Lecture 10 - Basal Ganglia

Question 1

Basal Ganglia overview

Answer 1

• gets input from many brain areas
• do complex information processing
• assist the IPSI motor cortices for proper movement, tone and posture
• play poorly understood role in cognitive and emotional functions
• lateral to lateral ventricle, next to internal capsule
• internal capsul is between the thalamus and the globus pallidus

-motor, cognition, emotion all determined

Question 2

Striatum

Answer 2

Caudate
putamen
-function as unit

Question 3

Globus pallidus

Answer 3

internal
external
-with putamen = lentiform/lenticular nucleus

Question 4

Subthalamic nucleus

Answer 4

ventral to thalamus

Question 5

Substantia nigra (midbrain)

Answer 5

reticular

compact

Question 6

input

Answer 6

excitatory projections mostly from cerebral cortex to striatum

Question 7

output

Answer 7

inhibitory projections mostly from internal globus pallidus, reticular substantia nigra to thalamus (ventral anterior and ventral lateral nuclei)

Question 8

Thalamus

Answer 8

excites motor cortex

• direct pathway increases
• indirect pathwya decreases
• initiate vs. terminate motor programs

Question 9

Direct pathway

Answer 9

MORE movement

1. cortex excites inhibitory neuros in putamen (striatum)
2. striatum inhibits INT. globus pallidus and reticular substantia nigra
3. reduces globus pallidus and RSN inhibition of thalamus
4. increased excitation from thalamus to motor cortex

Question 10

Indirect pathway

Answer 10

LESS movement

1. cortex excites inhibitory neurons in striatum
2. striatum inhibits EXT. globus pallidus
3. reduces inhibition of subthalamic nucleus
4. subthalamic nucleus excites int. globus pallidus and RSN more
5. int. globus pallidus and RSN increase inhibition of thalamus
6. decreased excitation from thalamus to motor cortex

Question 11

Dyskinesias

Answer 11

BG dysfunction 
-involuntary abnormal movements and/or postures without weakness 
-"movement disorders" 
     hyperkinetic
     hypokinetic
     both

Question 12

Ballism

Answer 12

involuntary, fast, large proximal limb movement
-lesion in subthalamic nucleus –> less excitation of inhibitory neuros to thalamus

*** shuts down indirect –> uncontrolled direct = more movement

Question 13

Tremor

Answer 13

involuntary alternating movement
-rhythmicity, amplitude, frequency, parts of body affected
rest tremor: at rest
action tremor: movement or posture
-postural tremor: with a position held against gravity
-kinetic tremor: during movement
intention tremor - when movement approaches a target (cerebellar issue)

Question 14

Dystonia

Answer 14

Hyperkinetic dyskinesia

Involuntary sustained contraction of one or more muscles causing abnormal movement/posture

Question 15

Chorea

Answer 15

Hyperkinetic dyskinesia

involuntary, fast, irregular, mostly distal limb movements that resemble dancing

Question 16

Athetosis

Answer 16

Hyperkinetic dyskinesia

involuntary, slower, writhing, mostly distal limb movements that resemble the movement of snakes

Question 17

Myoclonus

Answer 17

Hyperkinetic dyskinesia

Involuntary movement that are small and rapid (a jerk), usually of bilateral proximal limbs and trunk

Question 18

Tics

Answer 18

Hyperkinetic dyskinesia
seminvoluntary movements or vocalizations that relieve a progressively uncomfortable sensation and which may be briefly suppressed with concentration

Question 19

Compact Substantia Nigra

Answer 19

Inputs from many brain areas
-projects dopamine to IPSI striatum via nigrostriatal tract
-influence BG by:
increasing activity of direct pathway *** more movement
decreasing activity of indirect pathway
other stuff

Question 20

Parkinsonism

Answer 20

Dysfunctional nigrostriatal tract
-bradykinesia (hypokinetic) - involuntarily slowed
-rigidity (velocity-independent hypertonia)
-rest tremor (hyperkinetic) - usually distal limbs
sometimes also postural tremor

Question 21

Acetylcholine

Answer 21

Neurons in and out of BG
unclear wiring
mostly favors INDIRECT pathway

Question 22

Nonmotor functions

Answer 22

cognition and emotion

***nucleus accumbens (experience of reward –> motivation)