Exam 4: L5 Flashcards
Major Components of the Basal Ganglia:
- Dorsal Striatum
* * - Globus Pallidus:
* * - Substantia Nigra
* * - Subthalamic Nucleus
Major Components of the Basal Ganglia:
- Dorsal Striatum:
- caudate nucleus
- putamen
- Globus Pallidus
- Lateral aka external
- Medial aka internal
- Substantia Nigra
- Pars reticulata
- Pars compacta - dopaminergic
- Subthalamic Nucleus
What is the core function of the basal ganglia?
The core function of the basal ganglia is to choose between mutually exclusive actions
Action Selection:
- purpose of the _____
- process of selecting and promoting one action while
- ideally: strategy of selection favors _____
Relevant Neurophysiatric Disorders:
Action Selection:
- Purpose of the highly conserved basal ganglia circuitry
- process of selecting and promoting one action while supressing competing actions
- Ideally: strategy of selection favors emotional and physical state
- Relevant Neurophysiatric Disorders:
- OCD
- ADHD
- Tourette’s
The basal ganglia default condition is _______
The basal ganglia default condition is to do nothing
Basal Ganglia Default Setting?
At rest the basal ganglia ______
Basal ganglia releases _____ when the action becomes important or ______
Basal Ganglia Default Setting: TO DO NOTHING
At rest, the basal ganglia supresses all movement
Basal ganglia releases inhibition when action becomes important or salient
- present conditions
- past experiences
The basal ganglia releases ________ from inhibition
The basal gangli releases selected actions from supression
Choices of Basal Ganglia Circuitry:
______ the action
What else goes along with it?
Choices of Basal Ganglia Circuitry:
Chose the action
How long does it continue?
Is another action more urgent?
When does the action end?
What enables simultaneous actions?
Chunking together often repeated movements enables simultaneous actions
Chunking: The ______ at work
Chunking permits a ________ to occur without the need for deliberately intending each component of the movement
- No ________ involved
- Plastisity of striatal afferents (explain)
Chunking: the striatum at work
Chunking permits a sequence of movements to occur without the need for deliberately intending each component of the movement
- No cortical projections involved - don’t have to think about chunking, it is automatic
- Plasticity of striatal afferents: when a series of movements keeps occuring, synpatic changes reinforce those motor circuits
Chunking Simultaneous Movements:
Repeated selection of actions are grouped/chunked/hardwired together - aka ____
Can group chunks together as well as complex behaviors (allows for ______)
Free from contingences- free from ____
-Once actions are chunked, _____
Chunking Simultaneous Movements:
Repeated selection of actions are grouped/chunked/hardwired together - aka habits
Can group chunks together as well as complex behaviors (allows for multitasking)
Free from contingenies - independent from the outcome
Once actions are chunked - difficult to interrupt
Pathways through the basal ganglia employ____
Pathways through the basal ganglia employ the same input and output ports
Basal Ganglia Inputs and Outputs
What are the basal ganglia input areas?
Basal ganglia output areas?
Basal Ganglia
Inputs: Caudate and Putamen (within striatum)
Outputs:
- Internal globus pallidus
- substantia nigra parts reticulata
Feature of basal ganglia loops:
Number of inputs is greater/lesser than number of outputs
Default state of ______ is maintained by ___, ___ output
Medium spiny neurons = 90% of _____ neurons, ____-ergic
Feature of Basal Ganglia Loops:
Number of inputs is greater than number of outputs
Default state of no action is maintained by tonic GABAergic, inhibitory output
Medium spiny neurons = 90% of striatum neurons, GABA-ergic, spine covered dendrites
Cortical and Subcortical Loops
The ________ loop uses efference copy, and sensory and cognitive information to achieve action selection
The skeletomotor loop uses efference copy, and sensory & cognitive information to achieve action selection
Skeletalmotor Loop Action Selection:
- Explain the term “efference copy”
- Sesory, cognitive information
- Urgency or saliency of different actions
Skeletalmotor Loop Action Selection:
-Efference Copy: signal that serves as gold standard to which actual movement is compared
- neural copy of intended or desired outcome “corollary discharge”
- bias towards current actions, behavioral continuity
Sensory, cognitive and afferent into
Urgency or saliency of different actions
- importance of different actions, including the current action being performed
Operational Learning
- _________ process executed by the basal ganglia
- Instrumental, procedural, operant or reinforcement learning
- Process by which we associate our actions with ___
- Implicit Learning: we learn effects of self-generated actions
- biases our actions towards ones associated with ____
Operational Learning:
- Unconcious, associated process executed by the basal ganglia
- Instrumental, procedural, operant or reinforcement learning
- Process by which we associate our actions with their immediate concequences
- Implicit learning: we learn effects of self-generated actions
- biases our actions towards ones associated with rewards and away from ones with negative concequences
Basal Ganglia Functions and purpose:
- Action Selection: basal ganglia ______
- Brain ________ via chunking
- In operational learning, chunked actions when associated with ______ are repeated
Basal Ganglia Functions and Purpose:
- Action Selection: basal ganglia orchestrates what movements occur
- Brain groups multiple actions together via chunking
- In operational learning, chunked actions when associated with positive rewards are repeated
Explain the following Skeletomotor Loop Pathways:
- Hyperdirect pathway (global inhibition)
- through the _____
- stops what?
- Direct pathway (action initiation)
- through the ____ and ____
- releases a ____ from _____
- Indirect pathway (selective inhibition)
- through _____, ___, ___
- mixed effects
- Lateral Inhibition:
- local circuits
- facilitate ______ actions
- opposes ____ on action selection
- Hyperdirect pathway (global inhibition)
- through the subthalamus
- stops current movements immediately
- Direct pathway (action initiation)
- through the putamen and GPi
- releases a selected movement from suppression
- Indirect Pathway (selective inhibition)
- through the putamen, subthalamus, and GP
- mixed effects
- Lateral Inhibition:
- local circuits
- facilitate “winning actions”
- opposes indecision in action selection
Dopaminergic Projections of the basal ganglia:
- Substantia nigra pars compacta
- VTA, nucleus acummbens
Dopamine is required for all _____ movements
Dopamine facilitates _____ and modification of motor sequences as ____
Dopaminergic projections of the basal ganglia:
- Substantia nigra pars compacta:
* movement- need tonic release of dopamine to function optimally - VTA, nucleus acumbens - reward pathway
Dopamine is required for all goal-directed movements
Dopamine facilitates learning and modification of motor sequences as chunks
Dopamine and movement:
Dopamine promotes movement in a _____ fashion
Decrease in dopamine:
- disease
Increase in dopamine:
What is “tardive dyskinesia”?
Dopamine and Movement:
Dopamine promotes movement in a graded fashuon
Decrease in Dopamine:
- hypokinesia, akinesia
- Parkinson’s Disease
Increase in dopamine:
- excessive movement
- Amphetamines or cocaine
Tardive Dyskinesia: after long term treatment of a dopamine antagonist, develop super sensitivity to dopamine
The hyperdirect pathway _____ movement
Hyperdirect pathway:
- Axons from M1 to STN are ____
- Deep Brain Stimulation for Parkinson’s…… decreases STN output…
Impulsivity issues
The hyperdirect pathway opposes movement
Hyperdirect pathway:
Axons from M1 to STN are myleinated (fast)
Deep Brain stimulation for parkinson’s decreases STN output
Impulsitivity Issues
Hemiballism:
- symptoms:
- etiology
- damage to _____
- lesions to putamen, thalamus, or deep white matter
- Common causes:
- Treatments: aimed at cause of lesion, dopamine receptor _______
Hemiballism:
- symptoms: violent throwing of arms and legs
- etiology:
- damage to contralateral subthalamic nucleus
- lesions to putamen, thalamus, or deep white matter
- Common Causes:
- focal stroke
- hyperglycemia (secondary to T2DM)
- Toxoplasmosis lesion from HIV
- Treatments: aimed at cause of lesion, dopamine receptor antagonist
The direct pathway does what?
Direct Pathway:
- sensorimotor cortex input to the _____ via ______ axons
Direct Pathway is DISINHIBITION, meaning inhibiting inhibition, removing _______ from thalamic neurons
Direct pathway releases selected movements from ongoing supression
Direct Pathway:
- sensorimotor cortex input to the putamen via unmyelinated axons
Direct pathway: removes tonic inhibition from thalamic neurons
Parkinson’s Disease:
symptoms:
Treatments:
1.
2.
3.
Parkinson’s Disease:
Symptoms
- hypo-, brady-, or a-kinesia
- resting tremor
- rigidity
Treatment:
- L-DOPA
- Pallidotomy (GPi)
- STN deep brain stimulation
Parkinon’s Disease: The direct and indirect pathways
Direct Pathway: movement initiation is more difficult due to ________
Indirect Pathway: Excessive movement _____ through disinhibition
Normally there is a balance between D1 (+) and D2 (-) input coming from the _____
Parkinson’s Disease: The direct and indirect pathways
Direct pathway: movement initiaiton is more difficult due to disfacilitation (decrease excitation by D1R)
Indirect pathway: Excessive movement inhibition through disinhibition
Normally there is a balance between D1 and D2 inputs through the SNpc
Huntingon’s Disease:
4-5 million in the US, adult onset
Etiology: ______ repeat mutation on the huntington gene in chromosome 4 results in degeneration of _____ neurons, affecting the _____ pathway at least at first
Huntington’s Disease:
4-5 million in the US, adult onset
Etiology: CAG repeat mutation on the huntington gene in chromosome 4 results in degeneration of striatum neurons, affecting the indirect pathway at first
Huntington’s Disease:
Symtoms:
- initial ____kinesia
- chlorea (explain what this means)
- progressively becomes ___kinetic as pallidal and nigral neurons die
Treatment?
Huntington’s Disease:
Symptoms
- initial hyperkinesia
- chlorea (quick jerky dancing movements of extremities)
- progressively becomes akinetic as pallidal and nigral neurons die
Treatment: no cure, treatments focus on symptoms
Genetic test available
Explain the differences between the basal ganglia and the cerebellum:
Basal Ganglia:
- _____ & ______ input
- receives information about?
- ensures _____ actions take priority
Cerebellum:
- ______ or _____ input
- receives info about?
- Ensures that all movements are ____
Basal Ganglia vs the cerebellum:
Basal Ganglia:
- cortical and subcortical inputs
- receives info about moveemnts and actions
- ensures salient actions take priority
Cerebellum:
- peripheral or spinal input
- receives info about muscle contractions
- ensures that all movements are smooth
