Basal Ganglia Flashcards
Basal ganglia role - goal
Major role in goal-oriented movement; automaticity
You do have to think about doing things when do them
Basal ganglia role - motor plans
Production of motor programs; sequencing well-learned motor plans
Basal ganglia role - Selection
focusing neural activity and suppressing alternative movement patterns
When the cortex says I want to do this – the BG tells us what plan the choose
Basal ganglia role - Reward
Reward-based action or inaction
The BG want you to be the most efficient - if not it create a drive to get to it
Basal ganglia role - energizer
it wants to move when it is time to move
Issue seen with parks – bradycardia
BG Input regions
striatum: caudate, putamen & ventral striatum (sometimes seen)
BG loop Modulator regions
substantia nigra compacta
BG loop Output regions
globus pallidus: internal & external segments
substantia nigra reticulata
BG loop Facilitator regions
subthalamic nucleus
Basal ganglia general loop
cortex > BG (striatum) > thalamus > cortex
loops start and end in the cortex
what makes up the Dorsal striatum
caudate and putamen
thalamus areas
VL, VA, CM, MD
cortex areas
Primary motor cortex (M1), Premotor area, Supplemental motor area, prefrontal cortex, posterior parietal cortex
BG loop coordination
All of the loop are independent and can occur at the same time
Additional connections/associated targets
Pontine nuclei
cere
Pontine nucleitarget in BG
Pedunculopontine nucleus
Pedunculopontine nucleus
Connections both to
1) spinal cord
2) reciprocal connections with cerebellum and feedback to basal ganglia.
Impact motor behavior
Closed BG loops
back to cortical input
OPen BG loops
back to other cortical areas
The cortex activates the striatum- two paths
Direct
Indirect
When used together – selection and depression
Direct path
facilitates movement: selectively activates cortical pattern generating
neurons
Generates MN activity
Drives the cortex to start a plan
Indirect path
Inhibits movement: general inhibition of pattern generating cortical neurons
Reducing the number of CPG
BG circuits/loops
Motor(skeletal motor loop)
Oculomotor
Prefrontal (associative/executive)
Limbic
Motor(skeletal motor loop)
Action selection, execution, sequence, reinforcement learning
OculomotorBG loop
Gaze (motor control for action)
Prefrontal (associative/executive) BG loop - two and overall function
Dorsolateral prefrontal
Lateral orbitofrontal
This is a pattern of how you think
Dorsolateral prefrontal
Prefrontal (associative/executive) BG loop
organization of behavior for problem-solving)
Lateral orbitofrontal
Prefrontal (associative/executive) BG loop
socially appropriate behavior)
LimbicBG loop
Emotion/motivation
Direct path
facilitate movemnt: selectively activates cortical pattern generating
neurons
Generates MN activity
Drives the cortex to start a plan
Gpi is inhibitory to what strutcure
thalamus
Direct pathwayoverall
Drives the cortex, reduces the inhibition
positive feedback - do do this
Indirect pathwayoverall
inhibits the cortex
Gpe
negative feedback - do not do this
Indirect and direct pathways together
Paths function separately but ‘in concert’
Function influence on cortex decision for action
We are doing selection of action – which plans to use and not use
Hyperdirect pathway
WHOA’
Direction communication from the cortex to the subthalamic nucleus (STN)
STN facilitator of the Gpi: leads to a pause in the action
DIRECT PATHWAY activate what neurons
thalamocortical neurons
GPe > Gpi
GPe > -Gpi
GPe > STN
GPe > -STN
STN > Gpi
STN > +Gpi
SNc dopaminergic input to striatum does what
facilitates movement
D1 receptor SNc
Activates the direct pathway – dirves the neurons
Facilitates movement
D2 receptor SNc
Inhibits the indirect pathway – inhibits the neruons
Facilitates movement
BG hypokinetic disorders present as
a loss of ‘drive’
Parkinson’s disease –reduced facilitation of striatum
Consequences of loss of drive
Direct path
not facilitated
Indirect path not inhibited
Lose movement facilitation
Loss of drive to move
BG hyperkinetic disorders
lose the ‘reduction of drive’
Huntington’s Chorea
Hemiballism
Huntington’s Chorea mech
reduced inhibitory GPi output - Lose GPi inhibition of thalamus
Indirect path ‘lost’
Movement facilitated
There is no suppression of other movement, so there are multiple movement plans that are going on at once
Huntington’s Chorea presents as
Seen as: extra movement
Hemiballism
reduced inhibitory output of GPi
Lose STN drive of GPi(lose indirect path component)
Less inhibition and more movement
Reduced GPi- inhibition of thalamus
Movement facilitated
BG and internal
BG gets lots of info about you internal enviro – therefore knows a lot about your energy state
Therefore, will bias the selection of motor plans based on the energy of the body
prediction error resulting in what
an adjusting behavior
Practice is seen when
+ reward occurred, - reward expected
No practice (no change needed) is seen when
+ reward occurred, + reward expected
reward expectation is based on what
phasic dopamine firing
Phasic firing of dopaminergic neurons
reward prediction and error detection (ON and OFF, bursting and not continuous)
Tonic firing of dopaminergic neurons
enables the behavioral function of cortical neurons for cognition, movement and motivation (constant baseline)
Bring energy up to allow us to do things
what is dopes goal
to mediate reactions of the person to the environment; facilitates survival
If someone is reward due to something in their environment, then they are going to be driven to do it
Cortex action role
there to represent your intent, this is what I want to do
BG action role
selects the motor plan to use based on the intentions of the cortex
Brainstem action role
dope neurons
Provide the energy and the reward prediction error code
ACC action role
Regulation component: say not right now
Basal ganglia is a motor energizer - how does it do this
Energizes movements via midbrain connections
BG role in binding
BG- Allows area of the cortex to be at the energy level they need to be at the binding rhythm
Used when we are skilled at a task – not using multiple areas
BG and motor set
neurons in putamen and globus pallidus internus firing prior to movement but not during movements.
active when a visual cue for the direction of movement presented, prior to the actual movement
Basal ganglia involved during movement execution
Basal ganglia neurons in the motor circuit active after the onset of movement
Not working ahead of time
BG and cortex neuron - direction of movement of the limbs;not associated with specific muscle activation
30-50% of neurons in putamen and globus pallidus and in supplementary motor area
BG for ‘scaling’ aspects of movement
Intensity, amplitude, speed of motor actions
cere learing
supervised learning
Error dictions: climbing fibers will cause a pause
- get an error signal from the inferior olivary nucleus
Monitoring motor movement
Can reset and try again
BG learing
reinforcement learning
guided by the reward signal encoded in the dopaminergic input from the substantia nigra pars compacta
Cortex learning
unsupervised learning
guided by statistical properties of the input and neuromodulatory inputs
Basal ganglia role in motor learning
is consolidate motor acts /sequence, store & select when indicated
early learning
there are a lot of cortical areas that involved – lots of talk back and forth
Highly energetic
Hippocampus: lots happening here, this is the working memory
Later learning
The association talk goes down
Cortical to striatum instead of cortical to cortical
The action becomes efficient (the blue circle)
Basal ganglia primary role in motor skill acquisition and performance
Selects motor skills
Reward and reinforcement
Cerebellum primary role in motor adaption
Error detection and correction
Output - BG to cere
order
STN > PN > cere
reward-related signals in the basal ganglia to influence cerebellar function during learning
Output - Cere to BG
order
- DN > thalamus > striatum (BG)
park has what effect on BG output
reduction in the BG output > reduction in facilitation of movement
park and cere
greater activation of cerebellum during movement execution, during early learning, and at rest
the cere is trying to compenstate for the lack of movement
