Lecture 8- motor control Flashcards
How can we study motor control using behaviour
Using recordings such as videos or tracking equipment to records different body parts in space and time.
+ Allows us to systematically investigate the output of the motor system
- not a direct measurement of brain activity.
How can we us muscle physiology to study motor control
Use electromyography which uses electrodes to measure activity of individual muscles or muscle fibres
+ Understanding of how individual muscles operate
- not a direct measure of brain activity
How we can use single unit electrophysiology to study motor control
Implant electrodes in the brain to measure activity of individual neurons.
+ Great temporal and spatial resolution at the level of one neuron
- Cannot examine more than a small percentage of neurons at once and can only measure one at a time.
Explain the skeletal muscle
Muscles attach to the skeleton at the origin and the insertion.
feedback/ proprioceptive information from the muscles is provided by spindles and Golgi tendon organs
Muscles are organised into antagonistic pairs (extensors- extend, flexors- contract) working at alternate intervals.
Explain the neuromuscular junction
Motor neurons release neurotransmitters which cause muscle contraction at the neuromuscular junction.
Acetylcholine neurotransmitter binds to receptors causing depolarisation.
If depolarisation is high enough, ion channels open and calcium enters
Calcium causes Actin and myosin proteins to interact, leading to muscle contraction.
Acetylcholinesterase removes neurotransmitter, ending contraction
4 components in the motor system
1- Non-primary motor cortex
2- Primary motor cortex M1
3- Brainstem
4- Spinal cord - muscles + skeletal system
What does the spinal cord do?
Transfers input to motor neurons, controlling body movement.
Spinal reflexes are automatic responses. Proprioceptors detect a stretch, triggering a motor response to counteract the stretch.
Controls some locomotion aspects
Central pattern generator - generates rhythmic pattern of behaviour.
Pyramidal vs extra pyramidal systems
Pyramidal: sent through brain stem- spinal cord- muscles. Pyramidal tract from right hemisphere crosses over to left
Extra pyramidal run through brain and brain stem only rather than spinal cord. Including muscles in eye, neck jaw and face.
3 main motor control systems:
1) M1
2) Premotor cortex
3) Supplementary motor cortex
Explain the primary motor cortex
Voluntary movement planning, control and execution. It is the executive motor control mechanism. Source of many pyramidical tract neurons.
Transcranial magnetic stimulation: temporarily disrupts brain activity using high powered magnetic coil. Causing temporary lesions for msec to a min. Can cause twitching in the muscle when placed on different parts of the body so we can figure out the mapping. Known as Motor evoked potential.
Areas with more motor control are larger in the homunculus.
Controversies occur as the homunculus suggests neurons map directly onto a muscle however research finds that neurons can respond to an optimal direction of movement.
New research finds longer stimulation can lead to more complex movements. Meaning there are not simple explanations and representations are more complex.
Premotor cortex
Motor coordination
Lesions cause impairments in stability of stance, gait and hand coordination
Contains mirror neurons which are not only active when performing an action but also when watching some one perform action
Supplementary motor cortex
Initiates movement
Lesions cause deficit in voluntary movement or speech
What is included in the extra pyramidal system
Basal ganglia and cerebellum
Basal ganglia
Modulates patterns of motor activity and initiates it
3 main components:
Striatum (caudate and putamen)
and Globus pallidus
Functionally connected to subthalamic nucleus and substantia nigra damage of which can lead to Parkinson’s
Cerebellum
controls neural programs for execution of skilled movements (becoming practiced at something it requires little thought)
As well as motor coordination, impairment can cause damage to coordination, accuracy and timing of movements.
Sends connections to brain and spinal cord.
Fine tuned motor control
Combines sensory and motor information to predict where an object will be known as Forward modelling where trying to touch a moving object if you put hand at current position you will miss it. Use sensory feedback to find correct position
Involved in motivation, emotion and cognition. Damage to it impairs cognition, language perception and grammar
Libets task
PPT asked to take note of the time when they decided to press button. Intent to move occurred 200msec before movement but readiness potential even earlier.
Can use EEG to measure readiness potential
