Basal ganglia Flashcards
Striatum
Caudate and Putamen
Pallidum
Globus Pallidus External Segment
and
Globus Pallidus Internal Segment
Ventral Pallidum
Nucleus Accumbens
Olfactory tubercle
Parts of Substantia nigra
Pars Compacta
Pars Reticulata
Basal ganglia as defined by Gallatz
Striatum
Pallidum
Ventral Pallidum
Substantia Nigra
Subthalamic Nucleus
Nucleus accumbens
Fields of Forel
Aka the H-fields
Contained in the Subthalamus region
Field H1: The white matter Thalamic Fasciculus, above the Zona Incerta, between it and the Thalamus.
-Lenticular ansa and lenticular fascicle fibers, cerebellothalamic and rubrothalamic tracts.
Field H2: The initial part of the Lenticular Fasciculus, Going from the Pallidum to the thalamus, Under the Zona Incerta, between it and the Subthalamic nucleus.
H-field: The pre-rubral nucleus and the mixed fibrers of the pallidothalamic tracts, the ansa lenticularis and the fasciculus lenticularis.
Contents of the Subthalamus
The Subthalamic nucleus
The Zona Incerta
The 3 fields of Forel
Inputs to the Striatum (Caudate and Putamen)
All areas of the cortex except the Primary Auditory and Primary Visual Cortex V1. Excitatory inputs, Glutamate
Thalamostriate Fibers – From Intralaminar Nuclei
Nigrostriate Fibers – From Sub Nigra Dopamine inhibitory input
Brainstem Serotonergic inhibitory inputs
Basal Ganglia loops
Motor loop
Oculomotor loop
Prefrontal loop
Limbic loop
Motor loop:
Motor, Premotor, and Somatosensory Cortex
-
Putamen
-
Globus Pallidus, Internal
-
Ventral Lateral and Ventral Anterior Thalamic Nuclei, VL/VA nuclei
-Back to Primary, Pre- and Supplementary Motor cortices
Occulomotor loop: Posterior Parietal and Prefrontal Cortex - Caudate - GP internal AND Substantia Nigra Pars Reticulata - MedioDorsal and VA nucleus of Thalamus - Frontal Eye field, and Supplementray eye field in the Frontal Cortex.
The 3 major cortical motor fields and functions
Primary Motor Cortex:
Neurons producing the Pyramidal tract
Supplementary Motor Cortex:
Initiation and planning of voluntary movement
Premotor cortex:
Coordinating movements, maintaining posture and stability. Gait and Hand coordination
Pyramidal tract
Originates from Primary motor cortex neurons,
Contains Corticospinal AND Corticobulbar/Corticonuclear tracts.
Passes through the Genu and Posterior limb of the internal capsule,
Passes through the middle third of Crus Cerebri.
Corticobulbar tract synapses on ipsilateral and contralateral Cranial Nerve Motor Nuclei In the midbrain, pons, and medulla
Corticospinal tract: Continues downwards, forming the Pyramids of the medulla. Decussates in the pyramidal decussation immediately Caudal to the pyramids.
Decussated fibers –> Lateral Spinothalamic tract. ~80%
Ipsilateral fibers –> Form anterior Spinothalamic tract. ~10%
Also ~10% of the uncrossed fibers remain ipsilateral, but join the lateral spinothalamic tract.
What are the output nuclei of the Basal Ganglia
The Internal Globus Pallidus and the Substantia Nigra Pars Reticulata.
Both are GABAergic, inhibitory.
Tonically inhibit their targets in the brainstem and thalamus.
What is the only excitatory nucleus of the Basal Ganglia
The Subthalamic nucleus, which is glutamatergic
Direct pathway
Facilitates movement
Indirect pathway
Inhibits movement
