Lecture 10: Basal Ganglia and Dopamine Flashcards
what stage of movement is the basal ganglia involved in and how
planning
it regulates activity of UMN pathways
they turn motor programs off and on
what are the 5 distinct nuclei
- Caudate nucleus
- Putamen
- Globus Pallidus
* External (indirect pathway)
* Internal (direct pathway) - Substantia Nigra
- Subthalamic Nucleus
Cole puked, guess sprouse’s sick CPGSS
where do major inputs come from
the cerebral cortex
almost all inputs synapse with what?
the striatum
what is the striatum
the caudate nucleus and putamen
what are the 2 major outputs of the basal ganglia
Globus pallidus internal
Substantia nigra pars reticulata
are the main output pathways inhibitory or excitatory
inhibitory
what is the striatum’s job
inhibit whatever it synapses with
what are the 3 main targets of outputs from the basal ganglia
thalamus
Reticular formation
Superior colliculus
what is inhibition
A neuron is inhibiting another neuron, preventing it from being excited
what is Disinhibition
Neuron 1 inhibits neuron 2 that would inhibit neuron 4, so now neuron 4 is disinhibited so it can get excited by neuron 3
disinhibition = excitation
what are the 3 basal ganglia pathways
Hyperdirect pathway/STOP pathway
Direct/GO pathway
Indirect/NO-GO pathway
what is the Hyperdirect pathway/STOP pathway
Stopping ongoing movements
Internal globus pallidus inhibits the thalamus
what is the Direct/GO pathway
Initiation of Movement
Thalamus is less inhibited (disinhibited)
what is the Indirect/NO-GO pathway
Stops of unwanted competing movements
Subthalamic nucleus which inhibits the thalamus
how are the 3 pathways working while wanting to stop drinking water so you can eat a cookie
Hyperdirect/Stop pathway stops me from drinking water
Direct/Go pathway gets me to reach for cookie
- Indirect/No-go pathway prevents unwanted movements while I reach for the cookie
what types of programs use the Direct/GO pathway
Activation of intended and focused motor programs
what types of programs use the No-Go/Indirect and Hyperdirect Pathways
Broad suppression of motor programs
What happens with the Substantia nigra pars compacta
It modulates activity of both the direct and indirect pathways through dopamine release (dopaminergic pathway)
what are the 2 types of dopamine receptors in the striatum
D1 receptors: Makes the direct pathway more active
D2 receptors: Makes the indirect pathway less active
what is the Net effect of D1 and D2
less inhibition of thalamus = promoting movement
what does it mean that The effects of dopamine are TRANSIENT (temporary)
occurs with selection of a movement
what is the loop of the basal ganglia
The Basal Ganglia form a motor loop with the motor cortex in the same cerebral hemisphere
what are the 3 motor functions of the basal ganglia
Inhibiting ongoing movements
Selecting and executing
movements
Inhibiting unwanted
movements
what are the 2 non-motor loops of the basal ganglia
Prefrontal loop
Limbic loop
what is the prefrontal loop
Initiation and termination of
cognitive processes
what is the limbic loop
Regulates emotional and
motivated behaviour
Transitions from one mood state to another
what are the 2 clinical base ganglia conditions
Hyperkinetic Disorders
Hypokinetic Disorders
what are hyperkinetic disorders
Insufficient inhibition of the thalamus
(excessive amount of movement)
Examples:
* Huntington’s Disease
* Hemiballismus
what are Hypokinetic Disorders
Excessive inhibition of the thalamus
(hard time initiating movement)
- Parkinson’s Disease
do Basal Ganglia lesions or damage typically result in impairments on the ipsilateral or contralateral side of the body
contralateral
what is Huntington’s disease
Selective atrophy of the caudate and putamen
- Progressive degeneration of striatal neurons
- Indirect pathway affected first and is underactive; (not able to suppress unwanted movements)
eventually direct pathway becomes overactive
what does the Indirect and direct pathways being affected in Huntington’s disease result in
Less tonic inhibition of the thalamus
what is Hemiballismus
Lesion (e.g., stroke) affecting the subthalamic nucleus
Involuntary ballistic flinging of arm or leg Contralateral to the damage
what is Parkinson’s Disease
Progressive degeneration of
dopaminergic neurons in Substantia nigra pars compacta
Direct and Indirect pathways are affected
what are the main symptoms of Parkinson’s
TRAP:
Tremor
Rigidity
Akinesia - difficulty in movement
Postural instability
how are the direct and indirect pathways affected in Parkinson’s
Direct Pathway
* Less D1 facilitation
↑ inhibitory output to thalamus = ↓
movement
Indirect Pathway
* Less D2 facilitation
* Excessive inhibition of the thalamus
Net effect of dopamine loss = inhibition of thalamus (↓ cortical excitability)
why can’t we just give more dopamine to people with Parkinson’s
Dopamine can’t cross the blood-brain barrier
what is the main Parkinson’s Disease Treatment
L-DOPA – dopamine precursor that can cross the blood-brain
Does not treat the disease itself
what are the effects of L-DOPA for Parkinson’s
Effects of medication can fluctuate
Dyskinesias (involuntary movements)
Wearing off (Predictable decline in
function)
On-off fluctuations (unpredictability)
what are the targets of Deep brain stimulation for Parkinson’s
- Globus Pallidus internal
segment - Subthalamic nuclei
When dopamine is released, there is:
Less inhibition of the thalamus
Nothing happens to the thalamus
Inhibition of the frontal cortex
More inhibition of the thalamus
Less inhibition of the thalamus
Which of the following statements regarding Huntington’s disease is incorrect:
It is a hyperkinetic disorder
There is increased inhibition of the thalamus
There is decreased inhibition of the thalamus
The indirect pathway is affected
There is increased inhibition of the thalamus
Which pathway is affected first in Huntington’s disease?
Indirect pathway
Which of the following statements is true:
None of the responses is correct
The direct pathway of the Basal Ganglia is responsible for initiating movement
The indirect pathway of the Basal Ganglia is responsible for initiating movement
The direct pathway of the Basal Ganglia is responsible for suppressing movement
The direct pathway of the Basal Ganglia is responsible for initiating movement
