Neuroscience Week 4: Basal Ganglia and Thalamic Anatomy Flashcards
Striatum
Collective term for the
- Caudate
- Putamen
Lentiform nucleus
Collective term for the
Globus pallidus
Putamen
Lentiform nucleus (lens-shaped)
Given their lens-shaped appearance. This is an important term to know because it makes sense of the syndrome of hepato-lenticular degeneration
Pallidum
- Descriptor for the globus pallidus because bundles of myelinated fibers traverse the globus pallidus, giving it a pale appearance.
- The pallidum is sometimes referred to as the paleostriatum because the globus pallidus is derived from the phylogenetically older portion of the brain — the diencephalon.
- The neostriatum refers to the caudate and putamen, which are derived from the phylogenetically newer part of the brain — the telencephalon
The corpus striatum also encompasses several fiber pathways that pass between the globus pallidus and the subthalamic nucleus and thalamus
the ansa lenticularis, lenticular fasciculus, subthalamic fasciculus, and thalamic fasciculus
These fibers comprise a considerable portion of the white matter region inferolateral to the thalamus, which is called the fields of Forel (aka prerubral fields or Forel’s Field H)
Basal nuclei vs Basal ganglia
Basal nuclei vs Basal ganglia
nucleus accumbens
which is the bridge that persists between the head of the caudate and putamen after the anterior limb of the internal capsule separates the head of the caudate from the putamen.
It is important in rewarding behavior.
lateral medullary lamina separates
the putamen and globus pallidus.
The medial medullary lamina subdivides the
globus pallidus into an internal (or medial) segment and an external (or lateral) segment.
The internal capsule lies in between the
lentiform nucleus and the caudate
Beneath the globus pallidus lies the
basal forebrain and the horizontally-oriented anterior commissure in between them.
Note that the globus pallidus actually extends beneath the anterior commissure as the ventral pallidum
The prefrontal cortex acts through innervation of the
head and body of the caudate nucleus.
The parietal lobes act through innervation of
both the putamen and caudate
The primary auditory cortex projects to the
caudoventral putamen and tail of the caudate
The visual cortices project primarily to the
nearest portion of the caudate nucleus.
Fields of Forel
Additional fiber pathways pass through Field H and H1 in their ascent into the thalamus they include:
The cerebellothalamic fibers from the corticopontocerebellar pathway, the medial lemniscus, the nigrothalamic fibers, and the spinothalamic fibers of the anterolateral system pathway.
The thalamic fasciculus
The term is sometimes broadened to include the cerebellothalamic fibers and it is also sometimes used synonymously with the term Field H1, just as the term lenticular fasciculus is sometimes used synonymously with term Field H2.
The thalamic fasciculus projects to multiple thalamic nuclei, including the ventroanterior nucleus, which most notably communicates with the globus pallidus; the ventrolateral nucleus, which most notably communicates with the cerebellum; the dorsomedial nucleus, which most notably communicates with the prefrontal cortex and basal ganglia; and the centromedian and parafascicular nuclei (the main intralaminar nuclei), which most notably
communicate with the striatum and frontal lobes.
BASAL GANGLIA: NOMENCLATURE
The striatum further subdivides into dorsal and ventral divisions.
The dorsal striatum comprises the bulk of the caudate and putamen, whereas the ventral striatum is limited to only the ventromedial caudate and putamen, but the ventral striatum also encompasses the nucleus accumbens and select basal forebrain structures.
The dorsal striatum is involved in a wide array of processes, including the sensorimotor circuits, whereas the ventral striatum associates principally with the limbic system and is primarily involved in emotional and behavioral processes.
Just as the striatum divides dorsally and ventrally, so the pallidum further subdivides into a dorsal pallidum and ventral pallidum. Similar to the striatum, the dorsal pallidum refers to the bulk of the globus pallidus, whereas the ventral pallidum refers to the anteromedial portion of the globus pallidus that lies below the anterior commissure. However, although we consider the ventral striatum and ventral pallidum to be divisions of the striatum and pallidum, here, certain texts distinguish these ventral structures as entirely separate nuclei (ie, they distinguish the ventral pallidum from the pallidum, itself).
The corpus striatum also encompasses several fiber pathways that pass between the globus pallidus and the subthalamic nucleus and thalamus: the ansa lenticularis, lenticular fasciculus, subthalamic fasciculus, and thalamic fasciculus. These fibers comprise a considerable portion of the white matter region inferolateral to the thalamus, which is called the fields of Forel (aka prerubral fields or Forel’s Field H).
As a final note, the subthalamic nucleus and substantia nigra are functionally but not developmentally associated with the basal ganglia; therefore, although they are variably included as part of the basal ganglia, we do not include them in our definition of the basal ganglia, here, in accordance with the Terminologia Anatomica.
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What plane are these?
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Caudate tail
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Caudate body
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Caudate body
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Caudate body
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Globus pallidus (pallidum, paleostriatum)
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Globus pallidus (pallidum, paleostriatum)
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Globus pallidus (pallidum, paleostriatum)
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Caudate Head
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Caudate Head
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Caudate Head
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Caudate Head
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Ventral putamen
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Putamen
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Putamen
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Putamen
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Lateral medullary Lamina
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Posterior Limb
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Posterior Limb
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Genu
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Genu
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anterior limb
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anterior limb
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Internal Capsule
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Internal capsule
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Internal Capsule
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Caudate Head
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Caudate Head
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Pulvinar - visual attention
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Lateral Geniculate nucleus - visual system
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Medial geniculate nucleus - auditory system
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Lies along the anterior-posterior axis of the thalamus and bifurcates, anteriorly.
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- Anterior group nuclei
- Lies within this bifurcation and communicates with the limbic system (in particular with the mammillary bodies and cingulate gyrus as part of the Papez circuit)
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Medial Group Nuclei
The dorsomedial nucleus connects with the prefrontal cortex.
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The ventroanterior nucleus connects with the basal ganglia.
The ventrolateral nucleus connects with the cerebellum, red nucleus, and, to a lesser extent, the basal ganglia.
The ventroposterior nucleus further divides into medial and lateral nuclei, both of which receive sensory afferents (medial from the face, lateral from the body) and project them to the somatosensory cortex.
Sensory information in the thalamus has a very specific somatosensory map in which the fist is adjacent to the mouth.
Small ventroposterior strokes in the lateral portion of the ventroposteromedial nucleus and medial portion of the ventroposterolateral nucleus result in the characteristic cheiro-oral syndrome in which there is loss of sensation around the mouth and in the fist contralateral to the side of the thalamic infarct.
The ventroposterior inferior nucleus is a less commonly discussed nucleus.
The dorsolateral nucleus: communicates with the limbic system (along with the anterior group nuclei).
The lateral posterior nucleus, and posteriorly: visual attention.
Clinical Correlation: Dorsal Thalamic Stroke
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The pulvinar (part of the extrageniculate visual pathway).
Important for visual attention.
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The intralaminar group
Most notably helps form the ascending arousal system for wakefulness.
Also helps form the ascending arousal system
Intralaminar group subgroups
Rostral and Caudal subgroups which function in limbic processes and have important hippocampal connections
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Medial geniculate nucleus: underneath the medial aspect of the pulvinar.
Part of the auditory system; it receives afferents from the inferior colliculus, which it projects to the transverse temporal gyri (of Heschl).
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Lateral geniculate nucleus: underneath the lateral aspect of the pulvinar.
Involved in the visual system; it receives afferents from the optic tract, which it projects to the primary visual cortex.
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Posterior group nuclei
Span posteriorly from the caudal pole of the ventroposterior nucleus to the medial geniculate nucleus and they also extend medial to the medial geniculate nucleus.
Posterior nuclear group has broad cortical connections: secondary somatosensory cortical projections of the posterior nucleus, which are involved in nociceptive sensory processing.
Thalamic reticular nucleus
Function
- Forms a shell around the rostral/ventral/lateral thalamus.
- Modulates thalamic output through its GABAergic neurons.
- The posterior limb of the internal capsule lies lateral to the reticular nucleus.
- The external medullary lamina is a white matter layer that surrounds the lateral aspect of the thalamus.
external medullary lamina
The external medullary lamina is a white matter layer that surrounds the lateral aspect of the thalamus.
ADVANCED THALAMIC ANATOMY
- The anterior nuclear group comprises the principal anterior and anterodorsal nuclei.
- In nonhuman species, the principal anterior nucleus is subdivided into the anteromedial and anteroventral nuclei.
- The posterior nuclear group comprises the posterior, limitans, and suprageniculate nuclei.
- The intralaminar nuclei divide into caudal and rostral subgroups and has diffuse connections, including projections to other thalamic nuclei, notably the ventroanterior and ventrolateral nuclei, the basal ganglia, cortical and subcortical areas, and helps form the ascending arousal system.
- The caudal subgroup is the most notable; it comprises the centromedian and parafascicular nuclei.
- The rostral subgroup comprises a cluster of closely related nuclei: the central medial, paracentral, and central lateral nuclei.
- The midline nuclear group, by at least one definition, comprises the rhomboid, parataenial, paraventricular, and reuniens nuclei — the reuniens nucleus lies immediately ventral to the interthalamic adhesion.
- Divides into dorsal and ventral subgroups.
- The ventroanterior nucleus connects with the basal ganglia but there is tremendous inconsistency in the literature about ventroanterior nuclear afferent and efferent projections – texts variably state that the ventroanterior nucleus projects to primary motor cortex as well as premotor cortex or simply the premotor cortex and variably state whether its afferent fibers are primarily from the basal ganglia or cerebellum.
The ventroanterior nucleus of the thalamus connects with
Basal Ganglia
The ventroposterior nucleus of the thalamus connects with the
somatosensory cortex
The ventrolateral nucleus of the thalamus connects with the
cerebellum, red nucleus, and, to a lesser extent, the basal ganglia.
