Term
| Where are the basal ganglia located? Describe their bulk connections |
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Definition
Interconnected nuceli in the telencephalon, diencephalon, and mesencephalon
Input from the cerebral cortex, output to frontal lobes via thalamus and brainstem
No spinal connections |
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Term
| What are the parts of the Striatum? |
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Definition
| Caudate and Putamen (tail and shell) and accumbens septi (nucleus leaning agains the septum) |
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Term
| What are the parts of the Globus Pallidus? |
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Definition
Internal Segment
External Segment
Ventral Pallidum
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Term
| What is the lenticular nucleus composed of? |
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Definition
Putamen and globus pallidus
Lenticular = Lens-like |
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Term
| What are the parts of the Substantia Nigra? |
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Definition
Pars Reticulata (spotted)
Pars Compacta (dense) |
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Term
| What do the Basal Ganglia do? |
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Definition
Motor Control primarily, but also involved in cognitive, emotional, and motivational mechanisms.
Basal Ganglia act in parallel to allow desired motor movements and simultaneously inhibit competing mechanisms.
Traffic cop |
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Term
| Name the types of Neurons found in the striatum, and some characteristics |
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Definition
Medium Spiny (95%): extensive collateral connections
Large Aspiny (1%): Ach transmitter
Medium Aspiny (1%): Somatostatin Transmitter
GABAergic interneurons (1%): Fast spiking |
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Term
| What is the input to the striatum? |
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Definition
Excitatory, glutamatergic input from most of the cerbral cortex.
Excitatory input from the intralaminar thalamus (function unknown)
From SNpc, D1 Dopamine is excitatory, but D2 Dopamine is inhibitory (presynaptic connections to medium spiny neurons) |
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Term
| Describe the Outputs of the striatum |
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Definition
Intermixed populations of neurons (medium spiny)
GABA/Substance P: Inhibitory, go to GPi/SNpr, express dopamine D1 (direct path)
GABA/Enkephalon: Inhibitory, go to GPe and also SNpc, express dopamine D2 (2 separate paths) |
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Term
| What do the D1 and D2 neurons from the SNpc do in the striatum? |
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Definition
D1 facilitates the direct pathway to the GPi/SNpr
D2 inhibits the indirect pathway to the GPe
They input presynaptically, modulating medium spiny neurons in the striatum |
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Term
| What do the SNpc neurons fire in response to? |
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Definition
| significant events related to rewards, presentation of instructions, but not simuli that have been used over and over. |
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Term
| Describe the center surround organization throughout the basal ganglia pathways |
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Definition
Striatum (center excite surround inhibit)
GABA
GPi (center inhibit surround excite)
GABA
Thalamus (center excite surround inhibit) |
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Term
| What role does the subthalamic nucleus have in the basal ganglia? |
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Definition
Takes input from the frontal lobe areas (excitatory), preserves somatotopy, and sends excitatory output to both direct (GPi/SNpr) and and indirect (GPe) pathways.
The hyperdirect pathway!
Also receives inhibitory input from the GPe. |
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Term
| Why do spiny neurons not fire much? |
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Definition
They use a lot of energy, so there are a number of mechanisms to keep their firing rates down.
Long refractory periods, collateral inhibition |
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Term
| What are the Basal Ganglia output Nuclei? |
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Definition
Globus Pallidus pars interna
Substantia Nigra pars reticulata |
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Term
| Describe the neural input morphologies in the GPi |
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Definition
From the striatum, each neuron touches many other neurons before entwining one particular neuron. (slower pathway)
From the subthalamic nucleus, each neuron can entwine a number of GPi neurons. (faster pathway) |
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Term
| Describe the receptive field of the Globus Pallidus internal portion |
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Definition
From the subthalamic nucleus, bulk excitation, but from the striatal cortex, center inhibition
off-center on surround. |
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Term
| Describe the output of the GPi |
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Definition
Goes to Thalamus, which projects to the frontal lobes
Inhibitory GABA
Also collaterally projects to pedunculopontine area, projecting to reticulospinal system (coordinates bilateral movements) |
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Term
| Describe the structure and function of the Substantia Nigra pars reticulata |
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Definition
Like the GPi
Output is GABA and inhibitory, to the thalamus (VA, VLm, MD), and the pedunculopontine area, and the Superior colliculus (Frontal eye fields)
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Term
| Describe the discharge patterns of different parts of the basal ganglia |
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Definition
Putamen -> almost no activity
GPi/SNpr -> large amounts of activity
STN -> focused peaks of activity |
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Term
| When do the basal ganglia fire in relation to movement activity? |
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Definition
For limb movements, after the onset of muscles
For eye movements, the SNpr fires late to initiatory activity in the superior colliculus |
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Term
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Definition
Dance-like movements
Small amplitude twitches |
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Term
| What sort of motions can compete with desired voluntary motion |
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Definition
Posture (righting mechanisms)
Locomotion |
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Term
| Describe the asymmetric tonic neck reflex |
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Definition
| When the neck is twisted, you extend the side that the face is pointing towards, and contract the side that you are not facing |
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Term
| How are hypokinetic disorders characterized? |
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Definition
Slow movements, scarcity of movement, rigidity
Parkinson's Disease
Fail to excite the direct pathway enough/ excite the indirect pathway too much |
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Term
| How are hyperkinetic disorders characterized? |
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Definition
Abnormal involuntary movements and postures, chorea
Huntington's Disease
Failure to inhibit the direct pathway enough (too much D1), or excite the indirect pathway sufficiently (not enough D2) |
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Term
| Describe Parkinson's Disease: Pathology, symptoms, surgical treatments |
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Definition
Pathology: Degeneration of Dopaminergic neurons in the SNpc
Symptoms: Can't initiate movement, difficulty limiting patterns that result in abnormal coactivation and contraction.
Treatment: Lesion in the subthalamic nucleus decresases excitatory surround in the GPi, decreases surround inhibition at thalamus
Treatment: Lesion in the GPi provides less inhibition in the center, which means more excitation in the center at thalamus |
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Term
| Describe Huntington's disease: Pathology, symptoms |
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Definition
Pathology: D2 enkephalon receptors die, but D1 remain, creating less inhibition of the indirect pathway. Genetically based (chrom 4)
Symptoms: movement all the time, shrunken brain |
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Term
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Definition
Damage to the subthalamic Nucleus
Ballism -> large amplitude flinging movements on contralateral side compared to lesion source
Chorea -> small twitching movements. |
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