NEURO LEC 14: BG Flashcards
The basal ganglia is not only involved in motor control, but also _________, __________, __________
Goal directed behavior, social behavior, emotions
The basal ganglia and cerebellum adjust motor tract activity via the _________ and have no direct contacts with _______
Thalamus
Motor Neurons
The basal ganglia predicts ______________ of actions and then ____________ the plan by inhibiting competing movements and facilitating others
Outcomes
Chooses/executes
What are the 6 parts of the basal ganglia?
Caudate
Putamen
Globus Pallidus (int+ext)
Subthalamic Nucleus
Substantial Nigra
What 2 structures form the striatum?
Caudate and putamen
What is the nucleus accumbens
the ventral striatum
(front part of caudate and putamen)
What 2 structures form the lentiform nucleus?
Putamen and Globus Pallidus
the substantia nigra is found where
midbrain
input to the BG is
output is
excitatory
inhibitory (Gpi)
True or false: The amygdala and the red nucleus are a part of the basal ganglia
False
Putamen
Caudate Nucleus
1: Globus Palidus internus
- Globus Palidus Externus
What neurotransmitter travels via the striatum (caudate and putamen), substantia nigra pars compacta, and subthalamic nucleus TO THE BASAL GANGLIA?
Dopamine
The subthalamic nucleus is found _____ to the thalamus and _____ to the hypothalamus
Inferior to thalamus, Lateral to hypothalamus
What neurotransmitter travels from cerebrum through corticostriatal pathways to the basal ganglia?
Examples of corticostriatal pathways: Motor, Premotor, Supplemental Motor, Prefrontal, Somatosensory, Limbic
Glutamate (Excitatory)
What is the role of dopamine in the basal ganglia?
Role in Go pathways?
Role in No-Go pathways?
Adjusts transmission pathways between striatum and other basal ganglia nuclei?
Go pathways- excitatory
No-go pathways- inhibitory
ACH is a _____ neurotransmitter in the basal ganglia, and serotonin is ________
ACH- Excitatory
Serotonin- Inhibitory
What inhibitory neurotransmitter is an output from the basal ganglia to the thalamus/cortex/reticular formation/superior colliculus, and Premotor cortex and tectospinal tract
GABA (inhibitory)
What are the 2 motor loops of the basal ganglia?
Occulomotor loop
Motor loop
What are the non-motor loops of the basal ganglia?
Goal Directed behavior
Social Behavior
Emotion Loop
What loops are a part of the dorsal striatal pathways?
Occulomotor Loop, Motor Loop, and Goal directed behavior loop and social behavior loop
(Everything but the emotional loop)
What loops are in the ventral striatal pathway?
Emotional Loop (limbic channel)
What non-motor loops are in the pre-frontal channel (which is inside of the dorsal striatal pathway)
Goal Directed behavior loop
Social Behavior Loop
What is the loop pathway of the Goal Directed behavior loop?
Cortex (Lateral Prefrontal) -> Basal Ganglia (First to head of caudate then to Globus Pallidus Internus) -> Thalamus -> cortex
Note: This is the only one of the 3 pre-frontal loops that uses GPi
Deficits of the goal directed behavior loop can lead to….
Decision making deficits
Inattention, poor concentration, poor short term memory
In the goal directed behavior loop, the head of the caudate does what?
Evaluates inputs for decision making and picks the most appropriate action
In the goal directed behavior loop, the Thalamus is responsible for…
Linking action chosen by head of caudate (Basal ganglia) and preforming the selected movement
What is the pathway of the Social Behavior Loop?
Ventral Prefrontal Cortex -> Basal Ganglia (first to the head of caudate then to the substantia nigra reticularis) -> Thalamus -> Ventral Prefrontal Cortex
Note: does not include Globus Pallidus Internus or externus
How to remember: Social behavior gives you dopamine so therefore the social behavior loop includes the substantia nigra
What is the role of the head of caudate in the Social Behavior Loop?
Awareness of social cues, regulates self control, determines relevant and irrelevant info
Deficits of the social behavior loop can lead to
Impulsivity, Indifference, violent behaviors, risky behaviors
What is the pathway of the emotional loop?
Medial Prefrontal Cortex -> Basal Ganglia (ventral striatum) -> thalamus -> medial prefrontal cortex
Note: Goal directed behavior is lateral prefrontal cortex, social loop is ventral, emotional loop is medial
Note: All loops go cortex -> BG -> Thalamus -> cortex
What part of the cortex is responsible for the:
Emotional Loop?
Social Behavior Loop?
Goal Directed Behavior Loop?
Emotional: Medial Prefrontal
Social Behavior: Ventral Prefrontal
Goal Directed Behavior: Lateral Prefrontal Cortex
Deficits of the Emotional loop lead to…
Impaired reward seeking behavior/ addiction
Note: L Basal ganglia stroke can lead to depression and dulling of emotion
also apathy, paranoia
1
Caudate Nucleus
2
Globus Pallidus
3
Putamen
4
Thalamus
What is the pathway of the Oculomotor loop
Cortex (frontal and supplementary eye fields) -> Basal Ganglia (body of caudate) -> Thalamus -> Cortex
Deficits of the Oculomotor loop will lead to
Poor saccadic eye movements
Prosaccades vs Antisaccades
Prosaccades- towards an object
Antisaccades- away from an object
In the Oculomotor loop, what does the body of the caudate do?
Decides about motions of eyes and spatial attention
Particularly the use of saccades
What is the purpose of the motor loop
Regulates muscle contraction, force, multi joint movement and mvmvt sequencing
What is the only loop that the caudate is not a part of
Motor loop
What is the pathway of the motor loop
Cortex (Motor and Premotor) -> Basal Ganglia (Putamen -> Globus Pallidus) -> Thalamus -> cortex
Disinhibition requires at least 2 __________ and 1 _________
2- inhibitory neurons and 1 target neuron
Disinhibition is important for ________
Fine tuning of movement
What is the output nucleus of the 3 internal pathways of the motor loop?
Stop
Go
No-Go
All 3 use the Globus Pallidus Internus as the output nucleus
Note: all 3 are needed for normal movement
The Globus Pallidus Internus _____ the motor thalamus which ______ cortical motor areas, which ______ motor neurons in SC
Inhibits
Excites
Excites
Conditions that interfere with/ the basal ganglia cause either __________ or _________ movement
Excessive or insufficient
The STOP pathway is also called the……
Hyperdirect pathway
What is the fastest motor pathway?
Stop pathway/hyperdirect
In the stop pathway, the cortex sends an ______ signal to the subthalamic nucleus which then _______ the GPi
Excitatory
Excites
(Note: GPi is the main inhibitory output of inhibitory neurons in each loop)
In the STOP pathway, what does the GPi do once it’s excited by the subthalamic nucleus
Inhibits Motor thalamus immediately prior to movement initiation, inhibits current motor programs to stop irrelevant movements
The Go-Pathway is also called the…
Direct Pathway
In the go-pathway, the Motor areas of the cortex _____ the putamen which _______ the Globus Pallidus Internus, which sends less inhibition to the motor thalamus
Excites
Inhibits
What structure can inhibit the GPi?
What structure can excite the GPi?
Inhibit- Putamen
Excite- Subthalamic nucleus
Free Card Slot
30 second stretch break
The no-go pathway is also called the
Indirect pathway
In the no-go pathway, the Motor cortex _______ the putamen, which ______ the external Globus Pallidus which then has less inhibition on the subthalamic nucleus, the subthalamic nucleus _________ the GPi which inhibits the motor thalamus
Excites
Inhibits
Excites
What pathway inhibits unwanted movements
No-go pathway
Note: the STOP pathway stops current movements
What neurons compose 95% of the neurons within the striatum?
Medium Spiny Neuron
The motor loop requires ________ from the substantia nigra compacta
Dopamine
Note: Dopamine in normal quantities regulates tonic inhibition from GPi to motorthalamus and other structures
The Putamen’s D1 and D2 receptors bind to ______
Dopamine
D1 receptors binding to dopamine does what?
Excites the inhibitory neurons in GPi
(Inhibits GPi in GO pathway)
Note: D2 pathway involves exciting GPi in No-GO pathway
D2 receptors binding to dopamine do what?
Inhibits neurons from putamen to GPe which then disinhibits the subthalamic nucleus
Since the subthalamic nucleus normally excites the GPi, this pathway stimulates the GPi
Note: so both D1 and D2 excite the GPi in some way
Medium spiny neurons are _______ inhibitory cells
GABAergic
What are the 3 pathways that the Motor loop regulates motor output through?
Voluntary Muscle Activity
Postural and Proximal Limb Muscle Activity
Walking
The motor loop controls Voluntary Muscle Activity through..
Thru motor thalamus to motor tract cell bodies in
cortex
► Corticospinal, corticopontine, corticobrainstem
tracts
The motor loop controls Postural and proximal limb muscle activity through…..
Thru pedunculopontine nucleus in midbrain to reticulospinal tracts to spinal motor nerves
Basically the motor loop used the reticulospinal tract to control posture
The motor loop controls walking through..
Thru midbrain locomotor region to reticulospinal
tracts to stepping pattern generator
What is the most common basal ganglia disorder?
Parkinsons
It is an example of hypokinetic disorders
Too much BG inhibition of thalamus
Hyperkinetic vs hypokinetic disorders
Hyper- Too little inhibition of thalamus by BG
Hypo- Too much inhibition
Huntington’s Disease/Chorea
Dystonia
Tourette’s disorder
Dyskinetic cerebral palsy
Are all examples of what?
Hyperkinetic disorders
What is the primary mechanism of parkinsons?
Decreased dopamine output by substantia nigra leading to excessive GPi activity
What are 2 subtypes of parkinsons?
Postural Instability Gait Difficulty (PIGD)
Subtype
►Bradykinesia
► Poverty of movement (Hypokineisa)
► Postural instability
► Autonomic dysfunction
► Cognitive dysfunction
Tremor Dominant Subtype
►Resting tremors
► Action tremors
► Rigidity and slow movements
are relatively mild
What is huntington’s/Chorea disease?
Autosomal dominant hereditary disorder causes progressive degeneration of the cortex and striatum (especially putamen)
Huntington’s disease causes a 90% loss of subset of GABA-ergic inhibitory neurons in putamen and caudate so less input to…..
GPe (indirect/No-Go pathway)
In Huntington’s disease, Loss of excitatory output of subthalamic nucleus
to _______ causing ballistic involuntary movements of
limbs called Chorei-form movements:
involuntary, continuous movement of the body
Globus Pallidus Internus
Note: Includes motor, swallowing, and cognitive
deterioration
Thalamic neurons can fire randomly and inappropriately, causing the motor cortex to execute motor programs with no control by patient
What is dystonia?
Genetic, typically nonprogressive, movement disorder characterized
by involuntary sustained muscle contractions, causing abnormal
posture, twisting and repetitive movements
When does dystonia typically increase?
When does it completely vanish?
During activity or emotional stress
During Sleep
Examples of _____ dystonias include writer’s or musician’s cramp, cervical dystonia
Generalized dystonias can be __________, including limbs and trunk,
interfering with walking and other functions.
Focal
Progressive
