9-2 Flashcards
what does our cerebellum compare
- receives afferent (sensory) and efferent (motor)
- compares intention vs what happened
function of cerebellum
-Maintenance of balance and posture
-Coordination of voluntary movements
-Motor learning
Maintenance of balance and posture
- Important for making postural adjustments
- Integrates sensory information relevant to balance & modulates information
sent to motor neurons to control postural muscles
Coordination of voluntary movements
- Coordinates timing and force of different muscle groups to plan and produce
smooth movements
Motor learning
- Adapt and fine-tune motor commands to make accurate movement
- Trial-and-error process
4 symmetrical sections
- Hemisphere
- Vermis
- Intermediate zone
- Flocculonodular lobe
Spinocerebellar
- Location: vermis & intermediate zones
- Integrates sensory & motor information
- Motor coordination
Cerebrocerebellar
- Location: lateral hemisphere
- Involves cortical input
- Planning and timing of movements
Vestibulocerebellar
- Location: flocculonodular lobe
- Involves vestibular nuclei input
- Posture and vestibular reflexes
Cerebellum is important for
- planning smooth, coordinated movements (spinocerebellar
and cerebrocerebellar pathways) - balance control (vestibulocerebellar pathway)
ataxis
- Lack of coordination
- Decomposition of movement
- Jerky movement
Dysmetria
- Inability to make accurate
voluntary movements - Overshoot/undershoot of
movement
Hypotonia
Decrease in muscle
tone/resistance
Large amounts of sway
Efference
motor command sent from motor cortex to body
Efference copy
copy of motor command used to update other brain regions on the action about to be performed
Ex-afference
sensory information from an externally-generated action
Re-afference
sensory information from a self-generated action
Corollary Discharge
-Signal created within the cerebellum →
represents the feedback we EXPECT to get from
a self-generated movement
* Used to inhibit expected feedback from self-
generated movement that may interfere with
execution of motor task
-if there is any unexpected re-afference we get
from a voluntary movement →does NOT get
inhibited, and gets sent to cortex to update on
unexpected information
feedforward step 1
Movement goal is sent to Motor Cortex
* Select appropriate motor plan based on
previous experience
* Force, speed, direction of movement,
correct MU recruitment, etc.
feedforward step 2
Efference (motor command) sent
to effector muscles in the body
* execute appropriate motor
plan based on previous
experience
* Force, speed, direction of
movement, correct MU
recruitment, etc.
step 3 feedforward model
- Corollary discharge is
produced by the cerebellum
* created from efference copy
* represents the expected
sensory feedback we should
get from executed
movement
* used to inhibit any response
to self-generated movement
that may interfere with
execution of the motor task
step 4 feedforward
- Comparison of corollary
discharge and reafference occurs in the cerebellum
* Expected vs. actual sensory information
* Expected and actual information MATCH = successful movement execution
* if they don’t match = unsuccessful execution &
need to update cortex…
step 5 feedforwards
Cerebellum updates Motor Cortex about reafference
information that didn’t match
* adjust motor plan until desired movement is
achieved
“Tit for Tat” Experiment
Corollary discharge from self-generated
movement!
* Sensory information from external sources =
all information is perceived
* To replicate that force, you feel like you are
generating 0.25 N BUT…
* Re-afference inhibited by corollary discharge,
so you must push MUCH HARDER to feel
like you are exerting 0.25 N
* Other person perceives this higher force…
replicates and same phenomenon occurs
