Chapter 19: Cerebellum

True or false: The functional organization of the cerebellum is similar to the basal ganglia

True

True or false: The cerebellum can be divided into three major areas based on inputs.

True. The cerebellum can be divided into three major areas based on inputs: Cerebrocerebellum Spinocerebellum Vestibulocerebellum

The _______ cell is the cell type that is the main output from cerebellar cortex and is considered its prime computational element. a. Purkinje b. granule c. Golgi d. basket e. stellate

a. Purkinje

The part of the cerebellum that is highly developed in humans and involved with the planning and execution of complex spatial and temporal sequences is the a. cerebrocerebellum. b. spinocerebellum. c. vestibulocerebellum. d. flocculus. e. nodulus.

a. cerebrocerebellum.

Which of the following structures plays the largest role in cerebellar-cortical "closed loop" circuits? a. Dentate nucleus b. Interposed nucleus c. Fastigial nucleus d. Peduncular nucleus e. Accessory dorsal column nuclei

b. Dentate nucleus

The axons from the pontine nuclei into the cerebellum are referred to as _______ fibers. a. parallel b. basket c. mossy d. stellate e. climbing

c. mossy

The cell bodies that give rise to the largest number of fibers entering the cerebellum are located in the a. cerebral cortex. b. cerebellar cortex. c. pons. d. medulla. e. superior colliculus.

c. pons.

The frontal/parietal cortex isn't the only way input can be made to the cerebellar cortex. What other systems input to the cerebellar cortex? Where do they cross?

Both the spinal cord and the vestibular nuclei project their axons across the inferior cerebellar peduncle to make inputs to the cerebellar cortex.

Describe the functional orgtanization of cerebellar outputs, and their targets. (Hint: There are three distinct output centers that start in the cerebellar cortex, go to the deep cerebellar nuclei, and then end up at their targets).

Cerebrocerebellum makes projections to the denate nucleus, which travels the upper motor pathways to the premotor cortex. The spinocerebellum makes projections to the interposed and fastigial nuclei, which also tavels the upper motor pathways to the motor cortex and brainstem. The vestibulocerebellum makes projections to the vestibular nuclei, which does NOT take the upper motor pathway. Instead it goes to the lower motor neurons in the spinal cord and the brainstem.

True or false: The cerebellum is receiving more input than the basal ganglia.

False.

What happens when you lesion the vermis? (Hint: Think about the modification of saccadic eye movements)

If you lesion the vermis, you will not be able to correct motor behavior of the eyes.

Describe the difference between motor learning and motor correction.

If you section a tendon on the left eye, and put the patch on the left eye, the right eye is able to locate the target but the left eye falls short of the target. But if you move the patch to the right eye, the weakened eye will see that it's missing the target and will eventually make corrections. After five days, it will not take as long to make the correction and has learned how much it needs to correct.

Both the cerebellum and basal ganglia make (direct/indirect) cortical inputs

Indirect

What are olivary climbing fibers and what do they do? Where does the olive receive input from?

Olivary climbing fibers relay messages of motor error to Purkinje cells. The olive receives input from the cerebral cortex, spinal cord, red nucleus, and other locations. Extensive olivary activation reduces relevance of input from other parallel fibers. They compare the extensiveness and location of synapses. Olive cells are synchronized via gap junctions (when one of them fires, they all do). AMPA receptors on the Purkinje cells are endocytosed, meaning they are down-regulated.

What do purkinje cells receive inputs from? Which has the most influence?

Purkinje cells receive information from basket cells, from climbing fibers, and from parallel fibers (granule cell once it's parallel) The climbing fibers have more influence than the granule cells.

How does the cerebellar cortex make projections to the primary motor cortex and the superior colliculus?

The cerebellar cortex makes projections to the deep cerebellar nuclei dentate interposed. It travels via the superior cerebellar peduncle which then projects to either the SC or the thalamus. If it reaches the thalamus, it is then processed and signaled to the primary and premotor cortex.

What part of the cerebellum is involved in high, fine-skilled movements, such as hand movements and speech?

The cerebrocerebellum

The cerebrocellum receives inputs from the _________

The cerebrocerebellum receives inputs from cerebral cortex.

Identify the three layers of the cortex and the neurons of each.

The cortex is divided into three layers: -Molecular layer (mainly dendrites and axons of various cells. basket cells) -Purkinje cell layer (has purkinje cell layers) -Granule cell layer (granule cells, mossy fibers, climbing fibers)

Describe the functional organization of the inputs to the cerebellum

The frontal/parietal cortex can make inputs to either the red nucleus or the pontine nuclei. If it makes an input to the pontine nuclei, it will travel through the middle cerebellar peduncle which will make projections to the cerebellar cortex/deep nuclei If it makes the input to the red nucleus, it will make inputs to the inferior olive, which will cross through the inferior cerebellar peduncle to arrive to the cerebellar cortex. Both are examples of indirect pathway for inputs to the cerebellar cortex.

What is the main processing station of the cerebellum? What is the intermediate relay? Where does the cerebellum output to?

The main processing station is the cerebellar cortex. The cells doing the process of integration are called purkinje cells. The deep cerebellar nuclei function as the intermediate relay. The output is to the thalamus.

What are the pathways in which the axons enter and exit the cerebellum?

The pathways are the three types of the cerebellar peduncles. The superior, the middle, and the inferior.

What circuit provides feedback between the cerebellar output and input?

The red nucleus does. The circuit is contained from the cerebellar cortex, to the red nucleus, to the inferior olive.

What are all three parts of the cerebellum responsible for?

The spinocerebellum is involved with proximal muscles, eye movements, and gross limb movements. The cerebrocerebellum is involved in movements that require skill, including speech. The vestibulocerebellum is involved in postural movements and balance.

The spinocerebellum receives inputs directly from the _______

The spinocerebellum receives inputs directly from the spinal cord

The vestibulocerebellum receives inputs from the ________

The vestibulocerebellum receives inputs from the vestibular nuclei

Describe the different types of cerebellar peduncles.

There are three types: The superiror, middle, and inferior. They are all pathways in and out of the cerebellum. The superior is mostly efferent; axons from deep cerebellar nuclei project to the thalamus or directly to upper motor neurons in the SC Middle are mostly afferent; axons are from the pontine nuclei Inferior are afferent axons from the vestibular nuclei, the spinal cord, and the tegmentum. They are efferecnt to the vestibular nuclei and the reticular formation.

How do major decending outputs come out from the cerebellum?

There are two pathways. Both start from the cerebellar cortex and go to the deep cerebellar nuclei. One goes to the dentate/interposed nuclei and the other goes to the fastigial nuclei. The one that goes from the dentate nuclei crosses through the supeiror cerebellar peduncle, which then goes to the SC. From there, it goes to the RF and crosses through the anterior medial white matter to the lower motor neurons. The other goes through the fastigial nuclei, crosses the inferior cerebellar peduncle, where it can also cross the other pathways mentioned above. The cerebral cortex can also make direct projections to the vestibular nuclei.

Describe the excitatory and inhibitory connections in the cerebellar cortex and deep cerebellar nuclei

You have this deep excitatory loop that is regulated by the deep cortical inhibitory loop. The excitatory loop is compsed of mossy fibers making synapses to the granule cells and the deep cerebellar nuclear cell. The inhibitory loop is composed of the mossy fibers making synapses to the granule cell, which synapse to the purkinje cell, causing an inhibition on the deep cerebellar nuclear cell. This is where the error correction occurs.

Which of the following statements about recalibration of the VOR is false? a. The VOR is precisely recalibrated with each eye movement so that perfect fixation can be maintained during head rotation. b. The cerebellum is involved in adjusting the VOR when eye movements do not properly compensate for head rotation. c. The cerebellum integrates visual information, vestibular information, and motor information (efference copy) when performing recalibration. d. In the absence of the cerebellum, the VOR could not be recalibrated. e. All of the above statements are true; none is false.

a. The VOR is precisely recalibrated with each eye movement so that perfect fixation can be maintained during head rotation.

Which of the following statements about the reeler mutation in mice is false? a. The name reeler was given based upon its impaired locomotor abilities. b. Because of induced genetic abnormalities, it was impossible to determine which chromosome contained the reeler mutation. c. A "synthetic" reeler mutation was discovered by chance after inserting DNA marker fragments into the mouse genome. d. The mutation appears to interfere with the extracellular matrix in the cerebellum. e. In reeler mice, the Purkinje, granule and other cell types are found in incorrect locations in the cerebellum.

b. Because of induced genetic abnormalities, it was impossible to determine which chromosome contained the reeler mutation.

Which of the following statements about the cerebellar Purkinje cell is false? a. Its dendritic field branches in a narrow plane. b. Its dendritic field is oriented parallel to the parallel fibers. c. Each one is contacted by roughly 200,000 granule cells. d. Purkinje cells project to the deep cerebellar nuclei. e. Purkinje cells inhibit deep cerebellar nuclear cells.

b. Its dendritic field is oriented parallel to the parallel fibers.

Which part of the cerebellum receives input directly from the spinal cord? a. Cerebrocerebellum b. Spinocerebellum c. Vestibulocerebellum d. Flocculus e. Nodulus

b. Spinocerebellum

The large size of the cerebral peduncles in the midbrain is related to cerebellar inputs a. arriving through the superior cerebellar peduncles. b. arriving through the middle cerebellar peduncles. c. arriving through the inferior cerebellar peduncles. d. projecting to the vermis. e. projecting to the vestibulocerebellum.

b. arriving through the middle cerebellar peduncles.

During electrical recordings from cerebellar neurons, flipping the wrist back and forth a. elicits the firing of Purkinje cells and deep cerebellar neurons in alternation. b. leads to neuronal responses associated with relaxation or contraction of specific muscles and changes in joint position and movement direction. c. initiates a repeating sequence of activation: from granule cells, to Purkinje cells, to stellate cells, to deep cerebellar neurons. d. initiates a repeating sequence of activation: from Purkinje cells, to basket cells, to stellate cells, to deep cerebellar neurons. e. None of the above

b. leads to neuronal responses associated with relaxation or contraction of specific muscles and changes in joint position and movement direction.

In the weaver mutant strain of mouse, the defect associated with ataxia, hypotonia, and tremor is a. the disappearance of the cerebrocerebellum. b. a complete lack of Purkinje cells. c. a marked lack of granule cells. d. misplaced cells in cerebellar cortex due to an extracellular matrix deficit. e. a cerebellum shrunk to half its normal size, albeit with normal cellular architecture.

c. a marked lack of granule cells.

Alcohol-induced damage to the vermis of the cerebellum has been associated with a. chronically slurred speech. b. word-finding difficulties. c. a wide and staggering gait. d. inability to perform fine movements of the hands and fingers. e. impaired judgment.

c. a wide and staggering gait.

Mossy fibers synapse on a. Purkinje cells and deep cerebellar nuclei. b. Purkinje cells and granule cells. c. granule cells and deep cerebellar nuclei. d. deep cerebellar and pontine nuclei. e. Golgi, basket, and stellate cells.

c. granule cells and deep cerebellar nuclei.

Which of the following is not one of the deep cerebellar nuclei? a. Dentate nucleus b. Interposed nucleus c. Fastigial nucleus d. Peduncular nucleus e. All of the above are deep cerebellar nuclei.

d. Peduncular nucleus

Cerebellar ataxia is characterized by a. difficulty with initiating movements. b. an inability to perform goal-directed movements. c. an inability to perform complex sequences of movements. d. jerky, imprecise movements. e. All of the above

d. jerky, imprecise movements.

The _______ cells make an "inhibitory nest of synapses" with the Purkinje cell bodies. a. granule b. stellate c. Golgi d. basket e. All of the above

e. All of the above

Which is thought to be the role of the climbing fiber input to the cerebellar cortex? a. Summation of motor errors from different sources b. Provision of a difference error between two sources c. Making fast online adjustments of ongoing motor patterns d. Gradual correction of motor errors over many trials e. Provision of a training signal for the parallel fiber synapses onto Purkinje cells

e. Provision of a training signal for the parallel fiber synapses onto Purkinje cells

The distinct T-shaped parallel fibers emanating from the granule cells were shaped by evolution to a. calculate motor error signals. b. sequence complex motor programs. c. perform center-surround inhibition like calculations. d. transform sustained pontine nuclear signals into transient motor commands. e. do things that we still do not understand.

e. do things that we still do not understand.