11 - Movement Flashcards
Describe the cerebellum in terms of size and amount of neurons
10% of brain weight, but >50% of neurons
Overall, where does the cerebellum receive sensory input from and where does it’s project information to?
Receives sensory input from;
- Vestibular, somatosensory, proprioceptive and visual and auditory
- Cortex (via pons)
Output
- to red nucleus (via thalamus) to cortex
What is the primary role of the cerebellum?
Largely fine-tuning output from other motor centres
Important in smooth execution of coordinated sequences of movements
Explain how the connections from the cerebellum with the brain are crossed
Right hemisphere of cerebellum is linked to left hemisphere of brain.
Left hemisphere of brain controls right side of body.
So, right cerebellum involved in co-ordination of movements co-ordinates right side of body due to DOUBLE CROSS
What does damage to cerebellum do in terms of movement?
Jerky, poorly coordinated movements
Can’t use proprioceptive feedback
What types of learned complex skills is the cerebellum important for?
Flying, walking, playing musical instruments.
Eye blink conditioning
Short-term adaptation to visuo-motor distortion (flipping glasses for a few days)
Describe two things that demonstrate the connection between the “association cortex” (cognitive) and the cerebellum
After Cb damage, cognitive impairments occur (often “frontal” deficits in executive function)
Imaging studies
- cerebellum is more active in more cognitively demanding tasks.
- more active when attending to semantic rather than rhyming relationships between words
- left cerebellum more active during lying
What is the main role of the brainstem?
Control muscles of trunk, neck and proximal limbs (upper arms and legs)
Posture, correcting balance
What is the main role of the red nucleus?
Controls arms and legs
Limb movements independent of trunk (e.g. reaching)
What is the main role of the motor cortex and describe what can happen when a stroke occurs in this area?
Control muscles in arms, hands and fingers
Voluntary manual movements (e.g. writing, picking up an object)
Stroke in right motor cortex resulted in weakness in left hand and face. When a man was asked to show his teeth, lop-sided grin, but when told joke there was a symmetrical smile.
Could only move left side of face in involuntary movement.
What is the internal capsule?
Ribbons of fibres from cortex to thalamus, basal ganglia, brainstem and spinal cord (as travel from cortex they go through internal capsule)
Stroke can cause hemiparesis (trouble producing voluntary movements in that part of the body, very stiff) and hemianesthesia
Describe the neocortex
The frontal lobe contains three areas of the motor cortex:
Primary Motor Cortex (M1)
- strip of cortex in front of central sulcus
- contains topographical map of body
- involved in final execution of movement (output to spinal cord via direct corticospinal tracts and via red nucleus)
Supplementary Motor Area (SMA) and Pre-Motor Area (PMA)
- both involved in planning of movements
- neurons most active shortly before performing a movement of before an aborted movement. OR during imagined rehearsal of movement
Describe the coding of movement in the motor cortex, specifically the PMA and SMA
As the PMA and SMA code for anticipated direction or destination of movement, looked at those neurons in monkeys.
Move joystick towards a light; some cells only fire when monkey was about to move stick in a particular direction (even during a delay interval, if monkey had to wait before moving stick)
These cells also perform “mental rotation”
- Move joystick 90 degrees anticlockwise from light, activity spread through population of neurons mapping out the rotation transformation
- E.g. neurons for 12 fire first, then 11.
