Inactivation of the recording sites in the external segment of the GP resulted in an increase in the number of error trials in the antisaccade tasks, suggesting that signals in the GP may play roles in suppressing inadequate prosaccades in the task. 
The internal segment of the globus pallidus (GPi) receives motor-related cortical signals mainly through the striatum, the external segment of the globus pallidus (GPe) and the subthalamic nucleus (STN).
Neurons in the external segment of the globus pallidus (GPe) are autonomous pacemakers that are capable of sustained fast spiking.
Cytoplasmic immunoreactivity for Cu/ZnSOD was reduced in the external segment of globus pallidus, dentate nucleus and cerebellar cortex in DRPLA cases.
Methionine-enkephalin expression was reduced in the external segment of the globus pallidus in cases of acute and chronic postkernicteric BE, and immunoreactivity for substance P was severely altered in both internal and external segments in cases of chronic postkernicteric BE. A decrease in the number of parvalbumin-immunoreactive interneurons in the external segment of the globus pallidus was observed predominantly in cases of acute BE, whereas the number of interneurons immunoreactive for calbindin-D28K was reduced in the putamen in cases of chronic postkernicteric BE. These findings indicated that the putamen was impaired in BE and the pallidal external segment was also damaged in the acute form of BE, suggesting that oxidative damage to DNA is implicated in lesions of the basal ganglia..
The internal segment of the globus pallidus (GP(i)) gathers many bits of information including movement-related activity from the striatum, external segment of the globus pallidus (GP(e)), and subthalamic nucleus (STN), and integrates them.
The external segment of the pallidum (GP(e)) is a relatively large nucleus located caudomedial to the neostriatum (Str).
Longitudinal analyses revealed a significant association between an increase in severity of depression and a decrease in activity in the external segment of the right globus pallidus.
To further define the role of the external segment of the globus pallidus (GPe) in the development of parkinsonian motor signs, two rhesus monkeys were made parkinsonian with the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP).
The neurons in the external segment of the pallidum in the primate develop a characteristic firing pattern consisting of alternately occurring long, 2-20 s, strongly active phases and long completely silent phases when the subthalamo-pallidal excitatory inputs are blocked.
This limitation may be due to an incomplete restoration of the dopaminergic input to other basal ganglia structures such as the external segment of the globus pallidus (GPe, homologue of the rodent GP), which normally receives dopaminergic input from the substantia nigra (SN).
The volume of the external segment of the GP (GPe) was positively correlated with the severity of global symptoms, as measured by the Scale for the Assessment of Negative Symptoms and Scale for the Assessment of Positive Symptoms (SANS/SAPS, Andreasen and Olsen, 1982).
To chart the basal ganglia (BG) involvement in this association, we recorded the activity of 61 well isolated neurons in the external segment of the globus pallidus (GPe) of two monkeys performing a probabilistic visuomotor task.
The neurons in the external segment of the pallidum (GPe) in awake animals maintain a high level of firing activity.
There were no significant differences between MSA and PD patients, however, in firing rates of neurons in the external globus pallidus (GPe) or in the external segment of GPi (GPie).
(5) Enkephalin levels were increased in striatum and the external segment of the globus pallidus (GPe), but not in substantia nigra.
Given that a similar dysfunction of basal ganglia circuitry is thought to subserve the behavioral alterations seen in QA-lesioned rats and Huntington's disease (HD) patients, the present results raise the possibility that manipulations of the external segment of the globus pallidus (the primate analogue of the rat GP) could ameliorate some of HD symptoms..
Symptoms in the early stages of Huntington's disease (HD) are assumed to reflect basal ganglia circuit dysfunction secondary to degeneration of striatal projections to the external segment of the globus pallidus (GPe).
After either M1 or Area 46 injections, third-order neurons were found in the external segment of the globus pallidus (GPe), striatum and subthalamic nucleus (STN).
In parkinsonian tissue the level of CB(1) receptor mRNA was decreased in the caudate nucleus, anterior dorsal putamen and external segment of the globus pallidus, but remained unchanged in the other brain areas examined.
The typical finding is of bilaterally symmetrical hyperintense signal changes in the external segment of globus pallidus, with surrounding hypointensity on T(2)-weighted image.
Parkinsonian tremor is most likely due to oscillatory neuronal activities of central oscillators such as the subthalamic nucleus (STN)-external segment of the globus pallidus (GPe) pacemaker within the basal ganglia (BG).
To clarify the mechanism underlying improvement of parkinsonian signs by high-frequency electrical stimulation (HFS) of the subthalamic nucleus (STN), we investigated the effects of STN HFS on neuronal activity of the internal and external segment of the globus pallidus (GPi and GPe, respectively) in two rhesus monkeys rendered parkinsonian by administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine.
Striatal (35)S-labeled t-butylbicyclophosphorothionate ([ (35)S]TBPS) and [ (3)H]flunitrazepam binding to GABA(A) receptors were unchanged in patients with Parkinson's disease, whereas [ (125)I]CGP 64213 -specific binding to GABA(B) receptors was decreased in the putamen and external segment of the globus pallidus of parkinsonian patients compared with controls.
Much research now supports the view that the dopaminergic innervation of the globus pallidus external segment (GP) influences basal ganglia information processing via pallidal dopamine (DA) D2, D3, and possibly D1 receptors.
This indicates a compensatory neuronal plasticity that we now show to involve the nigropallidal dopamine pathway to the GPi but not to the external segment of the globus pallidus (GPe).
After MPTP treatment, firing rates decreased in the external segment of the globus pallidus (GP(e)) and increased in the internal segment (GP(i)).
Neurturin only protected gamma-aminobutyric acid (GABA)/enkephalinergic neurons that project to the external segment of the globus pallidus, whereas GDNF exerts its effects on GABA/substance P positive neurons, which project to the substantia nigra pars compacta and the internal segment of the globus pallidus.
Based on recent experimental data, we have developed a conductance-based computational network model of the subthalamic nucleus and the external segment of the globus pallidus in the indirect pathway of the basal ganglia.
These ideas are applied to a neural circuit consisting of the cortex and a subset of the nuclei in the basal ganglia-the subthalamic nucleus (STN) and the external segment of the globus pallidus (GPe).
Second, good matches between model globus pallidus external segment output and globus pallidus internal segment and substantia nigra reticulata area output, and neurophysiological data, have been found which are indicative of common architectural features in the model and biological basal ganglia.
In patients undergoing pallidotomy for Parkinson's disease, we recorded extracellularly from single neurons in the two internal segments (GPii, GPie) and the external segment (GPe) of the globus pallidus (GP) in response to active (cued) movements of the contralateral wrist, elbow or ankle.
An increase in the density of specific [ (3)H]-SCH23390 binding sites was found in the anterior putamen and a decrease in the external segment of the globus pallidus, no changes were detected elsewhere.
In vitro work using organotypic co-cultures has implicated the subthalamic nucleus (STN) and the external segment of the globus pallidus (GP(e)) as pacemakers for low-frequency bursting that is reminiscent of the activity produced in Parkinsonian tremor.
The increased activity of the subthalamic nucleus (STN) observed has been attributed to a reduction in inhibition mediated by the external segment of the globus pallidus (GPe), secondary to the loss of dopaminergic-neuron influence on D2-receptor-bearing striato-pallidal neurons.
Two patients, including the patient with hemiparkinsonism, had additional involvement of the external segment of the GP.
The indirect pathway projects polysynaptically on to the GR/SNpr complex after passing through the external segment of the globus pallidus (Gpe) and subthalamic nucleus.
The basal ganglia have another mechanism, involving the external segment of the globus pallidus and the subthalamic nucleus, with which the SNr-SC inhibition can further be enhanced.
No change was seen in the striatum, the thalamus, the external segment of the globus pallidus, and the substantia nigra pars reticulata following MPTP and dopaminomimetic treatments.
The grafted neurons also send efferents to the primary striatal targets, including the globus pallidus (GP, the rodent homologue of the external segment of the globus pallidus) and the entopeduncular nucleus (EP, the rodent homologue of the internal segment of the globus pallidus).
Axonal projections arising from the external segment of the globus pallidus (GPe) in cynomolgus monkeys (Macaca fascicularis) were mapped after labeling small pools (5-15 cells) of neurons with biotinylated dextran amine.
SP-like immunoreactive intensity in the internal segment of the globus pallidus, which was lower than that in the substantia nigra, was approximately twice as high as that in the external segment of the globus pallidus.
Underactivity of the external segment of the globus pallidus is thought to contribute to the generation of parkinsonian hypokinetic symptoms in association with striatal dopaminergic dysfunction and overactivity of the subthalamus. The aim of the present study was to compare the amount of neurodegeneration and changes in the calcium-binding protein parvalbumin in the external segment of the globus pallidus in parkinsonian disorders. The external segment of the globus pallidus in Parkinson's disease was not significantly different from that in control subjects. These results suggest that the parkinsonian symptoms in progressive supranuclear palsy are caused by the degeneration of the external segment of the globus pallidus because such degeneration would increase thalamic inhibition through the basal ganglia output nuclei, particularly in patients with a loss of excitatory drive from the subthalamus..
GABA concentrations remained unchanged in the striatum, external segment of globus pallidus and GPi following MPTP denervation.
fuscata labeled a large number of the globus pallidus external segment (GPe) neurons.
In the present study, tyrosine hydroxylase (TH)-immunoreactive elements were observed by light microscopy after antigen retrieval in the subthalamic nucleus and in the internal and external segments of the globus pallidus in postmortem human brain. Small islands of apparent neostriatal tissue with abundant arborization of fine, TH-immunoreactive axons in the vicinity of calbindin-positive small neurons resembling neostriatal medium spiny neurons were present in the external segment of the globus pallidus.
(2) Immunoreactivities for metabotropic glutamate receptors (mGluRs) 4 a, 7 a, 7 b and 8 were in axon terminals within the globus pallidus (external segment of the globus pallidus in primates).
A continuous rise in BP, HR, and RR was induced by stimulating in the external segment (GPe).
D2 binding sites were detected in all brain areas studied, with the highest concentration found in the striatum followed by the nucleus accumbens, external segment of the globus pallidus, substantia nigra and ventral tegmental area, medial preoptic area and tuberomammillary nucleus of the hypothalamus.
Dual probe microdialysis was employed in intact rat brain to investigate the effect of intrastriatal perfusion with selective dopamine D1 and D2 receptor agonists and with c-fos antisense oligonucleotide on (a) local GABA release in the striatum; (b) the internal segment of the globus pallidus and the substantia nigra pars reticulata, which is the output site of the strionigral GABA pathway; and (c) the external segment of the globus pallidus, which is the output site of the striopallidal GABA pathway.
These data demonstrate that the region of the ventral pallidum involved in the prefrontal cortex-basal ganglia circuit originating from the prelimbic and medial orbital areas represents essentially a ventral subcommissural extension of the external segment of the globus pallidus since it exhibits similar extrinsic connections and functional characteristics.
Postmortem examination revealed atrophy, gliosis, and neuronal loss in the external segment of the globus pallidus, subthalamic nucleus, red nucleus, and in the dentate nucleus.
In addition, this view states that striatal output reaches the basal ganglia output nuclei (the substantia nigra pars reticulata (SNR) and the internal segment of the globus pallidus (GPi)) via a 'direct' pathway, and via an 'indirect pathway' which traverses the external segment of the globus pallidus (GPe) and the subthalamic nucleus (STN).
COI mRNA expression remained unchanged in the external segment of the globus pallidus (GPe).
The hyperactivity of subthalamic neurons in Parkinsonism is viewed as a direct consequence of a pathological hypoactivity of the external segment of the pallidum. This article reviews recent data from different experimental approaches that challenge the established model of basal ganglia organization by reinterpreting the functional interaction between the external segment of the pallidum and the subthalamic nucleus in both the normal and pathological state.
The results of the present tracing study define the basic network underlying the interconnections between the external segment of the globus pallidus and the subthalamic nucleus, and their connections with the output neurons of the basal ganglia in primates..
At embryonic week 14, trk-ir neurons were seen within the subplate zone of the entorhinal cortex, basal forebrain, caudate nucleus, putamen, external segment of the globus pallidus, specific thalamic nuclei, lateral mammillary nucleus, habenula nucleus, select brainstem nuclei, and the dentate nucleus of cerebellum.
the internal segment of the globus pallidus and the substantia nigra pars reticulata, but remained unchanged in the external segment of the globus pallidus and the striatum.
In this regard, globus pallidus external segment (GPe) is indicated as a crucial station in the well-known indirect pathway of the basal ganglia.
Striatal enkephalin-containing neurons receive dopaminergic inputs from the substantia nigra and project to the external segment of globus pallidus.
Efferent signals mediated by the striatal projection neurons are fed to either the internal segment (GPi) or external segment (GPe) of the globus pallidus or substantia nigra pars reticulata (SNr).
At pallidal level, the intensity of GAD65 mRNA labeling in single neurons was increased in the internal but not the external segment of the pallidum of MPTP-treated monkeys.
The globus pallidus external segment forms a major target center of the mammalian striatum which is characterized by neurochemically distinct compartments. The present study was undertaken to determine if a corresponding compartmentalization exists within the globus pallidus external segment in the rat. The results indicate three neurochemically distinct compartments within the globus pallidus external segment: 1) an area in the medial aspect of the entire length of the globus pallidus that contains dense immunoreactivity for calbindin D28kDa; 2) a narrow rim at the striatopallidal junction in the rostral two-thirds of the globus palidus that contains calbindin D28kDa immunoreactivity designated as the "border zone" of the globus pallidus; and 3) an area between these two zones showing very poor immunoreactivity for calbindin D28kDa but containing parvalbumin immunoreactive neurons.
Microelectrode trajectories through the globus pallidus of 6 Parkinson's disease (PD) patients yielded neurophysiological 'landmarks' which enabled the identification of neurones located in the external segment (GPe) and internal segments, exterior (GPi,e) and interior (GPi,i) of globus pallidus and the surrounding borders (Bor).
Following inotophoretic injections into the lateral aspect of the globus pallidus external segment, the ipsilateral striatum showed patches of dense anterograde labeling separated by areas containing sparse anterograde labeling and isolated retrogradely labeled neurons.
In the MPTP-treated primate model of Parkinson's disease, loss of dopaminergic afferents to the striatum leads to increased activity in striatal efferents to the external segment of the globus pallidus.
The ultrastructure of synaptic terminals from the external segment of the globus pallidus and of other synaptic terminals positive for gamma-aminobutyric acid (GABA) was examined in the thalamic reticular nucleus (TRN) of squirrel monkeys.
The atrophy was more severe in the external segment (GPe) than in the internal segment (GPi).
Our observation may indicate that the inhibition of the subthalamic nucleus as the result of the decrease of the putaminal output to the external segment of the globus pallidus will induce hemiballism.
The population of cells is composed of large multipolar neurones and is located predominantly in the substantia innominata and at the ventral, medial and lateral margins of the external segment of the globus pallidus.
The external segment of the globus pallidus contained dense collections of NGFr-immunoreactive neurons between 16 and 26 weeks of gestation, whereas the internal segment was devoid of immunoreactive perikarya. The expression of NGFr-immunoreactive neurons within the external segment of the globus pallidus was paralleled by a dense granular NGFr-immunoreactive terminal-like staining pattern within the subthalamic nucleus.
The anterograde axonal tracing of Phaseolus vulgaris-leucoagglutinin revealed that projection fibers from the central amygdaloid nucleus to the basal ganglia ended in the globus pallidus (the feline homolog to the external segment of the globus pallidus of primates) and substantia nigra.
To block glutamatergic excitation, kynurenate (a glutamate antagonist) was locally injected into the putamen and the external segment (GPe) and the internal segment (GPi) of the globus pallidus contralateral to the arm tested.
Striatal neurons projecting to the external segment of the globus pallidus or the substantia nigra show evident loss, whereas those projecting to the internal segment of the globus pallidus appear relatively spared at presymptomatic and early stages of symptomatic Huntington's disease.
The first level is determined by the segregation of two major striatal output systems, one to the globus pallidus (external segment) and the other to the entopeduncular nucleus and substantia nigra.
In the distribution of degenerated foci, dominant OPCA is often associated with degeneration of not only substantia nigra, but also with other structures such as dentate nucleus, red nucleus, external segment of globus pallidus (GPe), and subthalamic nucleus.
Other anterogradely labeled fibers were also noted bilaterally in the pedunculopontine nucleus (TPP) and ipsilaterally in the external segment of the pallidum (GPe) and in the putamen.
In addition, "third-order" neurons were labeled in the cerebellar cortex (granule and Golgi cells) and in the globus pallidus (largely the external segment).
Iontophoretic injections of the fluorescent retrograde tract tracer, Fluoro-gold, into the entopeduncular nucleus of the rat (homologous to the internal segment of the primate globus pallidus) resulted in a substantial number of retrogradely labeled neurons in the ipsilateral globus pallidus (homologous to the external segment of the primate globus pallidus).
Small injections of biocytin in the external segment of the pallidum (GPe) of the squirrel monkey (Saimiri sciureus) led to anterograde labeling of fibers in the thalamic reticular nucleus (NRT).
In parkinsonian compared to intact monkeys, the mean spontaneous firing rate of the neurons of the internal segment of the globus pallidus (GPi) increased but that of the prevailing neuronal population in the external segment (GPe) inversely decreased.
In the pallidum, bursting was more prevalent in the external segment and bursts were more intense and more frequent than in the internal segment.
We studied the distribution of striatopallidal projection neurons in 9 adult squirrel monkeys by centering deposits of the retrograde tracer HRP-WGA in either the external segment or the internal segment of the globus pallidus.
Concentrations of gamma-aminobutyric acid (GABA) in the external segment (GPe) and internal segment (GPi) of GP and ST are decreased to 62, 45 and 55% of the control mean, respectively.
For 100 GP neurons [ 41 in the internal segment (GPi) and 59 in the external segment (GPe)], the activity of which changed with task performance, the discharge patterns varied greatly across tasks.
Even though the injected BIC or PTX often spread to the external segment of the globus pallidus, claustrum, or anterior sylvian gyrus, none of these areas was consistently associated with dystonia.
In the external segment of GP (GPe), most neurons responding to passive wrist movement were found to be clustered in four to five adjacent, closely positioned (separated by 200 microns) tracks in single coronal planes.
Small injections of the lectin Phaseolus vulgaris-leucoagglutinin (PHA-L) in the external segment of the pallidum (GPe) in the squirrel monkey (Saimiri sciureus) and in the rhesus monkey (Macaca mulatta) led to anterograde labeling of fibers in the internal segment of the pallidum (GPi).
This study concerns the expression of Met-enkephalin (MEnk) in the striatum and the external segment of the globus pallidus proper (GPe) in normal controls, idiopathic Parkinson's disease (PD), and striatonigral degeneration (SND).
Other structures showing statistically significant metabolic changes were the external segment of the globus pallidus (+40%), subthalamic nucleus (-17%), and pedunculopontine nucleus (+15%).
Using a sensitive immunoperoxidase technique we examined Met-enkephalin (MEnk) expression in the striatum and globus pallidus external segment (GPe) from patients with Alzheimer's disease (AD) and with progressive supranuclear palsy (PSP).
The structures whose LCMRg was most affected were the motor cortex, the intermediate zone of the putamen, the external segment of the globus pallidus, the medial part of the ventrolateral nucleus of the thalamus (VLm), visual cortex, locus ceruleus, and the dorsolateral segment of the substantia nigra pars compacta. The structure whose increase in LCMRg correlated most closely to the clinical severity of parkinsonism was the external segment of the globus pallidus..
Analysis of 17 HD specimens indicated that in early and middle stages of HD, enkephalin-containing neurons projecting to the external segment of the globus pallidus were much more affected than substance P-containing neurons projecting to the internal pallidal segment.
The external segment of the pallidum was extremely sparse in D1 binding, whereas the internal segment (or entopeduncular nucleus in the cat) was a site of high D1 binding density.
Glucose utilization was significantly reduced in the pars compacta of the substantia nigra and in the subthalamus, and increased in the external segment of the globus pallidus.
Previous immunohistochemical studies have provided evidence that the external segment of the globus pallidus extends ventrally beneath the transverse limb of the anterior commissure into the area of the substantia innominata.
The most striking finding was the total absence of DLI-positive woolly fibers in the dorsal part of the external segment of the globus pallidus; the ventral pallidum showed very faint staining.
Fibrillary gliosis was found in the white matter of the temporal lobes, external segment of the globus pallidus and the amygdaloid nucleus.
Some of the highest concentrations of enkephalin-positive fibers in the squirrel monkey brain were found in the external segment of the globus pallidus, the outer layer of the median eminence, and in the pars reticulata of the substantia nigra.
By its two main afferents (cortex and external segment of the pallidum), the subthalamic nucleus is in a position to compare direct cortical informations with cortical informations processed at the striatopallidal complex level..
In the normal brain, substance P immunoreactivity was identified in medium-sized neurons in the neostriatum, in neurons of the external segment of the globus pallidus, and in fine fibers in teh neostriatum, inner segment of the globus pallidus, and in the pars reticulata of the substantia nigra. Leucine-enkephalin immunoreactive processes were present throughout the neostriatum of normal brain, and were densely packed in the external segment of the globus pallidus and in the substantia nigra.
At pallidal levels, a moderate number of DP-labeled cells occurred within the dorsal half of the external segment of the globus pallidus (GPe), whereas the GPi was virtually devoid of labeled neurons.
The projection of the external segment appeared to be less dense than that of the internal segment.
Areas which showed the greatest density of immunoreactivity included substantia gelatinosa, nucleus tractus solitarius, nucleus parabrachialis, substantia nigra, median eminence, globus pallidus (external segment), patches within the striatum and the region of nucleus accumbens and the olfactory area.
Arm motor performance of eight Cebus monkeys was examined during reversible cooling in the ventral lateral region of the putamen and globus pallidus (primarily the external segment), where neurons discharging during arm movements have been found (DeLong 1972).
Moreover, in man, the pallidal substance P was almost exclusively seen in the internal segment while it spreads to the external segment in the rat.
Recovery of the display may occur with lesions predominantly involving the external segment, while destruction of the caudalmost pallidum is without effect.
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