, there are clues from electrophysiological studies to suggest that the hyperactivity found in the subthalamic neurons in Parkinsonism may not depend solely on the level of activity in the external pallidum. In such a framework, the hyperactivity of the subthalamic neurons would have to be explained, at least in part, by other sources of excitation or disinhibition. However, any explanation for the origin of the subthalamic overactivity in Parkinsonism remains speculative.

Animals↗
PubMed2006

Basal ganglia orient eyes to reward.

Expectation of reward motivates our behaviors and influences our decisions. Indeed, neuronal activity in many brain areas is modulated by expected reward. However, it is still unclear where and how the reward-dependent modulation of neuronal activity occurs and how the reward-modulated signal is transformed into motor outputs. Recent studies suggest an important role of the basal ganglia. Sensorimotor/cognitive activities of neurons in the basal ganglia are strongly modulated by expected reward. Through their abundant outputs to the brain stem motor areas and the thalamocortical circuits, the basal ganglia appear capable of producing body movements based on expected reward. A good behavioral measure to test this hypothesis is saccadic eye movement because its brain stem mechanism has been extensively studied. Studies from our laboratory suggest that the basal ganglia play a key role in guiding the gaze to the location where reward is available. Neurons in the caudate nucleus and the substantia nigra pars reticulata are extremely sensitive to the positional difference in expected reward, which leads to a bias in excitability between the superior colliculi such that the saccade to the to-be-rewarded position occurs more quickly. It is suggested that the reward modulation occurs in the caudate where cortical inputs carrying spatial signals and dopaminergic inputs carrying reward-related signals are integrated. These data support a specific form of reinforcement learning theories, but also suggest further refinement of the theory.

Animals↗
PubMed1981

Cholecystokinin receptors are decreased in basal ganglia and cerebral cortex of Huntington's disease.

Cholecystokinin (CCK) receptors were found to be significantly reduced in basal ganglia and cerebral cortex of post-mortem from Huntington's patients with matched controls. The magnitude of the reduction in CCK binding (69% in basal ganglia, 43% in cerebral cortex) is consistent with the degree of neuronal degeneration in basal ganglia, but suggests a possibly selective loss of CCK receptor-containing neurons in cerebral cortex of Huntington's patients.

Basal Ganglia↗
PubMed1990

Connections of the subthalamic nucleus with ventral striatopallidal parts of the basal ganglia in the rat.

The present study was undertaken to establish the precise anatomical relationship of the subthalamic nucleus (STh) with limbic lobe-afferented parts of the basal ganglia in the rat. The anterograde tracer Phaseolus vulgaris-leucoagglutinin (PHA-L), injected in the STh, the globus pallidus, the ventral pallidum, the ventral striatum, and the parafascicular thalamic nucleus, and the retrograde tracers Fluoro-Gold (FG) and cholera toxin B (CTb), injected in the globus pallidus, the ventral pallidum, the ventral striatum, and the ventral mesencephalon, were used for this purpose. The results of these tracing experiments confirm the general notion of reciprocal connections between the STh and pallidal areas. Thus the dorsomedial part of the STh is connected with the subcommisural ventral pallidum, whereas a more ventral and lateral part of the medial STh is related to the medial globus pallidus. The lateral hypothalamic area, directly adjacent to the STh, containing neurons with a morphology quite similar to those in the STh, projects to parts of the ventral pallidum related to the olfactory tubercle. The reciprocal projection from this pallidal area to subthalamic regions appears to be very sparse. The medial STh sends strong projections to the medial part of the entopeduncular nucleus and the adjacent lateral hypothalamic area. Sparser projections from the medial STh reach the rostral and medial part of the caudate-putamen and the nucleus accumbens. The nucleus accumbens sends a very sparse projection back to the medial STh. The projections of the medial STh to the ventral mesencephalon appear also to be topographically organized. The lateral hypothalamus and a few cells in the most medial part of the STh project to the ventral tegmental area, whereas progressively more lateral parts of the ventral mesencephalon, in particular the substantia nigra, receive input from successively more lateral and caudal parts of the STh. In addition, a number of STh fibers reach the midbrain extrapyramidal area. The lateral part of the parafascicular thalamic nucleus projects to the lateral part of the STh, whereas parafascicular neurons medial to the fasciculus retroflexus project to the dorsomedial portion of the STh. The medial part of the STh and the adjacent lateral hypothalamus are intimately connected with limbic parts of the basal ganglia in a way similar and parallel to the connections of the lateral STh with motor-related parts of the basal ganglia. These findings suggest a role for the STh in nonmotor functions of the basal ganglia.

Animals↗
PubMed1994

MR diagnosis of Creutzfeldt-Jakob disease: significance of high signal intensity of the basal ganglia.

OBJECTIVE: Creutzfeldt-Jakob disease is a rare dementing illness that usually affects older adults. Currently, neuroradiologic examinations play a minor role in the diagnosis of Creutzfeldt-Jakob disease. Several single case reports have noted a distinctive finding of hyperintense signal abnormalities in the basal ganglia on T2-weighted MR images of patients with Creutzfeldt-Jakob disease. In order to assess the diagnostic utility of this finding, we studied the imaging features of four patients with Creutzfeldt-Jakob disease in whom this MR finding was present. MATERIALS AND METHODS: Two neuroradiologists retrospectively reviewed the MR images of four patients who had pathologically proved Creutzfeldt-Jakob disease and signal abnormalities in the basal ganglia on T2-weighted MR images. The patients' clinical findings were also analyzed. RESULTS: The four patients had MR examinations between 6 months and 1 year after the onset of symptoms. In all four cases, the hyperintense signal abnormalities in the basal ganglia on T2-weighted images were diffuse and bilaterally symmetric. The T1-weighted images were normal. A CT scan was obtained on a single patient and was normal. CONCLUSION: Although a lack of signal abnormality in the basal ganglia on MR imaging cannot be used to rule out a diagnosis of Creutzfeldt-Jakob disease, our experience and review of published reports suggest that in the proper clinical setting, bilaterally symmetric, diffuse hyperintense abnormalities in the basal ganglia on T2-weighted images may be a specific sign of Creutzfeldt-Jakob disease.

Adult↗
PubMed2004

Intralaminar thalamic nuclei lesions: widespread impact on dopamine denervation-mediated cellular defects in the rat basal ganglia.

Intralaminar thalamic nuclei represent a major site of non-dopaminergic degeneration in Parkinson disease, but the impact of this degeneration on the pathophysiological functioning of basal ganglia remains unknown. To address this issue, we compared the effects of 6-hydroxydopamine-induced lesions of nigral dopamine neurons alone or combined with ibotenate-induced lesions of intralaminar thalamic neurons on markers of neuronal metabolic activity in the rat basal ganglia using in situ hybridization histochemistry. Thalamic lesions prevented most of the dopamine denervation-induced changes (i.e. the increases in mRNA levels of enkephalin and GAD67 in the striatum, of GAD67 in the globus pallidus and entopeduncular nucleus, and of cytochrome oxidase subunit-I in the subthalamic nucleus), but did not affect the downregulation of striatal substance P and upregulation of GAD67 in the substantia nigra pars reticulata. We also provide immunohistochemical evidence that thalamic lesions markedly decreased striatal expression of the vesicular glutamate transporter vGluT2, confirming the association of this transporter with the thalamic projections to the basal ganglia. Altogether, these data reveal a major antagonistic influence of thalamic and dopaminergic afferents onto the basal ganglia and suggest that degeneration of thalamic neurons in Parkinson disease may represent an important factor counteracting expression of the defects associated with the dopamine denervation.

Adrenergic Agents↗
PubMed1976

Alteration of basal ganglia evoked responses by reserpine and L-dopa.

The effects of reserpine and L-Dopa on basal ganglia evoked potentials were investigated in cats. The caudate response resulting from substantia nigra stimulation and the substantia nigra response elicited by globus pallidus stimulation were increased at several hours after the systemic administration of reserpine. L-Dopa in the presence of dopa decarboxylase inhibition (MK-486) depressed these responses and reversed the effect of reserpine at 0.5 h after administration. Reserpine did not reverse the L-Dopa effect. Reserpine and L-Dopa caused no significant change in responses between other basal ganglia structures. These data give evidence that the basal ganglia are major sites for reserpine and L-Dopa action.

Animals↗
PubMed2004

[Potential mechanisms of effects of endogenous neuromodulators on the interdependent activity of neurons in various nuclei of the basal ganglia].

A possible mechanism of influence of neuromodulators on interdependent activity of neurons in the diverse basal ganglia nuclei is suggested. According to modulation rules, an activation of postsynaptic Gs- or Gq/11-(Gi/0-) protein coupled receptors promotes induction of long-term potentiation (depression) of excitatory inputs to different neurons and augmentation (lowering) of their activity; an activation of presynaptic Gs- or Gq/11-(Gi/0-) protein coupled receptors promotes a rise (decrease) of release of GABA and co-peptides from striatal terminals and glutamate release from subthalamic terminals in the globus pallidus and output nuclei. It follows from the modulation rules that, since identical receptors are present on striatal neuron and their axon terminals, effects of neuromodulator action in diverse basal ganglia nuclei can be summarized. Neuromodulators released from striato-nigral and striato-pallidal fibers could promote interdependent activity of neurons in "direct" and "indirect" pathways through the basal ganglia due to convergence of these fibers on cholinergic interneurons and pallido-striatal cells.

Animals↗
PubMed1998

AIDS-related MR hyperintensity of the basal ganglia.

PURPOSE: Our goal was to describe the MR imaging appearance and clinical pathologic correlates of bilateral basal ganglia hyperintensity in acquired immunodeficiency syndrome (AIDS). METHODS: Medical records and laboratory data were reviewed retrospectively in nine cases of bilateral basal ganglia hyperintensity on long-repetition-time MR images. Opportunistic infections of the central nervous system were excluded by clinical and laboratory data. Postmortem neuropathologic examination was obtained in two cases. RESULTS: All patients presented acutely with new seizures or changes in mental status. A history of drug abuse was elicited in seven of the nine remaining patients. Renal failure was present in six cases. Symmetric bilateral caudate and putamen hyperintensity on T2-weighted images was found in all cases with variable extension to the surrounding white matter, thalamus, and brain stem. Postmortem neuropathologic examination in two cases revealed numerous microinfarcts in a distribution similar to the MR signal abnormalities. CONCLUSION: The MR appearance of basal ganglia hyperintensity in this series of AIDS patients represents ischemic tissue injury. We propose that this clinicopathologic entity is precipitated by the combined effects of human immunodeficiency virus infection and drug use, particularly cocaine and/or associated toxic contaminants.

AIDS Dementia Complex↗
PubMed2003

Basal ganglia calcification and psychotic symptoms in the very old.

BACKGROUND: Basal ganglia calcification (BGC) is associated with psychotic symptoms in young and middle-aged patient samples. METHODS: We studied the cross-sectional relationship between psychotic symptoms and BGC in a population sample of non-demented 85-year-olds, of whom 86 were mentally healthy, 11 had hallucinations or delusions, 21 had mood disorders and 20 had anxiety disorders. BGC was measured using computerized tomography (CT). Mental disorders were diagnosed using DSM-III-R criteria and psychotic symptoms were evaluated using information from psychiatric examinations, key-informant interviews and review medical records. RESULTS: BGC on CT was observed in 19% of mentally healthy and 64% of non-demented individuals with hallucinations or delusions [Odds Ratio (OR) 7.7, 95% Confidence Intervals (CI) 2.9-29.7, p=0.003]. There were no associations between BGC and mood or anxiety disorders. CONCLUSIONS: BGC is strongly associated with psychotic symptoms in very old age, possibly due to a disturbance in the basal ganglia dopaminergic system.

Affective Disorders, Psychotic↗
PubMed2001

Stepping out of the box: information processing in the neural networks of the basal ganglia.

The Albin-DeLong 'box and arrow' model has long been the accepted standard model for the basal ganglia network. However, advances in physiological and anatomical research have enabled a more detailed neural network approach. Recent computational models hold that the basal ganglia use reinforcement signals and local competitive learning rules to reduce the dimensionality of sparse cortical information. These models predict a steady-state situation with diminished efficacy of lateral inhibition and low synchronization. In this framework, Parkinson's disease can be characterized as a persistent state of negative reinforcement, inefficient dimensionality reduction, and abnormally synchronized basal ganglia activity.

Animals↗