PHTY209 Lecture Notes - Lecture 10: Saccade, Inferior Olivary Nucleus, Indirect Pathway Of Movement
Cerebellum and basal ganglia
Cerebellum
1. Describe the location, structure, blood supply, and connections within and with the
cerebellum: Anatomy and main components of the cerebellum
o Blood supply
• Posterior circulation
▪ The vertebro-basilar system supplies the brain stem, cerebellum and
occipital lobes
• 3 main cerebellar arteries
▪ Posterior inferior cerebellar artery (PICA)
▪ Anterior inferior cerebellar artery (AICA)
▪ Superior cerebellar artery
o Easily recognisable
• Two large hemispheres and a midline vermis (means "worm" - fitting description)
o Sits
• Under the occipital lobe
• In the posterior cranial fossa
• On the dorsal surface of the brainstem
o Lobes
• Divided into 12 lobules but the main divisions we will consider are the
▪ Flocculonodular lobe (posterolateral fissure)
▪ Anterior lobe (ant to primary fissure)
▪ Posterior lobe (post to primary fissure)
• The vermis
▪ A midline structure divides the cerebellum into two hemispheres
find more resources at oneclass.com
find more resources at oneclass.com
▪ The intermediate zone is directly lateral to this
• The lateral hemispheres are lateral to this intermediate zone
2. Describe the function of the cerebellum, including demonstrating an understanding of the role
of the cerebellum in cognition, feed-forward, feed-back control of movement and motor
learning/memory
o Regulator of motor input
o Depends on feedback for normal function - it's critical for normal function
o Works as a comparator - comparing what you intended to do (i.e. motor program you
have sent down the spinal cord - CST) with what you did do/what is actually happening
(comparing sensory information coming in - spinocerebellar tract)
o It can then adjust motor output by sending another message up to motor cortex to send
a different motor request down the SC
o Role to regulate movement and posture indirectly
o Unique features
• Receives a great deal of sensory input, but doesn't perceive sensation, rather it
uses this broad range of sensory input to evaluate, influence and modify
behaviour
• Electrical stimulation of the cerebellum doesn't precipitate motor activity, despite
the important role of the cerebellum in movement
• Related to this - pure cerebellar lesions don't result in paralysis - rather
decomposition of movement that is purposeful or productive
• Recent research suggests that the cerebellum may have other roles (e.g. cognition,
influence on visceromotor systems, motor learning)
o Function
• Based on what happens when the cerebellum is damaged, we surmise that the
cerebellum somehow helps to coordinate movement in terms of
▪ Direction
▪ Timing/speed
▪ Force
• Helps to create synergistic muscle contractions
• Integrates motor and sensory information to achieve accurate movement and
adjusts UMN output accordingly
• Diagram
▪ The cerebellum accomplishes its function by comparing what is actually
happening (green) with what was intended to happen (blue)
▪ To make this comparison, it needs information from the cerebrum
(intention) and from the brainstem and spinal cord (reality)
▪ Where there is a difference, between intention and reality, there is an error
signal
find more resources at oneclass.com
find more resources at oneclass.com
o Feedforward
• Cerebellum is able to make a prediction when you plan a movement of other motor
commands the body will need to make to cope with that planned movement (e.g.
lift arm forward need to also turn on stability trunk muscles to stop a fall)
o Feedback
• Cerebellum adjusts motor commands for output based on what actually is
happening (e.g. as a person reaches for a target is the movement refined enough
to be touching the target as intended - is what we wanted to happen happened?)
o Plays a role in
• Maintaining posture and balance
▪ Through its inputs from vestibular receptors and proprioceptors and makes
postural adjustments
• Coordination of voluntary movements
▪ Coordinates the timing and force and synchronisation of different muscle
groups to produce fluid movement
• Motor learning
▪ Adapts and fine tines motor programs through trial and error, some studies
suggest this is task-dependent
• Cognitive function
▪ Not as well understood
o Role of the cerebellum in cognition
• A relatively new idea about cerebellar function
• Mostly nominated through studies that looked at loss of function after injury ,
though also some imaging studies (lateral hemispheres)
• Role in
▪ Executive functions - planning, abstract reasoning, working memory
▪ Spatial cognition - visuospatial organisation and memory
▪ Personality - components of affect and of inhibition; mutism
▪ Language - stress, rhythm and pitch of speech (impairment - loss of melody,
intonation and flow; pseudo foreign accent syndrome)
o Role of the cerebellum in motor learning and memory
• Learning a new sequence
▪ Rapid and significant expansion of the relevant areas on the sensorimotor
cortices
▪ Plus increased input to the cerebellum (feedforward/feedback)
find more resources at oneclass.com
find more resources at oneclass.com
