W9 - Cerebellum and Motor Learning Flashcards
(47 cards)
What is the cerebellum often referred to as and why?
The “little brain” — it is highly folded but structurally simple with only one output layer (Purkinje cells).
What are the main functions of the cerebellum?
Motor coordination, Skilled movement, Error correction, Motor learning, Possibly cognitive processing
What input does the cerebellum receive?
From the sensory-motor cortex, posterior parietal cortex, brainstem, and spinal cord.
Where does the cerebellum send output to?
To the motor/premotor cortex, red nucleus, and spinal cord.
Quantitatively, how large is the cerebellum? (Sultan & Braitenberg, 1993)
~102 billion neurons, ~101 billion granule cells, ~15–30 million Purkinje cells; each Purkinje cell gets ~200,000 parallel fibre inputs and 1 climbing fibre input.
What are the three layers of the cerebellar cortex?
- Molecular layer — dendrites of Purkinje cells; receives sensory input. 2. Purkinje cell layer — the main output cells. 3. Granule cell layer — contains Golgi cells; relays mossy fibre input.
What are mossy fibres and climbing fibres?
Mossy fibres (from pons): carry sensory information to granule cells. Climbing fibres (from inferior olive): carry error signals directly to Purkinje cells.
Where does motor learning occur in the cerebellum?
At the synapses between parallel fibres and Purkinje cells — this is where sensory input is evaluated and modified.
What do Purkinje cells do?
They inhibit deep cerebellar nuclei, which then send excitatory output to motor areas.
How does the cerebellum refine movement?
By comparing intended and actual outcomes and using long-term depression (LTD) to correct errors.
What is the Marr-Albus model of cerebellar learning?
It describes associative learning at the parallel fibre–Purkinje cell synapse via LTD.
What happens when parallel and climbing fibres are activated simultaneously?
LTD reduces Purkinje output → deep nuclei are disinhibited → motor output is strengthened → learning is driven by the climbing fibre error signal.
How does the cerebellum contribute to the Vestibulo-Ocular Reflex (VOR)?
It adjusts eye movement gain to stabilise vision during head movement using retinal slip as the error signal.
What happens in cerebellar lesions during prism adaptation tasks?
Patients show no short-term adaptation — cerebellum is essential for visuo-motor recalibration.
What is eye-blink conditioning and how is the cerebellum involved?
A Pavlovian learning task where an air puff (US) and tone (CS) lead to a conditioned blink (CR); Purkinje cell LTD enables this learning.
What does skill learning look like in cerebellar cells?
Task-specific complex spike patterns emerge in Purkinje cells as learning progresses, even if LTD isn’t directly measurable.
How are different cortical areas functionally connected to the cerebellum?
Through resting-state fMRI, showing distinct cerebellar zones connected to motor, sensory, visual, auditory, and prefrontal regions.
Which cerebellar regions connect to prefrontal cortex?
Posterior-lateral hemispheres (lobule VI / Crus I & II).
What does this connectivity imply about cerebellar function?
That the cerebellum is involved in cognition, not just motor control (e.g., working memory, prediction, language).
What is hypermetria?
Overshooting a target due to impaired movement scaling (e.g., in finger-to-nose task).
What is intention tremor?
Tremor that worsens during voluntary, goal-directed movement (contrast with Parkinson’s resting tremor).
What is ataxia?
Poor coordination, unsteady gait, and impaired fine motor control due to cerebellar dysfunction.
What is nystagmus and how is it cerebellar-related?
Involuntary eye movement due to vestibulocerebellum disruption.
What is cerebellar affective disorder (Schmahmann’s syndrome)?
A condition involving emotional dysregulation, executive dysfunction, and personality changes, especially in children with cerebellar damage.
