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Hegeman DJ, Hong ES, Hernández VM, Chan CS. The external globus pallidus: progress and perspectives. Eur J Neurosci 2016; 43:1239-65. [PMID: 26841063 PMCID: PMC4874844 DOI: 10.1111/ejn.13196] [Citation(s) in RCA: 99] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 01/20/2016] [Accepted: 01/27/2016] [Indexed: 12/12/2022]
Abstract
The external globus pallidus (GPe) of the basal ganglia is in a unique and powerful position to influence processing of motor information by virtue of its widespread projections to all basal ganglia nuclei. Despite the clinical importance of the GPe in common motor disorders such as Parkinson's disease, there is only limited information about its cellular composition and organizational principles. In this review, recent advances in the understanding of the diversity in the molecular profile, anatomy, physiology and corresponding behaviour during movement of GPe neurons are described. Importantly, this study attempts to build consensus and highlight commonalities of the cellular classification based on existing but contentious literature. Additionally, an analysis of the literature concerning the intricate reciprocal loops formed between the GPe and major synaptic partners, including both the striatum and the subthalamic nucleus, is provided. In conclusion, the GPe has emerged as a crucial node in the basal ganglia macrocircuit. While subtleties in the cellular makeup and synaptic connection of the GPe create new challenges, modern research tools have shown promise in untangling such complexity, and will provide better understanding of the roles of the GPe in encoding movements and their associated pathologies.
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Affiliation(s)
- Daniel J Hegeman
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Ellie S Hong
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Vivian M Hernández
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - C Savio Chan
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
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Eid L, Parent M. Chemical anatomy of pallidal afferents in primates. Brain Struct Funct 2016; 221:4291-4317. [PMID: 27028222 DOI: 10.1007/s00429-016-1216-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 03/15/2016] [Indexed: 12/24/2022]
Abstract
Neurons of the globus pallidus receive massive inputs from the striatum and the subthalamic nucleus, but their activity, as well as those of their striatal and subthalamic inputs, are modulated by brainstem afferents. These include serotonin (5-HT) projections from the dorsal raphe nucleus, cholinergic (ACh) inputs from the pedunculopontine tegmental nucleus, and dopamine (DA) afferents from the substantia nigra pars compacta. This review summarizes our recent findings on the distribution, quantitative and ultrastructural aspects of pallidal 5-HT, ACh and DA innervations. These results have led to the elaboration of a new model of the pallidal neuron based on a precise knowledge of the hierarchy and chemical features of the various synaptic inputs. The dense 5-HT, ACh and DA innervations disclosed in the associative and limbic pallidal territories suggest that these brainstem inputs contribute principally to the planification of motor behaviors and the regulation of attention and mood. Although 5-HT, ACh and DA inputs were found to modulate pallidal neurons and their afferents mainly through asynaptic (volume) transmission, genuine synaptic contacts occur between these chemospecific axon varicosities and pallidal dendrites, revealing that these brainstem projections have a direct access to pallidal neurons, in addition to their indirect input through the striatum and subthalamic nucleus. Altogether, these findings reveal that the brainstem 5-HT, ACh and DA pallidal afferents act in concert with the more robust GABAergic inhibitory striatopallidal and glutamatergic excitatory subthalamopallidal inputs. We hypothesize that a fragile equilibrium between forebrain and brainstem pallidal afferents plays a key role in the functional organization of the primate basal ganglia, in both health and disease.
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Affiliation(s)
- Lara Eid
- Department of Psychiatry and Neuroscience, Faculty of Medicine, Centre de recherche de l'Institut universitaire en santé mentale de Québec (CRIUSMQ), Université Laval, F-6530-1, 2601, de la Canardière, Quebec, QC, G1J 2G3, Canada
| | - Martin Parent
- Department of Psychiatry and Neuroscience, Faculty of Medicine, Centre de recherche de l'Institut universitaire en santé mentale de Québec (CRIUSMQ), Université Laval, F-6530-1, 2601, de la Canardière, Quebec, QC, G1J 2G3, Canada.
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Parvalbumin+ Neurons and Npas1+ Neurons Are Distinct Neuron Classes in the Mouse External Globus Pallidus. J Neurosci 2015; 35:11830-47. [PMID: 26311767 DOI: 10.1523/jneurosci.4672-14.2015] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
UNLABELLED Compelling evidence suggests that pathological activity of the external globus pallidus (GPe), a nucleus in the basal ganglia, contributes to the motor symptoms of a variety of movement disorders such as Parkinson's disease. Recent studies have challenged the idea that the GPe comprises a single, homogenous population of neurons that serves as a simple relay in the indirect pathway. However, we still lack a full understanding of the diversity of the neurons that make up the GPe. Specifically, a more precise classification scheme is needed to better describe the fundamental biology and function of different GPe neuron classes. To this end, we generated a novel multicistronic BAC (bacterial artificial chromosome) transgenic mouse line under the regulatory elements of the Npas1 gene. Using a combinatorial transgenic and immunohistochemical approach, we discovered that parvalbumin-expressing neurons and Npas1-expressing neurons in the GPe represent two nonoverlapping cell classes, amounting to 55% and 27% of the total GPe neuron population, respectively. These two genetically identified cell classes projected primarily to the subthalamic nucleus and to the striatum, respectively. Additionally, parvalbumin-expressing neurons and Npas1-expressing neurons were distinct in their autonomous and driven firing characteristics, their expression of intrinsic ion conductances, and their responsiveness to chronic 6-hydroxydopamine lesion. In summary, our data argue that parvalbumin-expressing neurons and Npas1-expressing neurons are two distinct functional classes of GPe neurons. This work revises our understanding of the GPe, and provides the foundation for future studies of its function and dysfunction. SIGNIFICANCE STATEMENT Until recently, the heterogeneity of the constituent neurons within the external globus pallidus (GPe) was not fully appreciated. We addressed this knowledge gap by discovering two principal GPe neuron classes, which were identified by their nonoverlapping expression of the markers parvalbumin and Npas1. Our study provides evidence that parvalbumin and Npas1 neurons have different topologies within the basal ganglia.
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Ríos A, Barrientos R, Alatorre A, Delgado A, Perez-Capistran T, Chuc-Meza E, García-Ramirez M, Querejeta E. Dopamine-dependent modulation of rat globus pallidus excitation by nicotine acetylcholine receptors. Exp Brain Res 2015; 234:605-16. [DOI: 10.1007/s00221-015-4491-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 10/30/2015] [Indexed: 11/24/2022]
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Chiken S, Sato A, Ohta C, Kurokawa M, Arai S, Maeshima J, Sunayama-Morita T, Sasaoka T, Nambu A. Dopamine D1 Receptor-Mediated Transmission Maintains Information Flow Through the Cortico-Striato-Entopeduncular Direct Pathway to Release Movements. Cereb Cortex 2015; 25:4885-97. [PMID: 26443442 PMCID: PMC4635926 DOI: 10.1093/cercor/bhv209] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In the basal ganglia (BG), dopamine plays a pivotal role in motor control, and dopamine deficiency results in severe motor dysfunctions as seen in Parkinson's disease. According to the well-accepted model of the BG, dopamine activates striatal direct pathway neurons that directly project to the output nuclei of the BG through D1 receptors (D1Rs), whereas dopamine inhibits striatal indirect pathway neurons that project to the external pallidum (GPe) through D2 receptors. To clarify the exact role of dopaminergic transmission via D1Rs in vivo, we developed novel D1R knockdown mice in which D1Rs can be conditionally and reversibly regulated. Suppression of D1R expression by doxycycline treatment decreased spontaneous motor activity and impaired motor ability in the mice. Neuronal activity in the entopeduncular nucleus (EPN), one of the output nuclei of the rodent BG, was recorded in awake conditions to examine the mechanism of motor deficits. Cortically evoked inhibition in the EPN mediated by the cortico-striato-EPN direct pathway was mostly lost during suppression of D1R expression, whereas spontaneous firing rates and patterns remained unchanged. On the other hand, GPe activity changed little. These results suggest that D1R-mediated dopaminergic transmission maintains the information flow through the direct pathway to appropriately release motor actions.
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Affiliation(s)
- Satomi Chiken
- Division of System Neurophysiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki 444-8585, Japan
| | - Asako Sato
- Department of Laboratory Animal Science, Kitasato University School of Medicine, Sagamihara 252-0374, Japan National Institute for Basic Biology, Okazaki 444-8585, Japan
| | - Chikara Ohta
- Division of System Neurophysiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Makoto Kurokawa
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Satoshi Arai
- Department of Laboratory Animal Science, Kitasato University School of Medicine, Sagamihara 252-0374, Japan
| | - Jun Maeshima
- Department of Laboratory Animal Science, Kitasato University School of Medicine, Sagamihara 252-0374, Japan
| | - Tomoko Sunayama-Morita
- National Institute for Basic Biology, Okazaki 444-8585, Japan Department of Life Sciences, Graduate School of Arts and Science, The University of Tokyo, Tokyo 153-8902, Japan
| | - Toshikuni Sasaoka
- School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki 444-8585, Japan Department of Laboratory Animal Science, Kitasato University School of Medicine, Sagamihara 252-0374, Japan National Institute for Basic Biology, Okazaki 444-8585, Japan Department of Comparative and Experimental Medicine, Brain Research Institute, Niigata University, Niigata 951-8585, Japan
| | - Atsushi Nambu
- Division of System Neurophysiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki 444-8585, Japan
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Noblejas MI, Schechtman E, Adler A, Joshua M, Katabi S, Bergman H. Hold your pauses: external globus pallidus neurons respond to behavioural events by decreasing pause activity. Eur J Neurosci 2015; 42:2415-25. [PMID: 26263048 DOI: 10.1111/ejn.13041] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2015] [Revised: 07/26/2015] [Accepted: 08/03/2015] [Indexed: 11/29/2022]
Abstract
Awareness of its rich structural pathways has earned the external segment of the globus pallidus (GPe) recognition as a central figure within the basal ganglia circuitry. Interestingly, GPe neurons are uniquely identified by the presence of prominent pauses interspersed among a high-frequency discharge rate of 50-80 spikes/s. These pauses have an average pause duration of 620 ms with a frequency of 13/min, yielding an average pause activity (probability of a GPe neuron being in a pause) of (620 × 13)/(60 × 1000) = 0.13. Spontaneous pause activity has been found to be inversely related to arousal state. The relationship of pause activity with behavioural events remains to be elucidated. In the present study, we analysed the electrophysiological activity of 200 well-isolated GPe pauser cells recorded from four non-human primates (Macaque fascicularis) while they were engaged in similar classical conditioning tasks. The isolation quality of the recorded activity and the pauses were determined with objective automatic methods. The results showed that the pause probability decreased by 9.09 and 10.0%, and the discharge rate increased by 2.96 and 1.95%, around cue and outcome presentation, respectively. Analysis of the linear relationship between the changes in pause activity and discharge rate showed r(2) = 0.46 and r(2) = 0.66 upon cue onset and outcome presentation, respectively. Thus, pause activity is a pertinent element in short-term encoding of relevant behavioural events, and has a significant, but not exclusive, role in the modulation of GPe discharge rate around these events.
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Affiliation(s)
- Maria Imelda Noblejas
- Department of Neurobiology, Institute of Medical Research - Israel Canada (IMRIC), Hadassah Medical School, The Hebrew University, Jerusalem, 91120, Israel
| | - Eitan Schechtman
- Department of Neurobiology, Institute of Medical Research - Israel Canada (IMRIC), Hadassah Medical School, The Hebrew University, Jerusalem, 91120, Israel.,Edmond and Lily Safra Centre for Brain Sciences, The Hebrew University, Jerusalem, Israel
| | - Avital Adler
- Department of Neurobiology, Institute of Medical Research - Israel Canada (IMRIC), Hadassah Medical School, The Hebrew University, Jerusalem, 91120, Israel.,Edmond and Lily Safra Centre for Brain Sciences, The Hebrew University, Jerusalem, Israel
| | - Mati Joshua
- Department of Neurobiology, Institute of Medical Research - Israel Canada (IMRIC), Hadassah Medical School, The Hebrew University, Jerusalem, 91120, Israel.,Edmond and Lily Safra Centre for Brain Sciences, The Hebrew University, Jerusalem, Israel
| | - Shiran Katabi
- Department of Neurobiology, Institute of Medical Research - Israel Canada (IMRIC), Hadassah Medical School, The Hebrew University, Jerusalem, 91120, Israel
| | - Hagai Bergman
- Department of Neurobiology, Institute of Medical Research - Israel Canada (IMRIC), Hadassah Medical School, The Hebrew University, Jerusalem, 91120, Israel.,Edmond and Lily Safra Centre for Brain Sciences, The Hebrew University, Jerusalem, Israel
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Coinciding decreases in discharge rate suggest that spontaneous pauses in firing of external pallidum neurons are network driven. J Neurosci 2015; 35:6744-51. [PMID: 25926452 DOI: 10.1523/jneurosci.5232-14.2015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The external segment of the globus pallidus (GPe) is one of the core nuclei of the basal ganglia, playing a major role in normal control of behavior and in the pathophysiology of basal ganglia-related disorders such as Parkinson's disease. In vivo, most neurons in the GPe are characterized by high firing rates (50-100 spikes/s), interspersed with long periods (∼0.6 s) of complete silence, which are termed GPe pauses. Previous physiological studies of single and pairs of GPe neurons have failed to fully disclose the physiological process by which these pauses originate. We examined 1001 simultaneously recorded pairs of high-frequency discharge GPe cells recorded from four monkeys during task-irrelevant periods, considering the activity in one cell while the other is pausing. We found that pauses (n = 137,278 pauses) coincide with a small yet significant reduction in firing rate (0.78 ± 0.136 spikes/s) in other GPe cells. Additionally, we found an increase in the probability of the simultaneously recorded cell to pause during the pause period of the "trigger" cell. Importantly, this increase in the probability to pause at the same time does not account for the reduction in firing rate by itself. Modeling of GPe cells as class 2 excitability neurons (Hodgkin, 1948) with common external inputs can explain our results. We suggest that common inputs decrease the GPe discharge rate and lead to a bifurcation phenomenon (pause) in some of the GPe neurons.
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58
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Abstract
The basal ganglia (BG) play an important role in motor control, reinforcement learning, and perceptual decision making. Modeling and experimental evidence suggest that, in a speed-accuracy tradeoff, the corticostriatal pathway can adaptively adjust a decision threshold (the amount of information needed to make a choice). In this study, we go beyond the focus of previous works on the direct and hyperdirect pathways to examine the contribution of the indirect pathway of the BG system to decision making in a biophysically based spiking network model. We find that the mechanism of adjusting the decision threshold by plasticity of the corticostriatal connections is effective, provided that the indirect pathway counterbalances the direct pathway in their projections to the output nucleus. Furthermore, in our model, changes within basal ganglia connections similar to those that arise in parkinsonism give rise to strong beta oscillations. Specifically, beta oscillations are produced by an abnormal enhancement of the interactions between the subthalamic nucleus (STN) and the external segment of globus pallidus (GPe) in the indirect pathway, with an oscillation frequency that depends on the excitatory cortical input to the STN and the inhibitory input to the GPe from the striatum. In a parkinsonian state characterized by pronounced beta oscillations, the mean reaction time and range of threshold variation (a measure of behavioral flexibility) are significantly reduced compared with the normal state. Our work thus reveals a specific circuit mechanism for impairments of perceptual decision making associated with Parkinson's disease.
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Yoshida A, Tanaka M. Two Types of Neurons in the Primate Globus Pallidus External Segment Play Distinct Roles in Antisaccade Generation. Cereb Cortex 2015; 26:1187-99. [PMID: 25577577 DOI: 10.1093/cercor/bhu308] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The globus pallidus external segment (GPe) constitutes part of the indirect pathway of the basal ganglia. Because of inhibitory projections from the striatum, most GPe neurons are expected to reduce activity during movements. However, many GPe neurons in fact display increased activity. We previously found that both excitatory and inhibitory responses were modulated during antisaccades, when eyes were directed away from a visual stimulus. To elucidate the roles of these neurons during antisaccades, we examined neuronal activities as monkeys performed antisaccades, prosaccades, and NoGo tasks under 2 conditions. In the Deliberate condition, the task-rule was instructed by color of the fixation point, while in the Immediate condition, it was given by color of the target. Under both conditions, the increase-type neurons exhibited greater activity during antisaccades compared with the other tasks and neuronal activity negatively correlated with saccade latency. The decrease-type neurons also showed greater modulation during antisaccades but their activity was comparable between NoGo and antisaccade trials in the Immediate condition. These results suggest that the increase-type neurons might play a role in facilitating antisaccades, whereas the decrease-type neurons could mediate signals for reflexive saccade suppression. We propose that these GPe neurons are differently involved in basal ganglia pathways.
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Affiliation(s)
- Atsushi Yoshida
- Department of Physiology Department of Diagnostic and Interventional Radiology, Hokkaido University School of Medicine, Sapporo 060-8638, Japan
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Liénard J, Girard B. A biologically constrained model of the whole basal ganglia addressing the paradoxes of connections and selection. J Comput Neurosci 2014; 36:445-68. [PMID: 24077957 DOI: 10.1007/s10827-013-0476-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 05/30/2013] [Accepted: 08/04/2013] [Indexed: 11/28/2022]
Abstract
The basal ganglia nuclei form a complex network of nuclei often assumed to perform selection, yet their individual roles and how they influence each other is still largely unclear. In particular, the ties between the external and internal parts of the globus pallidus are paradoxical, as anatomical data suggest a potent inhibitory projection between them while electrophysiological recordings indicate that they have similar activities. Here we introduce a theoretical study that reconciles both views on the intra-pallidal projection, by providing a plausible characterization of the relationship between the external and internal globus pallidus. Specifically, we developed a mean-field model of the whole basal ganglia, whose parameterization is optimized to respect best a collection of numerous anatomical and electrophysiological data. We first obtained models respecting all our constraints, hence anatomical and electrophysiological data on the intrapallidal projection are globally consistent. This model furthermore predicts that both aforementioned views about the intra-pallidal projection may be reconciled when this projection is weakly inhibitory, thus making it possible to support similar neural activity in both nuclei and for the entire basal ganglia to select between actions. Second, we predicts that afferent projections are substantially unbalanced towards the external segment, as it receives the strongest excitation from STN and the weakest inhibition from the striatum. Finally, our study strongly suggests that the intrapallidal connection pattern is not focused but diffuse, as this latter pattern is more efficient for the overall selection performed in the basal ganglia.
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Abstract
What is the meaning of an action potential? There must be different answers for neurons that fire spontaneously, even in the absence of synaptic input, and those driven to fire from a resting membrane potential. In spontaneously firing neurons, the occurrence of the next action potential is guaranteed; only variations in its timing can carry the message. In the basal ganglia, the globus pallidus, the substantia nigra, and the subthalamic nucleus consist of neurons firing spontaneously. They each receive thousands of synaptic inputs, but these are not required to maintain their background firing. Instead, synaptic interactions among basal ganglia nuclei comprise a system of coupled oscillators that produces a complex resting pattern of activity. Normally, this pattern is highly irregular and uncorrelated, so that the firing of each cell is statistically independent of the others. This maximizes the potential information that may be transmitted by the basal ganglia to its target structures. In Parkinson's disease, the resting pattern of activity is dominated by a slow oscillation shared by nearly all of the neurons. Treatment with deep brain stimulation may gain its therapeutic value by disrupting this shared pathological oscillation, and restoring independent action by each neuron in the network.
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Affiliation(s)
- Charles J Wilson
- Department of Biology, University of Texas at San Antonio, San Antonio, TX, USA
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Nambu A, Tachibana Y. Mechanism of parkinsonian neuronal oscillations in the primate basal ganglia: some considerations based on our recent work. Front Syst Neurosci 2014; 8:74. [PMID: 24904309 PMCID: PMC4033056 DOI: 10.3389/fnsys.2014.00074] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Accepted: 04/14/2014] [Indexed: 11/13/2022] Open
Abstract
Accumulating evidence suggests that abnormal neuronal oscillations in the basal ganglia (BG) contribute to the manifestation of parkinsonian symptoms. In this article, we would like to summarize our recent work on the mechanism underlying abnormal oscillations in the parkinsonian state and discuss its significance in pathophysiology of Parkinson’s disease. We recorded neuronal activity in the BG of parkinsonian monkeys treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. Systemic administration of L-DOPA alleviated parkinsonian motor signs and decreased abnormal neuronal oscillations (8–15 Hz) in the internal (GPi) and external (GPe) segments of the globus pallidus and the subthalamic nucleus (STN). Inactivation of the STN by muscimol (GABAA receptor agonist) injection also ameliorated parkinsonian signs and suppressed GPi oscillations. The blockade of glutamatergic inputs to the STN by local microinjection of a mixture of 3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (glutamatergic NMDA receptor antagonist) and 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide (glutamatergic AMPA/kainate receptor antagonist) suppressed neuronal oscillations in the STN. STN oscillations were also attenuated by the blockade of GABAergic neurotransmission from the GPe to the STN by muscimol inactivation of the GPe. These results suggest that cortical glutamatergic inputs to the STN and reciprocal GPe-STN interconnections are both important for the generation and amplification of the oscillatory activity of GPe and STN neurons in the parkinsonian state. The oscillatory activity in the STN is subsequently transmitted to the GPi and may contribute to manifestation of parkinsonian symptoms.
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Affiliation(s)
- Atsushi Nambu
- Division of System Neurophysiology, National Institute for Physiological Sciences Okazaki, Japan ; Department of Physiological Sciences, Graduate University for Advanced Studies Okazaki, Japan
| | - Yoshihisa Tachibana
- Division of System Neurophysiology, National Institute for Physiological Sciences Okazaki, Japan ; Department of Physiological Sciences, Graduate University for Advanced Studies Okazaki, Japan
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63
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Schwab BC, Heida T, Zhao Y, Marani E, van Gils SA, van Wezel RJA. Synchrony in Parkinson's disease: importance of intrinsic properties of the external globus pallidus. Front Syst Neurosci 2013; 7:60. [PMID: 24109437 PMCID: PMC3789943 DOI: 10.3389/fnsys.2013.00060] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Accepted: 09/13/2013] [Indexed: 12/15/2022] Open
Abstract
The mechanisms for the emergence and transmission of synchronized oscillations in Parkinson's disease, which are potentially causal to motor deficits, remain debated. Aside from the motor cortex and the subthalamic nucleus, the external globus pallidus (GPe) has been shown to be essential for the maintenance of these oscillations and plays a major role in sculpting neural network activity in the basal ganglia (BG). While neural activity of the healthy GPe shows almost no correlations between pairs of neurons, prominent synchronization in the β frequency band arises after dopamine depletion. Several studies have proposed that this shift is due to network interactions between the different BG nuclei, including the GPe. However, recent studies demonstrate an important role for the properties of neurons within the GPe. In this review, we will discuss these intrinsic GPe properties and review proposed mechanisms for activity decorrelation within the dopamine-intact GPe. Failure of the GPe to desynchronize correlated inputs can be a possible explanation for synchronization in the whole BG. Potential triggers of synchronization involve the enhancement of GPe-GPe inhibition and changes in ion channel function in GPe neurons.
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Affiliation(s)
- Bettina C Schwab
- Applied Analysis and Mathematical Physics, MIRA Institute of Technical Medicine and Biomedical Technology, University of Twente Enschede, Netherlands ; Biomedical Signals and Systems, MIRA Institute of Technical Medicine and Biomedical Technology, University of Twente Enschede, Netherlands
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Wilson CJ. Active decorrelation in the basal ganglia. Neuroscience 2013; 250:467-82. [PMID: 23892007 DOI: 10.1016/j.neuroscience.2013.07.032] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2013] [Revised: 07/12/2013] [Accepted: 07/15/2013] [Indexed: 01/22/2023]
Abstract
The cytoarchitecturally-homogeneous appearance of the globus pallidus, subthalamic nucleus and substantia nigra has long been said to imply a high degree of afferent convergence and sharing of inputs by nearby neurons. Moreover, axon collaterals of neurons in the external segment of the globus pallidus and the substantia nigra pars reticulata arborize locally and make inhibitory synapses on other cells of the same type. These features suggest that the connectivity of the basal ganglia may impose spike-time correlations among the cells, and it has been puzzling that experimental studies have failed to demonstrate such correlations. One possible solution arises from studies of firing patterns in basal ganglia cells, which reveal that they are nearly all pacemaker cells. Their high rate of firing does not depend on synaptic excitation, but they fire irregularly because a dense barrage of synaptic inputs normally perturbs the timing of their autonomous activity. Theoretical and computational studies show that the responses of repetitively-firing neurons to shared input or mutual synaptic coupling often defy classical intuitions about temporal synaptic integration. The patterns of spike-timing among such neurons depend on the ionic mechanism of pacemaking, the level of background uncorrelated cellular and synaptic noise, and the firing rates of the neurons, as well as the properties of their synaptic connections. Application of these concepts to the basal ganglia circuitry suggests that the connectivity and physiology of these nuclei may be configured to prevent the establishment of permanent spike-timing relationships between neurons. The development of highly synchronous oscillatory patterns of activity in Parkinson's disease may result from the loss of pacemaking by some basal ganglia neurons, and accompanying breakdown of the mechanisms responsible for active decorrelation.
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Affiliation(s)
- C J Wilson
- Department of Biology, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, United States.
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Modulation of firing activity by endogenous GABAA receptors in the globus pallidus of MPTP-treated parkinsonian mice. Neurosci Bull 2013; 29:701-7. [PMID: 23839052 DOI: 10.1007/s12264-013-1351-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Accepted: 02/14/2013] [Indexed: 11/27/2022] Open
Abstract
The globus pallidus in rodents, equivalent to the external segment of the globus pallidus in primates, plays an important role in movement regulation. Previous studies have shown abundant γ-aminobutyric acid (GABA)ergic innervation and GABAA receptors in the globus pallidus. In this study, we investigated the effects of endogenous GABAA receptors on the spontaneous firing activity of pallidal neurons in both normal and MPTP-treated mice using multi-barrel electrodes extracellular recordings in vivo. We found that in normal mice, pressure ejection of 0.1 mmol/L gabazine, a specific GABAA receptor antagonist, increased the spontaneous firing rate of globus pallidus neurons by 27.6 ± 5.6%. Furthermore, in MPTP mice (14 days after MPTP treatment), 0.1 mmol/L gabazine increased the firing rates by 51.0 ± 7.9%, significantly greater than in normal mice. These results suggest that endogenous GABAA receptors modulate the activity of globus pallidus neurons. The present findings may provide a rationale for investigations into the potential role of GABAA receptors in Parkinson's disease.
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Signals through the striatopallidal indirect pathway stop movements by phasic excitation in the substantia nigra. J Neurosci 2013; 33:7583-94. [PMID: 23616563 DOI: 10.1523/jneurosci.4932-12.2013] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The striatum and subthalamic nucleus (STN) are the input stations of the basal ganglia and receive excitatory afferents from the cerebral cortex. The basal ganglia control voluntary movements through three parallel pathways mediated by the input stations: the hyperdirect pathway, which conveys direct cortical inputs to the substantia nigra pars reticulata (SNr), the output nucleus, through the STN; the direct pathway, which arises from striatal neurons expressing dopamine D1 receptors and projects to the SNr; and the indirect pathway, which arises from striatal neurons expressing dopamine D2 receptors (D2Rs) and projects indirectly to the SNr by way of the globus pallidus (GP) and STN. Our previous study showed that immunotoxin-mediated cell targeted ablation of D2R-expressing striatal neurons in mice induced motor hyperactivity. To elucidate the mechanism underlying the hyperactivity, here we examined neuronal activity in the GP and SNr. The ablation of D2R-expressing striatal neurons had little effect on spontaneous activity in the GP and SNr, but induced dramatic changes in the cortically evoked triphasic response composed of early excitation, inhibition, and late excitation in the GP and SNr (i.e., reduced inhibition in the GP, and reduced late excitation in the GP and SNr). In contrast, the ablation of striatal cholinergic interneurons, which also express D2Rs, did not show such effects. Therefore, the reduction of the cortically evoked late excitation in the SNr seems to be responsible for hyperactivity. These observations suggest that phasic late excitation in the SNr through the striatopallidal indirect pathway plays a key role in stopping movements.
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High-frequency pallidal stimulation disrupts information flow through the pallidum by GABAergic inhibition. J Neurosci 2013; 33:2268-80. [PMID: 23392658 DOI: 10.1523/jneurosci.4144-11.2013] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
To elucidate the mechanism of deep brain stimulation (DBS) targeting the internal segment of the globus pallidus (GPi), neuronal activity of the GPi and the external segment of the globus pallidus (GPe) was examined during local electrical microstimulation in normal awake monkeys. Single-pulse stimulation of the GPi evoked brief inhibition in neighboring GPi neurons, which was mediated by GABA(A) receptors. High-frequency stimulation of the GPi completely inhibited spontaneous firings of GPi neurons by activation of GABA(A) and GABA(B) receptors. Local single-pulse stimulation directly excited some GPi neurons. Such directly evoked responses were also inhibited by high-frequency stimulation through GABA(A) receptors. In contrast to the GPi, single-pulse and high-frequency stimulation of the GPe induced complex responses composed of GABAergic inhibition and glutamatergic excitation in neighboring GPe neurons. Cortically evoked triphasic responses of GPi neurons were completely inhibited during high-frequency GPi stimulation. These findings suggest that GPi-DBS dissociates inputs and outputs in the GPi by intense GABAergic inhibition and disrupts information flow through the GPi.
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68
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Sotoyama H, Namba H, Chiken S, Nambu A, Nawa H. Exposure to the cytokine EGF leads to abnormal hyperactivity of pallidal GABA neurons: implications for schizophrenia and its modeling. J Neurochem 2013; 126:518-28. [DOI: 10.1111/jnc.12223] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2012] [Revised: 02/03/2013] [Accepted: 02/15/2013] [Indexed: 10/27/2022]
Affiliation(s)
- Hidekazu Sotoyama
- Department of Molecular Neurobiology; Brain Research Institute; Niigata University; Niigata Japan
| | - Hisaaki Namba
- Department of Molecular Neurobiology; Brain Research Institute; Niigata University; Niigata Japan
| | - Satomi Chiken
- Division of System Neurobiology; National Institute for Physiological Sciences and Department of Physiological Sciences; Graduate University for Advanced Studies; Myodaiji Okazaki Japan
| | - Atsushi Nambu
- Division of System Neurobiology; National Institute for Physiological Sciences and Department of Physiological Sciences; Graduate University for Advanced Studies; Myodaiji Okazaki Japan
| | - Hiroyuki Nawa
- Department of Molecular Neurobiology; Brain Research Institute; Niigata University; Niigata Japan
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69
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GABAergic mechanisms for shaping transient visual responses in the mouse superior colliculus. Neuroscience 2013; 235:129-40. [PMID: 23337535 DOI: 10.1016/j.neuroscience.2012.12.061] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 12/10/2012] [Accepted: 12/18/2012] [Indexed: 11/21/2022]
Abstract
An object that suddenly appears in the visual field should be quickly detected and responded to because it could be beneficial or harmful. The superficial layer of the superior colliculus (sSC) is a brain structure capable of such functions, as sSC neurons exhibit sharp transient spike discharges with short latency in response to the appearance of a visual stimulus. However, how transient activity is generated in the sSC is poorly understood. Here, we show that inhibitory inputs actively shape transient activity in the sSC. Juxtacellular recordings from anesthetized mice demonstrate that almost all types of sSC neurons, which were identified by post hoc histochemistry, show transient spike discharges, i.e., ON activity, immediately after visual stimulus onset. ON activity was followed by a pause before the visual stimulus was turned off. To determine whether the pause reflected the absence of excitatory drive or inhibitory conductance, we injected depolarizing currents juxtasomally, which enabled us to observe inhibition as decreased discharges. The pause was observed even under this condition, suggesting that inhibitory input caused the pause. We further found that local application of a mixture of GABAA and GABAB receptor antagonists additively diminished the pause. These results indicate that GABAergic inputs produce transient ON responses by attenuating excitatory activity through the cooperative activation of GABAA and GABAB receptors, allowing sSC neurons to act as a saliency detector.
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70
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Pavlides A, Hogan SJ, Bogacz R. Improved conditions for the generation of beta oscillations in the subthalamic nucleus--globus pallidus network. Eur J Neurosci 2012; 36:2229-39. [PMID: 22805067 DOI: 10.1111/j.1460-9568.2012.08105.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
A key pathology in the development of Parkinson's disease is the occurrence of persistent beta oscillations, which are correlated with difficulty in movement initiation. We investigated the network model composed of the subthalamic nucleus (STN) and globus pallidus (GP) developed by A. Nevado Holgado et al. [(2010) Journal of Neuroscience, 30, 12340-12352], who identified the conditions under which this circuit could generate beta oscillations. Our work extended their analysis by deriving improved analytic stability conditions for realistic values of the synaptic transmission delay between STN and GP neurons. The improved conditions were significantly closer to the results of simulations for the range of synaptic transmission delays measured experimentally. Furthermore, our analysis explained how changes in cortical and striatal input to the STN-GP network influenced oscillations generated by the circuit. As we have identified when a system of mutually connected populations of excitatory and inhibitory neurons can generate oscillations, our results may also find applications in the study of neural oscillations produced by assemblies of excitatory and inhibitory neurons in other brain regions.
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Affiliation(s)
- Alex Pavlides
- Bristol Centre for Complexity Sciences, Department of Computer Science, University of Bristol, Bristol BS8 1UB, UK.
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71
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Deister CA, Dodla R, Barraza D, Kita H, Wilson CJ. Firing rate and pattern heterogeneity in the globus pallidus arise from a single neuronal population. J Neurophysiol 2012; 109:497-506. [PMID: 23114208 DOI: 10.1152/jn.00677.2012] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Intrinsic heterogeneity in networks of interconnected cells has profound effects on synchrony and spike-time reliability of network responses. Projection neurons of the globus pallidus (GPe) are interconnected by GABAergic inhibitory synapses and in vivo fire continuously but display significant rate and firing pattern heterogeneity. Despite being deprived of most of their synaptic inputs, GPe neurons in slices also fire continuously and vary greatly in their firing rate (1-70 spikes/s) and in regularity of their firing. We asked if this rate and pattern heterogeneity arises from separate cell types differing in rate, local synaptic interconnections, or variability of intrinsic properties. We recorded the resting discharge of GPe neurons using extracellular methods both in vivo and in vitro. Spike-to-spike variability (jitter) was measured as the standard deviation of interspike intervals. Firing rate and jitter covaried continuously, with slow firing being associated with higher variability than faster firing, as would be expected from heterogeneity arising from a single physiologically distinct cell type. The relationship between rate and jitter was unaffected by blockade of GABA and glutamate receptors. When the firing rate of individual neurons was altered with constant current, jitter changed to maintain the rate-jitter relationship seen across neurons. Long duration (30-60 min) recordings showed slow and spontaneous bidirectional drift in rate similar to the across-cell heterogeneity. Paired recordings in vivo and in vitro showed that individual cells wandered in rate independently of each other. Input conductance and rate wandered together, in a manner suggestive that both were due to fluctuations of an inward current.
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Affiliation(s)
- Christopher A Deister
- Department of Biology and Neurosciences Institute, University of Texas, San Antonio, Texas, USA.
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72
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Benhamou L, Bronfeld M, Bar-Gad I, Cohen D. Globus Pallidus external segment neuron classification in freely moving rats: a comparison to primates. PLoS One 2012; 7:e45421. [PMID: 23028997 PMCID: PMC3448641 DOI: 10.1371/journal.pone.0045421] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Accepted: 08/22/2012] [Indexed: 12/02/2022] Open
Abstract
Globus Pallidus external segment (GPe) neurons are well-characterized in behaving primates. Based on their firing properties, these neurons are commonly divided into two distinct groups: high frequency pausers (HFP) and low frequency bursters (LFB). However, no such characterization has been made for behaving rats. The current study characterizes and categorizes extracellularly recorded GPe neurons in freely moving rats, and compares these results to those obtained by extracellular recordings in behaving primates using the same analysis methods. Analysis of our data recorded in rats revealed two distinct neuronal populations exhibiting firing-pattern characteristics that are similar to those obtained in primates. These characteristic firing patterns are conserved between species although the firing rate is significantly lower in rats than in primates. Significant differences in waveform duration and shape were insufficient to create a reliable waveform-based classification in either species. The firing pattern analogy may emphasize conserved processing properties over firing rate per-se. Given the similarity in GPe neuronal activity between human and non-human primates in different pathologies, our results encourage information transfer using complementary studies across species in the GPe to acquire a better understanding of the function of this nucleus in health and disease.
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Affiliation(s)
- Liora Benhamou
- The Leslie and Susan Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat-Gan, Israel
| | - Maya Bronfeld
- The Leslie and Susan Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat-Gan, Israel
| | - Izhar Bar-Gad
- The Leslie and Susan Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat-Gan, Israel
| | - Dana Cohen
- The Leslie and Susan Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat-Gan, Israel
- * E-mail:
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73
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Jin XT, Paré JF, Smith Y. GABA transporter subtype 1 and GABA transporter subtype 3 modulate glutamatergic transmission via activation of presynaptic GABA(B) receptors in the rat globus pallidus. Eur J Neurosci 2012; 36:2482-92. [PMID: 22616751 DOI: 10.1111/j.1460-9568.2012.08147.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The intra-pallidal application of γ-aminobutyric acid (GABA) transporter subtype 1 (GAT-1) or GABA transporter subtype 3 (GAT-3) transporter blockers [1-(4,4-diphenyl-3-butenyl)-3-piperidinecarboxylic acid hydrochloride (SKF 89976A) or 1-[2-[tris(4-methoxyphenyl)methoxy]ethyl]-(S)-3-piperidinecarboxylic acid (SNAP 5114)] reduces the activity of pallidal neurons in monkey. This effect could be mediated through the activation of presynaptic GABA(B) heteroreceptors in glutamatergic terminals by GABA spillover following GABA transporter (GAT) blockade. To test this hypothesis, we applied the whole-cell recording technique to study the effects of SKF 89976A and SNAP 5114 on evoked excitatory postsynaptic currents (eEPSCs) in the presence of gabazine, a GABA(A) receptor antagonist, in rat globus pallidus slice preparations. Under the condition of postsynaptic GABA(B) receptor blockade by the intra-cellular application of N-(2,6-dimethylphenylcarbamoylmethyl)-triethylammonium bromide (OX314), bath application of SKF 89976A (10 μM) or SNAP 5114 (10 μM) decreased the amplitude of eEPSCs, without a significant effect on its holding current and whole cell input resistance. The inhibitory effect of GAT blockade on eEPSCs was blocked by (2S)-3-[[(1S)-1-(3,4-dichlorophenyl)ethyl]amino-2-hydroxypropyl](phenylmethyl)phosphinic acid, a GABA(B) receptor antagonist. The paired-pulse ratio of eEPSCs was increased, whereas the frequency, but not the amplitude, of miniature excitatory postsynaptic currents was reduced in the presence of either GAT blocker, demonstrating a presynaptic effect. These results suggest that synaptically released GABA can inhibit glutamatergic transmission through the activation of presynaptic GABA(B) heteroreceptors following GAT-1 or GAT-3 blockade. In conclusion, our findings demonstrate that presynaptic GABA(B) heteroreceptors in putative glutamatergic subthalamic afferents to the globus pallidus are sensitive to increases in extracellular GABA induced by GAT inactivation, thereby suggesting that GAT blockade represents a potential mechanism by which overactive subthalamopallidal activity may be reduced in parkinsonism.
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Affiliation(s)
- Xiao-Tao Jin
- Division of Neuroscience, Yerkes National Primate Research Center, Emory University, 954 Gatewood Road NE, Atlanta, GA 30329, USA
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74
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Hadipour-Niktarash A, Rommelfanger KS, Masilamoni GJ, Smith Y, Wichmann T. Extrastriatal D2-like receptors modulate basal ganglia pathways in normal and Parkinsonian monkeys. J Neurophysiol 2011; 107:1500-12. [PMID: 22131382 DOI: 10.1152/jn.00348.2011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
According to traditional models of the basal ganglia-thalamocortical network of connections, dopamine exerts D2-like receptor (D2LR)-mediated effects through actions on striatal neurons that give rise to the "indirect" pathway, secondarily affecting the activity in the internal and external pallidal segments (GPi and GPe, respectively) and the substantia nigra pars reticulata (SNr). However, accumulating evidence from the rodent literature suggests that D2LR activation also directly influences synaptic transmission in these nuclei. To further examine this issue in primates, we combined in vivo electrophysiological recordings and local intracerebral microinjections of drugs with electron microscopic immunocytochemistry to study D2LR-mediated modulation of neuronal activities in GPe, GPi, and SNr of normal and MPTP-treated (parkinsonian) monkeys. D2LR activation with quinpirole increased firing in most GPe neurons, likely due to a reduction of striatopallidal GABAergic inputs. In contrast, local application of quinpirole reduced firing in GPi and SNr, possibly through D2LR-mediated effects on glutamatergic inputs. Injections of the D2LR antagonist sulpiride resulted in effects opposite to those of quinpirole in GPe and GPi. D2 receptor immunoreactivity was most prevalent in putative striatal-like GABAergic terminals and unmyelinated axons in GPe, GPi, and SNr, but a significant proportion of immunoreactive boutons also displayed ultrastructural features of glutamatergic terminals. Postsynaptic labeling was minimal in all nuclei. The D2LR-mediated effects and pattern of distribution of D2 receptor immunoreactivity were maintained in the parkinsonian state. Thus, in addition to their preferential effects on indirect pathway striatal neurons, extrastriatal D2LR activation in GPi and SNr also influences direct pathway elements in the primate basal ganglia under normal and parkinsonian conditions.
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75
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Nambu A, Chiken S, Shashidharan P, Nishibayashi H, Ogura M, Kakishita K, Tanaka S, Tachibana Y, Kita H, Itakura T. Reduced pallidal output causes dystonia. Front Syst Neurosci 2011; 5:89. [PMID: 22164134 PMCID: PMC3224972 DOI: 10.3389/fnsys.2011.00089] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Accepted: 10/18/2011] [Indexed: 11/13/2022] Open
Abstract
Dystonia is a neurological disorder characterized by sustained or repetitive involuntary muscle contractions and abnormal postures. In the present article, we will introduce our recent electrophysiological studies in hyperkinetic transgenic mice generated as a model of DYT1 dystonia and in a human cervical dystonia patient, and discuss the pathophysiology of dystonia on the basis of these electrophysiological findings. Recording of neuronal activity in the awake state of DYT1 dystonia model mice revealed reduced spontaneous activity with bursts and pauses in both internal (GPi) and external (GPe) segments of the globus pallidus. Electrical stimulation of the primary motor cortex evoked responses composed of excitation and subsequent long-lasting inhibition, the latter of which was never observed in normal mice. In addition, somatotopic arrangements were disorganized in the GPi and GPe of dystonia model mice. In a human cervical dystonia patient, electrical stimulation of the primary motor cortex evoked similar long-lasting inhibition in the GPi and GPe. Thus, reduced GPi output may cause increased thalamic and cortical activity, resulting in the involuntary movements observed in dystonia.
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Affiliation(s)
- Atsushi Nambu
- Division of System Neurophysiology, National Institute for Physiological Sciences and Department of Physiological Sciences, Graduate University for Advanced Studies Okazaki, Japan
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76
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Cortical stimulation evokes abnormal responses in the dopamine-depleted rat basal ganglia. J Neurosci 2011; 31:10311-22. [PMID: 21753008 DOI: 10.1523/jneurosci.0915-11.2011] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The motor cortex (MC) sends massive projections to the basal ganglia. Motor disabilities in patients and animal models of Parkinson's disease (PD) may be caused by dopamine (DA)-depleted basal ganglia that abnormally process the information originating from MC. To study how DA depletion alters signal transfer in the basal ganglia, MC stimulation-induced (MC-induced) unitary responses were recorded from the basal ganglia of control and 6-hydroxydopamine-treated hemi-parkinsonian rats anesthetized with isoflurane. This report describes new findings about how DA depletion alters MC-induced responses. MC stimulation evokes an excitation in normally quiescent striatal (Str) neurons projecting to the globus pallidus external segment (GPe). After DA-depletion, the spontaneous firing of Str-GPe neurons increases, and MC stimulation evokes a shorter latency excitation followed by a long-lasting inhibition that was invisible under normal conditions. The increased firing activity and the newly exposed long inhibition generate tonic inhibition and a disfacilitation in GPe. The disfacilitation in GPe is then amplified in basal ganglia circuitry and generates a powerful long inhibition in the basal ganglia output nucleus, the globus pallidus internal segment. Intra-Str injections of a behaviorally effective dose of DA precursor l-3,4-dihydroxyphenylalanine effectively reversed these changes. These newly observed mechanisms also support the generation of pauses and burst activity commonly observed in the basal ganglia of parkinsonian subjects. These results suggest that the generation of abnormal response sequences in the basal ganglia contributes to the development of motor disabilities in PD and that intra-Str DA supplements effectively suppress abnormal signal transfer.
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77
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Jaeger D, Kita H. Functional connectivity and integrative properties of globus pallidus neurons. Neuroscience 2011; 198:44-53. [PMID: 21835227 DOI: 10.1016/j.neuroscience.2011.07.050] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 07/21/2011] [Accepted: 07/21/2011] [Indexed: 10/17/2022]
Abstract
The globus pallidus consists of the external (GPe) and the internal (GPi) segments. The GPe and GPi have different functional roles. The GPe is located centrally within multiple basal ganglia feedforward and feedback connections. The GPi is an output nucleus of the basal ganglia. A complex interplay between intrinsic pacemaking conductances and the balance of glutamatergic and GABAergic input largely determines the rate and pattern of firing of pallidal neurons. The initial part of this article introduces recent findings made in vivo that are related to the roles of glutamatergic and GABAergic inputs in the control of pallidal activity. The latter part describes the roles of intrinsic mechanisms of GPe neurons in the integration of the synaptic inputs. The presence of dendritic voltage-gated sodium channels may allow the initiation of dendritic spikes, giving distal inputs on the long and thin GPe dendrites an opportunity to strongly shape spiking activity. Basal ganglia disorders including Parkinson's disease, hemiballismus, and dystonias are accompanied by increased irregularity and synchronized bursts of pallidal activity. These changes may be in part due to changes in the GABA release in the GPe and GPi, but also involve intrinsic cellular changes in pallidal neurons.
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Affiliation(s)
- D Jaeger
- Department of Biology, Emory University, Atlanta, GA 30322, USA.
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78
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Kita H, Kita T. Role of Striatum in the Pause and Burst Generation in the Globus Pallidus of 6-OHDA-Treated Rats. Front Syst Neurosci 2011; 5:42. [PMID: 21713126 PMCID: PMC3113166 DOI: 10.3389/fnsys.2011.00042] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Accepted: 05/27/2011] [Indexed: 11/17/2022] Open
Abstract
Electrophysiological studies in patients and animal models of Parkinson's disease (PD) often reported increased burst activity of neurons in the basal ganglia. Neurons in the globus pallidus external (GPe) segment in 6-hydroxydopamine (6-OHDA)-treated hemi-parkinsonian rats fire with strong bursts interrupted by pauses. The goal of this study was to evaluate the hypothesis that dopamine (DA)-depletion increases burst firings of striatal (Str) neurons projecting to the GPe and that the increased Str–GPe burst inputs play a significant role in the generation of pauses and bursts in GPe and its projection sites. To evaluate this hypothesis, the unitary activity of Str and GPe was recorded from control and 6-OHDA-treated rats anesthetized with 0.5–1% isoflurane. The occurrence of pauses and bursts in the firings of GPe neurons was significantly higher in 6-OHDA than in normal rats. Muscimol injection into the Str of 6-OHDA rats increased average firing rate and greatly reduced the pauses and bursts in GPe. Recordings from Str revealed that most of the presumed projection neurons in control rats have very low spontaneous activity, and even the occasional neurons that did exhibit spontaneous burst firings did so with an average rate of less than 2 Hz. In DA-depleted Str, neurons having stronger bursts and a higher average firing rate were encountered more frequently. Juxtacellular labeling revealed that most of these neurons were medium spiny neurons projecting only to GPe. Injection of a behaviorally effective dose of methyl-l-DOPA into the Str of 6-OHDA rats significantly increased the average firing rate and decreased the number of pauses of GPe neurons. These data validate the hypothesis that DA-depletion increases burst firings of Str neurons projecting to the GPe and that the increased Str–GPe burst inputs play a significant role in the generation of pauses and bursts in GPe. These results suggest that treatment to reduce burst Str–GPe inhibitory inputs may help to restore some PD disabilities.
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Affiliation(s)
- Hitoshi Kita
- Department of Anatomy and Neurobiology, College of Medicine, The University of Tennessee Health Science Center Memphis, TN, USA
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79
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Sardo P, Carletti F, Rizzo V, Lonobile G, Friscia S, Ferraro G. Nitric oxide-active compounds modulate the intensity of glutamate-evoked responses in the globus pallidus of the rat. Life Sci 2011; 88:1113-20. [DOI: 10.1016/j.lfs.2011.04.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Revised: 01/28/2011] [Accepted: 04/04/2011] [Indexed: 11/29/2022]
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80
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Iwamuro H. Electrophysiological evidences of organization of cortical motor information in the Basal Ganglia. J Mov Disord 2011; 4:8-12. [PMID: 24868386 PMCID: PMC4027706 DOI: 10.14802/jmd.11002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2010] [Accepted: 01/03/2011] [Indexed: 01/22/2023] Open
Abstract
During the last two decades, the many developments in the treatment of movement disorders such as Parkinson disease and dystonia have enhanced our understanding on organization of the basal ganglia, and this knowledge has led to other advances in the field. According to many electrophysiological and anatomical findings, it is considered that motor information from different cortical areas is processed through several cortico-basal ganglia loops principally in a parallel fashion and somatotopy from each cortical area is also well preserved in each loop. Moreover, recent studies suggest that not only the parallel processing but also some convergence of information occur through the basal ganglia. Information from cortical areas whose functions are close to each other tends to converge in the basal ganglia. The cortico-basal ganglia loops should be comprehended more as a network rather than as separated subdivisions. However, the functions of this convergence still remain unknown. It is important even for clinical doctors to be well informed about this kind of current knowledge because some symptoms of movement disorders may be explained by disorganization of the information network in the basal ganglia.
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Affiliation(s)
- Hirokazu Iwamuro
- Service de Neurochirurgie, Hôpital Henri MONDOR, Crétail, France ; Division of System Neurophysiology, National Institute for Physiological Sciences, Okazaki, Japan
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81
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Nambu A. Somatotopic organization of the primate Basal Ganglia. Front Neuroanat 2011; 5:26. [PMID: 21541304 PMCID: PMC3082737 DOI: 10.3389/fnana.2011.00026] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Accepted: 03/31/2011] [Indexed: 11/18/2022] Open
Abstract
Somatotopic organization is a fundamental and key concept to understand how the cortico-basal ganglia loop works. It is also indispensable knowledge to perform stereotaxic surgery for movement disorders. Here I would like to describe the somatotopic organization of the basal ganglia, which consist of the striatum, subthalamic nucleus, globus pallidus, and substantia nigra. Projections from motor cortical regions representing different body parts terminate in different regions of these nuclei. Basal ganglia neurons respond not only to the stimulation of the corresponding regions of the motor cortices, but also to active and passive movements of the corresponding body parts. On the basis of these anatomical and physiological findings, somatotopic organization can be identified in the motor territories of these nuclei in the basal ganglia. In addition, projections from functionally interrelated cortical areas partially converge through the cortico-basal ganglia loop, but nevertheless the somatotopy is still preserved. Disorganized somatotopy may explain, at least in part, the pathophysiology of movement disorders, such as Parkinson's disease and dystonia.
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Affiliation(s)
- Atsushi Nambu
- Division of System Neurophysiology, National Institute for Physiological Sciences Okazaki, Japan
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82
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Nishibayashi H, Ogura M, Kakishita K, Tanaka S, Tachibana Y, Nambu A, Kita H, Itakura T. Cortically evoked responses of human pallidal neurons recorded during stereotactic neurosurgery. Mov Disord 2011; 26:469-76. [PMID: 21312279 DOI: 10.1002/mds.23502] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Revised: 09/01/2010] [Accepted: 10/03/2010] [Indexed: 11/11/2022] Open
Abstract
Responses of neurons in the globus pallidus (GP) to cortical stimulation were recorded for the first time in humans. We performed microelectrode recordings of GP neurons in 10 Parkinson's disease (PD) patients and 1 cervical dystonia (CD) patient during surgeries to implant bilateral deep brain stimulation electrodes in the GP. To identify the motor territories in the external (GPe) and internal (GPi) segments of the GP, unitary responses evoked by stimulation of the primary motor cortex were observed by constructing peristimulus time histograms. Neurons in the motor territories of the GPe and GPi responded to cortical stimulation. Response patterns observed in the PD patients were combinations of an early excitation, an inhibition, and a late excitation. In addition, in the CD patient, a long-lasting inhibition was prominent, suggesting increased activity along the cortico-striato-GPe/GPi pathways. The firing rates of GPe and GPi neurons in the CD patient were lower than those in the PD patients. Many GPe and GPi neurons of the PD and CD patients showed burst or oscillatory burst activity. Effective cathodal contacts tended to be located close to the responding neurons. Such unitary responses induced by cortical stimulation may be of use to target motor territories of the GP for stereotactic functional neurosurgery. Future findings utilizing this method may give us new insights into understanding the pathophysiology of movement disorders.
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Affiliation(s)
- Hiroki Nishibayashi
- Department of Neurological Surgery, Wakayama Medical University, Wakayama, Japan.
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83
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Osorio-Espinoza A, Alatorre A, Ramos-Jiménez J, Garduño-Torres B, García-Ramírez M, Querejeta E, Arias-Montaño JA. Pre-synaptic histamine H₃ receptors modulate glutamatergic transmission in rat globus pallidus. Neuroscience 2010; 176:20-31. [PMID: 21195747 DOI: 10.1016/j.neuroscience.2010.12.051] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Revised: 12/22/2010] [Accepted: 12/24/2010] [Indexed: 02/04/2023]
Abstract
The globus pallidus, a neuronal nucleus involved in the control of motor behavior, expresses high levels of histamine H(3) receptors (H(3)Rs) most likely located on the synaptic afferents to the nucleus. In this work we studied the effect of the activation of rat pallidal H(3)Rs on depolarization-evoked neurotransmitter release from slices, neuronal firing rate in vivo and turning behavior. Perfusion of globus pallidus slices with the selective H(3)R agonist immepip had no effect on the release of [(3)H]-GABA ([(3)H]-γ-aminobutyric acid) or [(3)H]-dopamine evoked by depolarization with high (20 mM) K(+), but significantly reduced [(3)H]-d-aspartate release (-44.8 ± 2.6% and -63.7 ± 6.2% at 30 and 100 nM, respectively). The effect of 30 nM immepip was blocked by 10 μM of the selective H(3)R antagonist A-331440 (4'-[3-[(3(R)-dimethylamino-1-pyrrolidinyl]propoxy]-[1,1-biphenyl]-4'-carbonitrile). Intra-pallidal injection of immepip (0.1 μl, 100 μM) decreased spontaneous neuronal firing rate in anaesthetized rats (peak inhibition 68.8±10.3%), and this effect was reversed in a partial and transitory manner by A-331440 (0.1 μl, 1 mM). In free-moving rats the infusion of immepip (0.5 μl; 10, 50 and 100 μM) into the globus pallidus induced dose-related ipsilateral turning following systemic apomorphine (0.5 mg/kg, s.c.). Turning behavior induced by immepip (0.5 μl, 50 μM) and apomorphine was partially prevented by the local injection of A-331440 (0.5 μl, 1 mM) and was not additive to the turning evoked by the intra-pallidal injection of antagonists at ionotropic glutamate receptors (0.5 μl, 1 mM each of AP-5, dl-2-amino-5-phosphonovaleric acid, and CNQX, 6-nitro-7-sulphamoylbenzo[f]quinoxaline-2,3-dione). These results indicate that pre-synaptic H(3)Rs modulate glutamatergic transmission in rat globus pallidus and thus participate in the control of movement by basal ganglia.
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Affiliation(s)
- A Osorio-Espinoza
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Av. Instituto Politécnico Nacional 2508, Zacatenco, 07360 México, D.F., México
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84
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Dendritic sodium channels regulate network integration in globus pallidus neurons: a modeling study. J Neurosci 2010; 30:15146-59. [PMID: 21068320 DOI: 10.1523/jneurosci.2662-10.2010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The globus pallidus (GP) predominantly contains GABAergic projection neurons that occupy a central position in the indirect pathway of the basal ganglia. They have long dendrites that can extend through one-half the diameter of the GP in rats, potentially enabling convergence and interaction between segregated basal ganglia circuits. Because of the length and fine diameter of GP dendrites, however, it is unclear how much influence distal synapses have on spiking activity. Dendritic expression of fast voltage-dependent Na(+) channels (NaF channels) can enhance the importance of distal excitatory synapses by allowing for dendritic spike initiation and by subthreshold boosting of EPSPs. Antibody labeling has demonstrated the presence of NaF channel proteins in GP dendrites, but the quantitative expression density of the channels remains unknown. We built a series of nine GP neuron models that differed only in their dendritic NaF channel expression level to assess the functional impact of this parameter. The models were all similar in their basic electrophysiological features; however, higher expression levels of dendritic NaF channels increased the relative effectiveness of distal inputs for both excitatory and inhibitory synapses, broadening the effective extent of the dendritic tree. Higher dendritic NaF channel expression also made the neurons more resistant to tonic inhibition and highly sensitive to clustered synchronous excitation. The dendritic NaF channel expression pattern may therefore be a critical determinant of convergence for both the striatopallidal and subthalamopallidal projections, while also dictating which spatiotemporal input patterns are most effective at driving GP neuron output.
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85
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Rommelfanger KS, Wichmann T. Extrastriatal dopaminergic circuits of the Basal Ganglia. Front Neuroanat 2010; 4:139. [PMID: 21103009 PMCID: PMC2987554 DOI: 10.3389/fnana.2010.00139] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Accepted: 09/23/2010] [Indexed: 11/20/2022] Open
Abstract
The basal ganglia are comprised of the striatum, the external and internal segment of the globus pallidus (GPe and GPi, respectively), the subthalamic nucleus (STN), and the substantia nigra pars compacta and reticulata (SNc and SNr, respectively). Dopamine has long been identified as an important modulator of basal ganglia function in the striatum, and disturbances of striatal dopaminergic transmission have been implicated in diseases such as Parkinson's disease (PD), addiction and attention deficit hyperactivity disorder. However, recent evidence suggests that dopamine may also modulate basal ganglia function at sites outside of the striatum, and that changes in dopaminergic transmission at these sites may contribute to the symptoms of PD and other neuropsychiatric disorders. This review summarizes the current knowledge of the anatomy, functional effects and behavioral consequences of the dopaminergic innervation to the GPe, GPi, STN, and SNr. Further insights into the dopaminergic modulation of basal ganglia function at extrastriatal sites may provide us with opportunities to develop new and more specific strategies for treating disorders of basal ganglia dysfunction.
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86
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Conditions for the generation of beta oscillations in the subthalamic nucleus-globus pallidus network. J Neurosci 2010; 30:12340-52. [PMID: 20844130 DOI: 10.1523/jneurosci.0817-10.2010] [Citation(s) in RCA: 150] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The advance of Parkinson's disease is associated with the existence of abnormal oscillations within the basal ganglia with frequencies in the beta band (13-30 Hz). While the origin of these oscillations remains unknown, there is some evidence suggesting that oscillations observed in the basal ganglia arise due to interactions of two nuclei: the subthalamic nucleus (STN) and the globus pallidus pars externa (GPe). To investigate this hypothesis, we develop a computational model of the STN-GPe network based upon anatomical and electrophysiological studies. Significantly, our study shows that for certain parameter regimes, the model intrinsically oscillates in the beta range. Through an analytical study of the model, we identify a simple set of necessary conditions on model parameters that guarantees the existence of beta oscillations. These conditions for generation of oscillations are described by a set of simple inequalities and can be summarized as follows: (1) The excitatory connections from STN to GPe and the inhibitory connections from GPe to STN need to be sufficiently strong. (2) The time required by neurons to react to their inputs needs to be short relative to synaptic transmission delays. (3) The excitatory input from the cortex to STN needs to be high relative to the inhibition from striatum to GPe. We confirmed the validity of these conditions via numerical simulation. These conditions describe changes in parameters that are consistent with those expected as a result of the development of Parkinson's disease, and predict manipulations that could inhibit the pathological oscillations.
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87
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Dynamic spike threshold and zero membrane slope conductance shape the response of subthalamic neurons to cortical input. J Neurosci 2010; 30:13180-91. [PMID: 20881137 DOI: 10.1523/jneurosci.1909-10.2010] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The subthalamic nucleus (STN) provides a second entry point for cortical input to the basal ganglia, supplementing the corticostriatal pathway. We examined the way intrinsic properties shape the response of the STN to cortical excitation, recording from rat STN in vivo and in brain slices. STN cells exhibited a near-zero slope conductance-and hence an effectively infinite membrane time constant-at subthreshold potentials. This makes STN cells exceptional temporal integrators, consistent with the common view that basal ganglia nuclei use rate coding. However, STN cells also exhibited a drop in spike threshold triggered by larger EPSPs, allowing them to fire time-locked spikes in response to coincident input. In addition to promoting coincidence detection, the threshold dynamics associated with larger EPSPs reduced the probability of firing spikes outside of a narrow window immediately after the stimulus, even on trials in which the EPSP did not directly trigger a spike. This shift in stimulus-evoked firing pattern would allow downstream structures to distinguish coincidence-triggered spikes from other spikes and thereby permit coincidence detection and rate coding to operate in parallel in the same cell. Thus, STN cells can combine two functions-integration and coincidence detection-that are normally considered mutually exclusive. This could support rapid communication between cortex and basal ganglia targets that bypasses the striatum without disrupting slower rate coding pathways.
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88
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Kliem MA, Pare JF, Khan ZU, Wichmann T, Smith Y. Ultrastructural localization and function of dopamine D1-like receptors in the substantia nigra pars reticulata and the internal segment of the globus pallidus of parkinsonian monkeys. Eur J Neurosci 2010; 31:836-51. [PMID: 20374284 DOI: 10.1111/j.1460-9568.2010.07109.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The motor symptoms of Parkinson's disease (PD) are commonly attributed to striatal dopamine loss, but reduced dopamine innervation of basal ganglia output nuclei, the internal globus pallidus (GPi) and the substantia nigra pars reticulata (SNr) may also contribute to symptoms and signs of PD. Both structures express dopamine D1 and D5 receptors under normal conditions, and we have recently demonstrated that their local activation reduces neuronal discharge rates and enhances bursts and oscillatory activity in both nuclei of normal monkeys [M.A. Kliem et al. (2007)J. Neurophysiol., 89, 1489-1500]. Here, we determined the ultrastructural localization and function of D1-like receptors in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated parkinsonian monkeys. In both normal and MPTP-treated monkeys, most of the D1 and D5 receptor immunoreactivity was associated with unmyelinated axons, but we also found significant postsynaptic D5 receptor immunostaining in dendrites of GPi and SNr neurons. A significant proportion of axonal D1 immunostaining was bound to the plasma membrane in both normal and MPTP-treated monkeys. Local microinjections of the D1/D5 receptor agonist SKF82958 significantly reduced discharge rates in GPi and SNr neurons, while they increased burst firing and oscillatory activity in the 3-15-Hz band in SNr, but not in GPi, of parkinsonian monkeys. Together with our recent findings from normal monkeys, these data provide evidence that functional D1/D5 receptors are expressed in GPi and SNr in both normal and parkinsonian states, and that their activation by endogenous dopamine (under normal conditions) or dopamine receptor agonists (in parkinsonism) may regulate basal ganglia outflow.
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Affiliation(s)
- Michele A Kliem
- Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA
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89
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Xue Y, Han XH, Chen L. Effects of Pharmacological Block of GABA(A) Receptors on Pallidal Neurons in Normal and Parkinsonian State. Front Cell Neurosci 2010; 4:2. [PMID: 20204138 PMCID: PMC2831626 DOI: 10.3389/neuro.03.002.2010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Accepted: 01/26/2010] [Indexed: 11/19/2022] Open
Abstract
The globus pallidus plays a central integrative role in the basal ganglia circuitry. Morphological studies have revealed a high level of GABA and GABAA receptors in the globus pallidus. To further investigate the effects of endogenous GABAA neurotransmission in the globus pallidus of normal and parkinsonian rats, in vivo extracellular recording and behavioral tests were performed in the present studies. In normal rats, micro-pressure ejection of GABAA receptor antagonist gabazine (0.1 mM) increased the spontaneous firing rate of pallidal neurons by 28.3%. Furthermore, in 6-hydroxydopamine parkinsonian rats, gabazine increased the firing rate by 46.0% on the lesioned side, which was significantly greater than that on the unlesioned side (21.5%, P < 0.05), as well as that in normal rats (P < 0.05). In the behaving rats, unilateral microinjection of gabazine (0.1 mM) evoked consistent contralateral rotation in normal rats, and significantly potentiated the number of apomorphine-induced contralateral rotations in parkinsonian rats. The present electrophysiological and behavioral findings may provide a rational for further investigations into the potential of pallidal endogenous GABAA neurotransmission in the treatment of Parkinson's disease.
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Affiliation(s)
- Yan Xue
- Department of Physiology, Qingdao University Qingdao, China
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90
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Subthalamic nucleus evokes similar long lasting glutamatergic excitations in pallidal, entopeduncular and nigral neurons in the basal ganglia slice. Neuroscience 2010; 166:808-18. [PMID: 20074618 DOI: 10.1016/j.neuroscience.2010.01.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Accepted: 01/06/2010] [Indexed: 11/20/2022]
Abstract
The subthalamic nucleus (STN) modulates the activity of globus pallidus (GP), entopeduncular nucleus (EP) and substantia nigra pars reticulata (SNr) neurons via its direct glutamatergic projections. To investigate the mechanism by which STN affects activity in these structures and whether STN induced activity is comparable among STN target neurons, we performed patch clamp recordings in a tilted, parasagittal, basal ganglia slice (BGS) that preserves these functional connections. We report that single, brief stimulation of the STN generates a brief monosynaptic AMPA-mediated excitatory postsynaptic current (EPSC) in GP, EP and SNr neurons. A higher intensity, supra-threshold activation evokes a compound EPSC consisting of an early monosynaptic component followed by a slow inward NMDA-mediated current with an overlying barrage of AMPA-mediated EPSCs. These late EPSCs were polysynaptic and gave rise to bursts of spikes that lasted several hundreds of milliseconds. They were eliminated by surgical removal of the STN from the BGS slice, indicating that the STN is required for their generation. Reconstruction of biocytin-filled STN neurons revealed that a third of STN neurons project intra-STN axon collaterals that may underlie polysynaptic activity. We propose that activation of the STN yields comparable long lasting excitations in its target neurons by means of a polysynaptic network.
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91
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Allen K, Waldvogel H, Glass M, Faull R. Cannabinoid (CB1), GABAA and GABAB receptor subunit changes in the globus pallidus in Huntington's disease. J Chem Neuroanat 2009; 37:266-81. [DOI: 10.1016/j.jchemneu.2009.02.001] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Revised: 02/05/2009] [Accepted: 02/05/2009] [Indexed: 10/21/2022]
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92
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Cortically evoked long-lasting inhibition of pallidal neurons in a transgenic mouse model of dystonia. J Neurosci 2009; 28:13967-77. [PMID: 19091985 DOI: 10.1523/jneurosci.3834-08.2008] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Dystonia is a neurological disorder characterized by sustained or repetitive involuntary muscle contractions and abnormal postures. To understand the pathophysiology of dystonia, neurophysiological analyses were performed on hyperkinetic transgenic mice generated as a model of DYT1 dystonia. Abnormal muscle activity, such as coactivation of agonist and antagonist muscles and sustained muscle activation, was frequently observed in these mice. Recording of neuronal activity in the awake state revealed reduced spontaneous activity with bursts and pauses in both the external and internal segments of the globus pallidus. Motor cortical stimulation evoked responses composed of excitation and subsequent long-lasting inhibition in both pallidal segments, which were never observed in the normal mice. In addition, the somatotopic arrangements in both pallidal segments were disorganized. Long-lasting inhibition induced by cortical inputs in the internal pallidal segment may disinhibit thalamic and cortical activity, resulting in the motor hyperactivity observed in the transgenic mice.
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93
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van Albada SJ, Robinson PA. Mean-field modeling of the basal ganglia-thalamocortical system. I Firing rates in healthy and parkinsonian states. J Theor Biol 2008; 257:642-63. [PMID: 19168074 DOI: 10.1016/j.jtbi.2008.12.018] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2008] [Revised: 12/08/2008] [Accepted: 12/08/2008] [Indexed: 01/02/2023]
Abstract
Parkinsonism leads to various electrophysiological changes in the basal ganglia-thalamocortical system (BGTCS), often including elevated discharge rates of the subthalamic nucleus (STN) and the output nuclei, and reduced activity of the globus pallidus external (GPe) segment. These rate changes have been explained qualitatively in terms of the direct/indirect pathway model, involving projections of distinct striatal populations to the output nuclei and GPe. Although these populations partly overlap, evidence suggests dopamine depletion differentially affects cortico-striato-pallidal connection strengths to the two pallidal segments. Dopamine loss may also decrease the striatal signal-to-noise ratio, reducing both corticostriatal coupling and striatal firing thresholds. Additionally, nigrostriatal degeneration may cause secondary changes including weakened lateral inhibition in the GPe, and mesocortical dopamine loss may decrease intracortical excitation and especially inhibition. Here a mean-field model of the BGTCS is presented with structure and parameter estimates closely based on physiology and anatomy. Changes in model rates due to the possible effects of dopamine loss listed above are compared with experiment. Our results suggest that a stronger indirect pathway, possibly combined with a weakened direct pathway, is compatible with empirical evidence. However, altered corticostriatal connection strengths are probably not solely responsible for substantially increased STN activity often found. A lower STN firing threshold, weaker intracortical inhibition, and stronger striato-GPe inhibition help explain the relatively large increase in STN rate. Reduced GPe-GPe inhibition and a lower GPe firing threshold can account for the comparatively small decrease in GPe rate frequently observed. Changes in cortex, GPe, and STN help normalize the cortical rate, also in accord with experiments. The model integrates the basal ganglia into a unified framework along with an existing thalamocortical model that already accounts for a wide range of electrophysiological phenomena. A companion paper discusses the dynamics and oscillations of this combined system.
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Affiliation(s)
- S J van Albada
- School of Physics, The University of Sydney, New South Wales 2006, Australia.
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94
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Mean-field modeling of the basal ganglia-thalamocortical system. II Dynamics of parkinsonian oscillations. J Theor Biol 2008; 257:664-88. [PMID: 19154745 DOI: 10.1016/j.jtbi.2008.12.013] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2008] [Revised: 12/08/2008] [Accepted: 12/08/2008] [Indexed: 11/21/2022]
Abstract
Neuronal correlates of Parkinson's disease (PD) include a shift to lower frequencies in the electroencephalogram (EEG) and enhanced synchronized oscillations at 3-7 and 7-30 Hz in the basal ganglia, thalamus, and cortex. This study describes the dynamics of a recent physiologically based mean-field model of the basal ganglia-thalamocortical system, and shows how it accounts for many key electrophysiological correlates of PD. Its detailed functional connectivity comprises partially segregated direct and indirect pathways through two populations of striatal neurons, a hyperdirect pathway involving a corticosubthalamic projection, thalamostriatal feedback, and local inhibition in striatum and external pallidum (GPe). In a companion paper, realistic steady-state firing rates were obtained for the healthy state, and after dopamine loss modeled by weaker direct and stronger indirect pathways, reduced intrapallidal inhibition, lower firing thresholds of the GPe and subthalamic nucleus (STN), a stronger projection from striatum to GPe, and weaker cortical interactions. Here it is shown that oscillations around 5 and 20 Hz can arise with a strong indirect pathway, which also causes increased synchronization throughout the basal ganglia. Furthermore, increased theta power with progressive nigrostriatal degeneration is correlated with reduced alpha power and peak frequency, in agreement with empirical results. Unlike the hyperdirect pathway, the indirect pathway sustains oscillations with phase relationships that coincide with those found experimentally. Alterations in the responses of basal ganglia to transient stimuli accord with experimental observations. Reduced cortical gains due to both nigrostriatal and mesocortical dopamine loss lead to slower changes in cortical activity and may be related to bradykinesia. Finally, increased EEG power found in some studies may be partly explained by a lower effective GPe firing threshold, reduced GPe-GPe inhibition, and/or weaker intracortical connections in parkinsonian patients. Strict separation of the direct and indirect pathways is not necessary to obtain these results.
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95
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Nambu A. Seven problems on the basal ganglia. Curr Opin Neurobiol 2008; 18:595-604. [PMID: 19081243 DOI: 10.1016/j.conb.2008.11.001] [Citation(s) in RCA: 175] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2008] [Revised: 10/27/2008] [Accepted: 11/09/2008] [Indexed: 10/21/2022]
Abstract
Our knowledge on the functions of the basal ganglia has increased enormously during the last two decades. However, we still do not completely understand the primary function of the basal ganglia. In this article, I review fundamental problems on the basal ganglia that have emerged from recent findings, and propose their solutions in the following seven topics: first, organization of the cortico-basal ganglia loop, second, limitations of the 'direct and indirect pathways model', third, feedforward inhibition in the striatum, fourth, contribution of the basal ganglia to cortical activity through the thalamus, fifth, focused selection of movements and learning, sixth, firing rate model versus firing pattern model for the pathophysiology of movement disorders, and lastly mechanisms of stereotaxic surgery.
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Affiliation(s)
- Atsushi Nambu
- Division of System Neurophysiology, National Institute for Physiological Sciences, Myodaiji, Okazaki, Japan.
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96
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Differential inhibition of globus pallidus neurons by electrical or chemical stimulation of the striatum. Neurosci Res 2008; 62:240-5. [DOI: 10.1016/j.neures.2008.08.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Revised: 08/28/2008] [Accepted: 08/29/2008] [Indexed: 11/17/2022]
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97
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Elias S, Ritov Y, Bergman H. Balance of increases and decreases in firing rate of the spontaneous activity of basal ganglia high-frequency discharge neurons. J Neurophysiol 2008; 100:3086-104. [PMID: 18842958 DOI: 10.1152/jn.90714.2008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Most neurons in the external and internal segments of the globus pallidus and the substantia nigra pars reticulata (GPe, GPi, and SNr) are characterized by a high-frequency discharge (HFD) rate (50-80 Hz) that, in most GPe neurons, is also interrupted by pauses. Almost all (approximately 90%) of the synaptic inputs to these HFD neurons are GABAergic and inhibitory. Nevertheless, their responses to behavioral events are usually dominated by increases in discharge rate. Additionally, there are no reports of prolonged bursts in the spontaneous activity of these cells that could reflect their disinhibition by GPe pauses. We recorded the spontaneous activity of 385 GPe, GPi, and SNr HFD neurons during a quiet-wakeful state from two monkeys. We developed three complementary methods to quantify the balance of increases and decreases in the spontaneous discharge of HFD neurons and validated them by simulations. Unlike the behavioral evoked responses, the spontaneous activity of pallidal and SNr neurons is not dominated by increases. Moreover, the activity of basal ganglia neurons does not include bursts that could reflect disinhibition by the spontaneous pauses of GPe neurons. These findings suggest that the discharge increase/decrease balance during a quiet-wakeful state better reflects the inhibitory input of the HFD basal ganglia neurons than during responses to behavioral events; however, the GPe pauses are not echoed by comparable bursts either in the GPe or in the output nuclei. Changes in the excitatory drive of these structures (e.g., during behavioral activity) thus may lead to a remarkable change in this balance.
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Affiliation(s)
- Shlomo Elias
- Department of Physiology, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
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98
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Gatev P, Wichmann T. Interactions between cortical rhythms and spiking activity of single basal ganglia neurons in the normal and parkinsonian state. ACTA ACUST UNITED AC 2008; 19:1330-44. [PMID: 18842667 DOI: 10.1093/cercor/bhn171] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
In order to evaluate the specific interactions between cortical oscillations and basal ganglia-spiking activity under normal and parkinsonian conditions, we examined the relationship between frontal cortex electroencephalographic (EEG) signals and simultaneously recorded neuronal activity in the internal and external segments of the pallidum or the subthalamic nucleus (STN) in 3 rhesus monkeys. After we made recordings in the normal state, hemiparkinsonism was induced with intracarotid injections of the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in one animal, followed by additional recordings. Spiking activity in the pallidum and STN was associated with significant shifts in the level of EEG synchronization. We also found that the spectral power of beta- and gamma-band EEG rhythms covaried positively before the basal ganglia spikes but did not covary or covaried negatively thereafter. In parkinsonism, changes in cortical synchronization and phase coherence were reduced in EEG segments aligned to STN spikes, whereas both were increased in data segments aligned to pallidal spikes. Spiking-related changes in beta/gamma-band covariance were reduced. The findings indicate that basal ganglia and cortex interact in the processing of cortical rhythms that contain oscillations across a broad range of frequencies and that this interaction is severely disrupted in parkinsonism.
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Affiliation(s)
- Plamen Gatev
- Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
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99
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Role for subthalamic nucleus neurons in switching from automatic to controlled eye movement. J Neurosci 2008; 28:7209-18. [PMID: 18614691 DOI: 10.1523/jneurosci.0487-08.2008] [Citation(s) in RCA: 209] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The subthalamic nucleus (STN) of the basal ganglia is an important element of motor control. This is demonstrated by involuntary movements induced by STN lesions and the successful treatment of Parkinson's disease by STN stimulation. However, it is still unclear how individual STN neurons participate in motor control. Here, we report that the STN has a function in switching from automatic to volitionally controlled eye movement. In the STN of trained macaque monkeys, we found neurons that showed a phasic change in activity specifically before volitionally controlled saccades which were switched from automatic saccades. A majority of switch-related neurons were considered to inhibit no-longer-valid automatic processes, and the inhibition started early enough to enable the animal to switch. We suggest that the STN mediates the control signal originated from the medial frontal cortex and implements the behavioral switching function using its connections with other basal ganglia nuclei and the superior colliculus.
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Effects of cobalt and bicuculline on focal microstimulation of rat pallidal neurons in vivo. Brain Stimul 2008; 1:134-50. [DOI: 10.1016/j.brs.2008.05.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2008] [Revised: 05/15/2008] [Accepted: 05/19/2008] [Indexed: 01/11/2023] Open
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