Chapter 16: Basal ganglia

Question 1

Basal Ganglia

Answer 1

second control circuit- helps us execute and plan our voluntary movement. Sends output to cortical UMN and to brainstem UMN-

help plan movement in the context of what I want to do (goal directed behavior), in addition to the motor planning behaviors and control. Motor control is influenced by what goal directed behavior (what I want to do).

Question 2

Motor influence

Answer 2

Everything that goes to the cortex must go through the thalamus first.

Brainstem- Basal ganglia output down to brainstem goes through the pedunculopontine Nucleus (sits right at junction between peduncle and pons) a relay station on the way to the reticulospinal and vestibulospinal.
-Another path that goes through the midbrain locomotor region- a little switch to turn on the walking pattern generator. (outputs to brainstem to support voluntary movement along with the walking pattern generator)

Question 3

Components of the Basal ganglia- Substantia Nigra

Answer 3

Very important, contains the cells that make dopamine and dopamine runs the basal ganglia processor. When the cells die the basal ganglia doesn’t work correctly. Powers the basal ganglia.

Question 4

Input to Basal Ganglia

Answer 4

Glutamate, Acetylcholine, Serotonin

-excitatory neurotransmitters

Question 5

Output from Basal Ganglia

Answer 5

GABA is our inhibitory neurotransmitter of the NS

-Basal Ganglia is inhibitory to all other structures.

Question 6

Internal communication and processing

Answer 6

Dopamine- Synthesized in substantia nigra, cells where it gets produced. Dopamine helps to run the processor- regulates how much inhibition flows out of the basal ganglia (adjusts strength of output signals)

Question 7

Loops (non motor and motor functions

Answer 7

1) Goal-directed behavior loop
2) Emotion loop
3) Social behavior loop

4) Oculomotor loop
5) motor loop

Question 8

Goal-directed behavior loop

Answer 8

Hair line
Helps us with executive function (setting a goal and making a plan to get there) the what I want to do part of my brain. (evaluating information for making decisions)
-Adjusts motor plan depending on what is going on around me.
-Helps with some learning

Problems- hard time setting a goal, hard time making a plan, and influences motor behavior if it is damaged.

Question 9

Emotion loop

Answer 9

Right behind your forehead
Helps to incorporate emotions and motivation into motor plan
-reward seeking behavior into motor plan
-Helps to make predictions when the outcome is uncertain (stand next to a steep ledge and get a bad feeling about what could happened, this is the loop)
-Integrate emotions with facial expressions.

Problems-cant make predictions, become impulsive and they act without considering the consequences.

Question 10

Social behavior loop

Answer 10

Right behind eyebrows and eyes

• helps recognize social cues
• Helps regulate self control (helps adjust behavior and make a motor plan to respect personal space/ not pull a gun when mad in traffic)
• Helps piece out what information is relevant and what is not (what can I ignore)

problems- don’t recognize personal boundaries.

Question 11

Oculomotor loop

Answer 11

helps us to look where we want to look- create motor plan to move my eyes

Question 12

Motor loop

Answer 12

Most important- the loop that circle to the pre-central gyrus- spins up the plan that finally gets shot down (sent) to the spinal cord

• it helps regulate muscle contractions
• helps regulate how strongly we contract in light (what I want to do, what the context is, etc.)
• regulates what muscles contract, in what combination they contract, and in what order. Helps create normal synergies.

Motor part of basal ganglia.

Question 13

when creating a plan to move, the internal circuits of the basal ganglia:

Answer 13

1) Suppress any ongoing motor programs (stop irrelevant actions and “clear the slate” for new movement)
2) Facilitate appropriate muscles to move in the way you desire.
3) Inhibit muscles that produce unwanted (or unnecessary) movement

It suppresses any movement that doesn’t contribute to what you want to do. It creates normal synergies to help you do what you want to do= the JOB OF THE BASAL GANGLIA

Question 14

Motor loop output 1

Answer 14

1) Basal ganglia output to the cerebral cortex through the motor thalamus. High degree of voluntary control. Inhibit motor thalamus and so they control how much excitation gets to the cortex (can turn it down)

Question 15

Motor loop output 2

Answer 15

2) goes through the pedunculopontine nucleus down to the brainstem UMN (low degree of voluntary control) helps support movement but take direction from the cortex. Basal ganglia up to the cortex high degree, down to the brainstem- support voluntary movement. Inhibits the pedunculopontine nucleus (inhibits and inhibitor) allows the reticulospinal to be more active. counteract the inhibitor.

Question 16

Motor loop output 3

Answer 16

Inhibit the midbrain locomotor region- control how much activation of the stepping pattern generator.

Question 17

Basal ganglia motor control review

Answer 17

Basal ganglia regulates how much excitation of the cortical UMN.

• BG inhibits PPN which inhibits the brainstem so it can influence how much the brainstem UMN are let go. How much they are allowed to work.
• BG influences the walking pattern generator which excited UMN for the pattern of walking.

Question 18

Basal ganglia motor control

Answer 18

Output of BG is “tonic” (always being sent, can vary in amount but is always being sent) to inhibit the thalamus, PPN and the MLR.

• Dopamine powers the processor of the basal ganglia
• Normally dopamine raises and lowers the inhibition of thalamus so that I have just enough proximal stability and just enough direct voluntary control (raise and lower output so there is the perfect combination of proximal stability to support our voluntary cortical cortical control.

Question 19

BG and Parkinson’s disease

Answer 19

Hypokinetic disorder (too little movement)- one malfunction of the basal ganglia

PIGD- Postural Instability Gait Difficulty (most common type)
-small steps and very stiff trunk

Death of dopamine producing cells in substantia nigra
-substantia nigra is nearly gone (dopamine is not being produced to power processing).

Without the processor the output actually goes up. leads to:

• too little activation of voluntary muscles (voluntary muscles not facilitated enough)
• Too much activation of postural and girdle muscles. Thalamus inhibits inhibitor which means the postural muscles are too active leads to a very stiff core and limbs that are hard to make move the way that we want to do it.
• Too little activation of midbrain locomotor region- walking pattern generator is inhibited so it occasionally fails. stepping pattern generator occasionally fails and patient freezes cause they have to restart the pattern generator.

Question 20

BG and Huntington’s disease

Answer 20

Hyperkinetic disorders- Too much movement

Question 21

Signs and symptoms of PIGD

Answer 21

Rigidity- too much output of the brainstem UMN, turns on proximal core muscles too much and stiffens person up.
Cogwheel- rigidity with a tremor.
Postural unsteadiness- core is stiff, fall over and whole body goes when gets off balance (like a tree), feet and hands are hypokinetic and cannot move feet and hands quickly to regain balance.