Chapter 4

Question 1

cerebellum divided into three imperfectly delineated lobes

Answer 1

anterior lobe, posterior lobe, floccular lobe

Question 2

sign of increased intracranial pressure

Answer 2

the tonsils (T) may herniate through formen magnum— pressure on medulla
- life threatening

Question 3

function cerebellum

Answer 3

modulates and refines motor control; participates in acquiring and maintaining motor skills, from playing a musical instrument to pitching a baseball to texting

Question 4

3 parts of the brain involved in movement

Answer 4

1) motor cortex –> sends signals
2) basal ganglia –> initiates and stops movement
3) cerebellum –> ensures movement is smooth; fine tuning

Question 5

amount of neurons in the cerebellum vs. neocortex

Answer 5

despite its small size relative to the neocortex, the cerebellum contains about four times more neurons than the neocortex
- 69 billion neurons compared to 16 billion neurons

Question 6

somatotopy

Answer 6

body regions correspond to specific areas of the brain that control them

Question 7

somatotopy in the anterior lobe

Answer 7

body appears inverted; hindlimbs are on top (rostral) and forelimbs are next (more caudal), and the face at the very bottom

Question 8

somatotopy in the posterior lobe

Answer 8

the body appears straight, but dually represented (i.e., has one representation on each side of the midline); trunk is towards the midline; extremities are more lateral

Question 9

significance of somatotopy

Answer 9

disorders of one region of the brain will affect one region of the body
- disorders affecting the midline cerebellum = affect primarily trunk musculature and cause problems in balance and equilibrium

Question 10

different parts of the cerebellar hemispheres subserve different movements

Answer 10

• lateral –> associated with movements of the limbs, hands, feet, and digits
• medial areas –> associated with the face and the body’s midline

Question 11

pathways from the cerebellar hemispheres

Answer 11

project to cerebellar nuclei in its base, which in turn project to other brain regions, including the motor cortex

Question 12

lateral hemispheres of the cerebellum

Answer 12

• function: participates in the planning and programming of voluntary movements, particularly learned, skillful movements that become more rapid, precise, and automatic with practice
• dentate nucleus
• dentate neurons rate of firing tend to change during movement
• clinical observation: disrupts arm, hand, and finger movements; deficits in learned, skillful movements (e.g., piano playing) may be permanent

Question 13

lesions of lateral hemispheres of the cerebellum

Answer 13

problems in movement of extremities; affect muscles of extremities

manifestations:
- ataxia
- hypotonia
- asynergia/adiodockokinesia
- nystagmus
- dysmetria/dysarthria
- tremor

Question 14

hypotonia

Answer 14

decrease in resistance to passive stretching of muscle, and pendular tendon reflex

Question 15

asynergia/adiodockokinesia

Answer 15

asynergy between agonist/antagonist muscles (jerky movement) / inability to perform quick alternating movements

Question 16

dysmetria

Answer 16

e.g., miss touching nose with tip of finger

Question 17

medial (vermis) hemisphere of the cerebellum

Answer 17

• function: involved in posture and balance/equilibrium
• these areas are heavily connected to the vestibular nuclei and hence their role in the regulation of posture, maintenance of equilibrium, and coordination of eye movement
• clinical observation: tumors or damage in midline areas of the cerebellum disrupt balance, eye movements, upright posture, and walking; when lying down, a person with damage to the medial cerebellum may show few symptoms

Question 18

lesions of the medial cerebellum

Answer 18

manifestations:
- unsteadiness of gait and nystagmus
- very similar to vestibular signs
- potential problems with control of eye movement

Question 19

floccular lobe of the cerebellum

Answer 19

• receives projections from the vestibular system and so takes part in controlling balance
• many of its projections go to the spinal cord and to the motor nuclei that control eye movements

Question 20

complete loss of cerebellum

Answer 20

those experiencing this can walk, but with difficulty, and retain most cognitive function, but with impairments

Question 21

attempts to understand how the cerebellum controls movements center on two major ideas

Answer 21

1) role in movement timing
2) helps maintain movement accuracy

Question 22

motor test of timing in role in movement timing as an attempt to understand how the cerebellum controls movements

Answer 22

• patients with cerebellar damage and control participants were asked to tap a finger in rhythm with a metronome
• after many taps, the metronome was turned off, and both groups attempted to continue tapping to the same beat
• those with damage to the cerebellum, especially the lateral cerebellum, performed poorly

Question 23

perceptual test of timing in role in movement timing as an attempt to understand how the cerebellum controls movements

Answer 23

• patients and controls were presented with two pairs of tones
• silent period between the first two tones was always the same length
• silent period between the second two tones changed from trial to trial
• both groups were required to report whether the second silent period was longer or shorter than the first
• those with damage to the cerebellum performed poorly
• shows that the cerebellum acts like a clock or pacemaker to ensure that both movements and perceptions are appropriately timed

Question 24

helps maintain movement accuracy attempt to understand how the cerebellum controls movements

Answer 24

• patients and control participants throw darts at a target
• after a number of throws, both groups donned glasses containing wedge-shaped prisms
• both groups showed initial distortion in aim
• control participants saw the dart miss the mark, they adjusted each successive throw until reasonable accuracy was restored
• patients with damage to the cerebellum did not correct for this error

Question 25

cerebellum improves motor skills by making required adjustments to movements

Answer 25

1st attempt:
- aim at the bullseye, throw the dart, and find that it misses the board completely

2nd attempt:
- aim to correct for the original error
- notice that there are actually two versions of each throw: 1) the movement that you intended to make and 2) the actual movement

• sensory receptors in your arm and shoulder and by those in your eyes record 1) and 2); if the throw is successful, no correction is needed on your next try; but if you miss, an adjustment is called for (all by way of spinocerebellar tracts)

Question 26

how the brain corrects for the aim in the dart experiment

Answer 26

• cortex sends instructions to the spinal cord to throw a dart at the target
• cortex also sends a copy of the same instructions to the cerebellum through the inferior olivary nucleus
• cerebellum acts as servomechanism, which in engineering is a device that uses error-sensing negative feedback to correct an action (feedback via spinocerebellar tract)

Question 27

other functional considerations of the cerebellum

Answer 27

• involved in motor learning
• conditioned blink response
• possible that similar changes in the cerebellum may underlie the acquisition of skilled, voluntary movements in general

Question 28

conditioned blink response experiment

Answer 28

• a puff of air directed at a rabbit’s cornea elicits a reflex blink
• if the puff of air is regularly preceded by a sound, after a while the sound itself elicits the same blink
• various specific lesions in the pathways that lead from the ear (conditioned stimulus) or the eye (unconditioned stimulus) to the cerebellum interfere with learning of this conditioned response

Question 29

cerebellum involved in cognitive functions

Answer 29

• parts of the cerebellar cortex that deal with inputs from association cortex— the lateral hemispheres (or cerebroceebellum)— are greatly expanded in humans, and especially the association cortex fibers that come from the prefrontal cortex

cerebellar damage or malformation can be associated with a variety of cognitive or behavioral disturbances
- impairments in executive function (planning, set shifting, verbal fluency, abstract reasoning, working memory)
- impairments and spatial cognition (visual spatial organization and memory)
- impairments in spatial cognition (visual spatial organization and memory)
- impairments in linguistic processing (agrammatism and dysprosodia)
- mainly when the lesions involve the lateral hemispheric regions

Question 29

cerebellum involved in emotion

Answer 29

• connections between more medial parts of the cerebellum and limbic cortex (amygdala) (as well as cerebellum-hypothalamus interconnections) seem to play a role in affective and autonomic functions
• clinical observations: patients with the cerebellar lesions experience dysregulation of affect when their lesions encroach upon the more medial parts (towards the vermis); example is coupling cognition-emtion to proper motor and facial gestures

Question 30

pseudobulbar affect (PBA)

Answer 30

• pathologic (forced, spasmodic) laughing and crying
• involves inappropriate outbursts of laughter and crying: the slightest provocation or sometimes for no apparent reason, the patient is thrown into hilarious laughter or crying that may last for many minutes to the point of exhaustion
• the patients report that they don’t have the feeling accompanying the emotion they are expressing, i.e., they cry, but they are not feeling sad; they laugh, but they are not feeling happy