Movement L7

Question 1

Essentially, the PARAMETERS of movement (force, speed and timing) are computed by the ________.

Answer 1

Essentially, the PARAMETERS of movement (force, speed and timing) are computed by the cerebellum.

Question 2

what part of motion are basal ganglia involved in?

Answer 2

action selection

Question 3

basal ganglia

Answer 3

Question 4

D: basal ganglia

Answer 4

the basal ganglia are a collection of large subcortical forebrain nuclei.

Question 5

what are the main basal ganglia

Answer 5

The main nuclei are the Putamen & Caudate and the globus pallidus.

Question 6

what are the 2 mid brain basal ganglia

Answer 6

(substantia nigra & subthalamic nucleus

Question 7

inouts and outputs to the basal ganglia

Answer 7

Major inputs to the basal ganglia arise from the cerebral cortex (all lobes): the outputs are directed to the parts of the thalamus that supply the frontal lobes.

The ultimate output is inhibitory to the thalamus

Question 8

The nuclei in the basal ganglia are mainly interconnected by what type of neuronal connections?

Answer 8

The nuclei in the basal ganglia are mainly interconnected by sequential inhibitory connections (GABA)

Question 9

describe basal ganglia output to the thalamus

Answer 9

Basal ganglia output neurons (e.g.. internal globus pallidus) fire continuously, inhibiting the thalamus and therefore preventing movement.

In turn, Inhibition of these inhibitory neurons will ‘release’ the thalamus from inhibition (disinhibition) allowing it to respond to excitatory inputs and activate motor cortex.

Question 10

Picture for your aid

Answer 10

Question 11

describe the dirwect basal ganglia circuit

Answer 11

A ‘direct’ circuit:

1. corticostriate fibres activate neurons in the caudate or putamen nuclei.
2. These inhibit neurons in the internal globus pallidus, which tonically inhibit neurons in the thalamus. Increased activity in this pathway generates disinhibition in the thalamus, allowing movement.

Question 12

describe an indirect pathway dfor the basal ganglia

Answer 12

An ‘indirect’ pathway:

Corticostriate inputs activate different caudate or putamen neurons that in turn inhibit neurons in the external globus pallidus,

which inhibits the subthalamic nucleus.

Subthalamic neurons excite the internal globus pallidus.

Increased activity in this pathway disinhibits the subthalamic nucleus allowing it to increase activity in internal globus pallidus, increasing inhibition in the thalamus and preventing movemenT

Question 13

describe the hyper direct pathway for basal ganglia

Answer 13

3. A “hyper- direct” pathway.

Connections from the motor cortex directly excite the subthalamic nucleus,

which in turn excites the internal globus pallidus.

Activity in this pathway will abruptly inhibit the thalamus, to stop movement (an emergency brake).

Question 14

The internal globus pallidus can thus be seen as a ‘______’ on movement

Answer 14

The internal globus pallidus can thus be seen as a ‘brake’ on movement

Question 15

describe the role the substantia nigra plays

Answer 15

A critical role in the activity of these circuits provided by the substantia nigra, which provides dopaminergic projections to the caudate and putamen.

This connection differentially modulates the direct pathway (facilitating its activity) and the indirect pathway (depressing its activity).

The substantia nigra is therefore in a controlling position to either permit or forbid activity in the motor cortex which generates movement.

Question 16

describe basal ganglia movement problems

Answer 16

Basal ganglia dysfunction leads to characteristic problems with either an excess or a paucity of movement.

In hyperkinesia movements are produced not as random twitches, but often well coordinated – but are produced at inappropriate times

Question 17

do you understand the basal ganglia model for parkinsionism?

Answer 17

i hope so!

Question 18

role of dopamine in basal gangia movement pathway

Answer 18

Dopamine:

1. i) activates the inhibitory direct pathway to the internal globus pallidus via D1 receptors and
2. ii) suppresses the inhibitory projections to external globus pallidus (part of the indirect pathway) via D2 receptors.

Question 19

Loss of dopamine therefore leads to _____ activity in the direct pathway and ____ activity in the indirect path,

Answer 19

Loss of dopamine therefore leads to reduced activity in the direct pathway and more activity in the indirect path,

Question 20

in parkinsonism - internal globus pallidus -

more or less active?

Answer 20

more active! = increased inhibition

Question 21

2 treatments for parkinism

Answer 21

controlled lesions of the Globus Pallidus (pallidotomy) or, more common nowadays, deep brain stimulation in the subthalamic nucleus. These both disrupt the excessive inhibition of the thalamic neurons, alleviating the symptoms.

Question 22

The real physiological role of the basal ganglia is more complex and appears to be related to ….

Answer 22

The real physiological role of the basal ganglia is more complex and appears to be related to decision making.

Question 23

if all visual stimuli always drove saccades it would be bad. To prevent this, the superior colliculus is tonically inhibited by ….

Answer 23

tonically inhibited by basal ganglia output (substantia nigra/globus pallidus).

Question 24

fat

Answer 24

mamba