27 - Basal Ganglia Flashcards
What do the Basal Ganglia Modulate?
Descending Cortical and Brainstem Pathways
Cerebellum
Coordination
Basal Ganglion
Selection & Initiation
Basal Ganglion projects to
Cortical Motor Areas (Premotor & Motor)
Brainstem
Basal Ganglia Input Nuclei
Caudate Nucleus
Putamen
Nucleus Accumbens (NA)
Basal Ganglia Output Nuclei (to Thalamus)
Internal Segment of Globus Pallidus (GPi)
Substantia Nigra Pars Reticulata (SNpr; GABA)
Ventral Pallidum (VP)
Basal Ganglia Intrinsic Nuclei
External Segment of Globus Pallidus (GPe) Substantia Nigra Pars Compacta (SNpc; dopamine) Ventral Tegmental Area (VTA; dopamine) Subthalamic Nucleus (STN)
A lesion in where causes Parkinson’s?
Substantia Nigra Pars Compacta
Somewhere else in the Direct Pathway
Basic Flow of Information
Cortex
Basal Ganglia
Thalamus (VA/VL, MD)
Cortex
Cerebellum sends primary projections where?
VL
Basal Ganglia sends primary projections where?
VA
Limb Movement - Direct Pathway
Facilitates Movement
Excitatory
Enhances Motor Activity
Limb Movement - Indirect Pathway
Anti-Facilitates Movement
Reduces input to the Thalamus
Limb Movement Pathways
Excitatory inputs from the Cortex converge on the Striatum and activate the direct and indirect pathways, which result in different outputs to the thalamus
Striatum
Caudate
Putamen
Nucleus Accumbens (NA)
This is the same thing as the Input Nuclei of the Basal Ganglia.
Lesions of the Direct Pathway lead to
Parkinson’s (Hypokinetic)
Lesions of the Indirect Pathway lead to
Huntington’s (Hyperkinetic)
Lesions of the Subthalamic Nucleus lead to
Hemiballism
Uncontrolled ipsilateral flailing of the shoulder and upper arm
Cortex-Basal Ganglia-Thalamus Loops
Skeletomotor
Oculomotor
Cognitive
Emotional (Limbic)
Principal Input Nucleus of the Skeletomotor Loop
Putamen
Skeletomotor Loop
Putamen GPi/SNpr VA SMA/PMC/MC Putamen
Oculomotor Loop
Caudate (Body) SNpr/GPi VA/MD FEF Caudate (Body)
Cognitive Loop
Caudate (Head) SNpr/GPi VA/MD FAC Caudate (Head)
Emotional (Limbic)
Nucleus Accumbens VP/GPi/SNpr MD LAC/ACG Nucleus Accumbens
FEF
Frontal Eye Field
Lenticular Nucleus
Putamen
Globus Pallidus
Huntington’s Signs on Imaging
Cortical Atrophy Caudate Atrophy Putamen Atrophy Enlarged Ventricles Lateral Edge Flattened
If you only see one division of the Globus Pallidus, which one is it?
External!!!
Two types of output from the GPi to the Thalamus
Ansa Lenticularis
Lenticular Fasciculus
Ansa Lenticularis
Originates - Ventral aspect of GPi
Courses ventrally toward midline
Hooks around Internal Capsule (posterior limb)
Courses towards the thalamus
Lenticular Fasciculus
Arises - Dorsal aspect of GPi
Small fascicles of fibers pierce directly through Internal Capsule rostral to STN
Collect to form a well-defined bundle
What is the difference between the information in the Ansa Lenticularis and the Lenticular Fasciculus?
Nothing! They carry the same information!
Where do the Ansa Lenticularis and Lenticular Fasciculus enter the Thalamus?
Thalamic Fasciculus
They join fibers from the cerebellar nuclei
They terminate in VA/VL
Where do the Ansa Lenticularis and Lenticular Fasciculus rejoin to form the Thalamic Fasciculus??
Medial to the Zona Incerta
The most peripheral nucleus of the Thalamus
Zona Incerta
