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[0] Shink E, Bevan MD, Bolam JP, Smith Y, The subthalamic nucleus and the external pallidum: two tightly interconnected structures that control the output of the basal ganglia in the monkey.Neuroscience 73:2, 335-57 (1996 Jul)

[0] Bevan MD, Magill PJ, Terman D, Bolam JP, Wilson CJ, Move to the rhythm: oscillations in the subthalamic nucleus-external globus pallidus network.Trends Neurosci 25:10, 525-31 (2002 Oct)[1] Bevan MD, Magill PJ, Hallworth NE, Bolam JP, Wilson CJ, Regulation of the timing and pattern of action potential generation in rat subthalamic neurons in vitro by GABA-A IPSPs.J Neurophysiol 87:3, 1348-62 (2002 Mar)[2] Magill PJ, Bolam JP, Bevan MD, Dopamine regulates the impact of the cerebral cortex on the subthalamic nucleus-globus pallidus network.Neuroscience 106:2, 313-30 (2001)[3] Magill PJ, Bolam JP, Bevan MD, Relationship of activity in the subthalamic nucleus-globus pallidus network to cortical electroencephalogram.J Neurosci 20:2, 820-33 (2000 Jan 15)

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ref: Iansek-1980.04 tags: globus pallidus GPe GPi electrophysiology 1980 date: 02-29-2012 18:17 gmt revision:2 [1] [0] [head]

PMID-7411442 The monkey globus pallidus: neuronal discharge properties in relation to movement.

  • motor units are generally inactive during inactivity. the relationship to movement of the discharges of such neurons was found to be very specific
    • This is in comparison to other results, which report a sustained firing, esp in GPi.
  • the discharges (as analyzed through histograms) of many neurones were related to only a particular direction of movement about one joint in the right limb.
  • some discharges were related to multijoint movements -> probably due to control of contraction of particular muscles.
    • nonetheless, this relationship was a loose one; there is not a tight coupling between pallidal activity and muscle contraction.
  • some responded to ipsilateral as well as contralateral movements.
    • PMID-7925805 Unilateral leasions in the GP results in bilateral increase in reaction time. hence, GP is involved in initiation. RT speed eventually recovered.
  • only the posterior globus pallidus - well posterior to the maximum expansion - contained movement related cells.
    • the a-p stereotaxic coordinates were less useful than the location of the maximum mediolateral width of the structure.
    • cells occurred in clusters, separated by regoins of non-movement related.
  • cells in the internal segment had no such organization.
  • many of the non-movement related neurons were tonically active.
  • this was before there was A/D recording, apparently!

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ref: Parent-1995.01 tags: basal ganglia anatomy review STN GPe DBS date: 02-22-2012 15:48 gmt revision:17 [16] [15] [14] [13] [12] [11] [head]

PMID-7711769[0] Functional anatomy of the basal ganglia. I. The cortico-basal ganglia-thalamo-cortical loop.

  • Pallidal and nigral neurons have wide dendritic arborizations at right angles to the unbranched incoming striatal axons, leading to (hypothetically) a confulence of information from distinct functional striatal territories on many neurons and to extreme reception convergence [242].
    • This pattern suggests that projections arising from very small areas of the cortex may extend through very large regions of the striatum, particularly along the rostrocaudal plane.
    • Individual striatal neurons receive relatively few synapses from restricted cortical areas; this makes it difficult to conceive how the cortico-striatal projection system could convey information in a highly specific manner; specificity does not exist at a cellular level.
  • Cortex to striatum:
    • Virtually all cortical functional areas contribute, at varying degrees, to the cortico-striatal projection, inputs from the sensorimotor cortex being particularly extensive and those from the visual cortex much less so.
    • Cortico-sriatal projection originates from neurons located in both supragranular (layers I-III) and infragranular (V,VI) cortical layers.
    • Cortical neurons project ipsilaterally or contralaterally, but not usually bilaterally.
    • Cortical cells arborize on restricted, topologically defined domains in the striatum.
    • Restricted cortical regions project to parasagitally elongated domains in the caudate nucleus.
      • this seems to be a general feature. see B and C below.
      • Reminds me of the cerebellum.
    • non-adjacent cortical areas (prefrontal and pareital cortices)project to adjacent striatal territories.
    • The association, sensorimotor, and limbic cortical areas project in a segregated manner onto threes distinct striatal regions referred to as the associative, sensorimotor, and limbic striatal territories.
    • In this view, cortical information is not directly transposed at striatal level, but is integrated and transformed into strict associative, sensorimotor, and limbic functional modalities.
  • Convergence and divergence:
    • There is a vast reduction in the number of neurons from the cortex to the striatum.
    • This has led many to infer overlap or convergence.
    • Actual projection is patchy -- divisions of striosomes and extrastriosomal matrix -- with the individual axons sending out further sub-patches.
      • This degree of segregation breaks down for sensorimotor territory.
    • cortico-striatal neurons in infragranular layers project principally to striosomes while those in supragranular layers send their axons to the matrix. things are tightly organized.
  • The output cells of the matrix are grouped in clusters in relation to the different projection systems that lead from the striatum to the GPe and GPi. These are called 'matrisomes'.
    • These might be a way of bringing into proximity different cortical signals so they can be recombined in novel ways.
    • That said, there was substantial topographical overlap of the frontal eye field and the supplementary eye field, and though these are closely interdigitated they do not mix.
  • Medium spiny neurons:
    • The primary projection neurons of the striatum.
    • GABA. Plus substance P, enkephalin, dynorphin and neurotensin. (!)
      • The coexistence of GABA with a given peptide in a spiny neuron is in correlation with it's target site.
      • At that time they didn't know what the peptides did.
    • Axon emits several collaterals:
      • Local axonal arborizations restricted tot he dendritic domain of its cell of origin or a nearby cell -- inluding an 'autonapse' or of nearby projection neurons.
      • Less common axonal arborization goes far beyond and often does not overlap the dendritic domain of the cell of origin.
    • Projected to by the cortex, thalamus, and the SNc.
    • Usually silent, except with cortical / thalamic input.
  • Interneurons in the striatum are non-spiny.
    • Less than 2% (of entire striatal population, not just interneurons) them are huge, cholinergic cells.
      • These form symmetric synapses on virtually all parts of MSN.
    • Medium, 1% of population, have short axons and are GABA ergic.
    • Second medium, nitrous oxide signaling interneurons.
    • SNc efferents synapes ontot the base of the spines, but only on MSN that have cortical afferents.
    • Thalamic input synapse onto morphologically distinct type of MSN.
    • Destruction of the dopaminergic nicgro-striatal pathway results in a decrease in levels of mRNA for substance P and increase in mRNA for enkephalin.
  • Striatal MSN projections:
    • Relatively discrete in cats and monkeys; highly collateralized in rats, where many neurons project to GPe, GPi, SN, or some pair.
  • Fibers from the associative territory massively invade the whole extent of SNr, without clear territorial demarcation.
    • Meanwhile, inputs from the limbic striatal territory appears to be widely distributed in the substantia nigra & VTA.
  • Most authors think that the distinction between the GPi and SNr is artificial -- they are split by the internal capsule.
    • However, GPi is mostly sensorimotor, while SNr is associative.
  • Projections from striatum to pallidus * SNr very organized and layered.
    • Pictures. read the paper. words do not do this justice.
    • For example, injections of anterograde tracers in various sectors of the striatum produce elongated, longitudinally oriented terminal fields that cover nearly the entire rostrocaudal extent of the substantia nigra.
    • "The dorsal climbing fibers and the corresponding wooly fibers from replicable modular units whose boundaries do not respect the limit between SNc and SNr compartments. ... They are distrinuted along the rostrocaudal extent of the substantia nigra according to a remarkably precise and constant sequence.
  • As in [1]: striatal and subthalamic terminals converge onto the same pallidal neurons within these regions of overlap, possibly in register with those from the striatum.
    • The striato-pallidal fibers and striato-nigral fibers arborize at least twice in the target structures, suggesting there are multiple copies of the same information to distinct subsets of pallidal/nigral populations.
      • Meanwhile, GPi/SNr axons are highly collateralized and not strictly confined to disctinct subnuclei.
      • That is, output is both convergent and divergent.
      • There are several multi-laminar models of the SNr [54] or the globus pallidus [243].
  • Regarding information funneling due to the very large dendritic fields of pallidal neurons:
    • anterograde double-labeling experiments in the squirrel monkey clearly indicate that neighboring striatal cell populations do not have overlapping terminal fields in the GP or SN.
      • Axons from adjacent striatal cell populations produce two sets of terminal fields that interdigitate but never mix.
      • cortical information is conveyed and integrated along multiple, segregated channels.
  • Output of GPi/SNr = VA, VL thalamus, both ipsi and contralateral.
    • Lesser: pedunculopontine tegmental nucleus & centromedian thalamus, superior colliculus.
    • Highly collateralized output.
    • Lamellar distribution of cells that share similar functional characteristics.
    • Synapse almost exclusively on thalamic projection neurons.
    • Centromedian nucleus: no projection to the cortex; rather projects to the striatum, hence is involved in regulation.
    • Pedunculopontine nucleus: mostly re-afferent back to the BG!
      • innervation of the SNc, subthalamic nucleus, and the pallidum. [95,149,186-188,202,207,215,263,277].
      • Acetylcholine output.
      • Deep cerebellar nuclei project to the pedunculopontine nuclei in primates.
  • GPe: efferent fibers from large terminal boutons that make synapses mostly of the symmetrical type with proximal dendrites and soma of GPi/SNr neurons. These GABA synapses may be of ultimate importance in regulating activity.
    • Also projects to the reticulothalamic region, which supplies GABA synapses to the rest of the thalamus, hence GPe can disinhibit most of the thalamus. Such complexity.

____References____

[0] Parent A, Hazrati LN, Functional anatomy of the basal ganglia. I. The cortico-basal ganglia-thalamo-cortical loop.Brain Res Brain Res Rev 20:1, 91-127 (1995 Jan)
[1] Parent A, Hazrati LN, Functional anatomy of the basal ganglia. II. The place of subthalamic nucleus and external pallidum in basal ganglia circuitry.Brain Res Brain Res Rev 20:1, 128-54 (1995 Jan)

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ref: Shink-1996.07 tags: STN GPe GPi globus_pallidus anatomy retrograde tracing DBS date: 02-22-2012 15:34 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-8783253[0] The subthalamic nucleus and the external pallidum: two tightly interconnected structures that control the output of the basal ganglia in the monkey.

  • interconnected neurons in the subthalamic nucleus and the globus pallidus external innervate the same population of neurons in the internal segment of the globus pallidus.
    • e.g. there is a consistent functional organization between the three areas! (need to look up the organization of the striatum, too).
  • they did a similar study with injections of dextran amine into the GPi, and found that the labeled neurons in the STN and GPe were, as before, in register.
    • labeled GPe axons were not reactive to GABA & seemed to be from STN
    • labeled STN axons seemed to be from the GPe & were GABA reactive.
  • Has anyone traced out the connection in the brain of a Parkinson's patient? Does it change with the disease?

____References____

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ref: Bevan-2002.1 tags: STN GPe globus pallidus oscillations parkinsons DBS date: 02-22-2012 15:13 gmt revision:8 [7] [6] [5] [4] [3] [2] [head]

PMID-12220881[] Move to the rhythm: oscillations in the subthalamic nucleus-external globus pallidus network.

  • !!! autonomous oscillation of STN and GPe underlies tonic activity and is important for synaptic activity (e.g. normal??)
    • this is a review, of course.
  • during quiet wakefulness, neurons in STN and GPe fire differently without rhythm or strong correlation.
    • this is more pronounced when STN/GPe neurons are isolated from synaptic input (e.g. when prepared in a slice)-- they have inherent oscillatory characteristics. hum.
      • this may allow persistent activity or timed (gating) of planned activity (as opposed to timing of compensatory movement, which are mostly handled by the cerebellum).
      • the persistent activity must be more complicated than synchronized firing as in PD.
      • Random thought: I wonder if you 'clocked' the brain you would get discrete reaction times. Longshot; would need to review up and down states in the cortex?
  • during voluntary movement, GPe and STN neurons display a complex relationship to features of motor activity.
  • GPe and STN are reciprocally connected (STN with the Glu, GPe with the GABA)
    • as in other original papers, most of the axons from these regions have branched axons that mediate both reciprocal connections and innervation of output nuclei.
  • interesting thought: STN/GPe network could act as a 'generic' recursive pattern generator.
  • see figure 1 - single IPSP regulate the timing of spikes in the STN. large IPSP can synchronize and entrain the intrinsic high firing rate of STN neurons by prolonging the interspike interval.
    • bursts of IPSP can lead to rebound excitation, and hence a paradoxical increase in activity inn the STN. PMID-11877509[]
      • large IPSPs reset STN neurons oscillatory cycle & lead to synchronization
      • small IPSPs lead to phase-dependent delays and probably lead to desynchronization.
      • neuromodulators, like ACh, serotonin, and dopamine, can influence the polarization of STN neurons, and hence will have a profound effect on activity.
      • STN activity is more dependent one the pattern of afferent activity (of course!) than the gross magnitude of incoming spikes.
  • figure 2 - the network configuration between STN and GPe can markedly affect resulting activity. When there are possible reciprocal connections, the network produces tremor; when the network is more organized so that STN cannot recurrently activate GPe, multiple rhythms occur.
    • recall that both structures have extensive & sparsely connected dendritic fields, and are highly topographically organized.
  • figure 3 - [2,3]- oscillatory activity in the STN is a consequence of dopamine depletion and is also a feature of normal activity.
    • this is dependent on the presence of cortex. lack of cortex = regular firing.
    • GPe firing is tonic and constant in normal animals, and becomes oscillatory in 6-OHDA treated animals.
  • administration of dopamine agonists in PD patients causes higher frequency rhythms (30-70hz); without treatment, oscillations are in the 8-12 and lower range.

my notes:

  • IPSPs seem to have a very interesting and complex effect on the firing properties of tonically-active STN nenurons. who knows how this is being used, and in what representation the associated information is being processed?
  • still need to understand what dopamine is doing, and why absence leads to oscillations!
    • dopamine must modulate basal ganglia insensitivity to cortex.

____References____

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ref: Sato-2000.01 tags: globus_pallidus anatomy STN GPi GPe SNr substantia nigra tracing DBS date: 01-26-2012 17:20 gmt revision:6 [5] [4] [3] [2] [1] [0] [head]

PMID-10660885[0] Single-axon tracing study of neurons of the external segment of the globus pallidus in primate.

  • wow, check out the computerized tracing! the neurons tend to project to multiple areas, usually. I didn't realize this. I imagine that it is relatively common in the brain.
  • complicated, tree-like axon collateral projection from GPe to GPi.
    • They look like the from through some random-walk process; paths are not at all efficient.
    • I assume these axons are mylenated? unmylenated?
  • dendritic fields in the STN seem very dense.
  • study done in cyno. rhesus

____References____

[0] Sato F, Lavallée P, Lévesque M, Parent A, Single-axon tracing study of neurons of the external segment of the globus pallidus in primate.J Comp Neurol 417:1, 17-31 (2000 Jan 31)

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ref: SidibAc)-1997.06 tags: GPi anatomy retrograde tracing VL ventrolateral CM centromedian thalamus GPe striatum date: 03-11-2007 06:08 gmt revision:0 [head]

PMID-9183697 Efferent connections of the internal globus pallidus in the squirrel monkey: I. Topography and synaptic organization of the pallidothalamic projection.

  • ventrolateral (e.g. toward the bottom & side :) GPi projects to the postcommisural putamen & the VL thalamus & central CM.
  • dorsal GPi projects to the caudate and ventral striatum ("limbic striatum")
  • both areas also project to nuclei in the thalamus:
    • parvocellular ventral anterior nucleus (VApc)
    • dorsal VL
    • caudal CM/PF
  • the parafasicular nucleus (PF) was a site of a large number of associative/limbic projections.

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ref: Grabli-2004.09 tags: basal_ganglia gobus_pallidus pathology GPe date: 03-11-2007 04:22 gmt revision:0 [head]

PMID-15292053 Behavioural disorders induced by external globus pallidus dysfunction in primates: I. Behavioural study.

  • there is a functional map within the basal ganglia according to its cortical projections.
  • reversible and focal dysfunction induced by microinjections if bicuculline in the sensorimotor territory of the external globus pallidus can generate abnormal movements. They wanted to test this in the other parts.
  • We found that bicuculline microinjections induced stereotypy when performed in the limbic part of the GPe, and attention deficit and/or hyperactivity when performed in the associative part
  • the behavioural effects shared similar features with symptoms observed in Tourette's syndrome, attention deficit/hyperactivity and compulsive disorders

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ref: Kita-1999.05 tags: globus pallidus GPe caudate putamen anatomy projection date: 03-11-2007 04:09 gmt revision:0 [head]

PMID-10380964 Monkey globus pallidus external segment neurons projecting to the neostriatum.

  • horseradish-peroxidase study in rhesus monkeys.
  • 30% of GPe neurons project to the neostriatum (caudate and putamen)